Chapter 3

Question 1

Describe the structure of the cell membrane (3)

Answer 1

1) 75% Phospholipid bilayer and proteins in a fluid mosaic
- separates ICF from ECF
- polar, hydrophilic head & nonpolar, hydrophobic tail with kinks (unsaturated fatty acids)
2) 5% glycolipids: lipids with sugar molec on the outer membrane surface
3) 20% cholesterol: increases membrane stability and fluidity

interstitial fluid (IF): ECF that surrounds cells

Question 2

What is the membrane potential (3)?

Answer 2

• more Na+ in the ECF, more K+ in the ICF
• resting membrane potential: voltage measured in resting state
• due to movement K+ and large anions trapped inside cell

Question 3

What does it mean to say that the cell membrane is selectively permeable?

Answer 3

• allows specific substances to pass through
• passive: small/fat-soluble/nonpolar molecules
• requires channel proteins to let polar/water-soluble substances into cell

Question 4

How does the arrangement of the phospholipids help make it selectively permeable?

Answer 4

-the small kinks in the phospholipid bilayer due to unsaturated bonds allows small/fat-soluble/nonpolar molecules throgh

Question 5

Give several functions of the 2 types of proteins in the cell membrane.

Answer 5

1. integral proteins: inserted into the membrane
   - most transmembrane but some protrude from one side only
   - functions: transport proteins (channels and carriers), enzymes, receptors
2. Peripheral proteins: loosely attached to integral proteins
   - functions: enzymes, cell to cell links

Question 6

What is glycocalyx (5)

Answer 6

• sugar covering at the cell surface (cell surface markers)
• lipids and proteins attached with carbs
• every cell type have different pattern of sugars (ID tag - specific biological markers for cell to cell recognition)
• allows immune system to recognize self and non self
• cancerous cells change it continuously

Question 7

Describe these membrane junctions and where each might be found in the body.

• Tight junction
• Desmosome
• Gap junctions

Answer 7

Tight junction: impermeable
-line the digestive tract to prevent digestive organisms and enzymes from seeping through into the blood stream

Desmosome: anchor junctions, reduces chances of cell being torn apart due to force
-abundant in tissues subjected to great mechanical stress such as in the skin & heart muslce

Gap junctions: communicating junctions: allows small molec to pass through
-in electrically excitable tissues such as heart and smooth muscle

Question 8

What is the function of microvilli? Where are they found?

Answer 8

• increase SA

- found on absorptive cells such as kidney and intestinal cells

Question 9

What factors determine whether a substance can cross the cell membrane?

Answer 9

-whether it is hydrophobic, small, or existence of energy & receptors for active transport

Question 10

4 types of passive transport

Answer 10

diffusion, osmosis, facilitated diffusion (glucose), filtration

Question 11

4 kinds of diffusion

Answer 11

1. simple diffusion: molecules move from high to low concentration
2. channel-mediated facilitated diffusion: diffusion of large molecules
3. carrier-mediated facilitated diffusion: molecules attach onto carriers and changes its shape (ex glucose)
4. osmosis: movement of H2O

Question 12

Rate increases or decreases:

• higher temperature
• large SA
• larger diffusion molecule
• larger diffusion distance
• larger steepness of gradient

Answer 12

• temperature: higher temp = faster
• SA: high SA = faster
• large diffusion distance: slower
• size of substance: slower
• steepness of gradient: faster

Question 13

Osmosis (5)

Answer 13

-specific kind of diffusion for water
-tonicity: percentage of salt
(9% salt = 9g salt, 91g water)
-isotonic: when the concentration of water is same and no movement; same concentration of molecules in both ECF and ICF
-either wiggle through bilayer or move through aquaporins
-osmolarity: measure of total concentration of solute particles

Question 14

What happens to cells in a hypertonic environment? What happens in a hypotonic environment?

Answer 14

• hypertonic: more salt on the outside of the cell
• water diffuses out, causing the cell to shrivle. water follows salt!
• hypotonic: water moves into the cell, causing it to swell and lyse

Question 15

2 active processes

Answer 15

-active transport, vesicular transport

Question 16

2 types of channel/carrier proteins

Answer 16

1. Ligand channel proteins (substances/ligands attach to receptors)
   Ex. H2O binds to receptor, which then becomes a 2nd messanger used for chemical reactions
2. voltage channel proteins: electrical gradient

Question 17

Active transport (6)

Answer 17

• ATP required
• transport against the gradient
• primary: energy comes from ATP hydrolysis
• secondary: energy comes from the energy stored in ionic gradients created by primary transport
• ATP energy changes the shape of transport protein to pump ions across the membrane
• symporters in same directions, antiporters opposite

Question 18

3 types of endocytosis

Answer 18

1. pinocytosis: transport of water into cell
2. receptor-mediated pinocytosis
3. phagocytosis: engulfs large molecules, later fuses with the lysosome to make a phagosome

Question 19

exocytosis (1) examples (5)

Answer 19

• transport out of cell

- hormone secretion, neurotransmitter release, ejection waste, oil secretion from sebaceous glands, sweat production

Question 20

In diffusion, osmosis and facilitated diffusion, is the movement “down” the gradient or “uphill” against the gradient? Do each of the above processes depend on a concentration or pressure gradient?

