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Biology > Chapter 5 - Plasma Membranes > Flashcards

Chapter 5 - Plasma Membranes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define compartmentalisation

A

The formation of separate membrane -bound organelles

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2
Q

Why are phospholipids suited as membranes?

A

Because their hydrophilic heads can interact with water

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3
Q

What does the fluid-mosaic model show?

A

That the phospholipids are free to move within the layer relative to each other

Membrane is flexible

Because proteins embedded in the bilayer vary in shape, size and position

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4
Q

What are intrinsic proteins?

A

Transmembrane proteins that are embedded through both layers of a membrane

Have aa w hydrophobic R-groups on external surfaces which interact w the hydrophobic core of the membrane

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5
Q

Give 4 examples of intrinsic proteins

A

Channel proteins
carrier proteins
glycoproteins
glycolipids

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6
Q

Why do we need compartmentalisation?

A

Because the metabolic reactions require different conditions (e.g. chemical gradients to be maintained)

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7
Q

Describe the function of a channel protein?

A

To provide a hydrophilic channel that allows the passive movement of polar mol. and ions down a concentration gradient through membranes

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8
Q

How are channel proteins held together?

A

Through the interactions between the hydrophobic core of membrane and hydrophilic R-groups on outside

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9
Q

What is the role of a carrier protein?

A

Helps in the passive transport (down conc grad) and active transport (against conc) into cells

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10
Q

Where are glycoproteins found?

A

Embedded in the cell surface membrane w attached carbohydrate chains of varying length and shape

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11
Q

What role do glycoproteins have?

A

Cell adhesion and act as receptors for chemical signals

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12
Q

How do glycoproteins help with cell signals?

A

When the chemical binds to the receptor it creates a response from the cell

Either direct response or set of a cascade of events

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13
Q

Give examples of when cell signalling is used with glycoproteins

A

Receptors for neurotransmitters at nerve synapses

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14
Q

Which protein can be both intrinsic and extrinsic?

A

Glycolipids

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15
Q

What is the difference between glycolipids and glycoproteins?

A

Glycolipids are lipids with carbohydrate attached whereas glycoprotein is a protein

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16
Q

What is the function of a glycolipid?

A

To act as cell markers or antigens, can be recognised by immune system as self

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17
Q

What are extrinsic proteins?

A

Present in one side of the bilayer

Normally have hydrophilic R-groups on their outer surfaces and interact w polar heads of phospholipids or intrinsic proteins

18
Q

What is the function of cholesterol?

A

To regulate the fluidity of the membrane

Positioned between hydrophobic heads and interacts

19
Q

What is the effect of an increase in temperature on the phospholipid membrane?

A
  1. Increase in temp = more KE
  2. Each phospholipid moves more
  3. Membrane becomes more fluid
  4. Begins to lose its structure as the pplds move further away from each other
  5. loss of structure increases the permeability of the mem, so easier for particles to cross it

Channel and carrier proteins in mem will be denatured at high temp

20
Q

What type of molecule can disrupt the bilayer?

A

Anything non-polar

21
Q

How does alcohol affect the bilayer?

A

The presents of the alcohol molecule disrupts the structure of the bilayer, the individual phospholipids are further apart

More fluid and more permeable

22
Q

Define diffusion

A

The net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient

23
Q

Is diffusion active or passive?

A

Passive

24
Q

Suggest and explain two factors affecting diffusion

A
  1. Temperature
    - higher temp, particles have more KE, move at higher speed, frequency of successful collisions increases
  2. Concentration difference
    - The higher, the faster rate of diffusion bc the overall movement is larger
25
Q

What molecules is the membrane permeable to? and why

A

non-polar molecules e.g. O2

Polar molecules will repel with the hydrophobic interior
Small polar molecules can pass (e.g. water)

26
Q

What factors affect diffusion across a membrane?

A

Surface area

Thickness of membrane

27
Q

What is facilitated diffusion?

A

Diffusion across a membrane through protein channels down a conc gradient

When a mem is selectively permeable the membrane has protein channels which are specific to one mol or ion (or protein channel)

28
Q

What are the factors which affect facilitated diffusion?

A

Temperature
Conc gradient
Mem SA and thickeness
number of channel proteins present

29
Q

Describe the process of active transport

A
  1. The molecule or ion to be transported binds to receptors in channel of the carrier protein on the outside of the cell
  2. On the inside of the cell ATP binds to the carrier protein and is hydrolysed into ADP and phosphate
  3. The binding of the phosphate molecule to the carrier protein causes the carrier protein to change shape (opening up to the inside of the cell)
  4. The molecule or ion is released to the inside of the cell
  5. The phosphate molecule is released from the carrier protein and recombines with ADP –> ATP
  6. The carrier protein returns to its OG shape
    - Process is selective (only specific proteins are transported)
30
Q

What is bulk transport?

A

A form of active transport where large molecules are moved into or out of the cell by endocytosis or exocytosis

31
Q

What is endocytosis and name the two types

A

Bulk transport of material into cells

Phagocytosis - solids
Pinocytosis - Liquid

32
Q

Describe the process of endocytosis

A
  1. Cell surface membrane invaginates when it comes into contact with the material to be transported
  2. Membrane enfolds the material until the membrane fuses forming a vesicle
  3. Vesicle pinches off and moves into the cytoplasm via the cytoskeleton
33
Q

Describe the process of exocytosis

A

The vesicles usually formed by the Golgi Apparatus move towards and fuse w the cell surface membrane

The microtubules allow the vesicles to move

Contents released

34
Q

What is necessary for endo and exocytosis?

A

Energy in form or ATP to move vesicles along the cytoskeleton, changing shape to engulf materials

35
Q

What is water potential?

A

The pressure exerted by water molecules as they collide with a membrane or container

Measured in Pa

36
Q

What is the water potential of pure water?

A

0kPa

37
Q

What is the hydrostatic pressure?

A

The pressure created by osmosis in an enclosed system

38
Q

What is cytolysis?

A

The bursting of an animal cell caused by increasing hydrostatic pressure as water enters by osmosis

39
Q

How do animals control that not all of their water is diffused out?

A

Blood, an isotonic solution (cells surrounded by aqueous solutions with an equal water potential)

40
Q

What is turgor?

A

The pressure exerted by the cell surface membrane against the cell wall in plants

41
Q

What happens in plasmolysis?

A

The contents of the plant cell shrink because of a lower water potential outside the cell

42
Q

Explain the difference between isotonic, hypertonic and hypotonic

A

Isotonic = no net water movement ( water potential is the same inside and out)

Hypertonic = water flow out of cell ( lower wp outside than inside)

Hypotonic = flow water into cell (higher wp outside than in)

Biology (15 decks)

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