The Cell BioSci 105 Lecture 4 Read Chapter 3 (Pages 47 – 62)

The Cell

BioSci 105

Lecture 4

Read Chapter 3 (Pages 47 – 62)

Copyright © 2009 Pearson Education, Inc.

Outline

I. Prokaryotic vs Eukaryotic

II. Eukaryotic

A. Plasma membrane – transport across

B. Main features of animal cells and their functions


Cells

Cells are the basic unit of life

Cells are highly structured

They are enclosed in a membrane—the Plasma Membrane

Cells vary in size but there is a limit on how big a cell can be and survive

There are different types of cells – specialized cells


Some organisms are just one cell - yeast


Multi-celled organisms have specialized cells

Blood CellsBlood Cells Nerve CellsNerve Cells


Some cells are very small


Prokaryotic vs Eukaryotic

Prokaryotic – Pro (before) karyotic (nucleus) Eukaryotic – Eu (true) karyotic (nucleus)

The presence or absence of a nucleus is the biggest difference between these types of cells.


Prokaryotic vs Eukaryotic

Prokaryotic cells = bacteria and archaea have

no nucleus, no organelles, have ribosomes

In eukaryotic cells the DNA is contained within the nucleus Animal cells, Plant cells, Fungi, Protists


Figure 3.1 Prokaryotic cells, such as bacterium, lack internal membrane-bound organelles.

Ribosome

Cytoplasm

Cell wall

Plasma membrane

DNA region(no nucleus)

1–10 m


Table 3.1 Review of Features of Prokaryotic and Eukaryotic Cells


Which are examples of prokaryotic organisms?

1. Animals

2. Plants

3. Bacteria

4. Protists

5. Fungus


Prokaryotic cells have a nucleus.

1. True

2. False


Major Features of Eukaryotic Cells

Figure 3.2 (2 of 2)


Cell size

Cells vary in size, but they can never exceed the volume that can be nourished by materials passing through the surface membrane


Cell Size

Figure 3.3


Major Features of Animal Cells

Plasma membrane – controls entry in/out of cell

Cytoplasm – semi-fluid matrix (liquid is cytosol)

Cytoskeleton – gives shape, structure, transport

Ribosomes - assembling polypeptide chains


Major Features of Animal Cells

Organelles – membrane bound compartments

Nucleus – contains the DNA

Mitochonria – energy production

Endoplasmic reticulum – Rough: modifies new polypeptide chains Smooth: synthesizes lipids

Golgi body – modifies, sorts, ships new proteins and lipids

Vesicles – storage, transport, digestion


Organelles

Organelles are membrane-bound internal compartments in cells for specialized functions


Plasma Membrane

Fluid Mosaic model Molecules are free to move around mixture of phospholipids, steroids (cholesterol),

and proteins

Selectively permeable


Plasma Membrane

Bilayer

Phospholipids arrange to have the polar head on the outside and the non-polar, lipid portion on the inside

Proteins and sterols (cholesterol) are arranged on surfaces and can form channels


Table 3.2 Review of Plasma Membrane Functions


Four main components in membrane

1. Phospholipid bilayer

Phosphate head (hydrophilic) Fatty acid tail (hydrophobic) Function – controls what passes through

membrane

2. Cholesterol – maintains fluidity of membrane


Four main components in membrane

3. Proteins – transport, support, communication, recognition

4. Glycoproteins: chains of sugars attached to a protein Functions – attachment sites, cell recognition

5. Glycolipids: chains of sugars attached to a lipid Function - attachment sites, cell recognition


Plasma Membrane

Figure 3.6

Cytoplasm

Extracellularfluid

Carbohydrate

Cholesterol

Surfaceprotein

Filaments ofcytoskeleton

Embeddedprotein

Plasma membrane

Outer surface of plasma membrane

Inner surface of plasma membrane

Plasma membrane

Phospholipidbilayer

Glycoprotein

Glycolipid


Hydrophilic: Water loving = lipophobicHydrophobic: Water hating = lipophilic


Simple Diffusion

Figure 3.7


Concentration gradient Molecules will go from higher concentration to

lower concentration.

If you add molecules to water it will disperse (diffuse) until it is equally distributed in the water

Movement through the membrane


The plasma membrane divides inside the cell from outside the cell

It is semi-permeable – not everything can freely pass through it

Movement through the membrane


What can freely pass through the membrane

1.Gases – oxygen, carbon dioxide

2.Hydrophobic compounds (non-polar)

3.Very small uncharged molecules (Water, even though water is polar, it is small enough to pass)


What can not freely pass through the membrane

1. Ions

2. Hydrophillic (polar compounds) (larger than water)

3. Charged compounds

4. Macromolecules compounds (ex: large proteins, complex carbohydrates, triglycerides)


Osmosis

The cell membrane is semi-permeable:

This means that some things can pass while others can not pass through.

The cell membrane is somewhat permeable to water, but not to charged ions and molecules

Water will travel across the membrane to try to restore the balance of solutes = Osmosis


Hypertonic: Concentration of solutes is higher outside than inside

Isotonic: Inside and outside have same conc.

