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Year 12 Biology (module 2) > Enzymes And Membranes Oops > Flashcards

Enzymes And Membranes Oops Flashcards

1
Q

What is a biological catalyst?

A
  • A protein that speeds up a metabolic reaction without being used up in the reaction.
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2
Q

What is an intercellular enzyme?

A
  • An enzyme which works within cells.

- E.g catalase which catalyses the breakdown of hydrogen peroxide into oxygen and water.

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3
Q

What is an extracellular enzyme?

A
  • An enzyme which works outside cells.
  • Eg Amylase works in the saliva and catalyses the hydrolysis of starch into maltose in the mouth
  • Eg Trypsin is produced in the pancreas and deferred into the small intestine, it catalyses the hydrolysis of peptide bonds.
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4
Q

How to enzymes speed up reactions?

A
  • They reduce the amount of activation energy that’s needed meaning reaction can occur at lower temperatures speeding up the rate of reaction.
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5
Q

‘The Lock and key’

A
  • Substrates fit into tenedume in the same way a key fits into a lock.
  • The active site and substrate have a complementary shape.
  • However, scientists soon realised that the enzyme-substrate complex changed shape slightly to complete the fit.
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6
Q

The ‘induced fit’ model.

A
  • The substrate approaches he active site.
  • The substrate binds to the active site is complementary to.
  • This slightly changes the shape of the active site.
  • Enzyme-substrate complex is formed.
  • The substrate is then broken down into products.
  • Enzyme-product complex is formed.
  • The products then move away from the active site.
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7
Q

How does enzyme concentration affect enzyme activity?

A

-the rate of reaction increases as enzyme concentration increase -
there are more active sites for substrates to bind to.-
however increasing the enzyme concentration beyond a certain point has no effect on the rate of reaction.
- there are more active sites than substrates so substrate concentration becomes the limiting factor

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8
Q

How does substrate concentration affect enzyme activity?

A
  • as concentration of substrate increases, rate of reaction increases
  • more enzyme-substrate complexes are formed.
  • However, beyond a certain point the rate of reaction no longer increases as enzyme concentration becomes the limiting factor
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9
Q

How does temperature affect enzyme activity?

A
  • rate of reaction increases up to the optimum temperature,
  • which is the temperature at which enzymes work at their maximum rate.
  • Rate of reaction decreases above the optimum temperature.
  • Enzymes denature.
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10
Q

How does PH affect enzyme activity?

A
  • Each enzyme has an optimum pH range.
  • Changing the pH outside of this range will slow enzyme activity.
  • Extreme pH values can cause enzymes to denature.
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11
Q

What does the temperature coefficient show?

A
  • How much the rate of reaction changes when the temperature is raised by 10*c.
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12
Q

How to draw a tangent to estimate the initial rate of reaction

A
  • Draw a tangent at t=0.
  • Calculate the gradient of the tangent (change in y/change in x).
  • Workout the unit, units of y/units of x.
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13
Q

What is a coenzyme?

A
  • organic cofactors which do not bind permanently to the enzyme.
  • They facilitate the binding of substrate to enzyme.
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14
Q

What is a cofactor?

A
  • a non-protein compound required for the enzyme’s activity to occur.
  • There are three types of cofactors: coenzymes, activators and prosthetic groups.
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15
Q

What is an activator?

A
  • inorganic metal ions which temporarily binds to the enzyme
  • This alters the shape of the active site.
  • Which makes the reaction more feasible.
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16
Q

Where are phosphetic groups?

A

A cofactor which permanently binds to the enzyme.

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17
Q

What is an inhibitor and what are the two types?

A

a -substance which slows down or stops a reaction by affecting the binding of substrate to the enzymes.
- Inhibitors can either be reversible and irreversible.

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18
Q

What does an irreversible inhibitor do?

A
  • cause disulphide bonds within the protein structure to break
  • causing the shape of the active site to change
  • affecting protein activity.
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19
Q

What do Reversible inhibitors do? And what’s are the two types?

A
  • They bind to the active site through hydrogen bonds and weak ionic interactions therefore they do not bind permanently.
  • Reversible inhibitors can either be competitive or non-competitive.
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20
Q

What do competitive inhibitors do?

A
  • They are similar in structure to the substrate molecule
  • Therefore they bind to the active site of the enzyme,
  • This decreases it’s activity as they compete with substrate for the enzyme.
  • The amount of product formed remains the same.
    However the rate at which product formation occurs decreases.
  • The higher the concentration of competitive inhibitor the lower the reaction rate.
  • Increasing the substrate reverses the effect of competitive inhibitors by outcompeting them.
21
Q

What do Non-Competitive inhibitors do?

A
  • They bind to a site on the enzyme known as the allosteric site.
  • This changes the shape of the active site therefore preventing the binding of the substrate.
  • Increasing the concentration of substrate has no effect on non-competitive inhibition.
22
Q

Which bond is required for the inhibition to be irreversible?

A

Covenant bonds

23
Q

Which bond is required for inhibitor to be reversible?

A
  • hydrogen or weaken ionic bonds.
24
Q

Types of drugs which are enzyme inhibitors

A
  • penicillin which is used to fight bacterial infections,

- it is an inhibitor of enzyme transpeptidase which plays an important role in cell wall formation.

25
Q

What is a metabolic poison?

