AP BIOLOGY Membranes & Proteins Cell Membranes Membranes ...

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AP BIOLOGY

Membranes & Proteins

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Membranes & Proteins

· Cell Membranes

· Enzymatic Proteins

· Transport Proteins

· Signaling Proteins

Click on the topic to go to that section

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Cell Membranes

Return toTable ofContents

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Biological Membranes

The term membrane most commonly refers to a thin, film-like structure that separates two fluids.

Membranes act as a container for biological systems, surrounding protobionts, cells, and organelles.

The video below shows experiments done at a laboratory in France to study the properties of lipids. The only substances used in the making of this video are lipids, water and dye . The lipids and dye were mixed and then injected into aqueous solution.

Try to figure out some of the properties that make lipids useful as membranes by watching the video.

Click here for the video

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Phospholipids

The most important lipid that composes the majority of biological membranes is the phospholipid.

The amphiphilic nature of these lipids cause them to naturally form a spherical bilayer.

http://www.njctl.org

http://www.njctl.org

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http://www.wired.com/underwire/2012/08/mouse-on-mars/

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Lipids and the Membrane

Phospholipids form two parallel lines with their hydrophobic ends in between. The hydrophobic ends are protected from the water by the hydrophilic ends, creating a bilayer.

In animals, cholesterol inserts itself into the membrane in the same orientation as the phospholipid. Cholesterol immobilizes the first few hydrocarbons in the phospholipid, making the bilayer more stable, and impenetrable to water molecules.

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Selective Permeability

Membranes act as selectively permeable barriers, allowing some particles or chemicals to pass through, but not others.

The properties of the phospholipid bilayer dictate what can pass through a membrane.

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When phospholipids come together, they create a wall that is tightly packed with a core that is nonpolar. However, the individual molecules are not fixed and small gaps form as they fluidly move around in the membrane.

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So what molecules CAN pass through a membrane made of just phospholipids?

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1 Will O2 pass through?

YesNo

Why?

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1 Will O2 pass through?

YesNo

Why?

[This object is a pull tab]

Ans

wer 02 will pass through

because it is neutral and very small, only 2 atoms big.

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2 Will H2O pass through?

YesNo

Why?


2 Will H2O pass through?

YesNo

Why?


Ans

wer

H2O will pass through. Even though there is a charge on water, it is partial and the molecule is extremely small. It is slow to diffuse because of its partial charge.

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3Will Na+ pass through?

YesNo

Why?


3Will Na+ pass through?

YesNo

Why?


Ans

wer

Even though sodium is a very small ion, it has a strong positive charge. The neutral, hydrophobic barrier prevents even the smallest ions from passing.

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4Will C6H12O6 pass through?

YesNo

Why?


4Will C6H12O6 pass through?

YesNo

Why?


Ans

wer

Glucose is a large molecule that can not pass through the small gaps between the phospholipids.

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Selective PermeabilityTo recap...

Large molecules or charged molecules will not make it through a lipid bilayer.

Some examples: sugars, ions, nucleic acids, proteins

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How do cells get what they need?

We know that cell membranes are made of lipid bilayers, and we know that cells require things like sugar and nucleic acids and proteins and sodium that can't pass through this barrier.

So how do cells get the materials they need?

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Fluid MosaicProteins embedded in the cell membrane facilitate the movement of large or charged molecules through the barrier. By doing this, the internal chemistry of the cell becomes far different than its surroundings.

The pattern of lipids and proteins in the cell membrane is referred to as the fluid mosaic model.

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Proteins Regulate What is in a Cell

Proteins are long chains of amino acids that fold up on each other to form useful structures in biological systems. Below is a ribbon diagram of an amino acid chain that forms a channel protein.

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Types of Membrane Proteins

Peripheral proteins stay on only one side of the membrane.

Integral proteins pass through the hydrophobic core and often span the membrane from one end to the other.

Proteins in the plasma membrane can drift within the bilayer. They are much larger than lipids and move more slowly throughout the fluid mosaic.

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Carbohydrates and the Membrane

Glycoproteins have a carbohydrate attached to a protein and serve as points of attachment for other cells, bacteria, hormones, and many other molecules.

Glycolipids are lipids with a carbohydrate attached. Their purpose is to provide energy and to act in cellular recognition.

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An integral protein forms a pore that allows specific substances to diffuse across the membrane, even if they are large or have charge.

Proteins Regulate What is in a Cell

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Review Membrane Transport

Watch this video to review the way in which membranes can regulate by transport.

Click here for a review of solute moving through membranes

If further review is needed please see NJCTL's first year biology course.

Membranes First Year Course

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5When diffusion has occurred until there is no longer a concentration gradient, then _______________ has been reached.

A equilibriumB selective permeabilityC phospholipid bilayerD homeostasis


5When diffusion has occurred until there is no longer a concentration gradient, then _______________ has been reached.

A equilibriumB selective permeabilityC phospholipid bilayerD homeostasis


Ans

wer

A

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6In osmosis, water molecules diffuse fromA inside the plasma membrane to outside only

B outside the plasma membrane to inside only

C from areas of high solute concentration to areas of low solute concentration

D from areas of low solute concentration to areas of high solute concentration


6In osmosis, water molecules diffuse fromA inside the plasma membrane to outside only

B outside the plasma membrane to inside only

C from areas of high solute concentration to areas of low solute concentration

D from areas of low solute concentration to areas of high solute concentration


Ans

wer

D

http://www.bozemanscience.com/science-videos/2011/9/14/016-transport-across-cell-membranes.html

http://njctl.org/courses/science/biology/membranes-and-enzymes/

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7What type of environment has a higher concentration of solutes outside the plasma membrane than inside the plasma membrane?

A hypertonic

B isotonic

C normal

D hypotonic


7What type of environment has a higher concentration of solutes outside the plasma membrane than inside the plasma membrane?

A hypertonic

B isotonic

C normal

D hypotonic


Ans

wer

A

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8What type of solution has a greater flow of water to the inside of the plasma membrane?

