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Anatomy & Physiology of CellsChapters 3 & 4

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Basic Cell Info

•Cell Theory - the cell is the fundamental organizational unit of lifeSchleidon & Schwann – first to suggest that all living things are

composed of cells

•Human body – 100 trillion cells

•Cell diameter range: 7.5 micrometers (RBC) – 150 micrometers (ovum)

•Composite cell – generalized cell illustration we study that exhibits most important characteristics of many different dinstinctive cell types; no such cell exists in the body

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Cell Structures

3 Main Cell Structures: plasma membrane, cytoplasm (with organelles), and nucleus

1. Plasma membranea. Outer boundary of cell (about 0.0000003 inch thick)

b. Made of lipids, proteins, and other molecules - PRIMARILY non-polar

c. Fluid mosaic model -molecules slowly float around the membrane-molecules bound tightly enough to form continuous sheet-molecules bound loosely to slip past one another

d. Phospholipid bylayer Chemical attractions / polar and non-polar forces hold membrane together - non-polar tails repelled by water and are packed close as far as possible

away from H2O molecules - polar heads not repelled and form H bonds with water.

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e. Without cholesterol (steroid lipid), membranes would break easily

g. Selectively permeable1. Lipid-soluble molecules pass through easily (primarily NON-polar membrane) Water-soluble molecules can not pass through easily2. Membrane proteins: how the cell controls movement of molecules;

“gates” that open and close to allow only certain water soluble molecules into and out of the cell

a. Carbohydrates attached to some proteins form glycoproteins

-identification markers that distinguish between normal and abnormal cells and how immune system

knows to attack bacteria, cancer, etc. b. Enzymes attached – catalyze cellular reactions c. Other proteins attached – form connections between

cells d. Other proteins in membrane are Receptors – react to

hormones, etc. to trigger metabolic changes in cell; translation of the signal by the cell is called signal transduction (carry across)

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*Coloring plasma membrane*

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Cell Structures cont.

2. Nucleusa. One of largest cell structuresb. Occupies central portion of cellc. Shape and number in a cell vary (most common is one spherical nucleus)d. Nuclear membrane - double membrane with pores called nuclear envelope

- encloses the nucleoplasm- pores called nuclear pore complex (NPCs) that selectively permit

molecules to enter or leave nucleus- extensions of the ER membrane

e. Contains DNA- contains thread-like chromatin in non- dividing cells

- contain tightly coiled, short, rod-like structures called chromosomes in dividing cells

- 46 chromosomesf. Dictates structure and function of the cellg. Contains nucleolus

- nonmembranous- contains RNA- synthesizes ribosomal RNA (rRNA) to combine with proteins to make ribosomes- cells that make more protein (pancreas that makes protein insulin) have

bigger nucleolus

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Cell Structures cont.

3. Cytoplasm a. Gel-like substance that makes up inside of cellb. Contains various organelles suspended in intracellular fluid (cytosol)c. Membranous organelles - specialized sacs or canals made of cell

membrane1. Endoplasmic reticulum2. Golgi apparatus3. Lysosomes4. Peroxisomes5. Mitochondria6. Nucleus

d. Nonmembranous organelles - not made of a membrane; made of microscopic filaments1. Ribosomes2. Cytoskeleton

a. Protein microfilaments and microtubulesb. Centrosome- area of cytoplasm near nucleus that

builds microtubuesc. Cell extensions – microvilli (brush like borders of

cells of small intestine) cilia, flagella3. Nucleolus

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Organelles

1. Endoplasmic Reticulum (ER)a. Flat, curving sacs in parallel rowsb. Two types

1. Rough ERa. Contains ribosomesb. Extends from nucleusc. Protein synthesis and

intracellular transportation - proteins move through canals to the golgi

2. Smooth ERa. Synthesizes lipids and

carbohydrates- steroid hormones, glycoproteins, membrane lipids

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Organelles cont.

2. Ribosomea. Every cell contains thousandsb. rER and free in cytoplasmc. Nonmembranousd. Protein synthesis (cell’s “protein factory”)e. Ribosomes on ER – export and cell membrane usef. Free ribosomes – make proteins for domestic use

- make structural and functional proteins (enzymes)g. Made of a large and small subunit

-each has rRNA bonded to protein

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Organelles cont.

