Physiology - Exam 1

which of the following is/are true regarding lipid-soluble signaling molecules (e.g. steroid hormones)?

a. typically bind to receptors in the nucleus of the cell

b. function in the regulation of gene expression

c. transported through the blood stream bound to a protein carrier

d. both (a) and (c)

e. all of the above

e. all of the above

this protein facilitates vesicle formation during receptor-mediated endocytosis by promoting an inward folding of the cell membrane

a. clathrin

b. phosphodiesterase

c. phospholipase

d. guanyl cyclase

e. oxytocin

a. clathrin

the intracellular fluid (i.e. cytoplasm) makes up what percentage of our total body water?

a. 10%

b. 33%

c. 50%

d. 66%

e. 90%

d. 66%

what is the approximate number of Na+ in the intracellular fluid of cells?

a. 0.0001 mM

b. 10 mM

c. 50 mM

d. 80 mM

e. 140 mM

b. 10 mM

tylenol (acetaminophen) reduces fever and pain - but has little to no inflammatory action - by blocking this enzyme(s) thereby reducing the formation of prostaglandins and thromboxanes

a. phosphodiesterase-5 (PDE-5)

b. phospholipase A2

c. cyclooxygenase-2 (COX-2)

d. protein kinase A and C (PK-A and -C)

e. cyclooxygenase-1 and 2 (COX-1 and -2)

c. cyclooxygenase-2 (COX-2)

which of the following are true regarding positive and negative feedback?

a. positive feedback increases deviation from the homeostatic setpoint

b. positive feedback results in the establishment of a new/different homeostatic setpoint

c. positive and negative feedback both rely upon afferent and efferent pathways

d. both A and C

e. all of the above

d. both A and C

Nitric oxide activates this effector protein in smooth muscle cells, leading to smooth muscle relaxation and the vasodilation of blood vessels

a. guanyl cyclase

b. lipooxygenase

c. phospholipase C

d. adenyl cyclase

e. CFTR

a. guanyl cyclase

this physiologist coined the term 'homeostasis' and realized that all reflex pathways requires sensors, an integrating center, and effectors

a. George Bartholemeuw

b. Walter cannon

c. Knut Schmidt-Nielson

d. Claude Bernard

e. Mike Elnitsky

b. Walter cannon

Histamine is released from mast cells in the integument following a mosquito bite. Histamine functions as a/an ____________, by affecting cells and blood vessels in the local area following the bite.

a. autocrine agent

b. hormone

c. paracrine agent

d. second messenger

e. effector protein

c. paracrine agent

a rare genetic mutation was found in the gene coding for phospholipase C rendering it inactive. Which of the following would not occur?

a. formation of second messengers

b. GTP binding to G-protein

c. release of Ca++ from endoplasmic reticulum

d. first messenger binding

e. neither (a) nor (c) would occur

e. neither (a) nor (c) would occur

Relative to mammalian cells, how would you describe the tonicity of a solution of 225 mOsm calcium chloride (calcium chloride is not membrane permeable); when placed into the solution the mammalian cells increased in size/volume

a. isotonic

b. hyposmotic

c. hyperosmotic

d. isosmotic

e. hypotonic

e. hypotonic

this condition is caused by the flux of Cl-; via the CFTR, and water into the lumen of the small intestine by activation of the adenyl cyclase pathway

a. cholera

b. botulism

c. cystic fibrosis

d. conotoxin poisoning

e. ion channelopathy

a. cholera

these pathways convey sensory information toward the integrating center (i.e., brain) in a homeostatic system

afferent pathway

this subunit of G proteins dissociates upon activation and subsequently activate an effector protein

alpha

these cells of the pancreas produce the hormone glucagon and are critical in the homeostatic control of blood glucose

alpha cells

the adenyl cyclase signaling pathways is terminated when this enzyme degrades the second messenger cAMP to AMP; this enzyme also degrades cGMP to GMP

phosphodiesterase

this term describes an in-balance of charge movement across the cell membrane through a pump or transporter such as occurs with the Na/K-ATPase

electrogenic

conotoxin acts as a/an ____________, by binding to the acetylcholine receptor on the surface of muscle cells but does not induce contractions (blocks response)

antagonist

provide an example of a solute that is likely to be moved across the membrane via endo-/exocytosis

proteins

this term is used to describe molecules with hydrophilic and hydrophobic domains, for example phospholipids

amphipathic

what is the approximate concentration of Cl- in the intracellular fluids of the body (be sure to include units)

Cl- = 7 mM

these chemical signals are produced by endocrine glands and released into the vasculature (blood stream) to reach their target

hormones

NSAIDs

ibuprofen and aspirin

block both COX-1 and COX-2 making them good fever reducers and anti-inflammatory drugs, but they can cause GI bleeding.

