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AQA GCSE BIOLOGY > Organisation > Flashcards

Organisation Flashcards

1
Q

definition of enzyme

A

biological catalyst that speeds up the rate of a chemical reaction without being altered or used up itself in the reaction

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2
Q

definition of active site

A

small dent on the surface of the enzyme where the substrate binds and where the chemical reaction takes place.

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3
Q

State what type of molecule enzymes are

A

Proteins

large molecule made from many amino acids joined together

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4
Q

State 4 factors that affect the activity of enzymes

A

pH

temperature

concentration of enzyme

concentration of substrate

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5
Q

State the two different types of chemical reaction

A

Catabolic

Anabolic

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6
Q

Definition of a catabolic reaction

A

chemical reaction that breaks down larger molecules into smaller molecules

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7
Q

Definition of an anabolic reaction

A

A chemical reaction that builds up smaller molecules into a larger molecules (the product)

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8
Q

Define the term metabolism

A

sum total of all chemical reactions that take place inside a cell

(includes all the catabolic and anabolic reactions)

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9
Q

Describe the structure of an enzyme

A

enzyme has a dip on its surface (called the active site)

The active site has a complementary shape to its specific substrate

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10
Q

Explain why enzymes are specific

A

Each enzyme has an active site uniq​ue to specific substrates for one chemical reaction

active site is only complementary to one substrate

Hence each enzyme can only catalyse one specific reaction

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11
Q

Describe the relationship between the active site and the substrate

A

complementary to each other

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12
Q

Name the model that describes how enzymes work

A

Lock and key theory

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13
Q

Explain the lock and key theory model

A

active site on enzyme acts as a lock

complementary substrate acts as a key that fits into the active site

chemical reaction then takes place

The substrate is converted to the product

The product is released

The enzyme remains unaltered and can carry out further identical reactions

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14
Q

Define the term enzyme-substrate complex

A

An enzyme that has it specific substrate bound to its active site

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15
Q

Explain the effect of low temperatures on enzyme activity

A

substrate and enzyme have very little kinetic energy

very few collisions between the substrate and the active site

Very few enzyme-substrate complexes form

very little product is made

enzyme is described as inactive

The rate of reaction is very low

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16
Q

Explain the effect of high temperatures on enzyme activity

A

substrate and enzyme have a high amount of kinetic energy

many collisions between the substrate and the active site

high temperature changes the shape of the enzyme

alters the shape of the active site

substrate is no longer complementary to the active site

NO enzyme-substrate complexes form

NO product is made

The enzyme is described as denatured

The rate of reaction is zero

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17
Q

Describe the effect the optimum temperatures on enzyme activity

A

both the substrate and enzyme have very high kinetic energy

many collisions between the substrate and the active site

High numbers of enzyme-substrate complexes form

lot of product is made

enzyme is described as working at its maximum rate

The rate of reaction is at its maximum

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18
Q

What is the typical optimum temperature for human enzymes?

A

37oC

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19
Q

Name an human enzyme that works at an optimal pH of 1-2 (acidic)

A

Pepsin

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20
Q

State 2 human enzymes that work at an optimal pH of 7 (neutral)

A

Amylase

Catalase

Lipase

Carbohydrases

Proteases (except trypsin)

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21
Q

How do you calculate the rate of reaction?

A

Amount of product formed divided by the time

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22
Q

State the 3 main groups of enzymes that are involved in digestion

A

Lipases

Carbohydrases

Proteases

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23
Q

Describe the action of a protease enzyme

A

break proteins down into amino acids

24
Q

Describe the action of a lipase enzyme

A

break lipids down into 3 fatty acids and 1 glycerol

25
Q

Describe the action of a carbohydrase enzyme

A

break complex carbohydrase down into simpler sugars (e.g. glucose)

26
Q

State how you can investigate the effect on pH on enzymic activity

A
  • put a drop of iodine solution into every well of a spotting tile
  • place bunsen burner on a heat-proof mat and a tripod and gauze over bunsen burner
  • heat beaker of water until its 35 degrees
  • add 1cm of amylase solution and 1cm of buffer solution to a boiling tube and put in the water
  • mix
  • record and repeat
27
Q

what do digestive enzymes do

A

convert food into small soluble molecules that can be

absorbed into the bloodstream.

