Animal tissues, Organs and Organ systems

Question 1

The Digestive System

Answer 1

Large food molecules are digested into smaller molecules and then the products of digestion are absorbed into the bloodstream.

Question 2

What organs is the Human Digestive System made up of and why?

Answer 2

Glands (salivary glands + pancreas) - which produce digestive enzymes which break down food.

Stomach - produces hydrochloric acid to kill bacteria and to provide the optimum pH for the protease enzyme to work.

Small intestine - where soluble molecules are absorbed into the blood.

Liver - produces bile (stored in gall bladder) which helps the digestion of lipids.

Large intestine - absorbs water from undigested food to produce faeces, which pass out your body via rectum and anus.

Question 3

What are enzymes?

Answer 3

• They speed up reactions
• Present in many reactions so that they can be controlled
• Can break up large molecules and join small molecules
• They are protein molecules
• Each enzyme has its own uniquely shaped active site where the substrate binds

Question 4

What is the Lock and Key hypothesis?

Answer 4

• The shape of the substrate fits to the shape of the active site, so when they bond it forms an enzyme-substrate complex
• Once bound, the reaction takes place and the products are released from the surface of the enzyme.

Question 5

What do enzymes require?

Answer 5

Optimum temperature - (around 37 Celsius)
- If temperature gets too hot, bonds in the structure break which changes the shape of the active site, so the substrate no longer fits. The enzyme denatures and can no longer work.

Optimum pH - (usually 7)
- If pH is too high or low, the forces holding the amino acid chains that make up the protein will be affected, which will change the shape of the active site, so the substrate no longer fits. The enzyme denatures and can no longer work.

Question 6

The 3 different types of enzymes:

Answer 6

Carbohydrase
- Convert carbohydrates and starches into simple sugars

Protease
- Convert proteins into amino acids

Lipase
- Convert lipids into fatty acids and glycerol

Question 7

The 4 tests that determine what a solution is made up of:

Answer 7

Benedict’s test - for sugars (turns red)

Iodine test - for starch (turns blue-black)

Biuret test - for protein (turns purple)

Emulsion test or Sudan III test - for lipids

Question 8

Bile:

Answer 8

• Made by the liver, stored in the gall bladder
• Bile is released into the small intestine after we eat
• Breaks down large molecules of lipids into smaller ones
• Neutralises stomach acid as bile is alkaline

Question 9

What are the products of digestion used for?

Answer 9

• To build new carbohydrates, lipids and proteins
• Some of the glucose produced is used in respiration

Question 10

Stomach:

Answer 10

• Produces protease enzymes which breaks down proteins into amino acids
• Produces hydrochloric acid which provides the right pH for protease enzymes and kills microorganisms

Question 11

The process of the Digestive System:

Answer 11

1) Food is chewed in the mouth. Enzymes in saliva digest the starch into smaller sugar molecules

2) Goes down the oesophagus, into the stomach, which contains hydrochloric acid which helps enzymes start to digest proteins

3) Churning action of stomach muscles turns food into fluid, increasing surface area for enzymes to digest

4) Fluid passes into small intestine. Chemicals are released into it from liver and pancreas.

5) The pancreas releases enzymes, to continue digestion of starch and protein and start digestion of lipids.

6) The liver releases bile which speeds up lipid digestion. Bile neutralises stomach acid.

7) Walls of small intestine release enzymes to continue digestion of protein and lipids.

8) Small intestine absorbs small food molecules by diffusion or active transport

9) Fluid goes through large intestine, where water is absorbed into bloodstream

10) Faeces released from the body

Question 12

What are proteins and how are they digested?

Answer 12

• Proteins are long chains of amino acids
• When digested, protease enzymes convert them into individual amino acids, which are absorbed into the bloodstream

Question 13

How is the small intestine adapted for absorption? (Villi)

Answer 13

• Interior is covered with millions of villi - which increases surface area.
• Villi have a very good blood supply so the bloodstream rapidly removes the products of digestion - increasing the concentration gradient.
• Villi have a thin membrane so there is a short diffusion path