Claude Bernard

The father of physiology, created the concept of homeostasis, but called it "milieu interieur"

G protein

proteins that couple with membrane receptors and upon binding of a signal can dissociate to activate an effector protein.

osmolarity vs. tonicity

osmolarity - concentrations of ALL solutes and compares it to standard 300 mOsm in mammalian cells

tonicity - considers intracellular concentration to extracellular, focusing on where water will move (into cell or out)

Nitric oxide

a signal molecule that is produced in endothelial cells that activates the guanyl cyclase pathway in smooth muscle cells and causes vasodilation

Eiocosanoids

arachadonic acid splits into lipoxygenase and cycloxygenase

lipoxygenase = leukotrienes which mediate allergies/immune response

cycloxygenase = prostaglandins and thromboxanes which mediate pain, inflammation, and fever

Primary vs. secondary active transport

Primary active transport - requires ATP to transport molecules against the concentration gradient

secondary active transport - no additional ATP, uses the already open pathway to cross (syn/antiport)

agonists vs. antagonists

agonists - mimics the effects of an endogenous substance

antagonists - blocks typical effects by binding/blocking receptors

membrane fluidity

ease with which molecules can cross the membrane can be very fluid with more unsaturated bonds and rigid/viscous with saturated bonds

second messengers

intracellular signals that get activated by an effector protein that was induced by a first messenger that may not cross the phospholipid membrane.

Includes DAG, IP3, and cAMP

explain the 3 categories of mutations to the cystic fibrosis transmembrane conductance regulator (CFTR), as identified in the A Breath of Fresh Air article, in patients with cystic fibrosis

Blocked CTFR - the protein channel has gating problems; makes up 4% of cases

-first ever treatment w/ kalydeco

Truncated CTFR - mutation leads to incomplete protein synthesis and is stopped too early, resulting in mutated CTFR; makes up 10% of cases. No treatment.

Misfolded CTFR - most common type w/ 86%, mutation causes a misshapen protein that is not inserted in the membrane, but is still functional

explain the pathway of activation and how cholera bacteria (Vibrio cholerae) cause the characteristic watery stool and severe risk of dehydration

1. prolonged activation of adenyl cyclase due to cholera toxin

2. causes production of cAMP which uses protein kinase A to phosphorylate proteins

3. CTFR is opened in response to phosphorylation of proteins

4. chloride ions move through the open CFTR channel at a high rate

5. this chloride moved into the colon where the imbalance causes excessive water in the colon and therefore severe persistent diarrhea and dehydration

what is physiology?

the study of how organisms work using a metric to measure success

makeup of body fluid

Extracellular fluid: 33%

- 7% plasma

- 26% interstitial fluid

Intracellular fluid: 67%

Claude Bernard

Came up with the idea of homeostasis as "milieu interieur"

Was the first to recognize the idea of homeostasis

Water Cannon

First to actually coin the term homeostasis

said all homeostatic mechanisms must have these 3 components:

-sensors (receptors)

-integration center (brain or spinal cord)

-effectors (muscles, glands, organs)

Afferent pathway

carries signals to the brain to say "hey something is wrong!"

ex: tells the brain blood glucose is high

Efferent pathway

carry signals from the brain to the effector organ with instructions to mitigate the issue

ex: tells the pancreas to secrete insulin when blood glucose rises

Negative feedback

Most common form

-occurs when something takes the body away from homeostasis

-nerves send afferent signals to the brain

-brain interprets a solution

-brain sends efferent signals to organs to return the body to normal

examples of negative feedback

-body temp control

-blood glucose levels (dynamic consistency)

Positive feedback

Uncommon

-stimulus occurs taking body away from homeostasis

-signal is sent to brain

-brain sends efferent signals to increase the response, furthering away from homeostasis

-stops when stimulus is removed from environment

example of positive feedback

childbirth

fluid mosaic model

cell membrane structure

-fluid: cell wall is not rigid, it has motion and its composition is always changing based on types of lipids, amount of protein, etc.

