Enzymes and Digestion

Question 1

Basic steps in the digestion of food

Answer 1

Ingestion
Digestion
Absorption
Assimilation 
Egestion

Question 2

Ingestion

Answer 2

Food is taken into the alimentary canal/Buccal cavity

Question 3

Digestion

Answer 3

Large, insoluble molecules are broken down to small molecules

Question 4

Absorption

Answer 4

The small molecules are absorbed into the blood

Question 5

Egestion

Answer 5

Food, which could not be digested or absorbed is removed from the body via the rectum

Question 6

Molecules that can enter the blood

Answer 6

Vitamins
Minerals
Simple sugars/glucose

Question 7

Molecules that need to be broken down

Answer 7

Starch
Protein
Fats

Humans can not digest cellulose and passes through the system relatively unchanged

Question 8

Mechanical digestion

Answer 8

This is breaking food down without the aid of any chemicals
There are two major sites:
-The mouth
-Bile

In the mouth the teeth break down food into small chunks
The action of bile emulsifies fats creating a greater surface area for enzymes to work on

Question 9

Chemical digestion

Answer 9

This method results in the breakage of bonds holding large molecules together. This results in smaller more soluble compounds that can enter the blood.
Enzymes are responsible for this

Question 10

The mouth/ Buccal cavity

Answer 10

Food is broken down mechanical by teeth

Starch is chemically digested into maltose via the action of salivary amylase
The salvia moistens the food to allow is to pass easily down the oesophagus

Question 11

Oesophagus

Answer 11

A muscular tube leading from the mouth to the stomach. The muscles help move chewed food along by a process of peristalsis.
This is how food is moved throughout the alimentary canal

Question 12

Stomach

Answer 12

J shape muscular bag
The inner lining of stomach is lined with gastric pits
Gastric pits produce gastric juice

Question 13

Types,of digestion in the stomach

Answer 13

Chemical digestion through the use of enzymes PEPSIN
Mechanical digestion via churning of the muscular walls
This ensures food and gastric juice is mixed

Question 14

The small intestine

Answer 14

Has two major roles:

• digestion
• absorption

Digestion takes place in the duodenum
Absorption takes place in large intestine

Question 15

Bile

Answer 15

Produced in the liver and stored in the gall bladder

Contains mineral salts and bile salts and no enzymes

Question 16

Mineral salts in bile

Answer 16

These have an alkaline pH and are involved in neutralising the acid chyme
The enzymes of the small intestine can only work efficiently at a neutral pH

Question 17

Bile salts in bile

Answer 17

These emulsify lipids, this involves breaking large fat globules into much smaller droplets with an increased surface area

Question 18

Intestinal juice

Answer 18

Includes:
Mineral salts
Mucus
Enzymes

Question 19

Mucus in intestinal juice

Answer 19

Lubricates intestinal walls allowing easier movement and also protects the intestinal wall from self digestion

Question 20

Enzymes found in intestinal juice

Answer 20

Protease
Amylase
Maltese
Lactase 
Sucrose

Question 21

Pancreatic juice

Answer 21

Leaf shape organ situated below stomach

Includes:
Mineral salts
Protease enzymes
Pancreatic amylase
Lipase enzyme

Question 22

Protease enzyme in pancreatic juice

Answer 22

Breaks down proteins onto polypeptides

Breaks down polypeptides into amino acids

Question 23

Pancreatic amylase in pancreatic juice

Answer 23

This completes the digestion of starch begun in the mouth

Question 24

Lipase enzyme in pancreatic juice

Answer 24

This involves the chemical break down of the lips droplets produced by the action of bile

Question 25

Food in the ileum

Answer 25

Food molecules have been completely digested into simple molecules that can gross the gut wall and enter the bloodstream

Question 26

Features of the ileum for efficient absorption

Answer 26

Long: food will spend a long time passing through (6m)
Highly folded: increases surface area
Villi: increase surface area and thin permeable walls
Blood supply: maintain concentration gradients in blood stream

Question 27

How molecules are absorbed through villi

Answer 27

Substances enter through capillaries
Includes:
Fatty acids
Glycerol enters lacteals which carry lymph

These fatty substances enter the blood in the vein. They are carried to the liver where they will either be stored or used

Question 28

Enzyme definition

Answer 28

Protein molecules that act as biological catalysts increasing the rate of biological reactions

Question 29

Lock and key model

Answer 29

Each enzyme is specific to one molecule called the substrate. This will only react to the uniquely shaped pocket on the surface of the enzyme known as the active site.

Question 30

Factors that can affect the rate of the enzyme

Answer 30

Temperature
pH
Enzyme concentration

Question 31

The affect of temperature on an enzyme

Low/optimum/high

Answer 31

Low temperature:
The reacting molecules move more slowly and less likely to collide and react less often. Rates of reaction are low at low temperatures

Optimum temperature:
As temperature increases so does the movement of molecules. They collide more often and so the rate increases. (30-40)

High temperatures:
Above optimum level the rate of the enzyme drops suddenly. This is because the active sure has be denatured and doesn’t recognise its substrate. This is an irreversible change. (60)

Question 32

Affects of pH on an enzyme

Answer 32

It can also affect the shape of an enzymes active site
Pepsin acts in acidic conditions in the stomach
Amylase acts in neutral slightly alkaline conditions

Question 33

Affects of enzyme concentration on an enzyme

Answer 33

As a enzyme concentration increases so does the rate of reaction. This is because there is a greater chance of collision between the enzyme and the substrate. Eventually the rate will level off as the substrate gets used up. If no more substrate is available the rate will drop as the enzyme has nothing to react with.

Question 34

Commercial uses of enzyme

Answer 34

One of the biggest uses of enzymes is in the manufacture of biological washing powders

Question 35

Reabsorption in the colon

Answer 35

All digestive juices contain high levels of water
Much of the the water passes into the colon with the in digested food and fibre.
This changes the liquid food into semi solid faeces.
Colon has a large surface area
Without this process we would become rapidly dehydrated

Question 36

The content of faeces

Answer 36

Indigestible food
Dead cells from the lining of the intestine
Bile pigments