Hypotonic: concentration of solutes is lower outside the cell than inside.

How does the salt concentration effect a cell?


Osmosis

Osmosis is the movement of water across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration

Osmosis restores the solute balance


Transporting molecules across the membrane

Passive transport – does not require energy, uses concentration gradient Simple diffusion Facilitated diffusion

Active Transport – requires energy, goes against concentration gradient


Simple Diffusion

Figure 3.7


Passive Transport – Simple Diffusion

Simple diffusion: molecules that can freely pass through the membrane are controlled by concentration gradient

Gases like oxygen and CO2

Very small molecules that are not charged (H2O) hydrophobic (non-polar) molecules


Facilitated diffusion

Figure 3.8


Passive Transport – Facilitated Diffusion

Facilitated diffusion: Aided by a transport protein, still controlled by concentration gradient

Hydrophilic molecules like glucose and amino acids


Active Transport

Figure 3.10


Active Transport

Sometimes our cells want to move a molecule across the membrane but there is not a gradient. The cell wants more of the solute on one side of the membrane.

The cell will use energy to maintain the higher concentration

Used to transport sugars, amino acids and ions


Active Transport

Movement often from a region of lower to higher concentration with the aid of a carrier protein and energy (usually from ATP)


Can Calcium (Ca2+) pass freely through the membrane?

1. Yes

2. No


Can glucose pass freely through the membrane?

1. Yes

2. No


If a transport protein is used to move glucose using a concentration gradient this is called:

1. Simple diffusion

2. Facilitated diffusion

3. Active transport


Transporting using a vesicle

When the cell needs to transport larger things (i.e. macromolecules, bacteria, fluids) they can use vesicles to transport things in and out of the cell.

Exocytosis: moving things out of the cell using a vesicle

Endocytosis: moving things into the cell using a vesicle

Used to transport macromolecules including: whole cells (bacteria), cholesterol, fluids, and proteins


Endocytosis

Phagocytosis – when cells transport large particles and cells (bacteria) into the cell using vesicles

Pinocytosis – when cells transport fluid into the cell using vesicles


Endocytosis - phagocytosis

Figure 3.11a


Endocytosis - pinocytosis

Figure 3.11b


Exocytosis

Figure 3.12


Table 3.3 Review of Mechanisms of Transport Across the Plasma Membrane


Major Features of Eukaryotic Cells

Figure 3.2 (2 of 2)


Nucleus

Nucleus contains DNA = instructions for building proteins

Number of DNA molecules vary between species Humans have 46 DNA molecules in each cell Frogs have 26 DNA molecules in each cell

Nucleus protects DNA

Separates DNA from rest of cell

Place where DNA duplicates itself


Chromosomes

Humans chromosomes They are visible in the light microscope

during cell division when they shorten and condense

At other times the chromosomes are extended uncondensed and are called chromatin


Nucleus

Figure 3.14a


Chromatin

Figure 3.14b


Parts of the Nucleus

1. Nuclear Envelope – Double membrane (two different bilayers) Inside layer contains sites for DNA to attach Outside surface layer has many ribosomes

2. Nucleolus – dense area in the nucleus where ribosomes are produced

3. Nucleoplasm – area inside the nucleus

4. Chromatin – DNA and its associated proteins


Nucleus


Ribosomes

Function: Site of protein synthesis

This is where amino acids are chained together with a peptide bond to make a polypeptide chain

Ribosomes are composed of proteins and ribosomal RNA (rRNA)


Endoplasmic Reticulum

There are two types of Endoplasmic Reticulum:

Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum


Figure 3.15 The endoplasmic reticulum (ER)

Rough endoplasmic reticulum (RER) has ribosomes attached to its surface and is involved in modifying proteins made by the ribosomes.

Smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in detoxifying certain drugs and in producing phospholipids forincorporation into membranes.

Endoplasmicreticulum

Nucleus


Rough Endoplasmic Reticulum

Endoplasmic reticulum that has ribosomes associated with it is called rough endoplasmic reticulum


Rough Endoplasmic Reticulum

Functions: Important in protein modification

1. It is here that polypeptide chains (chains of amino acids) are folded into their shape by chaperones

2. Here carbohydrate tags are added to the proteins


Smooth Endoplasmic Reticulum

Endoplasmic reticulum that does not have ribosomes associated with it is called smooth endoplasmic reticulum

Functions: 1. Phospholipids and steroids are

synthesized here

2. contain enzymes that detoxify alcohol and some drugs


Transport vesicles

Membrane bound compartments used for transporting molecules around in the cell, also can be used to transport molecules in and out of cell


Golgi Complex

The golgi complex – series of flattened membranous sacs

Vesicles from rough and smooth endoplasmic reticulum bring their products to the golgi to be modified and repackaged

Functions: processes, sorts, packages proteins and lipids


Figure 3.16a The Golgi complex

Golgicomplex

New vesicleforming

(a) Diagram of the Golgi complex. This organelle serves as tsite for protein processing and packaging within the cell.


