B3: Organisation and the Digestive System

Question 1

What is a tissue?

Answer 1

A group of same type cells

Question 2

What is an organ?

Answer 2

A group of tissues working together for the same function

Question 3

What is an organ system?

Answer 3

A group of organs which work together to perform one function

Question 4

What are the adaptations of muscle cells?

Answer 4

They have special protein fibres which can change their length (useful for contraction)
They are packed with mitochondria (provides the energy needed for contraction)

Question 5

What are the 3 main nutrients in food?

Answer 5

Carbohydrates, Protein and Lipids

Question 6

What is the purpose of the digestive system?

Answer 6

To break down large molecules into smaller molecules to be digested

Question 7

What happens during digestion?

Answer 7

Large molecules are broken down using enzymes, the small molecules are now able to be absorbed into the bloodstream

Question 8

Describe the process of digesting food (mouth - stomach)

Answer 8

The food enters the mouth, where it is chewed and broken down by enzymes in the saliva (starch is digested into smaller sugar molecules). The food then passes down the oesophagus and into the stomach, where the digestion of proteins begins (HCl assists in the process). The churning action of the stomach turns the food into a fluid (increasing the SA for enzymes to digest more efficiently).

Question 9

Describe the process of digesting food (stomach - large intestine)

Answer 9

The churned fluid is passed to the small intestine (chemicals are released by the pancreas (protease, lipase (starts digestion of lipids) and amylase) and the liver(bile to neutralise the acid, and increase lipase efficiency). The walls of the small intestine release protease and lipase. The small food molecules produced are absorbed into the bloodstream (either by diffusion or active transport

Question 10

Describe the process of digesting food (large intestine - anus)

Answer 10

The fluid makes its way down the large intestine, where excess water is absorbed into the bloodstream,
and the faeces is released from the body

Question 11

What happens to the products of digestion?

Answer 11

Used to build new carbohydrates, lipids and proteins.
Glucose produced is used in respiration

Question 12

Which organs release amylase?

Answer 12

Salivary glands
Pancreas
Small intestine

Question 13

Which organs release protease?

Answer 13

Stomach
Pancreas
Small Intestine

Question 14

Which organs release lipase?

Answer 14

Pancreatic fluid
Small Intestine

Question 15

What is the purpose of enzymes and what is their shape?

Answer 15

They are biological catalysts and are large protein molecules with a groove on their surface (active site) where the substrate goes

Question 16

How do enzymes catalyse reactions?

Answer 16

Each type of enzyme has a specific active site shape designed to fit a specific substrate. Thus, when the specific substrate enters the active site, it is broken down (if it does not fit, it is not broken down)

Question 17

What happens when proteins are digested?

Answer 17

Long chains of amino acids, when digested, they convert back to individual amino acids, which are absorbed into the bloodstream. When absorbed by body cells, they are joined together in a different order to make human proteins

Question 18

What is the structure of starch?

Answer 18

A chain of glucose molecules

Question 19

What happens when starch is digested?

Answer 19

Simple sugars are produced

Question 20

What is the structure of a lipid?

Answer 20

A molecule of glycerol which is attached to 3 molecules of fatty acids

Question 21

What happens when lipids are digested?

Answer 21

Glycerol and fatty acids are produced

Question 22

Where is bile made and stored?

Answer 22

Made in liver and stored in the gall bladder

Question 23

What is the role of bile?

Answer 23

Increases the efficiency of lipid digestion - it emulsifies fatty acids and increasing their SA to increase the efficiency of lipase.
Bile is alkaline, allowing it to neutralise stomach acid, creating alkaline conditions in the small intestine (optimum for lipase)

Question 24

How does temperature affect enzyme activity?

Answer 24

As temp increases, reaction is faster as the collisions per second between enzyme and substrate are more frequent.
At a certain temp, the optimum temp is reached, which is the maximum possible frequency of successful collisions.
Past the optimum, activity rapidly decreases to 0, this is because high temperatures denatures the active site and changes it shape, thus the substrate no longer fits

Question 25

How does pH affect enzyme activity?

Answer 25

Every enzyme has a specific optimum pH, the active site will denature if conditions are too acidic or alkaline

Question 26

What are the optimum pH s of all 3 enzymes?

Answer 26

Protease - acidic (in the stomach)
Lipase - alkaline (released from pancreas)
Amylase - Neutral

Question 27

How is the small intestine adapted to absorb the products of digestion?

Answer 27

Very long - provides a large surface area for efficient digestion
Interior contains villi - increase surface area, very good blood supply to rapidly absorb the products of digestion, increasing the conc. gradient, thin membrane, short diffusion path
Villi have microvilli - increasing surface area even further