A hypertonic

B isotonic

C normal

D hypotonic


8What type of solution has a greater flow of water to the inside of the plasma membrane?

A hypertonic

B isotonic

C normal

D hypotonic


Ans

wer

D

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9A red blood cell will lyse when placed in which of the following kinds of solution?

A hypertonic

B hypotonic

C isotonic

D any of these


9A red blood cell will lyse when placed in which of the following kinds of solution?

A hypertonic

B hypotonic

C isotonic

D any of these


Ans

wer

B

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10Dialysis tubing is permeable to monosaccharides only. Which solute(s) will exhibit a net diffusion out of the cell?

A sucrose

B glucose

C fructose

D sucrose, glucose, and fructose

E sucrose and glucose

Cell:0.05M sucrose0.02M glucose

environment0.01M sucrose0.01M glucose0.01M fructose


10Dialysis tubing is permeable to monosaccharides only. Which solute(s) will exhibit a net diffusion out of the cell?

A sucrose

B glucose

C fructose

D sucrose, glucose, and fructose

E sucrose and glucose




Ans

wer

B

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11Is the solution outside the cell isotonic, hypotonic, or hypertonic?

A Hypertonic

B Hypotonic

C Isotonic




11Is the solution outside the cell isotonic, hypotonic, or hypertonic?

A Hypertonic

B Hypotonic

C Isotonic




Ans

wer

B

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12The process by which a cell ingests large solid particles, therefore it is known as "cell eating".

A Pinocytosis

B Phagocytosis

C Exocytosis

D Osmoregulation


12The process by which a cell ingests large solid particles, therefore it is known as "cell eating".

A Pinocytosis

B Phagocytosis

C Exocytosis

D Osmoregulation


Ans

wer

B

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13Antibodies are embedded in cell membranes and bind to antigens on the surface of foreign cells. What type of molecule is an antibody?

A phospholipid

B glycolipid

C glycoprotein

D enzyme


13Antibodies are embedded in cell membranes and bind to antigens on the surface of foreign cells. What type of molecule is an antibody?

A phospholipid

B glycolipid

C glycoprotein

D enzyme


Ans

wer

C

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OsmosisIn animal cells, water moves from areas of low solute concentration to areas of high solute concentration during osmosis. In plants, bacteria, and fungi, however, the cell wall exerts a force on the internal environment of the cell and affects the net flow of water through the cell membrane.

The effects of solute concentration and the pressure provided by the cell wall are incorporated into a quantity called water potential ( ).

Osmosis moves water from areas of high water potential to areas of low water potential.

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Water Potential

Water potential is calculated using the following equation:

Note: Animal cells do not have cell walls so pressure potential = zero

Water potential is measured in megapascals (MPa) or bar.

1 MPa = 10 bar

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14 An animal cell with a solute potential of -0.30 MPa (megapascals) is placed in a sucrose solution with a solute potential of -0.55 MPa. What is the net direction of osmosis?

A into the cell

B out of the cell

C not enough information


14 An animal cell with a solute potential of -0.30 MPa (megapascals) is placed in a sucrose solution with a solute potential of -0.55 MPa. What is the net direction of osmosis?

A into the cell

B out of the cell



Ans

wer

B

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15 A fungal cell with a solute potential of -2.5 bar is place in a saline solution with a potential of -1.2 bar. What is the net direction of osmosis?

A into the cell

B out of the cell



15 A fungal cell with a solute potential of -2.5 bar is place in a saline solution with a potential of -1.2 bar. What is the net direction of osmosis?

A into the cell

B out of the cell



Ans

wer

A

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16 In a given plant cell, the cell wall exerts 2.3 bar of pressure and the solute potential is -3.0 bar. Calculate the water potential.


16 In a given plant cell, the cell wall exerts 2.3 bar of pressure and the solute potential is -3.0 bar. Calculate the water potential.


Ans

wer

-0.7 bar

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17 In a given animal cell, the solute potential is -0.25 MPa. Calculate the water potential.


17 In a given animal cell, the solute potential is -0.25 MPa. Calculate the water potential.


Ans

wer

-0.25 MPa

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18 A turgid plant cell with a solute potential of -7.0 bar is placed in pure water. When the cell reaches osmotic equilibrium with its surroundings, what is the pressure potential of the cell?


18 A turgid plant cell with a solute potential of -7.0 bar is placed in pure water. When the cell reaches osmotic equilibrium with its surroundings, what is the pressure potential of the cell?


Ans

wer

7.0 bar

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19 A bacterial cell with a solute potential of -9.0 bar is placed in a sucrose solution with a solute potential of -4.0 bar. No net movement of water occurs. What is the pressure potential of the cell?


19 A bacterial cell with a solute potential of -9.0 bar is placed in a sucrose solution with a solute potential of -4.0 bar. No net movement of water occurs. What is the pressure potential of the cell?


Ans

wer

5.0 bar

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Solute Potential

Solute potential is dependent upon type and concentration of solute. Its value can be determine using the following equation:

= -iCRTs

i =# of particles/ions in one molecule of solute after dissociationC = molar concentration (M)R = pressure constant (0.0831 L bar/mol K or 0.0083 L MPa/mol K)T = temperature (K)

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20 What does i equal for NaCl?

= -iCRTs

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20 What does i equal for NaCl?

= -iCRTs


Ans

wer

2(NA + and Cl -)

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21 What does i equal for fructose?

= -iCRTs


21 What does i equal for fructose?

= -iCRTs


Ans

wer

1 (no dissociation)

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22 What does T equal for a solution at 260C?

= -iCRTs


22 What does T equal for a solution at 260C?

= -iCRTs


Ans

wer

299 K

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23 Calculate water potential (in bar) for a cell that contains 0.9M NaCl and is stored at 19oC.


23 Calculate water potential (in bar) for a cell that contains 0.9M NaCl and is stored at 19oC.


Ans

wer

-43.7 bars

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24 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side A.

