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CCEA AS Biology Units 1, 2 And 3 > (U1) Cell Physiology > Flashcards

(U1) Cell Physiology Flashcards

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1
Q

What is simple diffusion? (2)

A
  • The net movement of a substance
  • down the concentration gradient
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2
Q

What factors affect simple diffusion and how? (5)

A
  • concentration gradient: greater = faster diffusion
  • size of molecule: smaller = faster diffusion
  • temperature: higher = quicker (more kinetic energy)
  • thickness of exchange surface: thinner = faster diffusion
  • surface area of membrane: greater SA = faster diffusion
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3
Q

What proteins are involved in facilitated diffusion? (2)

A
  • carrier proteins
  • channel proteins
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4
Q

How do carrier proteins facilitate diffusion? (3)

A
  • take in the polar diffusing molecule
  • change shape due to specific receptor sites bonding to the molecule
  • release molecules on the other side
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5
Q

How do channel proteins facilitate diffusion? (3)

A
  • central pore allows polar molecules to pass through e.g. ions
  • some permanently open, others gated
  • gated channels open or close to control movement
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6
Q

What factor affects the rate of facilitated diffusion that doesn’t affect simple diffusion?

A

Number of channel or carrier proteins

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7
Q

Why does a graph showing increasing concentration and rate of uptake of a membrane for facilitated diffusion level off?

A

Lack of availability of carrier / channel proteins —> saturated membrane

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8
Q

What is active transport? (2)

A
  • net movement of substances against the concentration gradient
  • requiring ATP
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9
Q

What are the differences between active transport and facilitated diffusion? (2)

A
  • AT: substances moved against concentration gradient, FD opposite
  • AT requires ATP, FD does not
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10
Q

What does cytosis transport? (2)

A
  • large molecules too big for carrier proteins
  • bulk transport of smaller molecules e.g. water
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11
Q

What is endocytosis?

A

Movement of substances into the cell

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12
Q

Outline endocytosis (3)

A
  • cell membrane invaginates around substance entering cell
  • forming a vesicle which pinches off inside the membrane
  • membrane reforms
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13
Q

What are the 2 types of endocytosis?

Describe both

A
  • Phagocytosis: transport of solid material into cell e.g. engulfing bacteria by phagocytes
  • pinocytosis: transport of fluid into cell
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14
Q

What is exocytosis?

Describe it

A
  1. Movement of substances out of the cell
    • secretory vesicles fuse with cell surface membrane
    • contents of vesicle released outside cell
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15
Q

State the equation linking solute potential, water potential and pressure potential

A

Ψcell = Ψs + Ψp

Water potential of cell = solute potential + pressure potential

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16
Q

What is osmosis? (4)

A
  • net movement of water molecules
  • through a selectively permeable membrane
  • from a solution of less negative water potential / higher water potential
  • to a solution of more negative water potential / lower water potential
17
Q

What is the name of channel proteins that allow water through?

A

Aquaporins

18
Q

What is the difference between hypotonic and hypertonic solutions?

A
  • hypotonic = more water, hypertonic = less water
  • hypotonic = lower solute potential, hypertonic = higher solute potential
19
Q

What name is given to 2 solutions of equal concentration / water potential

A

Isotonic solutions

20
Q

What is water potential? (3)

A
  • tendency to take in water by osmosis
  • from pure water
  • across a selectively permeable membrane
21
Q

What unit is water potential measured in?

A

KPa (kilopascals)

22
Q

What the water potential of pure water?

Why?

A
  • 0 kPa
  • no water molecules form associations with other molecules
23
Q

What do molecules of water form around solutes?

A

Hydration shells (largely made up of hydrogen bonds)

24
Q

What is the impact of greater concentration on water potential?

What does this cause?

A
  • More negative water potential
  • cell is more likely to take in water by osmosis
25
Q

What is solute potential? (2)

A
  • potential of a solution to take in water by osmosis
  • relates to solute concentration
26
Q

What factor affects water potential, but doesn’t affect solute potential?

A

Space in a cell which alters pressure potential —> turgid cell means lower water potential

27
Q

What is pressure potential? (2)

What values can it have?

A

1.

  • the effect of pressure on the solution
  • influences the ability of a cell to take in water
  1. +ve kPa, but can be 0kPa
28
Q

What structure exerts pressure potential in a plant cell?

A

Cell wall

29
Q

What is turgor? (2)

A
  • The force exerted by the cell membrane on a cell wall
  • by having a full vacuole
30
Q

When are plant cells described as being flaccid? (2)

On a large scale what does this cause?

A
    • when cells lack turgor pressure due to not having a full vacuole,
    • therefore the cell membrane doesn’t press against the cell wall
  2. Wilting
31
Q

What is plasmolysis? (3)

A
  • vacuole loses water by osmosis
  • shrinks the contents of the cell
  • pulls membrane from the cell wall
32
Q

What is incipient plasmolysis? (2)

A
  • the point at which a plasmolysed cell membrane first makes contact with the cell wall
  • or the last time a flaccid cell has its membrane touch its cell wall
33
Q

What is the effect of increasing water potential outside a cell on:

  • Ψcell
  • Ψp
  • Ψs

Inside a cell
(2)

(until incipient plasmolysis)

A
  • as cell takes in water, contents become less concentrated, Ψs rises
  • No Ψp to restrict water uptake as cell wall isn’t in contact with cell membrane, therefore Ψs = Ψcell (both rise together)
34
Q

What is the effect of increasing water potential outside a cell on:

  • Ψcell
  • Ψp
  • Ψs

Inside a cell
(2)

(at incipient plasmolysis)

A
  • Ψp becomes positive and starts to hinder water entering the cell
  • therefore Ψcell and Ψs diverge —> graphs don’t increase together
35
Q

What is the effect of increasing water potential outside a cell on:

  • Ψcell
  • Ψp
  • Ψs

Inside a cell
(3)

(at full turgor)

A
  • max Ψp between cell membrane and cell wall
  • Ψcell = 0 —> no further water can enter
  • Ψs is still negative as solutes are still present in the cell

CCEA AS Biology Units 1, 2 And 3 (15 decks)

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