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BIO107- CELL AND MOLECULAR BIOLOGY > LESSON 2a: CELL MEMBRANE STRUCTURE > Flashcards

LESSON 2a: CELL MEMBRANE STRUCTURE Flashcards

1
Q

-Gateway of the cell
-Acts as boundary
-Controls what enters and exits the cell
-regulate chemical composition
-Maintains homeostasis

A

Cell Membrane

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2
Q

The cell membrane
is _______ and
allows a
unicellular
organism to
move

A

flexible

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3
Q

Studies of the_______________ provided the first evidence that biological membranes consist of lipid bilayers

A

red blood cell plasma
membrane

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4
Q

Plasma Membrane models

A
  1. Sandwich Model
  2. Unit Membrane Model
  3. Fluid-Mosaic Model
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5
Q

-2 layers of globular proteins with phospholipid inside to make a layer
and then join 2 layers together to make a channel for molecules to pass

A

Sandwich Model

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6
Q

Proponent of Sandwich Model

A

Danielli and Davson

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7
Q

-Outer layer of protein with phospholipid bilayer inside,
-believed all cells same composition,
-does not explain how some molecules pass through or the use of
proteins with nonpolar parts
-used transmission electron microscopy

A

Unit Membrane Model

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8
Q

Proponent of Unit Membrane Model

A

Robertson

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9
Q

Phospholipid bilayer with proteins partially or fully imbedded, electron
micrographs of freeze-fractured membrane

A

Fluid Mosaic Model

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10
Q

Proponent of Fluid Mosaic Model

A

Singer and Nicolson

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11
Q

How did they examine the plasma membrane under SEM?

A

1) Rapidly freeze specimen
2) Use special knife to cut membrane in half
3) Apply a carbon + platinum coating to the surface
4) Use scanning electron microscope to see the surface

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12
Q

According to the electron micrograph which membrane model is
correct?

A

Fluid-Mosaic Model

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13
Q

The lipids in a membrane are organized into a _____________

A

liquid crystalline lattice.

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14
Q

The lattice becomes a _____________ at
the transition temperature

A

frozen crystalline gel

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15
Q

The Plasma Membrane is composed of two layers of lipids. Why is this important?

A

This allows the membrane to repel too much water around it to prevent the cell to burst.

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16
Q

-plasma membrane has consistency of olive oil at body temperature,
due to unsaturated phospholipids.
-phospholipids and proteins move around freely within the layer, like it’s a
liquid

A

Fluid

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17
Q

plasma membrane has consistency of olive oil at body temperature,
due to ______________

A

unsaturated phospholipids

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18
Q

– proteins form a collage that differs on either side of membrane
and from cell to cell (greater than 50 types of proteins)
-proteins span the membrane with hydrophilic portions facing out and
hydrophobic portions facing in.
-mosaic pattern produced by scattered protein molecules when membrane
is viewed from above.

A

Mosaic

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19
Q

Hydrocarbons are tightly packed

A

Gel phase- Low temperature

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20
Q

Bilayer “Melts”, movement is allowed

A

Higher temperature-moves to fluid state

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21
Q

Formation of sphere is _____________

A

energetically favorable

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22
Q

a harsh ionic detergent

A

SDS

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23
Q

a gentler non-ionic detergent, are
commonly used solubilizing agents

A

Triton X-100

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24
Q

A Scheme to Study a
Membrane Protein

A

-Solubilization,
-Purification, and
-Reconstitution in Liposomes

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25
Q

Membrane Proteins Can Be
Solubilized by _________ That
Disrupt the Membrane

A

Detergents

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26
Q

*Most of the lipids and some proteins drift _________ on either
side.

A

laterally

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27
Q

Phospholipids _________ switch from one layer to the next.

A

do not

28
Q

The lipids and proteins in the cell membrane are not fixed in position but _________ moving

A

constantly

29
Q

The ________ move laterally within the cell membrane –lateral diffusion

A

proteins

30
Q

While the ______ can move both laterally and rotate 360 degrees – flip-flop diffusion

A

lipids

31
Q

Cholesterol Affects fluidity: At Body Temp

A
  • it lessens fluidity by restraining the movement of phospholipids;
    -also reduce permeability to small mol
32
Q

Cholesterol Affects fluidity: colder temp

A

maintains fluidity by not allowing
phospholipids to pack close together.

33
Q

The Planar Rings of Cholesterol Make
the Membrane More _____, ___________, and ___________

A

-Rigid
-Less Permeable
-Resistant to Low Temperature Crystalization

34
Q

Major component of animal cell

A

Cholesterol

35
Q

Cholesterol is not found in _________, how ever it has ______ that perform the same function.