0.4 M NaCl 0.5 M Sucrose

37oC




37oC


Ans

wer

-20.6 bars

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25 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side B.


37oC




37oC


Ans

wer

-12.9 bars

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37oC

26 In what direction will the net flow of water occur?

A toward side A

B toward side B




37oC


A toward side A

B toward side B



Ans

wer

A

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0.2 M NaCl0.2 M Sucrose


25oC





25oC

[This object is a pull tab]A

nsw

er

-14.9 bar

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25oC





25oC


Ans

wer

-12.4

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A toward side A

B toward side B




25oC



A toward side A

B toward side B




25oC


Ans

wer

A

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Just as individual cells utilize their membranes to maintain homeostasis, so must multicellular organisms maintain a balance in their internal conditions.

Let's look at the mammalian urinary system as an example. Its ability to conserve water is a key adaptation to terrestrial life.

The fundamental unit of the kidney is a nephron. Nephrons rely on solute concentrations to power the reabsorption of water and other nutrients.

Homeostasis in Multicellular Organisms

Click here for an introduction to the urinary system

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Nephrons

Loop of Henle

As the filtrate descends the loop of Henle, increasing osmolarity of the interstitial fluid (fluid between the cells) causes water to diffuse outward.

As the filtrate ascends back up the tubule, decreasing osmolarity enables the facilitated diffusion of NaCl from the filtrate. Some active transport of NaCl also occurs.

The filtrate then enters the collecting ducts where more water is reabsorbed through osmosis.

The water and nutrients are then passively transported back into the blood supply.

Collecting Duct

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30 As the filtrate descends the loop of Henle, the extracellular solute potential ________________ causing the transport of ____________ across the membrane.

A increases, salts

B decreases, salts

C increases, water

D decreases, water


30 As the filtrate descends the loop of Henle, the extracellular solute potential ________________ causing the transport of ____________ across the membrane.

A increases, salts

B decreases, salts

C increases, water

D decreases, water


nsw

er

D

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31 Natural selection should favor the highest proportion of nephrons in which of the following species?

A a mouse species living in a tropical rain forest

B a mouse species living in a temperate rain forest

C a mouse species living in a desert

D they would all possess the same proportion of nephrons


31 Natural selection should favor the highest proportion of nephrons in which of the following species?

A a mouse species living in a tropical rain forest

B a mouse species living in a temperate rain forest

C a mouse species living in a desert

D they would all possess the same proportion of nephrons


Ans

wer

C

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32 Antidiuretic hormone (ADH) is released to maintain homeostasis in response to low blood osmolarity. Which of the following is false regarding this hormone?

A It decreases the active transport of NaCl in the ascending tubule

B It increases the collecting ducts' permeability to water

C It results in a more concentrated urine

D It is a response to increases in perspiration


32 Antidiuretic hormone (ADH) is released to maintain homeostasis in response to low blood osmolarity. Which of the following is false regarding this hormone?

A It decreases the active transport of NaCl in the ascending tubule

B It increases the collecting ducts' permeability to water

C It results in a more concentrated urine

D It is a response to increases in perspiration


Ans

wer

A

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Transport Proteins


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Larger molecules and ions that cannot squeeze between the phospholipids need the help of a transport protein. This is called Facilitated Diffusion .

In Facilitated Diffusion, particles move from an area of high to low concentration with the help of a transport protein. Since the substances are going with the natural concentration gradient, this is a type of Passive Transport: no energy is needed.

Facilitated Diffusion

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Examples of Transport Proteins

In facilitated diffusion, transport proteins speed the passive transport of molecules across the plasma membrane.

Transport proteins allow passage of hydrophilic substances across the membrane.

Channel proteins, are one type of transmembrane transport proteins that provide corridors that allow a specific molecule or ion to cross the membrane.

Carrier proteins, are another type of transmembrane transport proteins that change shape slightly when a specific molecule binds to it in order to help move that molecule across the membrane.

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Facilitated Diffusion

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33 Facilitated diffusion moves molecules _____.

A against their concentration gradients using energy

B against their concentration gradients without the use of energy

C with their concentration gradients using energy

D with their concentration gradients without the use of energy


33 Facilitated diffusion moves molecules _____.






Ans

wer

D

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34 Glucose and amino acids are transported into the cell through permases which change their shape during transport. These molecules are examples of...

A channel proteins

B carrier proteins

C enzymes

D both B and C


34 Glucose and amino acids are transported into the cell through permases which change their shape during transport. These molecules are examples of...

A channel proteins

B carrier proteins

C enzymes

D both B and C


nsw

er

B

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Active Transport Active Transport uses energy to move solutes through a transport protein against their gradients.

Active transport requires energy.

Active transport is performed by specific proteins embedded in the membranes.

Carrier proteins can also be used in active transport when they are moving specific molecules against their concentration gradients.

energy

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Comparing Passive and ActiveTransport

Passive Transport

Active Transport

(REQUIRES ENERGY)

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35 Active transport moves molecule _____.






35 Active transport moves molecule _____.






Ans

wer

A

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36 Which protein can be used for both active and passive transport?

A carrier protein

B channel protein

C any integral protein

D any transmembrane protein


36 Which protein can be used for both active and passive transport?

A carrier protein

B channel protein

C any integral protein

D any transmembrane protein


nsw

er

A

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37 ATP synthase is an integral protein used to generate ATP, by allowing the flow of hydrogen ions across the membrane. This is an example of what type of transport?

A diffusion

B facilitated diffusion

C active transport

D exocytosis


37 ATP synthase is an integral protein used to generate ATP, by allowing the flow of hydrogen ions across the membrane. This is an example of what type of transport?

A diffusion

B facilitated diffusion

C active transport

D exocytosis


Ans

wer

B

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Sodium Potassium Pump

The sodium potassium pump is an example of the active transport mechanism. This system is utilized in every animal cell to transport Na+ and K+ maintaining a relatively high concentration of potassium and relatively low concentration of sodium inside the cell.

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1) The pump, binds ATP, and then binds 3 intracellular Na+ ions.

