B3 - Organisation and the Digestive System

Question 1

What is a tissue?

Answer 1

A group of cells that work together for a certain function. eg. muscular tissue contracts for movement.

Question 2

What are organs?

Answer 2

Organs are collections of tissue that work together for a certain function. For eg. the stomach has muscular tissue for contraction, glandular tissue for digestive tissue and epithelial tissue which covers all sides of the tissue.

Question 3

What’s an organ system?

Answer 3

A collection of organs working together for a certain function like the digestive system.

Question 4

What do enzymes do?

Answer 4

Break down large insoluble food molecules into smaller, soluble ones.

Question 5

Why is the small intestine good at its job?

Answer 5

It has a very large surface area due to villi - tiny hairs.

Question 6

What are carbohydrates?

Answer 6

Carbohydrates provide us with fuel that makes all reactions of life possible. They contain carbon, oxygen and hydrogen.

Question 7

What are carbs made of?

Answer 7

They contain carbon, oxygen and hydrogen. Some carbs only contain one sugar molecule - these are called simple sugars, like sucrose (2 units of sugar) and glucose (1 unit of sugar).

There are also complex carbs like starch and cellulose. These are made of long, complex chains of sugar units bonded together.

Question 8

What are carbs used for in the body?

Answer 8

Most of the carbohydrates will be broken down into glucose used in cellular respiration to provide energy for metabolic reactions in cells.

Question 9

What are lipids?

Answer 9

Lipids are fats and oils - most efficient energy store (most calorie dense) and source of energy.

Question 10

What are lipids made of?

Answer 10

Lipids are made of the same elements as carbs. Lipids are made up of three molecules of fatty acids joined to a molecule of glycerol. The glycerol number remains the same but the number of fatty acids can change - their different combinations determine whether the lipid is a fat or an acid.

Question 11

What are proteins?

Answer 11

Proteins are used for building up the cells and tissues of your body, as well as your enzymes.

Question 12

What are proteins made of?

Answer 12

Made of the same elements as carbs + nitrogen. Protein molecules are made up of long chains of small units called amino acids.

Question 13

What are amino acids?

Answer 13

Protein molecules are made up of long chains of small units called amino acids. These acids can be joined in different formations to give different proteins. They can join into 3D shapes, allowing for only specific shapes to fit the protein. If the temperature or pH of the solution rises or falls too much the bonds in these acids can be broken, changing the shape of the protein and making it denatured.

Question 14

What are proteins used for?

Answer 14

Components of tissues
Hormones like insulin
etc

Question 15

How do you test for carbs?

Answer 15

iodine test
yellow —–> blue/black if starch present
Benedict’s solution
blue —–> brick red if simple sugars present

Question 16

How do you test for lipids?

Answer 16

ethanol test

colourless —–> cloudy white layer formed at top if lipids present

Question 17

How do you test for proteins?

Answer 17

biuret test

blue —–> purple if protein present

Question 18

How do enzymes work?

Answer 18

Enzymes control the rate of chemical reactions. They are large protein molecules with active sites that can bind to a specific substrate molecule. Enzymes function on a lock and key model - substrate fits onto active site - substrate splits into products and leaves active site - enzyme ready for next usage. Enzymes are CATALYSTS)

Question 19

Examples of metabolic reactions

Answer 19

• Building large molecules from smaller ones (building starch, glycogen or cellulose from glucose etc, glucose and nitrate ions to make amino acids etc.)
• Breaking down large molecules into smaller ones, like carbs into constituent molecules.

Question 20

Effect of temperature on enzyme action

Answer 20

Optimum temperature for enzyme function = 37 - 40 degrees Celsius. If the temperature is too low the kinetic energy of the enzymes and substrates will decrease, not allowing for many reactions to take place upon collision + if the temperature rises too much, the amino chains in the enzyme can be unravelled, causing it to become denatured - shrivelled up. This damages the shape of the active site and does no allow for substrates to use the enzyme as a catalyst for a reaction.

Question 21

Effect of pH on enzyme action.

Answer 21

A change in pH affects the forces affecting the active site of an enzyme, making it change shape. Different enzymes work best at different pH levels.

Question 22

Digesting carbs

Answer 22

Enzymes that break down carbs are called carbohydrases. An example is amylase - produced in the salivary glands and pancreas, so the digestion starts in the mouth and then again in the small intestine where amylase is supplied by the pancreas.
The reaction of breaking down carbs is CATALYSED by amylase.

Question 23

Digesting proteins

Answer 23

Digesting proteins is catalysed by protease enzymes. these are produced by the stomach, the pancreas and the small intestine. The breakdown of proteins into amino acids takes place in the small intestine.

Question 24

Digesting fats

Answer 24

Broken down into fatty acids and glycerol in the small intestine. The reaction is catalysed by lipase enzymes, which are made in your pancreas and small intestine. Enzymes made in the pancreas are passed onto the small intestine.

Question 25

What happens to digested food molecules?

Answer 25

They leave the small intestine now that they are soluble. They are now carried by the blood where ever the body needs them.

Question 26

How is pH changed in the digestive system?

Answer 26

The stomach creates HCl acid to lower pH for pepsin enzymes to function. Bile produced by the liver is alkaline and so neutralises the acid produced by the stomach.

Question 27

How is surface area changed?

Answer 27

Bile breaks down large fat globules into smaller ones by emulsifying them. This means that there is more surface area for the enzymes to work with.