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Bio 1305 > Chapter 7 > Flashcards

Chapter 7 Flashcards

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1
Q

What is the plasma membrane

A

the boundary that separates the living cell from its surroundings.

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2
Q

Selective permeability

A

Allowing some substances to cross it more easily than others

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3
Q

What do cellular membranes have mosaics of?

A

Lipids and proteins

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4
Q

What are phospholipids

A

they are the most abundant lipid in the plasma membrane
A.) they are amphipathic molecules, containing hydrophobic and hydrophilic regions.

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5
Q

What does the fluid mosaic model say

A

It says that a membrane is a fluid structure with a mosaic of various proteins embedded in it

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6
Q

What are membranes made of

A

Membranes are made of proteins and lipids

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7
Q

Scientists studying the plasma membrane reasoned that it must be a _______

A

Phospholipid bilayer

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8
Q

In 1935, Hugh Davison and James Danielle proposed a _____ in which ____

A

Sandwhich model
It says that the phospholipid bilayer lies between two layers of globular proteins.

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9
Q

What are the two regions of the placement of membrane proteins?

A

Hydrophilic and Hydrophobic

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10
Q

In 1972, S. J. Singer and G. Nicholson proposed that _______

A

The membrane is a mosaic of proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water.

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11
Q

What is freeze-fracture?

A

A preparation technique that splits a membrane along the middle of the phospholipid bilayer

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12
Q

Phospholipids in the plasma membrane can move within the ____

A

Bilayer

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13
Q

Lipids and some proteins drift___

A

Laterally

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14
Q

What happens to membranes as temperatures cool?

A

They switch form a fluid state to a solid state

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15
Q

The temperature at which a membrane solidifies depends on _____

A

The types of lipids

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16
Q

Which membranes are more fluid?

A

Membranes that are rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids.

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17
Q

What is an example for how fluid membranes are?

A

salad oil

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18
Q

How does cholesterol effect membrane fluidity in different temperatures?

A

At warm temps, cholesterol restrains movement of phospholipids
At cool temperatures, it maintains fluidity by preventing tight packing

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19
Q

How has ability to change the lipid compositions in response to temperature changes evolved?

A

It has evolved in organisms that live where temperatures vary

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20
Q

Peripheral proteins

A

These are bound to the surface of the membrane

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21
Q

Integral proteins

A

Penetrate the hydrophobic core

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22
Q

Transmembrane proteins

A

These are integral proteins that span the membrane.

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23
Q

What do the hydrophobic regions of an integral protein consist of?

A

One ore more stretches of non polar amino acids, usually coiled into alpha helices.

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24
Q

Six major functions of membrane proteins

A
  • transport
  • enzymatic activity
  • signal transduction
  • cell-cell recognition
  • intercellular joining
  • attachment to the cytoskeleton and extra cellular matrix
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25
How do cells recognize each other
By binding to surface molecules that often contain carbohydrates on the extra cellular surface of the plasma membrane
26
What do membrane carbohydrates covalently bonded to lipids form?
Glycolipids
27
What do membrane carbohydrates covalently bonded to proteins form?
Glycoproteins
28
The asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined by what?
When the membrane is built by the ER and Golgi apparatus
29
What does it mean for plasma membranes to be selectively permeable?
It regulates the cells molecular traffic
30
What can dissolve in the lipid bilayer and pass through the membrane rapidly?
Hydrophobic molecules, such as hydrocarbons
31
What cannot cross the membrane easily?
Polar molecules, such as sugars
32
Transport proteins
These allow the passage of hydrophilic substances across the membrane
33
Aquaporins
Channel proteins that facilitate the passage of water
34
Carrier proteins
A type of transport protein that binds to molecules and changes shape to shuttle them across the membrane
35
Diffusion
This is the tendency for molecules to spread out evenly into the available space
36
Concentration gradient
The region along which the density of a chemical substance increases or decreases
37
Passive transport
The diffusion of a substance across a biological membrane that does not expend energy by the cell to make it happen
38
Osmosis
The diffusion of water across a selectively permeable membrane
39
What is the order of concentration that water diffuses in?
The region of lower solute concentration to the region of higher concentration until it is equal on both sides.
40
Tonicity
This is the ability of a surrounding solution to cause a cell to gain or lose water
41
Isotonic solution
Solute concentration is the same as that inside the cell — no net water movement across the plasma membrane
42
Hypertonic solution
Solute concentration is greater than that inside the cell — cell loses water
43
Hypotonic solution
Solute concentration is less than that inside the cell — cell gains water
44
Osmoregulation
The control of solute concentrations and water balance
45
Paramecium
A protist which is hypertonic to its pond water environment, has a contractile vacuole that acts as a pump
46
What do cell walls do in terms of water balance
It helps maintain water balance
47
What does it mean for a cell to be turgid
A plant cell in a hypotonic solution swells until the wall opposes uptake
48
How does a cell become flaccid
If a plant cell and its surroundings are isotonic, there is no net movement of water into the cell
49
What is plasmolysis
When plant cells lose water in a hypertonic environment, the membrane pulls away from the wall.
50
Facilitated diffusion
Transport proteins speed the passive movement of molecules across the plasma membrane
51
Channel proteins include
Aquaporins for diffusion of water and ion channels that open or close in response to a stimulus
52
Why is facilitated diffusion still passive
Because the solute moves down its concentration gradient, and the transport requires no energy
53
Active transport
Moves substances against their concentration gradients
54
What energy does active transport require
ATP
55
The sodium potassium pump
This is a type of active transport system
56
Membrane potential
The voltage difference across a membrane
57
How is voltage created
This is created by differences in the distribution of positive and negative ions across a membrane
58
Electrochemical gradient
Two combined forces that drive the diffusion of ions across a membrane.
59
Electrogenic pump
A transport protein that generates voltage across a membrane
60
What is the major Electrogenic pump in animals
The sodium-potassium pump
61
Main Electrogenic pump of plants, fungi, and bacteria
A proton pump
62
Exocytosis
Transport vesicles migrate to the membrane, fuse with it, and release their contents
63
Endocytosis
The cell takes in macromolecules by forming vesicles from the plasma membrane
64
There are 3 types of endocytosis
- phagocytosis - pinocytosis - receptor-mediated endocytosis
65
Phagocytosis
A cell engulfs a particle in a vacuole.
66
Pinocytosis
Molecules are taken up when extra cellular fluid is “gulped” into tiny vesicles
67
Receptor mediated endocytosis
Binding of ligands to receptors triggers vesicle formation
68
Ligand
Any molecule that binds specifically to the receptor site of another molecule

Bio 1305 (18 decks)

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