2) ATP is hydrolyzed, leading to phosphorylation of the pump and subsequent release of ADP.

3) A conformational change in the pump exposes the Na+ ions to the outside. The phosphorylated form of the pump has a low affinity for Na+ ions, so they are released.

4)The pump binds 2 extracellular K+ ions. This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the K+ ions into the cell.

5) The unphosphorylated form of the pump has a higher affinity for Na+ ions than K+ ions, so the two bound K+ ions are released. ATP binds, and the process starts again.

Sodium Potassium Pump

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38 The sodium-potassium pump is a major contributor in establishing the ________ of a cell.

A pump direction

B osmolarity

C ATP

D membrane potential


38 The sodium-potassium pump is a major contributor in establishing the ________ of a cell.

A pump direction

B osmolarity

C ATP

D membrane potential


nsw

er

D

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39 In the sodium potassium pump, ___ sodium ions initially bind to the transport protein.

A 1

B 2

C 3

D 4


39 In the sodium potassium pump, ___ sodium ions initially bind to the transport protein.

A 1

B 2

C 3

D 4


Ans

wer

C

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40 The binding of the sodium ions does not change the shape of the protein until the potassium ions bind.

True

False


40 The binding of the sodium ions does not change the shape of the protein until the potassium ions bind.

True

False


Ans

wer

False

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41 The sodium potassium pump passes:

A more Na+ out than K+ in

B K+ out and Na+ in on a one-for-one basis

C Na+ out and K+ in on a one-for-one basis

D K+ and Na+ in the same direction


41 The sodium potassium pump passes:

A more Na+ out than K+ in

B K+ out and Na+ in on a one-for-one basis

C Na+ out and K+ in on a one-for-one basis

D K+ and Na+ in the same direction


Ans

wer

A

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Neurons rely on the unequal distribution of sodium and potassium ions to transmit signals (known as action potentials) throughout the nervous system.

In a resting neuron (one not sending signals) the ionic gradient produced by the Na+/K+ pump generates a resting potential of -60 to -80 mV.

A certain amount of Na+ and K+ is always leaking across the membrane through leakage channels, but Na+/K+ pumps in the membrane actively restore the ions to the appropriate side.

Neurons

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Nerve impulses are passed along neurons by a depolarization of the membrane. An action potential is triggered when the membrane potential increases to between -40 and -55 mV. When this threshold value is reached Na+ gates open causing sodium ions to move into the cell.

The influx of Na+ triggers K+ gated channels to open releasing potassium ions from the cell. This depolarization of the cell signals the next neuron in the pathway to depolarize.

The neuron returns to its original state through the action of sodium/potassium pumps embedded in the membrane and the original concentration gradients are reestablished.

Action Potential

Click here to see how an action potential travels

http://njc.tl/120

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Action Potential

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Signaling Proteins


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Cellular signaling is a part of a complex system of communication that governs basic cellular activities and coordinates cell actions.

The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity.

Cellular Signaling

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Cells within multicellular organisms must communicate with one another to coordinate all aspects of life. Single-celled organisms also communicate with one another to perform certain symbiotic tasks.

Correct and appropriate signaling pathways are generally under strong selective pressure and show shared evolution among organisms with shared pathways.

Evolution of Signaling

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42 Which of the following organisms would likely not show similar communication pathways to the others?

A peacockB turtleC butterflyD shark

E alligator


42 Which of the following organisms would likely not show similar communication pathways to the others?

A peacockB turtleC butterflyD shark

E alligator


Ans

wer

C

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Transcription factors are cofactors regulating the initiation of gene transcription. They cause a cell to respond to a signal in the environment in a very specific way. This signal is anything that the cell has the ability to respond to. It could be light, a chemical, a hormone, heat, etc.

A signal transduction pathway proceeds with reception of a signal, transduction of that signal through the cell to the DNA, and finally results in expression of a transcription factor.

Signal Transduction

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Signal Transduction Pathway

DNA

Cell

Signal

The pathway starts when a new signal reaches a cell.

Reception

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DNA

Cell

Receptor

External signal activates membrane-bound protein know as a receptor.

Signal

These receptors are like enzymes in that they will bind with only 1 kind of substrate (signal).

Reception

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DNA

Cell

Activated Receptor

The activated receptor triggers a cascade reaction, a metabolic pathway.

Transduction

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Activated Receptor

The metabolic pathway produces a specific transcription factor in response to signal. The product initiates transcription of a response gene.

DNATranscription Factor

Cell

Transduction

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Activated Receptor

DNATranscription Factor

Cell

Transcription factors initiate the transcription of additional genes, which coordinate the cell's response to stimuli.

Response

Signal Transduction Video

http://njc.tl/st

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43 Which of the following is an example of a signal that can start a signal transduction pathway?

A heatB lightC hormoneD all of the above


43 Which of the following is an example of a signal that can start a signal transduction pathway?

A heatB lightC hormoneD all of the above


Ans

wer

D

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44 The activated metabolic process in a signal transduction pathway produces

A A transcription factorB Cell movementC A signalD Receptors on the cell membrane


44 The activated metabolic process in a signal transduction pathway produces

A A transcription factorB Cell movementC A signalD Receptors on the cell membrane


nsw

er

A

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45 Which of the following correctly illustrates a signal transduction pathway?

ALight is absorbed by chlorophyll molecules. Chlorophyll releases a transcription factor.

BAntigens bind to the antibodies on the surface of a cell. Antibodies break down the foreign cell's membrane, causing cell death.

C

Glucose enters the cell via transport proteins. A metabolic pathway within the cell causes the synthesis and release of insulin

D All of the above are correct


45 Which of the following correctly illustrates a signal transduction pathway?

ALight is absorbed by chlorophyll molecules. Chlorophyll releases a transcription factor.

BAntigens bind to the antibodies on the surface of a cell. Antibodies break down the foreign cell's membrane, causing cell death.