3. Golgi Apparatusa. Membranousb. Cisternae (sacs) stacked near nucleusc. Processes and packages molecules for export from cell

Steps to processing and packaging1.ER delivers protein via vesicles2.Enters first cisternae3.Chemical modifications according to function4.Sent to next cisternae via vesicle5.Further modification6.Repeated until last cisternae7.Packaged in secretory vesicle8.Migrates to cell surface9.Combines with membrane10.Secretes contents

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4. Lysosomes: DESTROYa. Membraneous sacb. Vesicles that pinched off from Golgic. Size and shape change depending on activityd. Contains enzymes that if bust can kill the celle. Destroy bacteria, etc.f. “digestive bags” , “cellular garbage disposals”

5. Peroxisomes: DETOXIFYa. membraneous sacb. Smaller than lysosomec. Contains enzymes (peroxidase, catalase)d. Detoxify harmful substancese. Seen in kidney and liver cells

Organelles cont.

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Organelles cont.

6. Mitochondriaa. Membraneousb. Double membranec. Form a sac within a sacd. Cristae – inner membrane folds

1. contain enzymes that catalyse the making of ATPe. Membranes have same structure as plasma membranef. “power house”g. Amount of work a cell does determines number of

mitochondria: Ex. Liver Cell: +1000 mitochondria vs. Sperm cell: 25 mitochondria

Exercise – increases number of mitochondria cause more ATP required

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Cytoskeleton

1. Cell’s internal supporting network2.Made of rigid, rodlike pieces (support and movement)3.Muscle-like groups of fibers4.Twisted protein molecules

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Cytoskeleton cont.

1.Cell Fibersa. Microfiliaments

1. smallest fibers2. serve as “cellular muscles”3. muscle cells – proteins slide past each other

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Cytoskeleton cont.

1.Cell Fibersb. Intermediate filaments

1. slightly thicker than microfilaments2. supporting framework3. dense arrangement in cells on outer skin layer

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Cytoskeleton cont.

1.Cell Fibersc. Microtubules

1. thickest cell fiber2. “engines” of the cell3. move things around in

cell4. cause movement of

entire cell5. movement of vesicles6. movement of

chromosomes in mitosis

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Cytoskeleton cont.

2.Centrosomea. nonmembraneousb. Very active sitec. Near nucleusd. Coordinates building and breaking of microtubulese. “microtubule organizing center” (MOC)f. Important role incell divisiong. Centrioles found here

1. form nicrotubular cell extensions2. form spindle in cell division

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Cytoskeleton cont.

3. Cell extensionsa. Microvilli

1. found in epithelial cells that line intestines

2. found in areas where absorption is important

3. cover surface of cell4. contain

microfilaments

5.increases surface area of cell 6.allows faster rate of absorption

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Cytoskeleton cont.

3.Cell extensionsb. Cilia and flagella

1. contain microtubules2. main purpose – movement3. cilia shorter and more numerous than flagella4. line respiratory tract; cilia moves mucus to be swallowed5. flagella only in sperm cells

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Cell ConnectionsPROTEINS!!!!!

• Desmosomes: like “spot-welds that hold cells together. The fibers on the surface of each desosome interlock (skin cells)

• Gap Junctions: membrane channels adhere to one another and fuse plasma membranes into single structure (cardiac muscle cells) to stimulate many cells simultaneously

• Tight Junctions: tight “collars that do not allow molecules to leak between (intestinal lining cells)

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TransportTable 4-1 pg. 92

Passive1.Simple diffusion – movement of particles through bilayer from high to low conc2.Dialysis – diffusion of small solute particles through selectively permeable membrane3.Osmosis – diffusion of water4.Facilitated diffusion – diffusion of particles through membrane with help of transmembrane carrier proteins

Active1.Active transport – movement of solute particles from LOW to HIGH conc via transmembrane carrier proteins called transporters2.Phagocytosis – (endocytosis) taking in of solute particles by vesicles fusing with plasma membrane 3.Pinocytosis – (endocytosis) taking in of dissolved particles (fluid) by vesicles fusing with plasma membrane4.Exocytosis – movement of particles out of the cell via secretory vesicles fusing with plasma membrane

Diffusion

1. molecules densely packed when enter water 2. molecules collide in high conc. 3. gradually move away from each other 4. toward low conc. 5. eventually evenly distributed

1.semipermeable membrane2.left – unbalanced3.right - homeostasis

Simple Diffusion

Dialysis

OsmosisOsmotic pressure / tonicity – water pressure that develops in the solution with the higher concentration of impermeable solute (low water concentration)

Osmosis cont.

