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biol 1334 > Reading 3: Cell Structures > Flashcards

Reading 3: Cell Structures Flashcards

1
Q

Define phospholipid bilayer

A

forms the basic structure of the plasma membrane

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2
Q

What does each phospholipid consist of?

A

a glycerol backbone with two fatty acid tails on one side and a phosphate head group

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3
Q

amphipathic

A

Molecules with both polar an non polar regions

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4
Q

Hydrophilic

A

Polar

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5
Q

Hydrophobic

A

Non-polar

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6
Q

Transmembrane (integral) proteins participate what kind of functions

A

molecular transport, cell adhesion, cell-cell recognition, signal transduction, and enzymatic activity

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7
Q

Plasma membrane protein classifications

A

Transmembrane and peripheral

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8
Q

Where are peripheral proteins located?

A

the edge, or periphery, of the membrane.

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9
Q

Another word for edge

A

periphery

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10
Q

How do peripheral proteins interact with the membrane ?

A

by reversibly interacting with the polar head group of phospholipids, or by permanently embedding into the bilayer using a glycosylphosphatidylinositol (GPI) anchor

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11
Q

How do peripheral protiens function?

A

as accessories in signal transduction, enzymatic activity or cell adhesion processes.

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12
Q

what is the function of cholesterol within the membrane?

A

regulating membrane fluidity

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13
Q

What is the fluid mosaic model?

A

the phospholipids, membrane proteins, and cholesterol molecules are constantly in motion as they maintain the bilayer structure, similar to the movement of sailboats bobbing in the ocean.

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14
Q

transverse migration

A

membrane components spontaneously flip from one side of the bilayer to the other

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15
Q

In the case of transverse migration what enzymes become active?

A

flippase, floppase, and scramblase

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16
Q

Why is transverse migration not ideal?

A

flipping to the other side of the bilayer would cause the polar head group to intermix briefly with the nonpolar fatty acid tails, this movement is thermodynamically unfavorable

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17
Q

What is the basic structure of a plasma membrane?

A

phospholipid bilayer, carbohydrates, and cholesterol

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18
Q

How do membrane components move within the membrane?

A

rotate clockwise or counterclockwise and move laterally from side to side or front to back

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19
Q

What determines membrane fluidity?

A

Temperature, saturation, cholesterol

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20
Q

As temperature rises what happens to the phospholipid?

A

Speeds up the movement of the phospholipid bilayer, and the hydrophobic interactions between the fatty acid tails are disrupted.

21
Q

As temperature rises what happens to the membrane fluidity?

A

membrane fluidity to increase and, thus, weakens the membrane structure

22
Q

As temperature drops what happens to the phospholipid?

A

slows movement of the phospholipid bilayer, enhancing the association between membrane phospholipids.

23
Q

As temperature drops what happens to the membrane fluidity?

A

membrane becomes more rigid

24
Q

Saturated fatty acid tails causes what?

A

a crowding effect minimizes movement and causes a rigid phenotype

25
Q

Unsaturated fatty acid tails causes what?

A

the membrane becomes more fluid due to the “kinked” structure of the tail, which arises from the presence of one or more double bonds.

26
Q

How do cells regulate membrane fluidity?

A

modifying the ratio of saturated to unsaturated phospholipids.

27
Q

what is the main regulator of membrane fluidity

A

cholesterol

28
Q

At standard temperatures, such as body temperature, increased cholesterol causes

A

a reduction in membrane fluidity by packing between the “kinked” fatty acid tail structures of unsaturated phospholipids

29
Q

Low temperatures with increased cholesterol causes

A

cholesterol actually serves as a spacer between phospholipids to prevent solidification of the membrane

30
Q

Define Lipid rafts

A

are localized regions of the plasma membrane that contain a specialized collection of membrane proteins that work together to carry out cellular signaling

31
Q

central dogma of genetics

A

cell types are programmed to express only a particular subset of genes

32
Q

define chromatin

A

DNA’s relaxed, uncoiled organizational state

33
Q

define heterochromatin

A

DNA that is tightly coiled

34
Q

What is the function of heterochromatin?

A

protects genes that are not to be actively used and prevents gene expression

35
Q

define euchromatin

A

DNA in a more relaxed conformation

36
Q

What is the function of euchromatin?

A

permits access to genes for transcription

37
Q

define chromosome

A

condensed supercoiled DNA for the mitotic phase

38
Q

what is the de novo gene expression signal?

A

A signal to make brand new proteins from scratch

39
Q

transcription factors

A

Proteins that bind to promoters and initiate RNA transcription

40
Q

promoter regions

A

initiating site for RNA transcription

41
Q

the transcription process

A

activate transcription factors, bind to specific promoter regions

42
Q

pre-mRNA transcript contains

A

a combination of introns and exons

43
Q

Introns

A

non coding regions of the genome

44
Q

alternative splicing

A

certain exons are retained and others are spliced out

45
Q

How can we protect the mRNA from degradation

A

add a 5’ cap, and polyadenylation

46
Q

What is the process of polyadenylation

A

adds ~100-200 adenine (A) nucleotides to its 3’ end

47
Q

poly-A tail

A

3’ end

48
Q

Why do we want to slow enzymatic degradation of the mRNA transcript

A

allowing sufficient time for protein translation before the mRNA degrades.

biol 1334 (12 decks)

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