C

Glucose enters the cell via transport proteins. A metabolic pathway within the cell causes the synthesis and release of insulin

D All of the above are correct


Ans

wer

D

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When a receptor receives an external signal from another cell, the response can either be to increase or decrease the concentration of a specific molecule within the cell.

Increasing the concentration is called upregulation and decreasing production of that molecule is called downregulation.

Regulation

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Upregulation

During upregulation , the number of receptors on the surface of target cells increase, making the cells more sensitive to a hormone or another agent.

For example, there is an increase in uterine oxytocin receptors in the third trimester of pregnancy, promoting the contraction of the smooth muscle of the uterus.

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Alternatively, downregulation is a decrease in the number of receptors on the surface of target cells, making the cells less sensitive to a hormone or another agent. Some receptors can be rapidly downregulated.

An example of downregulation occurs in Type II diabetes. This form of the disease is characterized by

Downregulation

elevated levels of insulin in the bloodstream but a loss of insulin receptors. This downregulation can sometimes be reversed through exercise, and occasionally, a change in diet can also resolve the issue.

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46 An increase of the number of receptors on a targeted cell's surface is known as

A upregulationB downregulation


46 An increase of the number of receptors on a targeted cell's surface is known as

A upregulationB downregulation


Ans

wer

A

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47 Which of the following is an example of downregulation?

A control of blood sugar levels

B milk production in lactating females

C nicotine addiction

D contractions during pregnancy

(Answer) / 181

47 Which of the following is an example of downregulation?

A control of blood sugar levels

B milk production in lactating females

C nicotine addiction

D contractions during pregnancy


Ans

wer

A

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In single-celled organisms, signal transduction pathways influence how the cell responds to its environment.

Many single-celled organisms live in symbiotic relationships with other organisms, responding to signals released by adjacent cells.

Single-Celled Signaling

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Bacteria will produce and release signaling molecules. The same bacteria also have receptors for that molecule on their surface.

When the signal binds to a receptor on another organism, it activates a system which typically causes another specific behavior in the group.

Quorum Sensing

Certain bacteria use chemical messengers to communicate to other nearby cells and regulate specific reproductive pathways in response to population density. This is known as quorum sensing.

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Pseudomonas aeruginosa use quorum sensing to coordinate cell aggregation. They grow within a host without harming it until they reach a certain concentration.

Once that concentration is reached, they release a signal to aggressively replicate in order to overcome the host's immune system. The bacteria create a biofilm wherein they form a layer that completely covers the host's tissue and then reproduce at a exponential rate.

Research has shown that garlic inhibits the formation of these Pseudomonas biofilms by blocking the quorum sensing pathway. This is called quorum inhibition.

Example of Quorum Sensing: Pseudomonas aeruginosa

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Biofilm Development in Pseudomonas aeruginosa

Slide 103 / 181

Quorum Sensing

Below is a longer video that ties in quorum sensing and antibiotic resistance. Teachers may want to pause and discuss for student understanding.

Click here for a TED talk on Quorum Sensing

Quorum Sensing Introduction

Quorum Sensing Explanation

http://njc.tl/su

http://njc.tl/sv

http://njc.tl/sw

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48 Quorum sensing would most likely occur when:

A an antibiotic attacks a bacterial infection

B bacteria reach a certain concentration

C bacteria sense the presence of an antibiotic

D a biofilm is broken down


48 Quorum sensing would most likely occur when:

A an antibiotic attacks a bacterial infection

B bacteria reach a certain concentration

C bacteria sense the presence of an antibiotic

D a biofilm is broken down


Ans

wer

B

Slide 105 / 181

In animal cells these cell junctions are:

Tight junctions: can bind cells together into leakproof sheets

Adhering junctions: fasten cells together into strong sheets. They are somewhat leakproof.

Multicellular Signaling

Communicating (Gap) junctions: allow substances to flow from cell to cell. They are totally leaky. They are the equivalent of plasmodesmata in plants.

Examples of Animal Cell Junctions

Multicellular organisms have physical pathways between adjacent cells to aid in communication and transfer of substances.

Slide 106 / 181

Plant cells connect using plasmodesmata which are channels that allow them to share water, food, and communicate via chemical messages.

Multicellular Signaling

Animal and plant cells have different types of cell junctions mainly because plants have cell walls and animal cells do not.

Slide 107 / 181

49 Which type of cell junction is found in plants?

A Tight junctionsB Gap junctionsC Adhering junctionsD Plasmodesmata


49 Which type of cell junction is found in plants?

A Tight junctionsB Gap junctionsC Adhering junctionsD Plasmodesmata


Ans

wer

D

http://flightline.highline.edu/jbetzzall/BI100/animations/cell_junctions_v3.html

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50 Which type of junction allows substances to flow between animal cells?

A Tight junctionsB Adhering junctionsC Gap juctionsD Plasmodesmata


50 Which type of junction allows substances to flow between animal cells?

A Tight junctionsB Adhering junctionsC Gap juctionsD Plasmodesmata


Ans

wer

C

Slide 109 / 181

Practice

Let us look at a few examples of different types of organisms adjusting to their surroundings.We will start with a protist. This protist is single celled, photosynthetic, and motile.

mitochondria

chloroplastsflagella

nucleus

Slide 110 / 181

Practice

The protist has the ability to move toward light by directing its flagella to oscillate in a particular direction, this is known as phototaxis. Moving closer to the light allows the cell to produce more sugar by photosynthesis.

Slide 111 / 181

Practice

Write down a step by step explanation of how this cell will start moving toward the light in terms of a signal transduction pathway.


Practice

Write down a step by step explanation of how this cell will start moving toward the light in terms of a signal transduction pathway.


Ans

wer

The light acts a signal that is received by a receptor on the cell membrane. The activated receptor initiates a metabolic process that produces a specific transcription factor. The transcription factor travels to the nucleus and the nucleus produces proteins that act as a signal to the flagella directing them to move toward the light.

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Practice

Lets look at a similar two-celled protist. Both cells must propel themselves together. If only one does, or one is slower than the other this organism will spin in circles.