A

-Plant Membrane
-Sterols

36
Q

Cholesterol has same molar amounts as _____________

A

Phospholipids

37
Q

Heat produces motion of acyl side chains this resulted to change from solid to ___________ transition.

A

Fluid

38
Q

By change in solid to fluid state, ________ in the plane bilayer is made possible

A

Lateral Diffusion

39
Q

Classification of Membrane Proteins

A

-Peripheral Proteins
-Integral Proteins
-Transmembrane Proteins

40
Q

are proteins that dissociate
from the membrane following
treatments with polar
reagents that do not disrupt
the phospholipid bilayer.

A

Peripheral membrane proteins

41
Q

can be released only by
treatments that disrupt the
phospholipid bilayer.

A

Integral membrane proteins

42
Q

span the lipid bilayer with
portions exposed on both
sides of the membrane

A

Transmembrane proteins

43
Q

Types of Membrane Proteins

A
  1. Transport Proteins (Channel and Carrier)
  2. Cell Recognition Protein
  3. Receptor Protein
  4. Enzymatic Protein
  5. Intercellular Junction Proteins
  6. Attachment Proteins
44
Q

-channel for lipid
insoluble molecules
and ions to pass freely
through

A

Channel Protein

45
Q

An inherited disorder that is caused by faulty Cl- channel creating a collection of thick mucus in the airways and in pancreatic and liver ducts

A

Cystic Fibrosis

46
Q

– bind
to a substance and
carry it across
membrane, change
shape in process

A

Carrier Proteins

47
Q

The inability of some persons to use energy for ___________ has been suggested as the cause of their obesity.

A

Sodium-Potassium Transport

48
Q

Bind to chemical
messengers (Ex.
hormones) which
sends a message into
the cell causing
cellular reaction

A

Receptor Proteins

49
Q

Some types of _____ result not because the body does not produce enough growth hormone but because the plasma membrane growth hormone receptor is faulty.

A

Dwarfism

50
Q

Carry out enzymatic
reactions right at the
membrane when a
substrate binds to the
active site

A

Enzymatic Proteins

51
Q

____________ releases toxin that interferes with the proper functioning of adenylate cyclase which is involved in ATP metabolism resulting to severe diarrhea.

A

Cholera Bacteria

52
Q

Glycoproteins (and
glycolipids) on
extracellular surface
serve as ID tags
(which species, type of
cell, individual).
Carbohydrates are
short branched chains
of less than 15 sugars

A

Cell Recognition Proteins

53
Q

The ______________ are different for each person, so organ transplant are difficult to achieve. When this is introduced and considered foreign the WBC (responsible for immunity) attacked it .

A

MHC (Major Histocompatibility Complex) Glycoproteins

54
Q

Attach to cytoskeleton (to
maintain cell shape and stabilize
proteins) and/or the extracellular
matrix (integrins connect to
both)

A

Attachment Proteins

55
Q

– protein fibers and carbohydrates
secreted by cells and fills the
spaces between cells and
supports cells in a tissue.
-can influence activity inside the cell
and coordinate the behavior of
all the cells in a tissue

A

Extracellular Matrix

56
Q

Bind cells together

A

Intercellular Junction Proteins

57
Q

Types of Cell Junctions

A
  1. Tight Junctions
  2. Desmosomes
  3. Gap Junctions
58
Q
  • Transmembrane Proteins of opposite cells attach in a tight zipper-like
    fashion
  • No intercellular space, No leakage Ex. Intestine, Kidneys, Epithelium of skin
    -bar the movement of dissolved materials from the lumen through space between epithelial cells.
A

Tight Junctions

59
Q

Long rows of tight junction protein form a ___________.

A

Complex meshwork

60
Q
  • Cytoplasmic plaques of two cells bind with the aid of
    intermediate filaments of keratin
  • Allows for stretching
  • Ex. Stomach, Bladder, Heart
A

Desmosomes

61
Q
  • Channel proteins of opposite cells join together providing
    channels for ions, sugars, amino acids, and other small
    molecules to pass.
  • Allows communication between cells.
  • Ex. Heart muscle, animal embryos
A

Gap Junctions

62
Q

Example of Mobility of Membrane Proteins

A
  1. The fusion of human cell and animal cell.
  2. After 40 minutes of incubation, the human and mouse protein spread out forming uniform distribution and no separation.
63
Q

Many Membrane Proteins
Move _____ in the Plane
of the Membrane

A

Freely

64
Q

________ membrane proteins
have this freedom of
motion

A

Not all

65
Q

Can Establish
the Rate of Membrane Component Movement

A

Fluorescence Recovery After Photobleaching (FRAP)

BIO107- CELL AND MOLECULAR BIOLOGY (13 decks)

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