Biochemistry - Membranes

Question 1

promotes the release of O2 from Hb and shifts the O2 dissociation curve to the right. It binds with greater affinity to deoxygenated hemoglobin (e.g. when the red cell is near respiring tissue) than it does to oxygenated hemoglobin (e.g., in the lungs) due to spatial changes. It fits in the deoxygenated hemoglobin configuration, but not as well in the oxygenated Hb. It interacts with deoxygenated hemoglobin beta subunits by decreasing their affinity for oxygen, so it allosterically promotes the release of the remaining oxygen molecules bound to the hemoglobin, thus enhancing the ability of RBCs to release oxygen near tissues that need it most.

Answer 1

2, 3 BPG

Question 2

Amphopathic. Steroid nucleus, polar head group oriented towards the hydrophilic. Up to 50% of membranes. Restricts fluidity.

Answer 2

cholesterol

Question 3

membrane lipids, amphatic. Shingomylrin snf glycosphingolipids. Ceramide hydrophobioic portion.

Answer 3

sphingolipids

Question 4

sphingolipids, glycerolphospholipids, cholesterol

Answer 4

ampathic membrane lipids

Question 5

integral proteins resemble “icebergs” floating in a two-dimensional lipid “sea”, and these proteins freely diffuse laterally in the lipid matrix, unless associations with other cell components (such as cytoskeletal fence) or confinement by epithelial tight junctions restrict their movements.

Answer 5

fluid mosaic model

Question 6

polar head groups and two fatty acids tails attached to glycerol. The polar head group and phosphate are hydrophilic, whereas the nonpolar fatty acid tails are hydrophobic

Answer 6

Glycerolphospholipids

Question 7

derived from the identity of the head group (choline, serine, ethanolamine). For example, phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS).

Answer 7

glycerophospholipids nomenclature

Question 8

sphingomyleins and glycolipids. All constructed from ceramine. The addition of a fatty acid tail to sphingosine forms a ceramide molecule.

Answer 8

Sphingolipids

Question 9

it contains the same head group (choline + phosphate), as phosphatidylcholine, but contains a sphingosine backbone instead of glycerol. behaves like glycerophospholipids..

Answer 9

Sphingomyelin

Question 10

Sphingolipid. sugar residues attached to ceramides. ONLY located in the outer leaflet of the lipid bilayer.

Answer 10

Glycolipids

Question 11

Glycolipid that contains a single glucose or galactose molecule attached to a ceramide. Important in nerve tissue and prevalent in the cell membrane of the brain.

Answer 11

Cerebrosides

Question 12

Glycolipid that has glycans as its head groups, primarily found in the ganglial cells of the central nervous system.

Answer 12

Gangliosides

Question 13

rich in both sphingolipids and galactocerebrosides. Help insulate axons from electrically charged atoms and molecules (hot wire sheath). Its loss associated with multiple sclerosis.

Answer 13

myelin

Question 14

autoimmune disease that causes destruction of the cells that prodice myelin.Can affect vision, sensation, coordination, movement, bladder and bowel ocntrol.

Answer 14

Multiple sclerosis

Question 15

A deficiency in sphingomyelinase, an anzyme that breaks down sphingomtelin in the tissue. Sphingomyelin over accumulates in various organs, leading to grossly enlarged cells of spleen, lungs, liver, lungs, bone marrow, brain. Progressive neurologic impairment is common.

Answer 15

Niemann-Pick Disease (type A and B)

Question 16

tiny polar head and hydrophobic structure. Increases level decreases membrane fluididity in bio membranes. Can comprise up to 50% of the total membrane.

Answer 16

Cholesterol

Question 17

ransmembrane lipid transporter enzymes located in the membrane responsible for aiding the movement of phospholipid molecules between the two leaflets that compose a cell’s membrane (transverse diffusion).

Answer 17

flipases

Question 18

Contain spans of hydrophobic amino acids that easily associate with the hydrophobic layer of the membrane. (intergral)

Answer 18

Transmembrane proteins

Question 19

Associated with the plasma-attached lipid molecules that tether the protein to the membrane. (integral)

Answer 19

Lipid-linked proteins

Question 20

Attached to the membrane by electrostatic or hydrogen bonds that noncovalently link them to integral membrane proteins or to phospholipid

Answer 20

Peripheral proteins head groups.

Question 21

made of glycolipids glycosphingolipids) and glycoproteins (glycosylated proteins). always found in the outer monolayer/extracellular surface of the plasma membrane.

Answer 21

Membrane carbohydrates

Question 22

glycolipid + glycoprotein. Cell recognition, protect against mechanical stress, blood clotting, egg-sperm interaction.