Slide 113 / 181

Practice

Looking more closely, these 2 cells share gap junctions. These ensure that the amount of transcription factor and nuclear signaling is consistent in both cells.

Slide 114 / 181

Practice

Now lets look at a multi-celled version of a similar protist.

Slide 115 / 181

Practice

If we add a light source, what problems does this organism face? How could the organism overcome these problems. Discuss in a small group then suggest problems and solutions to the class.

Slide 116 / 181

Practice

Problem:Light only signals on the front cells, not the back and they are the ones that need to propel the cell.

Solution:Cell-to-cell communication

Slide 117 / 181

Practice

There are several ways a cell can communicate with another cell. In this situation, receptor communication would be best. Lets look closely at 2 of these cells.

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Local Cell Communication

Unlike the single celled organism, cell 1 does not want to activate its flagella when contacted by light. That would cause it to move away. It would need to signal its partner, cell 2.

2 1

Slide 119 / 181

Local Cell Communication

2 1

A signal transduction pathway would still occur in cell 1, but the nucleus in 1 would produce proteins that become signals for cell 2.

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Local Cell to Cell CommunicationThe signal produced by the nucleus of 1 would set off a second transduction pathway that would make cell 2 engage its flagella.

2 1

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Local Cell to Cell CommunicationThe organism would move to the light. This system works well for smaller multi-celled organisms, and can be used for some systems in larger organisms.

Slide 122 / 181

Cell to Cell CommunicationWhat about much larger organisms with lots of specialized cells and complex responses? When many systems have to respond simultaneously?

Let us use Darwin as our example of a complex, multi-celled organism.

Slide 123 / 181

Cell to Cell CommunicationWhen Darwin sees a cheeseburger he smiles.Why?What is happening at a cellular level?What is the signal? What cells respond?

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Cell to Cell Communication

Cells

To Brain

Signal

What is the signal?

Neurotransmitters

Neurons are specialized cells. Neurotransmitters, protein signals, are released by neuron A in a certain pattern, based on the image of the bear. Neuron B receives them as a signal for a specific transduction pathway. Neuron A is the signaling optic neuron, neuron B acts as the receptor for the brain.

Slide 125 / 181

These regulators attach to receptors embedded in the plasma membrane of nearby cells .

Short Distance Cell Communication

Neurotransmitters are an example of short distance communication between cells. In this type of communication, regulator chemicals are released into the small space between the cells, a synapse.

Slide 126 / 181

Hormone ResponseWhen Darwin sees an angry bear...

Let us take a look at the hormone response that is responsible for most of what Darwin is feeling right now.

Slide 127 / 181

Cells

To Brain

Signal

Cell to Cell Communication

What is the signal?

The image of the bear (pattern of light waves) on the retinal cells in Darwin's eye use synaptic signaling to relay the image to the brain through the optic nerve.

Slide 128 / 181

Hormone Response

What is the signal?

The brain begins a massive cascade of synaptic signals through millions of nerve cells. It calculates the proper response and releases hormones into the blood stream. In this case, the "fight or flight" molecule will be released: epinephrine (adrenalin)

Slide 129 / 181

Hormone Response

Epinephrine is released into the blood stream, where it is sent throughout the body. Each cell it contacts will have a different response to the molecule.

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Hormone Response

Epinephrine

Since epinephrine is only a signal molecule it can have different effects on different cells. It all depends on what a particular cell is programed to do in the presence of epinephrine.

Hair follicle muscle cell - contract, hair stands up

Sweat gland muscle cell - contract, sweat is released

Lung cells - relax, take in more air

Heart cells - speed up, more oxygen to cells for respiration

Liver cells - release glucose, to supply more energy to cells

...among other responses

Slide 131 / 181

Hormone Response

Click here for an animation of fight or flight signalling

Slide 132 / 181

The hormone response illustrates how cells can communicate over long distances.

Hormones are produced within certain organs of the body and can travel long distances through the blood to reach different target cells in many regions of the body.

For example, the hormone testosterone is produced by endocrine cells, and travels through the blood stream stimulating increases in muscle mass, bone growth, and the development of male secondary sex characteristics.

Long Distance Cell Communication

Slide 133 / 181

51 Hormones, such as estrogen, act...

A between adjacent cells

B on neurons

C in prokaryotes only

D over long distances within an organism


51 Hormones, such as estrogen, act...

A between adjacent cells

B on neurons

C in prokaryotes only

D over long distances within an organism


Ans

wer

D

Slide 134 / 181

52 Why do liver cells and heart cells not have the same response to epinephrine?

A Heart cells have receptors for epinephrine but liver cells do not

B Heart cells and liver cells have variation in their genomes

CEpinephrine does not enter heart cells, but it does diffuse across the liver cell membrane

DHeart and liver cells initiate different transduction pathways in the presence of epinephrine

http://learn.genetics.utah.edu/content/begin/cells/cellcom/

(Answer) / 181

52 Why do liver cells and heart cells not have the same response to epinephrine?

A Heart cells have receptors for epinephrine but liver cells do not

B Heart cells and liver cells have variation in their genomes

CEpinephrine does not enter heart cells, but it does diffuse across the liver cell membrane

DHeart and liver cells initiate different transduction pathways in the presence of epinephrine


Ans

wer

D

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A feedback loop is the path that leads from the initial generation of a signal to the modification of an event. They are the cause-and-effect sequence in biology.

Feedback loops can either be positive or negative.

Feedback Loops

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When the thermostat senses it is too hot, it turns on the air conditioner to cool it off. If the house is too cool, it will send a signal to warm the house up.

Negative Feedback Loops

A negative feedback loop happens when the outcome of an action acts to reverse cause of the original signal. The thermostat in your house acts on a negative feedback circuit.

Slide 137 / 181

Negative Feedback ExamplesMost control systems in the body involve negative feedback systems. Cells send signals to other cells to fix problems they are sensing. This could involve the release of another signal to counteract a problem or more simply, the shut down of the original signal.

