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Bio 1305 > Chapter 7 > Flashcards

Chapter 7 Flashcards

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Biology 101 flashcards
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
Q

How do cells recognize each other

A

By binding to surface molecules that often contain carbohydrates on the extra cellular surface of the plasma membrane

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26
Q

What do membrane carbohydrates covalently bonded to lipids form?

A

Glycolipids

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27
Q

What do membrane carbohydrates covalently bonded to proteins form?

A

Glycoproteins

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28
Q

The asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined by what?

A

When the membrane is built by the ER and Golgi apparatus

29
Q

What does it mean for plasma membranes to be selectively permeable?

A

It regulates the cells molecular traffic

30
Q

What can dissolve in the lipid bilayer and pass through the membrane rapidly?

A

Hydrophobic molecules, such as hydrocarbons

31
Q

What cannot cross the membrane easily?

A

Polar molecules, such as sugars

32
Q

Transport proteins

A

These allow the passage of hydrophilic substances across the membrane

33
Q

Aquaporins

A

Channel proteins that facilitate the passage of water

34
Q

Carrier proteins

A

A type of transport protein that binds to molecules and changes shape to shuttle them across the membrane

35
Q

Diffusion

A

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

36
Q

Concentration gradient

A

The region along which the density of a chemical substance increases or decreases

37
Q

Passive transport

A

The diffusion of a substance across a biological membrane that does not expend energy by the cell to make it happen

38
Q

Osmosis

A

The diffusion of water across a selectively permeable membrane

39
Q

What is the order of concentration that water diffuses in?

A

The region of lower solute concentration to the region of higher concentration until it is equal on both sides.

40
Q

Tonicity

A

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

41
Q

Isotonic solution

A

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

42
Q

Hypertonic solution

A

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

43
Q

Hypotonic solution

A

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

44
Q

Osmoregulation

A

The control of solute concentrations and water balance

45
Q

Paramecium

A

A protist which is hypertonic to its pond water environment, has a contractile vacuole that acts as a pump

46
Q

What do cell walls do in terms of water balance

A

It helps maintain water balance

47
Q

What does it mean for a cell to be turgid

A

A plant cell in a hypotonic solution swells until the wall opposes uptake

48
Q

How does a cell become flaccid

A

If a plant cell and its surroundings are isotonic, there is no net movement of water into the cell

49
Q

What is plasmolysis

A

When plant cells lose water in a hypertonic environment, the membrane pulls away from the wall.

50
Q

Facilitated diffusion

A

Transport proteins speed the passive movement of molecules across the plasma membrane

51
Q

Channel proteins include

A

Aquaporins for diffusion of water and ion channels that open or close in response to a stimulus

52
Q

Why is facilitated diffusion still passive

A

Because the solute moves down its concentration gradient, and the transport requires no energy

53
Q

Active transport

A

Moves substances against their concentration gradients

54
Q

What energy does active transport require

A

ATP

55
Q

The sodium potassium pump

A

This is a type of active transport system

56
Q

Membrane potential

A

The voltage difference across a membrane

57
Q

How is voltage created

A

This is created by differences in the distribution of positive and negative ions across a membrane

58
Q

Electrochemical gradient

A

Two combined forces that drive the diffusion of ions across a membrane.

59
Q

Electrogenic pump

A

A transport protein that generates voltage across a membrane

60
Q

What is the major Electrogenic pump in animals

A

The sodium-potassium pump

61
Q

Main Electrogenic pump of plants, fungi, and bacteria

A

A proton pump

62
Q

Exocytosis

A

Transport vesicles migrate to the membrane, fuse with it, and release their contents

63
Q

Endocytosis

A

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

64
Q

There are 3 types of endocytosis

A
  • phagocytosis
  • pinocytosis
  • receptor-mediated endocytosis
65
Q

Phagocytosis

A

A cell engulfs a particle in a vacuole.

66
Q

Pinocytosis

A

Molecules are taken up when extra cellular fluid is “gulped” into tiny vesicles

67
Q

Receptor mediated endocytosis

A

Binding of ligands to receptors triggers vesicle formation

68
Q

Ligand

A

Any molecule that binds specifically to the receptor site of another molecule

Bio 1305 (18 decks)

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