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Biology A Level > 3.2.3 Transport Across Membranes > Flashcards

3.2.3 Transport Across Membranes Flashcards

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1
Q

Functions of cell membranes?

A

Define the boundary of the call
Control in and out of substances in the cell
Plays a role in cell recognition
Allows cell to change shape
Helps cells stick together
Provides receptor sites for hormones and enzymes

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2
Q

Function of internal membranes?

A

Compartmentalisation: isolating organelles from the rest of the cytoplasm allowing cellular processes to occur separately

A site for biochemical reactions

Controls which substances go in and out of

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3
Q

What are the main molecular components of a membrane?

A

Phospholipids
Proteins
Glycoproteins
Glycolipids
Cholesterol

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4
Q

What does the fluid mosaic mean?

A

Fluid: individual phospholipids and move laterally and change places with each other

Mosaic: when seen from above the membrane is like a mosaic of phospholipids with proteins of different shapes and sizes embedded in it

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5
Q

What organelles have a double membrane?

A

Mitochondria and nucleus

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6
Q

In terms of transport what are the 2 types?

A

Passive- no energy needed

Active- energy needed using ATP

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7
Q

What are the 5 ways substances can cross a membrane and is it passive or active ?

A

Passive:
Diffusion- simple
Diffusion - facilitated
Osmosis

Active:
Active transport and Co-transport

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8
Q

Explain simple diffusion

A

High conc—> low conc

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9
Q

What is NET movement?

A

Overall/total particles mived

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10
Q

What is Ficks law?

A

Rate Of Diffusion=
Surface Area x Difference in conc.
•/•
Thickness Of Exchange Surface

(ROD= SAD •/• TOES)

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11
Q

What affects Ficks law?

A

SA- increase in SA means faster rate
Diffrence in conc-greater the difference the faster the rate
Thickness- the thicker the slower the rate

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12
Q

What affects rate of diffusion?

A

Temp-inc means inc in rate
Conc gradient- inc means inc in rate
Stirring- inc in rate
SA- larger SA=inc in rate
Diffusion distance- thicker= slower
Size-smaller increases the rate of

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13
Q

What can diffuse through the cell membrane

A

Lipid soluble, small water ions (hydrophobic molecules)

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14
Q

What is osmosis?

A

Osmosis is the passage of water molecules from a high water potential to a low water potential through a selectively permeable membrane

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15
Q

What is a more concentrated solution called?

A

Hypertonic

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16
Q

What is a less concentrated solution are called?

A

hypotonic

17
Q

Solutions with the same concentration are called?

A

isotonic

18
Q

What is a solute and solvent ?

A

Solute- what you are dissolving
Solvent-liquid

19
Q

What is water potential and what is it measured in?

A

Water potential is the pressure created by water molecules trying to diffuse out of a solution down the conc. gradient (high-low)
Measured in kilopascals (kPa)

20
Q

What is the water potential of pure water?

A

0

21
Q

What has a higher water potential -35kPa or -65kPa and what is the movement of water molecules?

A

-35kPa is higher and moves from -35 to -65 until they are both -50

22
Q

What would happen in a cell with high water potential, equal and low
(Animal cells)

A

High- net movement in and cell bursts

Equal-nothing happens

Low- net movements out and cell shrinks

23
Q

What is incipient plasmolysis?

A

Cytoplasm has shrunk away and water left away via osmosis

24
Q

What would happens in a plant cell with a high, equal and low water potential

A

High- net movement in and cell become turgid

Equal- not net movement (incipient plamolysis-vacuole shrinks a little)

Low- water leave the cell and cell shrinks. It is flaccid and plasmolysed

25
Q

What substances use facilitated diffusion?

A

Hydrophilic polar molecules
Ions(sodium ions)
Large molecules (glucose)

26
Q

What is required in facilitated diffusion

A

Conc. gradient
Channel proteins or protein carriers

27
Q

What type of particles are transported by channel proteins?

A

Ions and small polar molecules

28
Q

What type of molecules are transported by carrier proteins?

A

Larger polar molecules such as amino acids

29
Q

How do channel proteins work?

A

Water filled pores lined with polar groups so the channel is hydrophilic
Most channels are gated so control entry and exit of ions

30
Q

How do carrier proteins work?

A

They are able to bind with a specific shaped molecule l. The binding site is alternately open to both sides of the membrane
The carrier changes shape to release the molecules to the other side of the membrane

31
Q

What happened to a graph of simple and facilitated diffusion with rate and concentration?

A

Simple-keeps going in a straight line from the origin (positive correlation)
Facilitated- starts the same as simple but at a certain point the proteins can only move a specific number of particles per minute so the graph levels of as rate reaches a constant

32
Q

What is active transport?

A

Low conc. -> high conc. using ATP and a carrier protein

33
Q

What does ATP do in active transport?

A

Directly move molecules
Use co-transport to indirectly move molecules

34
Q

How does active transport work?

A

Carrier protein spans plasma membrane and binds to molecule being transported.
Molecule bing to regular site.
ATP hydrolyses with carrier protein splitting into ADP and Pi.
Pi binds to carrier protein (phoshorylating it).
Carrier protein changes shape.
Opens opposite side and molecule is released.
Carrier protein returns to original shape.
Pi binds with ADP to form ATP again

35
Q

What is uniport, symport and antiport in co-transport

A

Uniport- 1 ion in/out in one go
Symport- 2 ions in/out in one go
Antiport- 1 in and 1 out at the same time

36
Q

How are cells that line the ileum adapted for absorption(small intestine)?

A

High SA
Larger no. Of transport proteins
One cell thick

37
Q

How does a sodium potassium pump work?

A

Na+ in
K+ out
ATP hydrolyses with carrier protein
Pi changes its shape so it allows Na+ out the other side and K+ in

Biology A Level (11 decks)

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