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Biology > 2.1.5 > Flashcards

2.1.5 Flashcards

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1
Q

What is the function of a plasma membrane?

A

barrier between the cell and it’s environment

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2
Q

What does the plasma membrane control?

A

the transfer of substances in and out of the cell
e.g water, ions , gases

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3
Q

What substances can pass through the plasma membrane?

A

water, ions, gases

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4
Q

What are the roles of membranes?

A
  • compartmentalisation
  • site of chemical reactions
  • site of cell commuication / cell signalling
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5
Q

What are 2 key roles of membranes within organelles?

A

allows for concentration gradients to be established and maintained
Embedding of enzymes into the membrane

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6
Q

How do cells communicate?

A

signals like hormones bind to a specific receptor with a complimentary shape

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7
Q

What is cell signalling?

A

communication between cells
cell recognition / identification
cells working together
to trigger a response

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8
Q

How does insulin regulate blood sugar levels?

A

1) Insulin is produced from beta cells in the islet of langerhans in the pancreas in reponse to high blood sugar
2) Insulin binds to receptors in the cell memrane of cells such as muscle and liver cells
3)This triggers a response inside the muscle or liver cell causing glucose to be taken up from the blood and reducing blood sugar level

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9
Q

How do beta blockers work to reduce the chance of a heart attack?

A

beta blockers stop neurotransmitters binding to heart muscle therefore decreasing the chance of a heart attack

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10
Q

How does botox work?

A

botox blocks receptors in muscke fibres
stopping them from working and causing paralysis

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11
Q

How does HIV get into a cell?

A

mimicking the receptor sites for a white blood cell

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12
Q

What is the structure of a phospholipid?

A

2 fatty acids, 1 glycerol molecule and a phosphate group

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13
Q

What part of the phospholipid is hydrophobic?

A

Fatty acid chains

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14
Q

What part of the phospholipid is hydrophillic?

A

glycerol and phosphate

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15
Q

Why do the phospholipids arrange themselves in a bilayer at the cell surface?

A

hydrophillic heads oreintate themselves towards water and the hydrophobic tails orenitate themselves away from water
Intracellular fluid inside the cell and extracellular fluid outside the cell

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16
Q

Why is it called the fluid mosaic model?

A

fluid - components in the membrane move around, flexible
Mosaic - proteins embedded in the membrane give it a mosaic look

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17
Q

What are the functions of glycoproteins and glycolipids?

A
  • Cell recogition / identification
  • Cell signalling
  • acts as antigens
  • Acts as receptors
  • Adhesion
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18
Q

What are the roles of the proteins in the fluid-mosaic model?

A

Carrier proteins transport large and polar substances

Channel proteins transport polar substances

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19
Q

What is the role of cholesterol in the membrane?

A

found between tails of phospholipids and regulates fluidity
more cholestrol - less fluid the membrane is

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20
Q

What factors affect membrane permeability?

A
  • heat
  • ethanol
  • detergent / soap / washing-up liquid
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21
Q

How does heat affect membrane permeability?

A
  • As temperature increases, phospholipids gain kinetic energy
  • causes gaps to appear between phospholipids
  • membrane becomes more permeable
  • At high temperatures proteins in the membrane denature
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22
Q

How does ethanol affect membrane permeability?

A
  • Alcohol dissolves the phospholipid bilayer
  • the higher the alcohol concentration the more permeable the membrane becomes
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23
Q

How does detergent affect the membrane permeability?

A

Detergents dissolve the phospholipid bilayer making the membrane more permeable

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24
Q

What are the control variables in the beetroot experiment?

A

Mass / length of beetroot
Same species of beetroot
Same volume of water
All beetroot cylinders in water for the same time

