GCSE Biology: Enzymes and Digestion Flashcards

Question 1

What is Enzyme?

Accepted Answer

A biological catalyst, made of protein, that speeds up one specific chemical reaction in living cells without being used up itself.

Question 2

What is Catalyst?

Accepted Answer

A substance that increases the rate of a chemical reaction without being changed or used up by the reaction it speeds up.

Question 3

Define Active site.

Accepted Answer

The region of an enzyme with a precise three-dimensional shape, where the substrate binds and the reaction takes place.

Question 4

What is Substrate?

Accepted Answer

The molecule an enzyme acts on, which fits into the enzyme's active site and is converted into one or more products.

Question 5

What is Product?

Accepted Answer

A molecule formed at the end of an enzyme-controlled reaction, after the substrate has been broken down or joined to something else.

Question 6

Define Lock and key model.

Accepted Answer

A model of enzyme action in which the substrate's shape is complementary to the active site, so only that substrate fits, like one key in one lock.

Question 7

What is Specificity?

Accepted Answer

The property that means an enzyme catalyses only one particular reaction, because only its own substrate has a shape that fits the active site.

Question 8

What is Denaturation?

Accepted Answer

A permanent change in the shape of an enzyme's active site, caused by high temperature or extreme pH, after which the substrate can no longer bind.

Question 9

Define Optimum temperature.

Accepted Answer

The temperature at which an enzyme works fastest; for most human enzymes this is about 37°C, and the rate falls sharply above it.

Question 10

Define Optimum pH.

Accepted Answer

The pH at which an enzyme works fastest, which differs between enzymes; pepsin prefers acidic conditions while enzymes in the small intestine prefer alkaline ones.

Question 11

Define Rate of reaction.

Accepted Answer

A measure of how quickly a reaction happens, found from how fast a product forms or a reactant disappears, or by dividing 1 by the time taken.

Question 12

What is Digestion?

Accepted Answer

The breakdown of large, insoluble food molecules into small, soluble molecules that can be absorbed into the blood, carried out mainly by enzymes.

Question 13

What is Carbohydrase?

Accepted Answer

A group of digestive enzymes that break down carbohydrates into simple sugars; amylase is the best-known example, acting on starch.

Question 14

What is Amylase?

Accepted Answer

A carbohydrase that breaks down starch into maltose, made in the salivary glands, the pancreas and the small intestine.

Question 15

What is Maltose?

Accepted Answer

A sugar made of two glucose units joined together, produced when amylase breaks down starch, and then broken down further into glucose.

Question 16

What is Protease?

Accepted Answer

A group of digestive enzymes that break down proteins into amino acids, made in the stomach, the pancreas and the small intestine.

Question 17

What is Pepsin?

Accepted Answer

A protease made in the stomach that works best in the strongly acidic conditions there, beginning the breakdown of proteins.

Question 18

Define Amino acids.

Accepted Answer

The small, soluble molecules that proteins are broken down into during digestion, which the body absorbs and then reassembles into its own proteins.

Question 19

What is Lipase?

Accepted Answer

A digestive enzyme that breaks down lipids, meaning fats and oils, into fatty acids and glycerol, made in the pancreas and small intestine.

Question 20

Define Fatty acids.

Accepted Answer

One of the two products of lipid digestion, absorbed along with glycerol and used by the body to build new lipids such as cell membranes.

Question 21

What is Glycerol?

Accepted Answer

A small molecule released together with fatty acids when lipase digests a lipid, which is absorbed and recombined with fatty acids to make new lipids.

Question 22

What is Bile?

Accepted Answer

An alkaline fluid made in the liver and stored in the gall bladder that neutralises stomach acid and emulsifies fats in the small intestine.

Question 23

What is Emulsification?

Accepted Answer

The breaking up of large fat droplets into many tiny droplets, which greatly increases the surface area so lipase can digest the fat faster.

Question 24

What is Liver?

Accepted Answer

The large organ that makes bile, which flows along the bile duct to the gall bladder for storage before it is released into the small intestine.

Question 25

Define Gall bladder.

Accepted Answer

A small organ that stores bile made by the liver and releases it into the small intestine through the bile duct when fatty food arrives.

Question 26

What is Pancreas?

Accepted Answer

A gland that makes amylase, protease and lipase and releases them into the small intestine, and also produces the hormone insulin.

Question 27

Define Salivary glands.

Accepted Answer

Glands in the mouth that release saliva containing amylase, which begins the digestion of starch while food is being chewed.

Question 28

What is Stomach?

Accepted Answer

A muscular bag that churns food with hydrochloric acid and pepsin, killing many microorganisms and beginning protein digestion in acidic conditions.

Question 29

Define Small intestine.

Accepted Answer

The long section of the gut where digestion is completed, using enzymes from the pancreas and gut wall, and where most digested food is absorbed.

Question 30

What is Villus?

Accepted Answer

A tiny finger-like projection on the wall of the small intestine, with a thin lining and rich blood supply, giving a large surface area for absorption.

Question 31

What is Absorption?

Accepted Answer

The movement of digested food molecules from the small intestine into the blood, by diffusion and active transport across the villi.

Question 32

Define Large intestine.

Accepted Answer

The final part of the gut, where water is absorbed from the undigested food that remains, leaving the solid waste called faeces.

Question 33

What is Peristalsis?

Accepted Answer

Waves of muscle contraction in the gut wall that squeeze food along the digestive system, starting in the oesophagus.

Question 34

Define Benedict's test.

Accepted Answer

A food test for reducing sugars: heat the sample with Benedict's solution, and a change from blue through green, yellow and orange to brick-red shows sugar is present.

Question 35

Define Iodine test.

Accepted Answer

A food test for starch: iodine solution is added, and the colour changes from orange-brown to blue-black if starch is present.

Question 36

Define Biuret test.

Accepted Answer

A food test for protein: Biuret solution is added, and the sample turns from blue to purple if protein is present.

Question 37

Define Ethanol emulsion test.

Accepted Answer

A food test for lipids: the sample is shaken with ethanol, then water is added, and a cloudy white emulsion forms if lipid is present.