Ch 6 - Interactions between Cells and Extracell Environment

Question 1

Where is the interstitial fluid derived from? What does it do?

Answer 1

1. Derived from blood plasma that filters through pores between cells of capillary walls
2. Delivers nutrients and regulatory molecules to the tissue cells

Question 2

What % body water is contained in the intracellular compartment/extracellular compartment?

Answer 2

67% intracellular

33% extracellular

Question 3

What consists of protein fibers, collagen and elastin, as well as gel-like ground substance?

Answer 3

Extracellular Matrix

Question 4

What two molecules basically make up the ground substance?

Answer 4

glycoproteins

proteoglycans

Question 5

What are the functions of integrins in the plasma membrane?

Answer 5

• class of glycoprotein
• extend from cytoskeleton within a cell, through its plasma membrane, and into extracellular matrix
  
  • glue between cell and extracellular matrix
• relay signals between the two compartments
• “assign polarity” - basal and apical side

Question 6

What are the three types of passive transport across a plasma membrane?

Answer 6

Simple Diffusion (Including Osmosis)

Diffusion through protein channels

Facilitated Diffusion

Question 7

Water is a polar molecule, why is it able to generally diffuse through the plasma membrane?

Answer 7

Water’s small size, and lack of a net charge allow it to diffuse to a limited degree.

Question 8

What “channel” greatly aids the passage of water through the plasma membrane?

Answer 8

aquaporins

Question 9

What disease is caused by a genetic defect involving a particular glycoprotein that forms chlroide channels in the apical membrane of the epithelial cells?

Answer 9

Cystic Fibrosis - protein is known as CFTR

Question 10

What are 4 factors on the rate of diffusion?

Answer 10

1. magnitude of the concentration difference across the membrane
2. permeability of the membrane
3. temperature of the solution
4. surface area of the membrane though which the substances are diffusing

Question 11

Solutes that cannot freely pass through the membrane can promote the osmotic movement of water and are said to be….

Answer 11

osmotically active

Question 12

What are 2 requirements for osmosis?

Answer 12

1. there must be a difference in the concentration of a solute on the two sides of a selectively permeable membrane
2. the membrane must be relatively impermeable to the solute

Question 13

What could a low concentration of plasma proteins result in?

Answer 13

• Edema - excessive accumulation of fluid in the tissues
• Protein concentration of the plasma is higher thatn interstitial fluid, pulling water from interstitial tissue into capillary blood
  
  • Albumin is main protein of blood, liver makes it. So if liver stops producing it….edema could happen

Question 14

What ratio does osmotic pressure depend on?

Answer 14

ratio of solute to solvent, not on chemical nature of the solute molecules

Question 15

How much does 1 mole of solute per liter depress the freezing point by?

Answer 15

-1.86 degree C

Question 16

Plasma freezes at about -.56 C, what is it’s Osm?

Answer 16

.56 / 1.86 = .3 Osm, or 300 milliosmolal

Question 17

What is the term used to describe the effect of a oslution on the osmotic movement of water?

Answer 17

tonicity

Question 18

The expression for the total molality of a solution?

Answer 18

Osmolality

Question 19

What are 2 responses to dehydration from the osmoreceptors?

Answer 19

1. Water leaves the osmoreceptors in the hypothalmus and they shrink. This shrinkage stimulates the osmoreceptors, making the person thirsty…if water is available they drink
2. Dehydration also excretes lower volumes of urine
   
   1. increased plasma osmolatity stimulates osmoreceptors in the hypothalamus
   2. Osmoreceptors then stimulate a tract of axons that terminate int eh posterior pituitary; this causes the posterior pituitary to release antidiuretic hormone (ADH) , or vasopressin, into the blood
   3. ADH acts on the kidneys to promote water retention, so that a lower ovlume of more concentrated urine is excreted.

Question 20

ADH is released from what gland? What does it normally act on?

Answer 20

1. Posterior Pituitary
2. Acts on the kidneys, to retain water

Question 21

What are the 3 common characteristics of enzymes and carrier proteins?

Answer 21

1. Specificity
2. Competition
3. Saturation

Question 22

What is diabetes mellitus, caused by?

Answer 22

inadequate secretion and/or action of insulin

Question 23

What is glycosuria?

Answer 23

A condition where - a hyperglycemic diabetic’s glucose carriers, in the kidney, are over saturated. Typical reabsorption cannot take place and excess glucose is expelled in the urine.

Question 24

Using a GLUT carrier, how can a skeletal or adipose cell increase its uptake of glucose during excerise or insulin stimulation?

Answer 24

When excerising or insulin stimulation - GLUT4 proteins attached to a vesicle fuse with the plasma membrane…almost like exocytosis, but nothing is released. This increases the amount of glucose facilitated diffusers along the membrane, allowing the cell to take in more glucose

Question 25

What occurs when the hydrolysis of ATP is directly responsible for the function of the carriers, which are proteins that span the thickness of the membrane?

Answer 25

Primary Active transport

Question 26

What are two processes that are signaled by the rapid diffusion of Ca2+ down its concentration gradient?