A
  • They interfere with metabolic reaction causing damage, Illness of death.
  • There are often enzyme inhibitors.
26
Q

Example of metabolic poison.

A
  • Malonare is a competitive inhibitor of succumate dehydrogenase which catalyses the respiration reactions.
27
Q

What is end-products inhibition?

A
  • When the final product in a metabolic pathway inhibits an enzyme that acts earlier on the pathway.
28
Q

What is product inhibition?

A
  • When each reaction is catalysed by a different enzyme.
29
Q

Phospholipids.

A
  • Hydrophilic head and hydrophobic tail meaning they automatically arrange themselves into a bilayer.
  • Centre of bilayer is hydrophobic so doesn’t allow water-soluble substances (ions) to pass through it.
30
Q

Cholesterol

A
  • A type of lipid.
  • Binds to the hydrophobic tail of the phospholipids.
  • This causes them to pack more closely together.
  • This makes the membrane less fluid and more rigid.
31
Q

Glycolipids and glycoproteins

A
  • They stabilise the membrane by forming hydrogen bonds with surrounding water molecules.
  • They act as receptors for cell signalling.
  • They also act as antigens.
32
Q

Factors affecting membrane permeability

A
  • Temperature

- Solvent

33
Q

Membrane permeability when temp is below 0*c.

A
  • Phospholipids don’t have much energy so they can’t move much.
  • ## they’re pack closely together and the membranes is rigid.
34
Q

Membrane permeability when temp is between 0 and 45*c

A
  • phospholipids can move and aren’t packed as tightly together.
  • Membrane is partially permeable.
  • As the temperature increase, phospholipids move more because they have more energy.
  • This increase the permeability of the membrane.
35
Q

Membrane permeability when temperature is above 45*c

A
  • Phospholipid nils her start to melt and the membrane becomes more permeable.
  • Channel and carrier proteins deform so they can’t control what enter and leaves the cell this increase the permeability of the membrane.
36
Q

How do solvents affect membrane permeability?

A
  • Ethanol is a non-polar solvent so it is able to dissolve non-polar substances such as lipids.
  • This means that if you place a cell in ethanol, its membrane will become permeable and allow substances to leak into and out of the cell.
  • As the ethanol concentration increases, membrane permeability will increase.
  • If the ethanol concentration is high enough, enough phospholipids will dissolve to cause the plasma membrane to disintegrate completely which will kill the cell.
37
Q

How to investigate the permeability of a cell membrane

A
  • Cut 5 equal sized pieces of beetroot and rinse them to remove any pigment released during cutting.
  • Place pieces in separate test tubes each with 5cm3 of water.
  • Place each test tube in a water bath at a different temperature for the same length of time.
  • Remove the pieces of beetroot from the tubes leaving just the coloured liquid.
  • ## Use a colorimeter to work out the permeability, the higher the permeability, the higher the absorbable of the liquid.
38
Q

Diffusion

A
  • passive movement (doesn’t require energy)
  • small, non-polar lipid soluble molecules such as carbon dioxide and oxygen.
  • from an area of high concentration to an area of low concentration.
  • The molecules move directly through the phospholipid bilayer.
39
Q

Facilitated diffusion

A
  • Net movement of particles from an area of high concentration to an area of lower concentration.
  • Uses carrier proteins to aid diffusion of larger molecules.
  • Uses channel proteins to aid the diffusion of smaller ions.
  • Passive procces (doesn’t require energy).
40
Q
  • Osmosis
A
  • The net movement of water molecules
  • from an area of high water potential to and area of low water potential.
  • Through a partially permeable membrane.
  • Passive process (doesn’t require energy).
41
Q

Active transport

A
  • Movement of molecules against a concentration gradient.
  • Uses carrier proteins to transport molecules.
  • Active process (It requires ATP.)
42
Q

Exocytosis

A
  • Movement of molecules out of a cell.
  • Vesicles fuse with the plasma membrane and release their contents.
  • Active process (requires ATP).
43
Q

The rate of gas exchange by diffusion becomes more rapid as…

A

. Surface area of the surface increases
. Diffusion distance decreases
. Diffusion gradient becomes more steep

44
Q

What are isotonic solutions?

A
  • When two solutions have the same water potential.
  • Means there will me no net movement of water.
  • No cells in an isotonic solution will lose or gain any water
45
Q

What are Hypotonic solutions?

A
  • Solutions with a higher water potential than inside the cell.
  • Means water will move into the cell
  • Animal cell will swell and eventually burst, plant cell will become turgid.
46
Q

Hypertonic solutions

A
  • When the cell has a higher water potential than the solution.
  • Water will move out of the cell by osmosis.
  • Animal cell would shrink and plant cell would become flaccid.
47
Q

How to investigate her effect of water potential on plant cells.

A
  • Prepares sucrose solution with different concentrations.
  • Use a cork borer to cut potatoes into identically sized cylinders.
  • Divide the cylinders into groups of 3 and measure the mass of each group using a mass balance.
  • Place on group into each of the sucrose solutions.
  • Leave the cylinders in the solution for 20 minutes.
  • Remove the cylinders and dry them with a paper towel.
  • Weigh each group again and record the results.
  • Calculate the percentage change in ms for each group.
48
Q

Endocytosis

A
  • Movement of large molecules into a cell.

- Active process (requires ATP)

Year 12 Biology (module 2) (10 decks)

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