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BIO 101 EXAM 2 > CHAPTER 6 > Flashcards

CHAPTER 6 Flashcards

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1
Q

what is the fluid mosaic model and what does it describe?

A

A model for biological membranes with a fluid bilayer of phospholipids where proteins can move freely, like floating in a lake

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2
Q

describe the structure of a phospholipid.

A

They have polar hydrophilic “heads” facing outward and non-polar hydrophobic fatty acid “tails” facing inward.

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3
Q

how do phospholipids vary?

A

-fatty acid chain length
-degree of unsaturation
-phosphate groups

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4
Q

why is cholesterol important?

A

for membrane integrity and regulates fluidity

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5
Q

information about the membrane interior.

A

-The membrane interior is fluid, enabling lateral molecule movement
-Molecules rarely flip across the membrane
-The inner and outer sides of the bilayer can differ significantly.

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6
Q

membrane fluidity depends on?

A

-Depends on lipid composition and temperature
-Cholesterol and saturated fatty acids tightly pack, reducing membrane fluidity
-Unsaturated long-chain fatty acids create “kinks,” increasing membrane fluidity
-Membrane fluidity decreases as temperature decreases
-Some organisms adjust membrane lipid content based on external temperature.

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7
Q

which ways do organisms change the lipid content of the cell membrane in relation to external temperature?

A

-Cold: Replace saturated with unsaturated fatty acids, shorten tails.
-Hot: Replace unsaturated with saturated fatty acids, lengthen tails.

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8
Q

what are the proteins contained in the membrane (plus other information)

A

-integral
-peripheral
-anchored

-Protein quantity varies by membrane function
-Some proteins move freely within the bilayer

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9
Q

integral membrane proteins

A

-Proteins partly embedded in the bilayer.
-Hydrophilic domain extends inward or outward.
-Hydrophobic domain interacts with fatty acids inside.
-Some extend across the lipid bilayer, some partially embed.

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10
Q

peripheral membrane proteins

A

-Lack hydrophobic regions, don’t penetrate bilayer
-Located on one side of the membrane.

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11
Q

anchored membrane proteins

A

-are covalently attached to fatty acids or other lipids
-are anchored to specific regions

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12
Q

transmembrane proteins

A

-Extend through bilayer with transmembrane domains
-Inner and outer domains can have distinct functions

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13
Q

what happens when cells are fused experimentally

A

Proteins distribute uniformly around the membrane.

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14
Q

what are membranes constantly doing? what is an example of this

A

-Membranes are dynamic, forming, transforming, fusing, and breaking down.
-Example: Endomembrane system.

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15
Q

information about the chemistry of the membrane

A

-Sub cellular membranes differ chemically.
-Membranes change chemically when forming parts of specific organelles.

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16
Q

what do membranes also have on the outer surface? what are the names?

A

-Carbohydrates on outer surface serve as recognition sites for cells and molecules.
-glycolipids
-glycoproteins

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17
Q

glycolipids

A

carbohydrate + lipid

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18
Q

glycoproteins

A

carbohydrate (oligosaccharide) + proteins
-proteoglycans have higher percentage of carbohydrates

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19
Q

how do cells arrange themselves in tissues?

A

Cell recognition and adhesion rely on surface proteins and carbohydrates.

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20
Q

cell adhesion

A

-Cell adhesion can occur through interactions between carbohydrates, proteins, or both.
-usually homotypic

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21
Q

homotypic

A

the same molecule sticks out from both cells and bind to each other

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22
Q

heterotypic

A

the cells have different proteins that bind together

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23
Q

define cell junctions. what are the types of junctions?

A

-cell junctions are specialized structures that hold cells together
-tight junctions
-desmosomes
-gap junctions

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24
Q

tight junctions

A

-help ensure directional movement of materials

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25
Q

desmosomes

A

-like “spot welds”
-An adhering junction between animal cells

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26
Q

gap junctions

A

-allow communication

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27
Q

what do cell membranes also adhere to?

A

-They adhere to the extracellular matrix.
-Transmembrane protein integrin binds to matrix outside epithelial cells and actin filaments inside.
-Binding is noncovalent and reversible.

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28
Q

what is integrin?

A

In animals, this transmembrane protein is integrin, facilitating epithelial cell attachment to the extracellular matrix.

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29
Q

how do cells move within a tissue?why is this important?

A

-Cells move within tissues via integrin binding and reattaching to the extracellular matrix.
-This process is vital for cell movement in developing embryos and cancer cell spread.

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30
Q

what does it mean for a membrane to be selectively permeable

A

-this means some substances can pass through but others can not

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31
Q

passive transport

A

no energy input required (diffusion)

32
Q

active transport

A

-energy required

33
Q

what does the energy for passive transport come from?

A

-came from concentration gradient.
-Signifies a difference in concentration of ions or substances between locations, typically across a membrane.

34
Q

particles in a solution.

A

-they move randomly and at equilibrium they are evenly distributed

35
Q

diffusion

A

-the process of random movement toward equilibrium

36
Q

net movement?

A

-Net movement is directional until equilibrium (from high to low concentration).
-Diffusion is the net movement from regions of higher to lower concentration.

37
Q

what does diffusion rate depend on?

A

-size and mass of the molecules or ions
-temperature of the solution
-density of the solution
-concentration gradient
-area and distance

38
Q

what does surface area or short distances do for diffusion?

A

-larger surface area permits more rapid diffusion
-diffusion works very well over short distances (ex: within a cell)

39
Q

membranes relating to molecular movement

A

-Molecules move across a permeable membrane until concentrations are equal on both sides.
-Diffusion persists across the membrane, yet there’s no net change in concentrations.