Answer 26

1. release of neurotransmitters from axon terminals 2. Muscle contraction

Question 27

What functions do the steep Na/K gradient serve?

Answer 27

1. Steep Na+ gradient is used to provide energy for the coupled transport of other molecules 2. Gradient for Na and K are used in nerve and muscle cells for electrochemical impluses...(potentials) 3. active extrustion of Na is important for osmotic reasons; if the pumps stop, the increased Na concentration would promote the osmotic inflow of water, damaging cells

Question 28

Where are the two main places you'll find the cotransport of Na+ and glucose?

Answer 28

1. lumen of the intestine 2. kidney tubules

Question 29

In the Na/Glucose secondary transport, which molecule is moving up/down is concentration gradient?

Answer 29

The Na+ molecule is moving down its gradient (High -\> Low) while Glucose is moving up its gradient (Low --\> High)

Question 30

What 3 structures make the junctional complexes between epithelial cells?

Answer 30

1. Tight Junctions - space between two adjoining plasma membranes appears to be occluded and strands of proteins penetrate the plasma membranes to bridge the cytoskeleton actin fibers 2. Adherens junctions - plasma membranes ofthe two cells come very close together and are "glued" by interactions between proteins that span each membrane and connect to the cytoskeleton of each cell 3. Desmosomes - plasma membranes of the two cells are "buttoned together" by interactions between particular desmosomal proteins.

Question 31

How is cholesterol removed from the blood?

Answer 31

receptor-mediated endocytosis in the liver and through the walls of blood vessels

Question 32

What type of molecules require bulk transport?

Answer 32

Polypeptides and Proteins....big stuff

Question 33

Which cation is the most permeable in regards to the plasma membrane?

Answer 33

K+

Question 34

Why is K+ found in greater concentration within the cell? What are the intracellular and extra cellular concentrations of K+

Answer 34

* Negatively charged, "fixed anions" - like phosphates of ATP, and proteins are negatively charged. This negative charge pulls in the K+ since it is more permeable to the plasma membrane. * Intra = 150 mEq/L and Extra= 5 mEq/L

Question 35

What are some of the physiological processes that the **potential difference** of cells manages?

Answer 35

muscle contraction, heartbeat, generation of nerve impulses.

Question 36

What is the membrane potential that would stabilize the K+ concentration? What is it's numerical designation and what does that number mean?

Answer 36

1. K+ equilibirum potential, E_K 2. At equilibrium K+ = -90mV. This means that a membrane potential of -90 mV is need to produce an equilibrium in which K+ is 150 mM inside and 5 mM outside the cell. 1. If the number was more negativeit would draw more K+ in, if the number was more positive it would diffuse more K+ out

Question 37

What is the Na+ equilibrium potential, E_Na. What are the intracellular and extracellular concentrations causing this equilibrium?

Answer 37

1. +66mV 2. 12mM inside the cell and 145 mM outside the cell

Question 38

What would happen the the resting membrane potential of a cell if the Na+/K+ pumps stopped working?

Answer 38

There would be a excess build up of positively charged Na+ ions. This build up would make nerve impulses impossible, since the resting membrane potential its dependent on the K+ concentration inside the cell. If excess Na+ ions build up, the resting potential will be even more positive than the normal -70mV, thus causing more K+ to diffuse out of the cell.

Question 39

Hyperkalemia is an increase in plasma [blank]? What does this do?

Answer 39

1. Increase in plasma K+ 2. This causes the concentration of extracellular K+ to increase, thus increasing the intracellular concentration. It reduces membrane potential...cuasing heart problems. Heartbeats can be stopped entirely at 8 mEq/L of K+ in the plasma.

Question 40

What are the 3 general types of cell signaling?

Answer 40

Paracrine Synaptic Endocrine

Question 41

Which type of cell signaling is considered "local" because cells within the organ secrete regulatory molecules that diffuse through the extracellular matrix to nearby *target cells* within the same organ?

Answer 41

paracrine

Question 42

Which type of cell signaling requires the endocrine glands to secrete hormones into the blood?

Answer 42

Endocrine signaling...

Question 43

What are some examples of nonpolar regulatory molecules that interact with intracellular receptor proteins?

Answer 43

steroid hormones thyroid hormones nitrix oxide gas (paracrine hormone)

Question 44

What are some examples of large, polar molecules that interact with receptor proteins located on the outer surface of the plasma membrane?

Answer 44

Insulin acetylcholine epinephrine

Question 45

What is cAMP? How does it effect cell activity?

Answer 45

1. Cyclic adenosine monophosphate - **second messenger** 2. When a regulatory molecule binds with a plasma membrane receptor protein, cAMP is made from ATP on the intracellular side. 1. This increase in cAMP activates previously inactive enzymes in the cytoplasm 2. these enzymes change the cell to produce the action of the regulatory molecule

Question 46

What are the 3 G proteins?

Answer 46

1. Three protein subunits that shuttle between receptors and different membrane effector proteins, including specific enzymes and ion channels. 2. Alpha, Beta, and Gamma