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25
What should you do after cutting the beetroot?
pat beetroot dry once samples are cut to remove any excess pigment caused by damaging the membranes
26
What is the process of the beetroot experiment
Take samples of beetroot and place into water at different temperatures. Compare colour change.
27
What happens to the colour when the temperature is increased?
As temp increases, colour is darker Colorimeter absorption increases as more pigment has been released from samples of beetroot into the water
28
How do you calibrate the colorimteter?
Fill cuvette water (blank) put blank into colorimeter press calibrate and it should be 0% ensure red fliter and blue light Remove and blank and add a cuvette with solution from beetroot
29
What is the reasoning why absorption increases with temperature?
as temperature increases, phospholipids gain KE, Causes gaps to appear between the phospholipids membrane becomes more permeable therefore more pigment will leak out of the cell at high temperatures the proteins in the membrane will denature
30
What is diffusion?
net movement of molecules form an area of higher concentration to an area of lower concentration passive continues until particles are uniformly distributed throughout system in equilibrium
31
What is a concentration gradient?
the difference in concentration between 2 regions
32
What factors affect diffusion?
How lipid soluble a substance is the thickness of the cell membrane surface area difference in concentration
33
How does lipid solubility affect diffusion?
charged particles like ions and large molecules like glucose cannot pass readily through the plasma membrane
34
How does thickness of the membrane affect diffusion?
the thicker the membrane, the more time it takes for diffusion to occur
35
How does surface area affect diffusion?
when increased, we can increase the rate of diffusion
36
How does difference in concentration / maintaining a concentration difference affect diffusion?
steep concentration difference means particles move more rapidly in order to achieve an eqiulbrium
37
What is the difference between channel proteins and carrier proteins?
Channel proteins are pores that allow the movement of ions. Channels proteins are specific to different ions Carrier proteins allow movement of larger molecules across the membrane. Larger molecules are specific to the molecule they transport and involve a shape change to release the molecule on the opposite side of the membrane
38
What is faciliated diffusion?
Passive process requires a channel or carrier protein molecules move down the concentration gradient
39
What is active transport?
movement against concentration gradient from an area of low concentration to an area of higher concenration ATP required -> to change shape of carrier protein carrier proteins used
40
How does exocytosis occur?
Cytoskeleton contracts to move the vesicle to the plasma membrane the membrane of the vesicle and plasma membrane fuse releasing contents
41
How does endocytosis occur?
influx of substances that push into membrane membrane pinches off to form vesicle
42
What is osmosis?
net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane
43
What is water potential?
ability of water to move depending on solute
44
What is the water potential of pure water?
0 - the highest W.P
45
What would happen if you dissolved solutes into water?
W.P will become more and more negative
46
What would happen if cell A has a W.P of -450 and B has a water potential of 0?
B has a higher water potential than A so water moves from B to A down the water potential gradient by osmosis
47
What happens id cell B has a water potential of 0 and cell C has a water potential of -375?
B has a higher water potential than C so water moves down the concentration gradient by osmosis from B into C
48
What happens if cell A has a water potential of -450 and cell C has a water potential of -375?
Cell C has a higher water potential than A so water moves from Cell C to Cell A down the concentration gradient by osmosis
49
What happens if a cell is surrounded by pure water or a solution with a higher water potential ?
Water flows into the cell by osmosis
50
What is the name for the external solution if a cell is surrounded by pure water or a solution with a high water potential?
external solution is hypotonic
51
What happens if a cell is surrounded by a solutionw itha lower water potential than the cell content ?
water will flow out of the cell
52
What is the name for the external solution if a cell is surrounded by a solution with a lower water potential than the cell contents?
external solution is hypertonic
53
What happens if a cell and the surrounding solution have the same water potential?
no net movement of water
54
What is the name for a solution where the surrounding solution has the same water potential as the cell contents?
isotonic
55
What happens with red onion cells in a hypotonic solution>
Water enters cells by osmosis and they have become turgid
56
What would happen with red onion cell in a hypertonic solution?
Water has left the cells by osmosis and they have become flaccid Plant cells become plasmolysed as cell membrane pulls away from cell wall
57
What type of solution would cause RBC to appear shrivelled?
hypertonic solution water potential surrounding RBC is lower than water inside RBC so water moves out of RBC down the concentration gradient by osmosis
58
What type of solution woulf cause RBC to burst?
Hypotonic solution RBC in pure water water potential outside is higher so water moves into the cell by osmosis down the concentration gradient by osmosis causing cell to burst as there is no cell wall in animal cells
59
What are the control variables for the potato osmosis practical?
Same length cyclinders same potato sAMEvolume of solution Same length of time
60
Why is it important to dry the potato pieces?
to remove excess water as water has mass
61
What is the procedure of the potato osmosis practical?
1) Cut potato pieces 2) Prepare solutions 3) Weigh the mass of the potato pieces before placing them into solutions 4)Place potao into solution 5) After 40 minutes, take potato pieces out and pat dry 6) Weigh mass of potato pieces
62
Why do we use % change?
takes into consideration the starting masses / potatoes have different starting masses
63
Why did the potato lose weight in the sugar water?
- higher water potential inside the potato - water moves out of the potato into the solution by osmosis - down water potential gradient - so mass decreases
64
Why did the potato gain weight in the distilled water?
- higher water potential in solution/water - so water moves into the potato from the solution - by osmosis down the water potential gradient -so mass of potato increases

Biology (26 decks)

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