Answer 20

down, yes

Question 21

the sodium-potassium exchange pump is an example of what kind of transport? Why must ATP be used

Answer 21

• active transport
• used because pumping Na and K from a low to higher concentration
• 3 Na out. 2K in

Question 22

why would the sodium potassium exchange pump be shut down in poisoning that damage the cells mitochondria? What would happen to the cell

Answer 22

-there is not ATP to draw the energy to drive the Na/K pump. The cell’s electrical gradient would disappear

Question 23

Compared to the inside of the cell what is isotonic? hypertonic and hypotonic solutions? what happens to a cell red blood cell placed in each

Answer 23

• isotonic: same solute concentration as outside
• hypertonic sol: higher concentration of solute outside the cell; water from cell leaves and shrivels
• hypotonic: solute concentration inside cell higher; water enters and cell lyse

Question 24

what is hydrostatic pressure and what is osmotic pressure

Answer 24

• Osmotic pressure (OP): force of water due to solute concentration (hi solute = hi OP); sucks
• hydrostatic pressure (HP): force driving filtration; pushes

Question 25

what is membrane potential. Is it more positive or negative on the inside? what ion is more in the intracellular fluid

Answer 25

-more positive on the outside because of higher Na concentrations than K concentrations on the inside

Question 26

The Golgi body receives its products from

Answer 26

ER

Question 27

the vesicle pinches off the Golgi apparatus has three destinations. name all three of them

Answer 27

1. Exocytosis: secretion of contents outside the cell 2. Destroyed by fusion with lysosomes 3. Fuse and incorporate with the cell membrane

Question 28

Mitochondria (2)

Answer 28

- where cellular respiration occurs - has its own nucleus ``` 4 steps: Glycolysis Citric Acid Cycle Pyruvate oxidation Oxidative phosphorylation ```

Question 29

ER smooth & rough

Answer 29

- smooth: lipid synthesis & calcium storage | - rough: protein synthesis

Question 30

Golgi apparatus

Answer 30

- determines fate of protein | - modifies lipids and proteins

Question 31

Describe a lysosome and its function.

Answer 31

-acidic has digestive enzymes that break down waste

Question 32

how does the Tay-Sachs disease cause damage to the neurons? why is the membrane of the lysosome necessary

Answer 32

- lysosomes lack an enzyme needed to break down specific glycolipids in nerve cell membrane. - lysosome swell with indigested lipids, interfering with nervous system functioning

Question 33

What is the function of a peroxisome

Answer 33

detoxification

Question 34

what is the endomembrane system and what is its function in a cell. 5 organelles.

Answer 34

- produce, degrade, store, and export biological molecules | - includes the ER, golgi, secretory vesicles, lysosome, nuclear envelope

Question 35

describe the components of the cytoskeleton (3)

Answer 35

- microfilaments: semiflexible actin actively lengthens and elongates to change the shape of the cell and allow them to move - intermediate filaments: tetramer fibrils that resist tension (attach to desmosome) - microtubules: tubulin radiate from centrosome, determine shape of cell and positioning of organelles

Question 36

what components make up Cilia and flagella

Answer 36

-centrioles forming the base of cilia and flagella are called basal bodies

Question 37

give the function of Cilia and flagella

Answer 37

- cilia: moves substances across cell surface | - flagella: propels sperm

Question 38

What cell in the body does not contain a nucleus

Answer 38

red blood cells

Question 39

apoptosis

Answer 39

-apoptosis: controlled cell death to eliminate unneeded, stressed, or aged cells

Question 40

hyperplasia vs hypertrophy

Answer 40

-accelerated cell division -increase in organ/tissue due to an increase in number of cells Ex. in anemia, RBC divide at an accelerated rate -growth of an organ/tissue due to an increase in size of its cells

Question 41

atrophy

Answer 41

reduction in size or wasting away of an organ/cell resulting from disease or lack of use

Question 42

In protein synthesis, the flow of information is from the DNA to _______ to proteins

Answer 42

RNA

Question 43

What are the 6 functions of membrane proteins?

Answer 43

1. Transport 2. Receptors for signal transductions 3. Enzymatic activity 4. intracellular joining 5. cell-cell recognition 6. attachment to the cytoskeleton and the extracellular matrix

Question 44

ER smooth & rough

Answer 44

- smooth: lipid synthesis & calcium storage | - rough: protein synthesis