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BIO8 - Cell and Molecular Biology > Unit 3. Cell Membrane > Flashcards

Unit 3. Cell Membrane Flashcards

1
Q

T or F
All cells have a cell
membrane.

A

T

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2
Q

2 functions of cell membrane

A

a. Controls what enters
and exits the cell to
maintain an internal
balance called
homeostasis.
b. Provides protection and
support for the cell

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3
Q

Cell membrane contains almost
proteins called

A

Membrane proteins

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4
Q

It is a double layer of
phospholipids

A

lipid bilayer

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5
Q

T or F
Cell membranes have pores (holes) in it.

A

T

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6
Q

Lipid Bilayer contains: (3)

A

a. Phosphate head is polar
• (water loving)
b. Fatty acid tails are non-polar
• (water fearing)
c. Proteins embedded in
membrane

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7
Q

The property of cell membrane to allow some molecules in
and keeps other molecules out.

A

Selective permeability

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8
Q

In 1972, they proposed that the
membrane is a mosaic of proteins dispersed within the
bilayer, with only the hydrophilic regions exposed to
water. (Who at what model is it?)

A

Seymour Jonathan Singer and Garth L. Nicolson
Fluid Mosaic Model

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9
Q

T or F
A molecule always flip-flop
transversely across the membrane

A

F
always —> rarely

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10
Q

T or F
Variations in lipid composition of cell membranes of many species appear to be adaptations to specific environmental conditions

A

T

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11
Q
  • proteins that penetrate the hydrophobic core
  • 70% of Cell membrane proteins part
    and parcel of membrane structure
A

Integral proteins

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12
Q

proteins that are bound to the surface of
the membrane

A

Peripheral proteins

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13
Q

They transfer substances against Concentration/Electrical gradients

A

Pumps

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14
Q

Opened and closed by gates

A

Channel proteins

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15
Q

Involved in transport of substances

A

Carrier Proteins

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16
Q

Takes place in membrane reaction

A

Enzyme proteins

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17
Q

They bear appropriate sites for
recognition of Specific Ligands.

A

Receptor proteins

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18
Q

Which statement/s is/are true about the role of membrane carbohydrates
in cell-cell recognition?

A. Cells recognize each other by binding to surface
molecules, often containing carbohydrates, on
the extracellular surface of the plasma
membrane.
B. Membrane carbohydrates may be covalently
bonded to lipids (forming glycolipids) or more
commonly to proteins (forming glycoproteins)
C. Both statements are true.
D. None

A

C

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19
Q

Receptor and co-receptor where HIV binds.

A

CD4
CCR5

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20
Q

T or F
HIV cannot infect a cell lacking CCR5 on its surface

A

T

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21
Q

Which statement/s is/are true?
A. Hydrophobic (nonpolar) molecules, such
as hydrocarbons, cannot be dissolved in the lipid bilayer, thus, cannot pass through the membrane
• Polar molecules, such as sugars, can cross the membrane easily
C. Both statements are true.
D. None

A

D
- non polar can dissolve and pass through rapidly
- polar molecules cannot cross easily

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22
Q

allow passage of hydrophilic substances across the membrane

A

Transport proteins

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23
Q

have a hydrophilic channel that
certain molecules or ions can use as a tunnel

A

Channel proteins

24
Q

Channel proteins that facilitate
the passage of water

A

aquaporins

25
Q

bind to molecules and change
shape to shuttle them across the membrane

A

Carrier proteins

26
Q

T or F
A transport protein is specific for the
substance it moves.

A

T

27
Q

Example of Active Transport Mechanism

A

Primary Transport
Secondary Transport

28
Q

Example of Passive Transport Mechanisms

A

Simple Diffusion
Facilitated Diffusion
Osmosis
Bulk flow filtration

29
Q

is the tendency for molecules to
spread out evenly into the available space.

A

Diffusion

30
Q

Substances diffuse down their __________, the region along which the density of a
chemical substance increases or decreases.

A

concentration gradient

31
Q

T or F
No work must be done to move substances down
the concentration gradient.

A

T

32
Q

T or F
The diffusion of a substance across a biological membrane is active transport because energy is expended by the cell to make it happen

A

F
- PASSIVE transport
- NO energy is expended

33
Q

Factors that Influence
Diffusion Rates (5)

A

• Distance
• Molecular Size
• Temperature
• Steepness of Concentration Gradient
• Membrane of Surface Area

34
Q

Lipophilic substances can enter cells easily because they diffuse through the lipid portion of the membrane

A

Simple Diffusion

35
Q

■ Membrane channels are transmembrane proteins
■ Used by ions, very small water-soluble compounds
■ Much more complex than simple diffusion.

A

Channel-Mediated Diffusion

36
Q

is the diffusion of water across a
selectively permeable membrane

A

Osmosis

37
Q

is the ability of a surrounding solution to cause a cell to gain or lose water

A

Tonicity

38
Q

Solute concentration is the same as
that inside the cell; no net water movement across the plasma membrane

A

Isotonic

39
Q

Solute concentration is greater
than that inside the cell; cell loses water

A

Hypertonic

40
Q

Solute concentration is less than
that inside the cell; cell gains water

A

Hypotonic

41
Q

A plant cell in a hypotonic solution swells
until the wall opposes uptake; the cell is now _________

A

turgid (firm)

42
Q

If a plant cell and its surroundings are isotonic, there is no net movement of water
into the cell; the cell becomes __________, and the plant may wilt

A

flaccid
(limp)

43
Q

In a hypertonic environment, plant cells
lose water; eventually, the membrane pulls away from the wall, a usually lethal effect called

A

plasmolysis

44
Q

In _______ diffusion, transport
proteins speed the passive movement of molecules across the plasma membrane.

A

Facilitated

45
Q

moves substances
against their concentration gradients and allows cells to maintain
concentration gradients that differ from
their surroundings

A

Active transport

46
Q

T or F
The sodium-potassium pump is one type
of passive transport system.

A

F
passive —-> active

47
Q

is the voltage
difference across a membrane

A

Membrane potential

48
Q

Two combined forces, collectively called
the ___________, drive the
diffusion of ions across a membrane

A

electrochemical gradient

49
Q

is a transport protein that
generates voltage across a membrane

A

electrogenic pump

50
Q

The main electrogenic pump of plants, fungi, and bacteria is a

A

proton pump

51
Q

occurs
when active transport
of a solute indirectly
drives transport of
other solutes.

A

Cotransport

52
Q

Which statement is INCORRECT about the bulk transport across the plasma membrane that occurs by exocytosis and endocytosis?

A. Small molecules and water enter or leave
the cell through the lipid bilayer or via transport proteins
B. Large molecules, such as polysaccharides
and proteins, cross the membrane in bulk via vesicles
C. Bulk transport requires energy
D. None

A

D

53
Q

transport vesicles migrate
to the membrane, fuse with it, and release
their contents
which many secretory cells used to export their products

A

Exocytosis

54
Q

the cell takes in macromolecules by forming vesicles from the plasma membrane

A

Endocytosis

55
Q

Three types of endocytosis

A

– Phagocytosis (“cellular eating”)
– Pinocytosis (“cellular drinking”)
– Receptor-mediated endocytosis

BIO8 - Cell and Molecular Biology (5 decks)

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