Examples include:

body temperature controlthe regulation of pituitary hormonescontrol of blood glucose levels

Slide 138 / 181

Positive Feedback LoopsA positive feedback loop is one which involves cells continually amplifying a signal until an outcome is reached. The key to positive feedback loops is that any small change will be amplified.

A snowball rolling down an increasingly steep hill will continue to pick up speed until it gets to the bottom of the hill.

Slide 139 / 181

Positive Feedback Examples

Activities associated with childbirth offer two examples of positive feedback loops.

As contractions happen during labor, the hormone oxytocin is released into the bloodstream. As oxytocin levels increase, more contractions occur, until the baby is born which stops the feedback loop.

Another example involves lactation. The more a newborn baby suckles, the more milk is produced. This is due to a positive feedback loop involving the hormone prolactin.

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Feedback Loop Explanation

click here for a video explanation of

feed back loops

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53 The "fight-or-flight" adrenalin response to an emergency situation would be considered a:

A Negative Feedback Loop

B Positive Feedback Loop


53 The "fight-or-flight" adrenalin response to an emergency situation would be considered a:




Ans

wer

B

Slide 142 / 181

54 Calcitonin is a hormone released from cells in the thyroid gland which controls circulating blood levels of calcium in conjunction with the parathyroid hormone. This would be an example of a:




54 Calcitonin is a hormone released from cells in the thyroid gland which controls circulating blood levels of calcium in conjunction with the parathyroid hormone. This would be an example of a:




Ans

wer

A

Slide 143 / 181

Enzymatic Proteins


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page48svg

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A metabolic pathway begins with a specific molecule and ends with a product.

Each step is catalyzed by a specific enzyme.

No enzyme = no reaction

Metabolic Pathways

enzyme 1 enzyme 2 enzyme 3

A B C D

Starting Molecule

Product

Reaction 1 Reaction 3Reaction 2

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Enzymes are proteins that act as catalysts in biological systems.

This video covers an example of enzymes that is frequently used on the AP tests and reviews the function of enzymes.

Review of Enzymes

Click here for a review of catalase

If further review is needed please see NJCTL's first year biology course.

Enzymess First Year Course

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55 Which of the following is not part of allosteric regulation?

A other substrate molecules compete for the active site

B regulatory molecules bind to a site separate from the active site

C inhibitors and activators may compete with one another

D a naturally occuring molecule stabilizes an active conformation


55 Which of the following is not part of allosteric regulation?

A other substrate molecules compete for the active site

B regulatory molecules bind to a site separate from the active site

C inhibitors and activators may compete with one another

D a naturally occuring molecule stabilizes an active conformation


Ans

wer

A

Slide 147 / 181

56 In allosteric regulation both an inhibitor and an activator can bind to one substrate complex at the same time.

True

False


56 In allosteric regulation both an inhibitor and an activator can bind to one substrate complex at the same time.

True

False


Ans

wer

False

http://www.bozemanscience.com/science-videos/2011/11/30/048-enzymes.html

http://njctl.org/courses/science/biology/membranes-and-enzymes/

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57 Feedback inhibition is a type of _____.

A competitive inhibition

B product

C allosteric regulation

D enzyme


57 Feedback inhibition is a type of _____.

A competitive inhibition

B product

C allosteric regulation

D enzyme


Ans

wer

C

Slide 149 / 181

As complexity increases, the need to regulate digestion and optimize the food that is being ingested becomes greater. Human digestion is an example of a highly complex digestion system. Humans are capable of ingesting a wide range of food, absorbing many nutrients and adjusting absorption to match intake and need. Numerous enzymes are involved in this process.

Enzymes of Digestion: an example

Humans areomnivorousbulk feeders.

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Human Digestive SystemThe human digestive tract is composed of compartmentalized organs. It is regulated hormonally by the pancreas and the brain.

Slide 151 / 181

Cephalic PhaseThis phase occurs before food enters the stomach and involves preparation of the body for eating and digestion. Sight, smell, taste and thought of food stimulate the brain. Salivary glands are activated by neural control.

Amylase, an enzyme in saliva, hydrolyzes starch and glycogen into smaller polysaccharides.

Saliva combined with chewing and movements of the pharynx and tongue turn the food into a bolus, a ball of partially digested food.

Slide 152 / 181

Gastric PhaseThe bolus is passed into the esophagus from the mouth. Muscular contractions of the esophagus move the bolus to the stomach. There the bolus is mixed into the digestive "soup" of the stomach. The stomach is muscular and it churns the food into a homogenized acid chyme.

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Gastric PhaseThe stomach produces an enzyme that becomes active in the presence of acid. To avoid destruction of stomach cells, the active enzyme pepsin is released into the lumen of the stomach as inactive pepsinogen. Another cell releases HCl to make the lumen acidic. This activates the hydrolytic enzyme pepsin.

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Chief cells produce pepsinogen, parietal produce HCl and all cells produce mucous to ensure a lining in the stomach that will protect the cells from the products they release. Pepsin breaks down proteins.

Gastric Phase

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Intestinal PhaseThe pyloric sphincter is the transition from the gastric phase to the intestinal phase. The major change that happens here is that mechanical breakdown is ending and absorption is beginning.

pyloric sphincterduodenum lumen

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Intestinal PhaseThe duodenum is the central processing area for incoming food. The pancreas monitors the food entering the small intestine and releases hormones that engage multi organ responses. The liver and gallbladder release bile salts that help absorb fats, carbohydrates are given one last bath of hydrolytic enzymes and the brain is alerted to the influx of nutrients.

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Intestinal PhaseThe liver and gallbladder release bile salts that help absorb fats. The bile salts emulsify the fat and make it possible for cells to absorb them.

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Intestinal PhaseThe pancreas releases enzymes that breakdown proteins, lipids, and carbohydrates.

lipase -fats

amylase- carbs

trypsin- proteins

chymotrypsin- proteins

and many others

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Intestinal PhaseFinally the mix of enzymes and food move through the intestines where nutrients are absorbed and undigestible material is released via the anus.

