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Cell and Molecular Biology > 5 > Flashcards

5 Flashcards

1
Q

Gateway to the Cell

A

CELL MEMBRANE

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2
Q
  • Acts as a boundary
  • Controls what enters and leaves cell
  • Regulates chemical composition
  • Maintains homeostasis
A

CELL MEMBRANE

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3
Q

The ________
is flexible and
allows a
unicellular
organism to
move

A

cell membrane

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4
Q

Studies of the red blood cell plasma
membrane provided the ________ that
biological membranes consist of lipid
bilayers.

A

first evidence

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5
Q

Plasma Membrane Models

A
  1. Sandwich Model (Danielli + Davson)
  2. Unit Membrane Model (Robertson)
  3. Fluid Mosaic Model (Singer + Nicolson)
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6
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 (Danielli + 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 ( Robertson)

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8
Q

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

A

Fluid Mosaic Model
(Singer + Nicolson)

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9
Q

Which membrane model is correct?

A

Fluid-Mosaic Model

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10
Q

Basic paradigm of biological membrane structure

A

Fluid-Mosaic Model

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11
Q

According to the electron micrograph which membrane model is
correct?

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

The lipids in a membrane are organized into a
__________.

A

liquid crystalline lattice

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13
Q

The lattice becomes a _______ at
the transition temperature.

A

frozen crystalline gel

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14
Q

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

A

Having lipids in the plasma membrane means that at least a portion of
the membrane repels the water that constantly surrounds it. Allowing
too much water inside the cell could cause the cell to burst.

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15
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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16
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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17
Q

gel phase–low temperatures

A

hydrocarbons are tightly packed

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18
Q

at higher temperature

A

it moves to fluid phase

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19
Q

at higher temperature –> it moves to fluid phase

A

bilayer “melts”, movement is allowed

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20
Q

Formation of sphere is ________

A

energetically favorable

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21
Q

planar phospholipid bilayer with edges exposed to water

A

energetically unfavorable

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22
Q

sealed compartment formed by phospholipid bilayer

A

energetically favorable

23
Q

Planar Lipid Bilayers
Spontaneously Form
________

A

Vesicles

24
Q

Small tears in
membranes are
_______ this way.

A

repaired

25
Q

are commonly used solubilizing agents.

A
  1. SDS, a harsh ionic detergent
  2. Triton X-100, a gentler non-ionic detergent
26
Q

Membrane
Proteins Can Be
_______ by
Detergents That
Disrupt the
Membrane

A

Solubilized

27
Q

A Scheme to Study a
Membrane Protein –
___________

A

Solubilization,
Purification, and
Reconstitution in
Liposomes

28
Q

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

A

laterally

29
Q

Phospholipids ________ from one layer to the next

A

do not switch

30
Q

The lipids and proteins in the cell membrane are _______
in position but constantly moving.

A

not fixed

31
Q

The proteins move ______within the cell membrane –
lateral diffusion

A

laterally

32
Q

the lipids can move both laterally and rotate 360
degrees – ________

A

flip-flop diffusion

33
Q

Cholesterol affects fluidity:
* at body temperature

A

it lessens fluidity by restraining the movement
of phospholipids; also reduce permeability to small mol

34
Q

Cholesterol affects fluidity:
* at colder temperature

A

it maintains fluidity by not allowing
phospholipids to pack close together

35
Q

The Planar Rings of Cholesterol Make the Membrane ___

A

More Rigid
Less Permeable
Resistant to Low Temperature Crystalization

36
Q

*Major membrane component in
animal cells
*Cholesterol is not found in plant
membranes
-Sterols perform the same function
*Same molar amounts as
phospholipids

A

Cholesterol

37
Q

THE MEMBRANE PROTEINS CLASSIFICATION:

A
  1. Peripheral membrane proteins
  2. Integral membrane proteins
  3. Transmembrane proteins
38
Q

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

A

Peripheral membrane proteins

39
Q

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

A

Integral membrane proteins

40
Q

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

A

Transmembrane proteins

41
Q

Transport Proteins

A

Channel Proteins
Carrier Proteins

42
Q

channel for lipid
insoluble molecules
and ions to pass freely
through

A

Channel Proteins

43
Q

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

A

Carrier Proteins

44
Q

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

A

Receptor Proteins

45
Q

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

A

Enzymatic Proteins

46
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

47
Q

Attach to cytoskeleton (to
maintain cell shape and stabilize
proteins) and/or the extracellular
matrix (integrins connect to
both).
- Extracellular Matrix – protein
fibers and carbohydrates
secreted by cells and fills the
spaces between cells and
supports cells in a tissue.
- Extracellular matrix can
influence activity inside the cell
and coordinate the behavior of
all the cells in a tissue.

A

Attachment Proteins

48
Q

protein
fibers and carbohydrates
secreted by cells and fills the
spaces between cells and
supports cells in a tissue.

A

Extracellular Matrix

49
Q

Intercellular Junction Proteins

A

– Bind cells together
–Tight junctions
–Gap junctions

50
Q

Types of Cell Junctions

A

Tight Junctions
Desmosomes
Gap Junctions

51
Q
  • Transmembrane Proteins of opposite cells attach in a tight zipper-like
    fashion
  • No leakage Ex. Intestine, Kidneys, Epithelium of skin
A

Tight Junctions

52
Q

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

A

Desmosomes

53
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

Cell and Molecular Biology (10 decks)

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