Answer 22

Glycocalyx

Question 23

passive-mediated carrier in basolateral membrane. In liver, low affinity.

Answer 23

GLUT-2

Question 24

primary active carrier, requires ATP, and is responsible for maintaining a high electrochemical gradient for intracellular K+ and low electichemical gradient for intracelular Na+.

Answer 24

Na+-K+ ATPase

Question 25

secondary active carrier. Located in apical membrane of epithelium.

Answer 25

Na+-driven glucose symport

Question 26

passive-mediated channel. Present in the PM os muscle cells and opens when neurotransmitter ACH binfd, -> conformational change, allowing Na+ to flow down EC gragient, acrodd membrane.

Answer 26

acetylcholine-gated Na+ channel

Question 27

the movement of solute down its concentration gradient (uncharged solute, e.g. glucose) or down its electrochemical gradient (charged solute, e.g. ions).

Answer 27

Passive-mediated transport

Question 28

the movement of solute against its concentration or electrochemical gradient. Energy is required. Only carriers, no channels. ATP = primary, ion gradient = secondary.

Answer 28

Active transport

Question 29

The solute passes between adjacent cells, through tight junctions that have loosened in reponse to a meal.

Answer 29

Paracellular transport

Question 30

The solute is imported into the cell at the apical surface and exited from the cell at the basolateral surface. Glucose transport in intesitine uses this.

Answer 30

Transcellular transport:

Question 31

connect the plasma membranes of enterocytes, ensuring that transporters at the apical surface remain separate from transporters at basal surface. Na+ at basolateral side leaks back though them to the apical side. Those found in intestinal epithelium are very “leaky” for sodium ions. No kidney, just intestine.

Answer 31

tight junctions

Question 32

contains three types of carriers. 1. Na+-driven-glucose active carrier (secondary active) 2. a glucose carrier (passive-mediated) 3. Na+-K=ATPase active carrier (primary active).

Answer 32

enterocyte

Question 33

In brain, high affinity for glucose.

Answer 33

GLUT-3

Question 34

in muscle and adipose tissues (90% of body mass), low affinity, levels are regulated by insulin.

Answer 34

GLUT-4

Question 35

high concentrations of proteins and solutes…?

Answer 35

electrogenic pump

Question 36

an integral membrane protein that is involved in movement of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in the same direction, and is, therefore, a type ofcotransporter. Typically, the ion(s) will move down the electrochemical gradient, allowing the other molecule(s) to move against the concentration gradient. The movement of the ion(s) across the membrane is facilitated diffusion, and is coupled with the active transport of the molecule(s).

Answer 36

symporter

Question 37

present in erythrocytes. binds and transports O2, delivers O2 from lungs to the tissues and CO2 from the tissues to the lungs. It is a tetramer composed of two a-globin and two b-globin polypeptide chains.

Answer 37

hemoglobin

Question 38

higher affinity for O2 than adult hemoglobin (HbA), to ensure that the fetus obtains enough O2 during gestation.

Answer 38

Fetal hemoglobin (HbF)

Question 39

a monomer. It is a compact, globular structure with 75% a-helices (8 a-helices, named from A to H) mostly present in heart and skeletal muscle (only small amounts in smooth muscle). It binds and stores O2, releasing it when needed. (O2 storage mostly)

Answer 39

Myoglobin (Mb)

Question 40

the physical location where O2 is bound to Hb and Mb. a prosthetic group consisting of a protoporphyrin IX ring with a ferrous iron (Fe2+) in the center with 6 coordination sites. Allows O2-Fe interaction to be looser and reversible (otherwise… rust).

Answer 40

heme group

Question 41

a substrate for its target enzyme, as well as a regulatory molecule of the enzyme’s activity. It is typically an activator of the enzyme.

Answer 41

homotropic effectors

Question 42

a regulatory molecule that is not also the enzyme’s substrate. It may be either an activator or an inhibitor of the enzyme.

Answer 42

heterotropic allosteric modulator

Question 43

H+, CO2, and 2,3-bisphosphoglycerate, high temperature. stabilize the T state and shift the O2 binding curve to the right.

Answer 43

heterotropic allosteric modulators of hemoglobin

Question 44

stabilize the T conformation of Hb, decreasing the affinity for O2 and increasing the release of O2 from Hb, shift binding curve to the right.

Answer 44

negativeallosteric effectors

Question 45

1. stabilize the R-state 2. shift binding curve to the left 3. inhibit the release of O2 from Hb. (e.g. CO)

Answer 45

Positive allosteric effectors