-mosaic: cell wall is composed of many different molecule types; it is heterogenous

Phospholipid composition

-Polar heads that are hydrophilic, so they're outside

-Nonpolar tails that are hydrophobic; they face in

This makes molecules amphipathic because they have polar and nonpolar ends

saturated fatty acids

no double bonds, so they're straight and are tightly packed in.

make viscous fluid due to lack of water movement

unsaturated fatty acids

have double bonds in their tails, making them bent so they make looser membranes

more fluid, make thinner fluids due to easier water transfer

membrane fluidity

a measure of how well phospholipids can move in a membrane. Unsaturated fatty acids move more than those with saturated fatty acids.

unsaturated - fluid

saturated - viscous

Homeoviscous adaptation

maintenance of a relatively constant membrane fluidity. This occurs because cell membranes work best with consistency

consistency can be changed with saturation or environmental temperature (warm = fluid, cold = viscous)

Relationship between membrane fluidity and homeoviscous adaptation

membrane fluidity is how much a membrane moves and homeoviscous adapation is maintenance of that fluidity level

Integral proteins

embedded into lipid bilayer of the cell membrane

Peripheral proteins

freely adhere to one side of the cell membrane surface

integral protein function

transport

signaling

enzymatic activity

peripheral protein function

regulatory and structural

can anchor the cell membrane to filaments of the cytoskeleton

role of cholesterol in cell membranes

helps with homeoviscous adaptation/maintain membrane fluidity with temperature changes

slows down membrane movement in warm temperatures and speeds it up in cooler temperatures

Diffusion

passive movement of a solute down its concentration gradient

-no energy required

-small, lipid soluble solutes like oxygen, CO2, steroids like estrogen

-stops movement at equilibrium

what factors influence rate of diffusion

-membrane resistance

-concentration gradient (larger = faster movement, smaller = slower movement)

-lipid solubility

-membrane surface area (more surface area = quicker diffusion)

-composition of lipid bilayer

-molecular size (larger molecules diffuse slower)

Facilitated diffusion

-No energy required, moves with the concentration but requires solute binding to pass through

-The solute acts as a ligand, no additional compound is required (ex: glucose binds the protein, conformation occurs, glucose enters the cell)

Difference between diffusion and facilitated diffusion

Facilitated diffusion requires a binding protein to open a channel

Facilitated diffusion has a threshold due to limitation of number of proteins whereas diffusion has no threshold

Active transport

-goes against concentration gradient but requires ATP use

-solute must actually bind with protein to move through

active transport example

-sodium potassium pump takes 3 sodium using ATP from inside to outside the cell where concentration is already high

-2 potassium come from outside the cell to inside the cell where concentration is already higher

-these both bind to open the protein to move through

secondary active transport

-against the concentration gradient, but no direct ATP use

-a solute moving with the gradient binds to open the channel

-the secondary ion hitches a ride across the membrane while the channel is open

cotransport

part of secondary active transport

ion and second solute go in same direction

countertransport

part of secondary active transport

ion and second solute move in opposite directions

Diffusion via ion channels - NO CLASSIFICATION

-Passive transport, but ions move through an open channel

-a tunnel where ions can move with their gradient

-can be ligand-gated: ligand must bind for the ion to move through. ion and ligand are 2 different things

example of a ligand gated channel

binding acetylcholine opens sodium channels in neurons and muscle cells to allow sodium to enter

use of endo and exocytosis

is like phagocytosis

one goes in one comes out

is used for large molecule movement (like protein)

endocytosis

-membrane folds in forming a pocket around the molecule

-it is pinched off with the molecule incide to make intracellular, membrane-bound vesicles

-required a ligand to first bind to molecule receptor

exocytosis

intracellular vesicles around a molecule fuse with the membrane to release contents into the extracellular space

ligands are sent to lysosomes or golgi for processing

then expelled from cell

antagonists

ligands that bind and block the effect of an endogenous compound

agonists

ligands that bind and mimic the effect of an endogenous compound

electrogenic pump

generated an electrical separation of charge across a cell membrane

Na/K-ATPase

pump moves 3 sodium ions out (3 positives outside) and 2 potassium ions inside (2 positives inside)

this is known as an electrogenic pump

extracellular Na

140 mM

intracellular Na

12

extracellular K

5

intracellular K

150

extracellular Ca2+

1

intracellular Ca2+

0.0001

extracellular Cl-

100

intracellular Cl-

7

extracellular HCO3-

24

intracellular HCO3-

10

extracellular glucose

5.6

intracellular glucose

1

osmolarity

total concentration of solutes in a solution

normal intracellular osm

300 mOsm

hypoosmotic

<300

isosmotic

300

hyperosmotic

>300

tonicity

describes the effect a solution has on cell volume

where does the water go?

hypertonic

cell shrinkage

isotonic

no cell change

hypotonic

cell expands

Non-penetrating solutes tonicity and osmolarity

are the same

hyperosmotic = hypertonic

Penetrating solutes

must think about what happens when cell is dropped into solution

what does CFTR stand for

cystic fibrosis transmembrane conductance regulator

purpose of CFTR

code for the protein that is chloride channels in cell walls

about 1600 different mutations in CFTR can cause CF

What happens in CF

chloride channel is blocked, truncated, or misfolded which means chloride and water can't get through

makes mucous very thick and is difficult to breathe, bacteria get trapped increasing infection, and normal oxygenation of blood is prevented