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A LEVEL BIOLOGY > Cell Membranes- Topic 2B > Flashcards

Cell Membranes- Topic 2B Flashcards

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1
Q

What molecules can be found in a plasma membrane?

A 
Phospholipids
Proteins (carrier and channel) 
Cholesterol
Glycolipids
Glycoproteins
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2
Q

Name the functions of a cholesterol molecule in a membrane?

A

Reduces lateral movement of other molecules (phospholipids)
Makes membrane less fluid @ high temps
Prevents leakage of water and dissolved ions from the cell.

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3
Q

Name the functions of glycolipids

A

Act as recognition sites
Help maintain the stability of the membrane
Help cells to attach to one another and so form tissues.

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4
Q

The functions of glycoproteins in the membrane are…

A

Act as recognition sites
Help cells to attach to one another and so form tissues
Allows cells to recognise one another

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5
Q

Name the functions of proteins in the membrane

A

Provide structural support
Act as channels for transporting substances
Forms cell-surface receptors for identifying cells
Help cells adhere together
Act as receptors e.g hormones

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6
Q

Only what type of substances can be transported across the membrane?

A

Water-soluble substances

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7
Q

How does a colorimeter work?

A

Uses the light passed through the liquid & measures the amount of light that has been absorbed.

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8
Q

What two things could be your independent variable?

A

The concentration of solvent

The temperature of the water baths.

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9
Q

How can you remove any pigment released from cutting the beetroot?

A

Rinse the pieces after cutting them.

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10
Q

On a graph which axis do you plot which variables on?

A

The “independent variable” goes on the x axis

The “dependent variable” goes on the y axis

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11
Q

Define diffusion:

A

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration

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12
Q

Why would larger molecules take a while to diffuse through the bilayer?

A

Because they are so big

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13
Q

Other than large particles, what other molecules would diffuse slowly?

A

Ions and polar molecules because they’re water soluble and the centre of the bilayer is HYDROPHOBIC

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14
Q

What is different about facilitated diffusion?

A

Large or charged particles diffuse through carrier proteins or channel proteins

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15
Q

What type of process can diffusion and facilitated diffusion be classed as?

A

Passive processes- they don’t use energy.

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16
Q

Carrier proteins move ….. ……… across membranes

A

Carrier proteins move large molecules across membranes

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17
Q

Channel proteins form pores in the membranes for ……. ……… to diffuse through.

A

Channel proteins form pores in the membrane for charges particles to diffuse through.

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18
Q

What factors does the rate of (simple) diffusion depend on?

A

Concentration gradient
The thickness of the exchange surface
The surface area (microvilli in epithelial cells)

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19
Q

What factors does facilitated diffusion depend on?

A

The concentration gradient

The number of channel or carrier proteins

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20
Q

Define Osmosis

A

The diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential

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21
Q

What is water potential?

A

The potential of water molecules to diffuse out of or into a solution

22
Q

Pure water has the ……. water potential. This means ALL solutions have a ……. water potential than pure water.

A

Pure water has the highest water potential. All solutions have a lower water potential than pure water

23
Q

If two solutions have the same water potential, what are they said to be?

A

ISOTONIC

24
Q

List the factors affecting the rate of osmosis?

A

The water potential gradient
The thickness of the exchange surface
The surface area of exchange surface

25
Q

What type of protein does active transport use?

A

Carrier proteins.

26
Q

Co transporters are a type of ….. ……..

A

Carrier protein.

27
Q

What are the factors affecting the rate of active transport?

A

The speed of the individual carrier proteins
The number of carrier proteins
The rate of respiration in the cell and the availability of ATP.

28
Q

Glucose is absorbed by ……………….. in the Mammalian Ileum

A

Co transport

29
Q

Glucose enters the ileum epithelium with …. ……..

A

sodium ions

30
Q

Why is energy needed for active transport?

A

Energy is needed to transport solutes against the concentration gradient.

31
Q

Describe the process by which energy is released by the cell for active transport.

A

energy is released by the hydrolysis of ATP into inorganic phosphate.

32
Q

Why would the diffusion of chloride ions across a cell-surface membrane be extremely slow?

A

Because ions are water soluble and the centre of the phospholipid bilayer is hydrophobic.

33
Q

What are plasmids and where are they found?

A

Plasmids are small loops of DNA, found in bacterial cells.

34
Q

Name 5 ways that prokaryotic cells differ from eukaryotic cells

A

cytoplasm lacks membrane bound organelles
They are much smaller
smaller ribosomes
no nucleus
cell wall contains MUREIN. (glycoprotein)

35
Q

How many microns in 1mm?

A

1,000

36
Q

What is the difference between resolution and magnification?

A

Resolution=how well a microscope distinguishes between two points close together
Magnification= How much bigger the image is than the specimen

37
Q

What does an optical microscope use to form an image?

A

Light

38
Q

Why are electron microscopes better than light microscopes?

A

They have a higher resolution and magnification

39
Q

Why are light microscopes better than electron microscopes?

A

Can observe living cells.

40
Q

What are the two types of electron microscopes?

A

Transmission or Scanning

41
Q

How do Transmission microscopes work?

A

They use electromagnets to focus a beam of electrons which is transmitted through the specimen, the denser parts of the specimen absorb more electrons making it look darker.

42
Q

What is a pro and con to using a Transmission microscope?

A

Can only be used on thin specimens but have higher resolutions

43
Q

How do Scanning microscopes work?

A

Scan a beam of electrons across the specimen which knocks off electrons from the specimen and are gathered in a cathode ray tube to form an image.

44
Q

What is a pro and a con to using a scanning microscope?

A

They can be used on thick specimens BUT they have a lower resolution.

45
Q

What can you use on a specimen to highlight objects in the cell?

A

A stain, e.g. iodine in potassium iodide solution for starch granules

46
Q

Why should you avoid air bubbles in your specimen when using the cover slip ?

A

As they’ll obstruct your view of the specimen.

47
Q

Name the 3 stages of Cell fractionation

A

Homogenisation- breaking up the cells
Filtration- Getting rid of the big bits
Ultracentrifugation- separating the organelles

48
Q

What do channel proteins allow charged particles to do?

A

DIFFUSE through the membrane.

49
Q

How are phospholipids always arranged?

A

fatty acids towards the middle due to hydrophobic (repelled by water)
the hydrophilic phosphate (attracted to water) acts as a barrier

50
Q

How can we describe carrier proteins being “full”?

A

All working at their maximum= no further uptake

A LEVEL BIOLOGY (19 decks)

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