40
Q

simple diffusion

A

-small molecules pass through the lipid bilayer
-lipid-soluble molecules can diffuse across the membrane
-electrically charged and polar molecules cannot pass through easily

41
Q

what is osmosis? what are the types?

A

-diffusion of water (depends on the relative concentrations of water molecules)
-isotonic
-hypertonic
-hypotonic

42
Q

isotonic

A

equal solute concentrations

43
Q

hypertonic

A

higher solute concentration

44
Q

hypotonic

A

lower solute concentration

45
Q

if two solutions are separated by membrane that allows water, but not solutes, to pass through:

A

water will diffuse from the region of higher water concentration (hypotonic) to the region of lower water concentration (hypertonic)

46
Q

what happens to animal cells in hypotonic solutions and hypertonic solutions

A

-in hypotonic solutions the cell may burst
-in hypertonic solution the cell will shrink

47
Q

what is turgor pressure?

A

-plant cells with rigid cell walls build up internal pressure that keep more water from entering

48
Q

facilitated diffusion

A

polar and charged molecules diffuse with concentration gradients, but facilitated by protein channels or carriers

49
Q

channel proteins

A

integral membrane proteins that form a tunnel

50
Q

carrier proteins

A

-Membrane proteins bind substances, accelerating their diffusion through the bilayer.
-They transport polar molecules like glucose across membranes bidirectionally.

51
Q

how does glucose go through carrier proteins?

A

-glucose binds to the glucose transporter, causing it to change shape and release the glucose on the other side

52
Q

ion channels

A

-channel proteins with hydrophilic pores
-most are gated: can be closed or open to ion passage

53
Q

when do ion channel gates open?

A

-chemical signal (ligand)
-electrical charge difference (voltage-gated)

54
Q

what is aquaporins?

A

-water can cross membranes through special channels called aquaporins (ions are excluded)
-first identified by injection aquaporin proteins into a frog oocyte

55
Q

what does rate of diffusion depend on?

A

-Depends on concentration gradient and number of carrier proteins in the cell membrane.
-If carriers are fully loaded, diffusion is slow due to saturation.
-Cells requiring abundant energy, such as muscle cells, possess numerous glucose transporters for faster diffusion.

56
Q

define active transport

A

Moves substances against gradients, requiring energy, typically ATP.

57
Q

what are the proteins involved in active transport?

A

-uniporter
-symporter
-antiporter

58
Q

define uniporter. give examples.

A

-moves one substance in one direction

59
Q

define symporter. give examples.

A

-moves two substances in one direction

60
Q

define antiporter. give examples

A

-moves two substances in opposite directions
-EX: the sodium-potassium (Na+ - K+) pump

61
Q

what are the type of active transports?

A

-primary active transport
-secondary active transport

62
Q

define primary active transport. give example

A

-requires direct hydrolysis of ATP
-the sodium-potassium (Na+ - K+) pump

63
Q

define secondary active transport. give example

A

-Energy is sourced from an ion concentration gradient set by primary active transport.
-The Na⁺–K⁺ pump creates a Na⁺ concentration gradient. Some Na⁺ passively diffuses back into the cell, powering glucose transport against its gradient.

64
Q

what is the sodium-potassium pump?

A
  • it is an integral membrane glycoprotein; where it brings two K+ ions into the cell and exports three Na+ ions
65
Q

describe in detail what happens during the sodium-potassium pump.

A

-3 Na⁺ ions and 1 ATP bind to the pump protein.
-ATP hydrolysis yields ADP and phosphorylates a pump protein amino acid.
-Shape change moves 3 Na⁺ ions outside and 2 K⁺ ions inside.
-2 K⁺ ions bind to the pump.
-Dephosphorylation releases the phosphate, leading to 2 K⁺ ions moving inside and returning the pump to its original form.

66
Q

how are larger molecules like macromolecules transported to a cell?

A

-they can be taken in or secreted by means of membrane vesicles

67
Q

define endocytosis

A

-it brings molecules and cells into a eukaryotic cell
-the cell membrane folds inwards, or invaginates, around the material forming a vesicle

68
Q

define phagocytosis

A

-molecules or entire cells are engulfed
-a food vacuole or phagosome forms, which fuses with a lysosome where the contents are digested

69
Q

when is phagocytosis used?

A

-some protists feed in this way
-some white blood cells engulf foreign substances in this way

70
Q

define pinocytosis

A

-a vesicle forms to bring small dissolved substances or fluids into a cell
-vesicles are much smaller than in phagocytosis
-is constant in endothelial (capillary) cells

71
Q

Describe the process of receptor-mediated endocytosis.

A

Receptor-mediated endocytosis is like a targeted delivery system. Special receptor proteins on the cell membrane grab specific molecules. These receptors are coated inside with proteins such as clathrin.

72
Q

define receptor mediated endocytosis

A

Endocytosis initiated by macromolecular binding to a specific membrane receptor.

73
Q

define receptor porteins

A

-integral membrane proteins located at specific sites on the cell membrane
-these sites are also coated with proteins such as clathrin on the inside

74
Q

example of receptor proteins used to transport cholesterol

A

-mammalian cells take in cholesterol by receptor-mediated endocytosis
-in the liver, cholesterol is packaged into low-density lipoprotein, or LDL, and secreted to the bloodstream
-cells that need cholesterol have receptors for the LDLs in clathrin-coated pits

75
Q

define exocytosis

A

-materials packaged in vesicles (like digestive enzymes and neurotransmitters) are secreted from a cell when the vesicle membrane fuses with the cell membrane

-or, the vesicle touches the cell membrane and a pore forms, releasing the vesicle’s contents; no membrane fusion

BIO 101 EXAM 2 (4 decks)

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