Hypotonic Isotonic Hypertonic

Pressure Low Same High

Solute conc Low Same High

Water conc High Same Low

Cell change Swells Same Shrinks

Facilitated Diffusion

1.Carrier mediated2.Attracts solute to binding site3.Carrier protein changes shape 4.Solute can move to other side of membrane

Active Transport

Carrier protein uses ENERGY to move solute AGAINST conc gradient

Na+/K+ Pump

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Enzymes

1.Functional proteins2.Catalyst (lowers activation energy)3.Cofactor – A non-protein unit attached to an enzyme molecule (inorganic ions or vitamins) to allow enzyme to function properly4.Coenzyme – if cofactor is organic (C-H)5.Active site – part of enzyme where binds to substrate6.Lock-and-key model 7.Enzymes can bind substrates together or unbind components of a substrate8.Any molecule or other agent that changes the shape of an enzyme is an allosteric effector. (temp., pH., etc.)9.Most enzymes are produced as inactive proenzymes and are activated by substances called kinases by means of an allosteric effect.

Lock-and-key Model

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1. Catabolism a. net output of energyb. Breaks down large molecules into smaller onesc. ie. cellular respiration

2. Anabolism a. net input of energyb. Build large molecules from smaller onesc. ie. synthesizing DNA

Cell Metabolism

The Cell Cycle

• Interphase: - longest part of cell cycle G1 phase (first growth phase): Cell growth S phase (synthesis phase): DNA replication G2 phase (second growth phase): organelles

duplicated, microtubles are assembled to be used to build spindle, etc.

• Mitosis followed by cytokinesis

Cellular Respiration

- Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

O2 + C6H12O6 (yields) CO2 + H2O + ATP- Three Stages of Cellular Respiration: 1. glycolysis 2. Krebs Cycle (citric acid cycle) 3. Electron Transport

Cellular Respiration

• Glycolysis: 1. requires no oxygen (anaerobic) 2. occurs in the cytosol catalyzed by enzymes 3. 2 molecules of ATP are used to break one

molecule of glucose in 1/2, producing two molecules of pyruvic acid, NADH (containing high energy electrons), and 4 molecules of ATP

Cellular Respiration- Krebs Cycle (citric acid cycle) 1. requires oxygen (aerobic) 2. occurs in the inner membrane of mitochondria 3. pyruvic acid is broken down into carbon dioxide (released)

and acetyl-CoA. 4. Acetyl-CoA joins with a 4-carbon molecule and becomes

citric acid 5. Citric acid is broken down, more carbon dioxide is released,

and large amounts of NADH and FADH2 (high energy electrons) are produced

**If no oxygen is present, fermentation will occur instead of the

Krebs Cycle.

Cellular Respiration- Electron Transport: 1. The high energy electrons of NADH and FADH2 are

transferred to special energy accepting molecules (Electron Transport System) within the cristae of the inner mitochondria converting ADP and a phosphate into 34 more ATP from each molecule of glucose

**36 molecules of ATP represents 38% of total energy from glucose. Remaining 62% is given off as heat.

Cellular Disease(cell abnormalities)

1.Cystic fibrosis (cell transport disorder)a. Cl ion pumps in membrane missingb. W/O Cl ions, sweat & mucus salty

and thickc. Thick mucus causes lung infectiond. Respiratory & digestive problems

2.Diabetes mellitus/type 2 (Receptor disorder)a. Adult onsetb. Non-insulin dependentc. Cell response to obesityd. Reduces insulin receptors (glucose

intake) in membranes of cells

3.Cancers (Cell reproduction disorder)a. Abnormalities in mitosisb. Cause tumors

4.Genetic Disorders (passed from parent)a. Sickle-cell anemia: mutation in hemoglobin protein

5. Bacteria and viruses