28
Q

State 3 places in the human body where amylase is produced

A

Mouth (salivary amylase)

Pancreas

Small intestine

29
Q

State 3 places in the human body where proteases are produced

A

Pancreas

Stomach

Small intestine

30
Q

State 2 places in the human body where lipase is produced

A

Pancreas

Small intestine

31
Q

Describe what happens to the fatty acids and glycerol that are produced after digestion

A

fatty acids and glcyerol are absorbed into the blood stream

This absorption occurs in the small intestine

They are absorbed into the lacteals

then used by cells to make new lipids

The new lipids are used to make new cell membranes for the production of new cells or stored for energy

32
Q

What is the function/role of bile?

A
  • neutralises stomach acid
  • emulsifies lipids

It breaks large lipids into smaller droplets of lipid

This increases the surface area for the lipase enzymes

Hence the rate of reaction increases

33
Q

How does the emulsification of lipids affect the activity of lipases?

A

Emulsifying the fats into smaller droplets increases the surface area

This increases the activity of lipase

34
Q

Explain why the pH falls (becomes more acidic) in during a reaction catalysed by lipase

A

Lipase breaks down lipids into 3 fatty acids and glycerol

As more lipids are broken down more fatty acids are produced

The greater the accumulation of fatty acids the more the pH decreases (becomes more acidic)

35
Q

State where bile is stored

A

Gall bladder

36
Q

Explain why it is important bile is released into the small intestine to allow digestion to occur

A
  • hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly
  • bile is alkaline so neutralises the acid and makes conditions alkaline
  • enzymes work best in these alkaline conditions
37
Q

State where bile is produced

A

Liver

38
Q

What test would you use to detect the presence of reducing sugars?

A

Benedict’s test

39
Q

Describe the results of a positive Benedict’s test

A

solution would change from blue to green to yellow to orange to brick red

40
Q

What colour is a negative Benedict’s test?

A

Blue

41
Q

Describe how to carry out a Benedict’s test

A

1) prepare a food sample and transfer 5cm to a test tube
2) prepare a water bath so it is set to 75 degrees
3) Add 10 drops of Benedict’s solution to test tube using a pipette
4) Place test tube in water bath and leave for 5 mins

42
Q

State 3 safety precautions you should take when carrying out a Benedict’s test

A
  • Wear safety goggles
  • Make sure the test tube is pointing away from you in the water bath
  • Do not ingest the Benedict’s solution – it is harmful
43
Q

What test would you use to detect the presence of starch?

A

Iodine solution

44
Q

Describe the results of a positive starch test

A

A blue-black solution

45
Q

What colour is a negative starch test?

A

A yellow-brown solution

46
Q

Describe how to carry out a starch test

A

1) make a food sample and transfer 5cm to a test tube

2) add a few drops of iodine solution and shake the tube to mix contents

47
Q

What test would you use to detect the presence of lipids?

A

Sudan III stain solution

48
Q

Describe the results of a positive Sudan III test

A

2 layers will form

The top layer will be bright red

49
Q

Describe the results of a negative Sudan III test

A

No separate red layer will form

50
Q

Describe how to carry out a Sudan III test

A
  • prepare a sample of food and transfer 5cm to a test tube

- using pipette add 3 drops of Sudan III stain solution to test tube and shake it

51
Q

What test would you use to detect the presence of proteins?

A

Biuret solution

52
Q

Describe the results of a positive Biuret test

A

Purple solution

53
Q

Explain the purpose of digestion (3 key points)

A
  • To use enzymes to break down large insoluble molecules
  • into small and soluble molecules
  • that can be absorbed into the bloodstream
54
Q

Describe the results of a negative Biuret test

A

Blue solution

55
Q

Describe how to carry out a Biuret test

A
  • prepare a sample of your food and transfer 2cm to a test tube
  • add 2cm of biuret solution to the sample and gently shake it
56
Q

Give 2 properties that amino acids, glycerol, simple sugars and fatty acids have that enable them to be absorbed into the plasma

A

Small and soluble

AQA GCSE BIOLOGY (8 decks)

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