Chapter 4 - Guyton

Question 1

Higher concentration in extracellular fluid.

Answer 1

sodium, calcium, chloride, bicarbonate, glucose

Question 2

Higher concentration in intracellular fluid.

Answer 2

potassium, magnesium, phosphates, sulfate, amino acids, fats, proteins

Question 3

Protein components of the lipid bilayer.

Answer 3

contains large amounts, no fluid, transport proteins, channel proteins, carrier proteins, all are highly selective

Question 4

Simple Diffusion

Answer 4

kinetic movement of ions/molecules occurs through a membrane or opening or intermolecular spaces without interaction of carrier proteins

Question 5

What are the two pathways through which simple diffusion can occur?

Answer 5

1) interstices of the lipid bilayer if lipid soluble; 2) watery channels that penetrate through large transport proteins

Question 6

Explain facilitated diffusion.

Answer 6

requires carrier proteins to pass the molecule by binding chemically and shuttling through the membrane

Question 7

What factors determine the rate of diffusion?

Answer 7

amount of substance available, velocity of kinetic motion (temperature?), number and sizes of openings in membrane

Question 8

Which substances have a high lipid solubility (and thus diffuse directly through the membrane)?

Answer 8

oxygen, nitrogen, carbon dioxide, and alcohol

Question 9

The rate of diffusion for lipid-soluble substances is directly related to amount of ______ _______.

Answer 9

lipid solubility (oxygen moves through as if the membrane isn’t even there…)

Question 10

Which type of proteins form the “pores” in the cell membrane?

Answer 10

integral proteins

Question 11

Which factors determine the selectivity of pores?

Answer 11

diameter and electrical charge

Question 12

Although it is not lipid-soluble, water readily passes through the cell membrane. How?

Answer 12

aquaporins allow rapid passage of water through the membrane, narrow pores to permit water molecules to pass through in a single file

Question 13

Name some factors that affect selectivity of selectively permeable protein channels.

Answer 13

diameter, shape, electrical charges, chemical bonds

Question 14

Describe potassium channels.

Answer 14

have a tetrameric structure (4 identical subunits) around a center pore, pore loops at top for a selective filter, carbonyl oxygens are at the loop and dehydrate potassium allowing them to pass

Question 15

Describe a sodium channel.

Answer 15

only 0.3-0.5 nm in diameter, lined with negatively charged amino acids which dehydrate sodium

Question 16

Gated protein channels are an extension of which membrane protein.

Answer 16

transport protein

Question 17

Explain the two types of gated protein channels.

Answer 17

voltage-gated - conformation of gate responds to electrical potential on inside of the cell, basic mechanism for action potentials; chemical (ligand) gated - opened by binding of a chemical substance which causes a conformational change in protein to open or close the gate

Question 18

Example of a ligand-gated channel.

Answer 18

acetylcholine channel for nerve signals

Question 19

Do channels ever partially open?

Answer 19

no, gates are “all or none” and open and close very rapidly (milliseconds)

Question 20

Explain the patch-clamp method for recording ion current flow through single channels.

Answer 20

micropipette is put against outside of cell membrane and suction applied to create seal, micropipette is then inserted into a solution to allow concentrations inside and outside cell to be altered, the purpose is to determine the transport characteristics of single channel and its gating properties

Question 21

In facilitated diffusion, the rate of diffusion approaches a maximum called:

Answer 21

Vmax

Question 22

Define facilitated diffusion.

Answer 22

carrier-mediated diffusion because substance transported diffuses through membrane using a specific carrier protein to help

Question 23

What sets the max rate of facilitated diffusion?

Answer 23

the rate can never be greater than the rate at which the carrier protein can undergo conformational changes back and forth

Question 24

The most important substances that cross the membrane by facilitated diffusion.

Answer 24

glucose and most amino acids

Question 25

Nernst Potential

Answer 25

effects of membrane electrical potential on diffusion of ions, electrical charges of ions causes them to move even if no concentration difference exists, important for transmission of nerve impulses

Question 26

Net movement of water by a concentration difference is called:

Answer 26

osmosis

Question 27

Osmotic Pressure

Answer 27

the exact amount of pressure to stop osmosis

Question 28

What factor determines osmotic pressure of solution?

Answer 28

concentration of the solution in terms of number of particles (osmolality)

Question 29

Osmole

Answer 29

1 gram molecular weight of osmotically active solute

Question 30

Relation of osmolality to osmotic pressure.

Answer 30

the actual osmotic pressure of body fluids is about 0.93 times the calculated value

Question 31

What is the distinguishing characteristic of active transport?

Answer 31

cell membrane moves molecules against the concentration gradient

Question 32

Substances transported through active transport:

Answer 32

sodium, potassium, calcium, iron, hydrogen, chloride, sugars, most amino acids

Question 33

Primary active transport

Answer 33

energy is derived from breakdown of ATP, depends on carrier protein, ex. sodium-potassium pump

Question 34

Sodium-Potassium Pump

Answer 34

sodium out and potassium in, responsible for maintaining differences across cell membrane and establishing a negative electrical voltage inside the cell

Question 35

Describe the carrier protein of the sodium-potassium pump.

Answer 35

complex of 2 globular proteins (alpha and beta), alpha subunit has 3 receptor sites for binding sodium on inside, 2 receptor sites for potassium on outside, inside portion near sodium binding site has ATPase activity

Question 36

What factors control the direction of enzyme reaction in the sodium-potassium pump?

Answer 36

concentrations of ATP, ADP, and phosphate, electrochemical gradients of sodium and potassium

Question 37

How does the sodium-potassium pump control cell volume?

Answer 37

large numbers of proteins inside the cell attract positive ions, molecules cause osmosis, the pump prevents this by pumping out 3 sodium ions for every 2 potassium ions pumped inside (water follows ions)

Question 38

Why is there a low concentration of calcium in the intracellular cytosol?

Answer 38

2 calcium pumps, one in the cell membrane to pump calcium out of cell and one to pump calcium into organelles within the cell

Question 39

What two places in the body is primary active transport of hydrogen ions important?

Answer 39

parietal cells in gastric glands of the stomach, distal tubules of cortical collecting ducts of kidneys (into urine to eliminate it)

Question 40

Name the two types of secondary active transport.

Answer 40

co-transport and counter-transport

Question 41

And what is secondary active transport anyway?

Answer 41

energy is derived secondarily from energy that has been stored in the form of ionic concentration differences of secondary molecule between the two sides of the membrane, depends on carrier protein

Question 42

What occurs during co-transport?

Answer 42

carrier protein is the attachment point for ion and substance to be co-transported, when they are attached the energy gradient of sodium allows the substance to be transported together into the cell

Question 43

Substances that are co-transported along with sodium?

Answer 43

glucose and amino acids

Question 44

Where does sodium co-transport of glucose and amino acids occur?

Answer 44

through epithelial cells of intestines and renal tubules

Question 45

Where does sodium counter-transport of calcium and hydrogen occur?

Answer 45

calcium - all cell membranes (sodium in and calcium out); hydrogen - proximal tubules (sodium in and hydrogen out)

Question 46

Where in to body does active transport through cellular sheets occur?

Answer 46

epithelium of intestines, renal tubules, exocrine glands, gallbladder, choroid plexus of brain (basic movement through sheet is active transport on one side of cell and then either simple or facilitated diffusion on opposite side of cell)