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Human Digestive HormonesAs stated, the digestive system exhibits hormonal control over other systems in the body. This is largely accomplished through communication with the brain, pancreas and liver.

Slide 161 / 181

Human Digestive HormonesNormal blood glucose level is 90mg per 100 ml of blood. This must be maintained for normal body function to proceed. When the pancreas recognizes an influx of glucose into the blood it releases insulin.

insulin insulin

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Human Digestive HormonesThis hormone causes an uptake of sugar by the liver to store and convert to fat. At the same time it suppresses hunger in the brain.

insulin insulin

Hunger GlucoseUptake

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Human Digestive HormonesIf the pancreas recognizes a situation where blood glucose will drop too low, it releases a hormone called glucagon. This effect is the opposite of insulin.

glucagon glucagon

Hunger GlucoseUptake

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58 Which of these enzymes operates in low PH

A Trypsin

B Amylase

C Lipase

D Pepsin

(Answer) / 181

58 Which of these enzymes operates in low PH

A Trypsin

B Amylase

C Lipase

D Pepsin


Ans

wer

D

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59 Which of these enzymes digest proteins?

A Trypsin

B Amylase

C Lipase

D All of the above


59 Which of these enzymes digest proteins?

A Trypsin

B Amylase

C Lipase

D All of the above


Ans

wer

A

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60 Which of these enzymes is the first to start digestion?

A Trypsin

B Amylase

C Lipase

D Pepsin


60 Which of these enzymes is the first to start digestion?

A Trypsin

B Amylase

C Lipase

D Pepsin


Ans

wer

B

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61 Which of these foods would cause the most insulin to be released?

A Ice Cream

B Hamburger

C Tomato

D Salmon

(Answer) / 181

61 Which of these foods would cause the most insulin to be released?

A Ice Cream

B Hamburger

C Tomato

D Salmon


Ans

wer

A

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"Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often referred to as an overactive thyroid."- US department of Health and Human Services

This disease effects more than 5% of woman in the United States (10x the rate in men).

Practicing Enzyme Metabolism Control

Swelling of the thyroid gland is a sign of hyperthyroidism.

Slide 169 / 181

The thyroid gland controls how much energy is being produced by the body, by increasing or decreasing the amount of Thyroid hormone (T3) that is circulating in the blood.

The thyroid is controlled by the brain which monitors levels of thyroid hormone and adjusts its signal to the thyroid accordingly.


lhttp://www.endocrine.niddk.nih.gov/pubs/Hyperthyroidism/

Slide 170 / 181



Increased TSH means more production of T3

Increased T3 means more production of energy in the body

This is known as a feedback loop. Thyroid stimulating hormone (TSH) acts as a co-enzyme in thyroid cells that activates the metabolic pathway for production of T3.

Slide 171 / 181



When the brain has determined that there is sufficient T3 in the blood, it slows the release of TSH so the thyroid reduces the amount of T3 it is producing.

In this way, the brain is exhibiting allosteric regulation of the enzymes in the thyroid via release of a co-enzyme (TSH).

Brain monitors T3 and adjusts release of THS

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62 Organic molecules that aid in the action of the enzyme are called _____.

A products

B coenzymes

C substrates

D helpers

(Answer) / 181

62 Organic molecules that aid in the action of the enzyme are called _____.

A products

B coenzymes

C substrates

D helpers


Ans

wer

B

Slide 173 / 181

The enzyme at the start of the metabolic pathway that produces T3 requires TSH to work. TSH stabilizes the active site of the enzyme allowing it to bind with substrate A.

Allosteric Control


A B C T3Starting Molecule

Product


Enzyme 1TSH

Active site only works when THS is present

Slide 174 / 181

Allosteric Control

enzyme 1

A T3Starting Molecule

Product

Reaction 1

Enzyme 1TSH

Active site deforms without TSH

No T3 produced

Without TSH, substrate B can not be produced and the pathway is shut down.

Slide 175 / 181

Remember that there are millions of enzymes so the amount of TSH dictates how much T3 the pathway will produce

Enzyme Concentration



Product


Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

Enzyme 1

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

TSH

Excess TSH = Highest production of T3

Only a small amount = less production

Slide 176 / 181

Now that you understand the process of thyroid control, suggest ways in which this regulation may be lost, thus producing hyperthyroidism.

Work with a partner or group to suggest at least 2 ways that this may happen.

Back to Hyperthyroid



Product



Slide 177 / 181

Some actual reasons for the disease...

-Enzyme 1 is defective and remains on even if TSH is present.-A substance similar to B or C is present in the system so regulation of Enzyme 1 does nothing.-The brain fails to recognize too much T3 is present and makes TSH regardless.- TSH molecule is defective and bonds too strongly to enzyme causing increased activity (TSH does not breakdown normally).

Back to Hyperthyroid



Product



/ 181

Enzymes in a Chloroplast

Chloroplast

C OO

C6H12O6

Below is a simple diagram of a chloroplast. Imagine it is part of a larger biological system that needs to control when sugar is made.

Slide 179 / 181


Water used up and concentration decreases

Carbon dioxide used up and concentration decreases

Glucose formed so concentration increases

6

We will need to expand this simple diagram to understand how this biological system can control the reaction

Slide 180 / 181


enzyme 1

enzyme 2

enzyme 3Reaction 1

Reaction 3

Reaction 2

OH

H

e-

C

O

O

Work with a group to formulate a plan that would allow a system to monitor the amount of glucose present and adjust production accordingly. Draw a diagram and share with the class.

Slide 181 / 181

Enzymes in a ChloroplastThough this is still simplified (we will see this expanded further soon), it is enough to pose a question: What would be a good way for a biological system to regulate sugar production?

enzyme 1

enzyme 2

enzyme 3Reaction 1

Reaction 3

Reaction 2

OH

H

e-

C

O

O

AP BIOLOGY Membranes & Proteins Cell Membranes Membranes ...

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