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Biology GCSE > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

What are enzymes?

A

Biological catalysts

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2
Q

What is a catalyst?

A

A substance that increases the rate of reaction without being changed or used up in the reaction

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3
Q

What are enzymes made from?

A

Large proteins - formed from amino acids

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4
Q

How are enzymes specific?

A

Folded into a specific shape - active site is specific - can only catalyse a specific reaction

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5
Q

Describe the induced fit model of enzyme action

A

When the substrate is close to the active site, the active site changes shape to bind to the substrate

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6
Q

Describe how the rate of enzyme catalysed reactions can be changed

A

By changing the temperature and pH
As temperature increases there are more frequent collisions as particles have more energy so rate of reaction increases up until a point where the temperature becomes so high the enzyme denatures and rate of reaction decreases as the enzyme can no longer catalsye the reaction.
The pH interferes with the bonds in the protein in the active site changes the shape of the active site and denaturing the enzyme.

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7
Q

At what pH does pepsin work best at?

A

2

Found in acidic conditions in the stomach

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8
Q

At what pH do most enzymes work best at?

A

7 - neutral

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9
Q

How can you investigate the effect of pH on enzyme activity?

A

Practical with amylase catalysing the breakdown of starch to maltose using iodine solution

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10
Q

How is the rate of reaction calculated?

A

Amount something has changed / time taken

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11
Q

Describe the digestion of starch

A

Starch is digested into maltose and other sugars e.g dextrins by carbohydrase enzyme amylase

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12
Q

Where is amylase made?

A

Salivary glands
Pancreas
Small intestine

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13
Q

Describe the digestion of proteins

A

Proteins are digested by proteases into amino acids

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14
Q

Where are proteases made?

A

Stomach (pepsin)
Pancreas
Small intestine

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15
Q

Describe the digestion of fats/lipids

A

Lipids are digested by lipases into fatty acids and glycerol

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16
Q

Where are lipases made?

A

Pancreas

Small intestine

17
Q

Where are the products of digestion used?

A

To make new proteins and carbohydrates

Glucose used in respiration

18
Q

Why is digestion necessary?

A

Large molecules like proteins and fats cant diffuse into the blood and can not be absorbed so must be broken down into smaller molecules

19
Q

Where is bile produced, stored and release?

A

Produced by liver and stored in the gallbladder before it is released into the small intestine

20
Q

What is the purpose of bile?

A

Neutralises the hydrochloric acid from the stomach and provides an optimum pH for enzymes to work in the small intestine
Emulsifies fats- breaks the fats into smaller droplets increasing the surface area for which lipases can work

21
Q

Describe the function of the salivary glands in digestion

A

Produce amylase in the saliva

22
Q

Describe the function of the oesophagus in digestion

A

Passage of food from mouth to the stomach

23
Q

Describe the function of the stomach in digestion

A

Pummels food with its muscular walls
Produces protease enzyme pepsin
Produces hydrochloric acid which kills bacteria and gives the right pH for the protease enzyme to work (pH 2)

24
Q

Describe the function of the pancreas in digestion

A

Produces protease, amylase and lipase enzymes

Releases these into the small intestine

25
Q

Describe the function of the small intestine in digestion

A

Produces protease, amylase and lipase enzymes to complete digestion
This is where all the food is absorbed out of the digestive system into the blood

26
Q

Describe the function of the liver in digestion

A

Produces bile which neutralises stomach acid and emulsifies fats

27
Q

Describe the function of the gallbladder in digestion

A

Stores bile and releases it into the small intestine

28
Q

Describe the function of the large intestine in digestion

A

Where excess water is absorbed from the food

29
Q

Describe the function of the rectum

A

Where the faeces are stored before they leave the anus

30
Q

How do you prepare a food sample for a food test?

A

Break up food using pestle and mortar
Transfer food to beaker and add distilled water
Stir mixture with glass rod to dissolve the food
Filter solution using funnel lined with filter paper to get rid of solid bits of food

31
Q

Describe the benedicts test

A

Used to test for reducing sugars
Prepare food sample and transfer 5cm3 into a test tube

Prepare water bath so it is set to 75degreesC

Add benedicts solution to test tube using a pipette (10drops)

Place test tube in a water bath and leave it there for 5 mins

If the food sample contains a reducing sugar the solution will change colour from normal blue colour to green, yellow or brick red - depending on how much reducing sugar is present

32
Q

Describe the iodine test

A

Used to test for the presence of starch
Make food sample and transfer 5cm3 into test tube
Add few drops of iodine solution and gently shake to mix contents
If solution contains starch the colour of the solution will change from browny-orange to black or blue-black

33
Q

Describe the biuret test

A

Used to test for protein
Prepare sample of food and transfer 2cm3 into a test tube
Add 2cm3 of biurets solution and mix by shaking gently
If protein is present the sample will turn from blue to pink or purple. It will stay blue if no protein is present

34
Q

Describe the sudan III test

A

Test for lipids
Prepare sample of food and transfer 5cm3 to test tube
Use pipette to add 3 drops of sudan III stain solution to test tube and gently shake
Sudan III stain solution stains lipids, if the mixture contains lipids the mixture will separate out into two layers the top layer will be bright red. If no lipid is present no separate red layer will form at the top of the liquid

Biology GCSE (14 decks)

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