Figure 3.17 Transport of proteins from RER to Golgi to plasma membrane

Transportvesicle

Secretoryvesicle

Proteinexpelled

Lysosomewithproteins

Proteins

Roughendoplasmicreticulum

Ribosome

Golgi complex

Plasma membrane

Vesicles carrying proteins from the RER arrive at the “receiving” side of the Golgi complex and empty their contents to the inside, where the proteins are modified.

Vesicles containing the modified proteins leave the “shipping” side of the Golgi complex and travel to their specific destinations.


Lysosomes

Figure 3.18


Lysosomes

Lysosomes are digestion vesicles that contain strong acids and enzymes, can fuse with plasma membrane to expel waste

Made by the golgi

Functions: Engulf molecules and digest them Fuse with other organelles to destroy them Destroy bacteria


Tay-Sachs disease

Tay-Sachs is a hereditary disease where people don’t have a enzyme normally found in lysosomes that breaks down lipids in nerve cells.


Mitochondria

All Eukaryotic cells contain mitochondria

Bound by a double membrane

Outer membrane faces cytoplasm Inner membrane folded = forms cristae that increases

surface area for cellular respiration


Mitochondria

Functions: 1. Produces energy for the cell (ATP). This process

requires oxygen

2. Important in apoptosis (planned cell death)


Mitochondria

Figure 3.19


Where are polypeptide chains/proteins produced

1. Nucleus

2. Ribosomes

3. Golgi complex

4. Rough Endoplasmic Reticulum


Where are polypeptide chains/proteins folded

1. Nucleus

2. Ribosomes

3. Golgi complex



What organelle produces energy for the cell?

1. Nucleus

2. Ribosomes

3. Mitochondria



Cytoskeleton

Interconnected system of fibers and lattices between the nucleus and the plasma membrane

Functions: Gives cells their organization, shape, ability to move, transport things in cell, aid in cell division


Cytoskeleton

Wide variety of cytoskeleton: Microfilaments microtubules (including cilia and flagella) Intermediate filaments

Some permanent (intermediate) others self assemble and are only present

when needed (microfilaments and microtubules)


Microtubules - functions

1. Microtubules serve as tracks along which organelles or vesicles move.

2. Aid in cell division

3. Microtubules are also responsible for the structure and movement of cilia and flagella Cilia are numerous short extensions in a

cell that move back and forth Flagella are larger than cilia and move in

an undulating manner


Microtubules – cilia and flagella

cilia and flagella are composed of microtubules

Cilia are numerous short extensions in a cell that move back and forth

Flagella are larger than cilia and move in an undulating manner


Cytoskeleton - Microtubules.


Cytoskeleton - Microtubules serve as tracks along which organelles or vesicles move.


Cytoskeleton – Microtubules of a centriole

Figure 3.21


Microtubules - cilia

Figure 3.22a


Microtubules - flagella

Figure 3.22b


Cytoskeleton - Microfilaments

Made of the protein actin Functions

1. Important function in muscle contraction

2. Responsible for the movement of pseudopodia

3. Role in dividing cells during cell division


Intermediate Filaments

A diverse group of ropelike fibers

Functions: maintain cell shape and anchor organelles


Cilia is made of this type of cytoskeleton

1. Intermediate filaments

2. Microtubules

3. Microfilaments


Important Concepts

Read Ch 4 Why are most cells small? What are the main differences between

prokaryotic cells and eukaryotic cells, and know examples of prokaryotic cells and eukaryotic cells.

Major features of cells and their function; includes: Plasma membrane, Cytoplasm, Nucleus,

Cytoskeleton, Mitochondria, Ribosomes, Endoplasmic reticulum (smooth and rough), Golgi body, Vesicles, lysosomes


Important Concepts

What are lysosomes, what disorder is associated with a missing enzyme in lysosomes

What are the functions of cytoskeleton and examples of cytoskeleton

What are the functions of microtubules

What cytoskeleton makes up cilia and flagella

Know the functions of microfilaments, what protein makes up microfilaments

Know the functions of intermediate filaments


Functions of the plasma membrane

Know the main components in the plasma membrane and the function of each component.

Be able to draw a membrane.

Be able to identify what can pass freely through a membrane and what can’t pass freely.

Important Concepts


Know how small molecules are transported into the cell, know the differences between passive diffusion, facilitated diffusion, and active transport. Know what molecules each mode can transport

Know how things are transported in and out of a cell using a vesicle

Important Concepts


Definitions

Prokaryotic cells, eukaryotic cells, semi-permeable, osmosis, hypertonic, hypotonic, isotonic, hydrophobic compounds, non polar, hydrophillic compounds, polar, passive transport, active transport, simple diffusion, facilitated diffusion, exocytosis, endocytosis, phagocytosis, pinocytosis, nucleolus, nuclear envelope, nucleoplasm, chromatin, cristae, apoptosis

The Cell BioSci 105 Lecture 4 Read Chapter 3 (Pages 47 – 62)

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