Biology - Digestion

What are cells?

Basic building blocks of all living organisms.

What are tissues?

Group of cells with similar structures and functions

What are organs?

Aggregations of tissues performing specific functions

What are organ systems?

Organisation of organs which work together to form organisms

Name some tissues in the stomach.

Muscular tissue, glandular tissue and epithelial tissue.

What does muscular tissue do?

It churns up content

What does glandular tissue do?

It produces enzymes

What does epithelial tissue do?

It is a layer of cells covering the inside and outside of the stomach

Name the 8 main tissues in the digestive system in order of food passing through your body.

Salivary glands, oesophagus, stomach, liver, pancreas, small int., large int. and rectum

What is digestion?

The process of breaking larger insoluble molecules into small soluble molecules to be absorbed by the small and large intestine.

What do the salivary glands do in the process of digestion?

They release amylase to begin to break down starch.

What does the oesophagus do in the process of digestion.

Moves chewed food called bolus down into the stomach by peristalsis

What does the stomach do in the process of digestion?

Releases HCl and protease for chemical digestion. Contracts muscles to churn food for manual digestion.

What does the liver do in the process of digestion?

The liver makes bile to store into the gall bladder.

What do the pancreas do in the process of digestion?

Release all 3 enzymes for digestion in the small int.

What does the small int. do in the process of digestion?

Releases all 3 enzymes to absorb small soluble products of digestion.

What does the large int. do in the process of digestion?

Re-absorbs water back into the body.

What does the rectum do?

It stores faeces.

Name the substrate and product of amylase.

starch, glucose

Name the substrate and product of lipase.

The substrate is fats and the products are fatty acids and glycerol.

Name the substrate and product of protease.

proteins, amino acids

Where is amylase produced?

Salivary glands, pancreas and small intestine

Where is lipase produced?

pancreas and small intestine

Where is protease produced?

stomach, small intestine and pancreas

What does bile do?

In the small intestine, bile neutralises the stomach acid and emulsifies fats.

How does bile help in the digestion of fats?

Bile doesn't digest fats it acts as an emulsifier, making large insoluble fat molecules into smaller soluble fat molecules. The fat then has a larger surface area for the lipase to act on.

Where are the villi found?

Along the linings of the small intestine.

What are the adaptations of villi?

Millions of folded structures of villi so there is a larger surface area.

Good blood supply, many capillaries maintaining the concentration gradient.

Villi are lined with a layer of cells which are thin so there is a short diffusion path.

What does the lock and key model show us?

It shows us that the enzyme's active site is complementary to the substrate.

How can we detect proteins?

Using a biuret test. If protein is present the solution turns from blue to purple. If protein is absent it remains a blue colour.

How can we detect starch?

Using an iodine test. If starch is present the solution turns from orange to blue / black. If starch is absent it remains orange.

How can we detect sugars?

Using a benedict's test. If the solution is blue there is no sugar whilst if it is green, orange or red there is sugar present.

What is qualitative food testing?

Qualitative food testing will show you if a substance is present or not.

What is quantitative food testing?

Quantitative food testing will show you how much of a substance there is.

Assess common risks when in a quantitative food testing experiment.

The solutions can be irritant so you must wear eye protection / clean the surface after.

Some people may be allergic to the food samples so don't taste the food.

For sugar test: Hot waterbath spillage, clean up immediately after so people don't slip.

How can we detect lipids?

Using an emulsion test, we add ethanol. If a layer of cloudy white suspension forms at the top of the solution, lipids are present, but if it's clear lipids are not present.

Where does protease work best in?

Works bets in the acidic conditions in the stomach where HCL is produced.

Name the 3 main factors affecting enzyme rate of reaction.

Substrate concentration, pH, temperature

How does temperature affect enzyme rate of reaction?

At a low temperature, there is not enough kinetic energy for particles to collide.
At optimum temperature enzyme rate of reaction is at it’s optimum.
At a high temperature, it is too hot and the enzyme denatures

How does pH affect enzyme rate of reaction?

Rate of enzyme action is low at pH other than a pH within the optimum range as the enzymes get denatured

How does substrate concentration affect the rate of reaction?

Low substrate concentration = low reaction rate due to limited enzyme-substrate collisions.

High substrate concentration = high reaction due to many enzyme - substrate collisions rate until all enzyme active sites are filled, then the rate plateaus.

Name the two main types of lipids.

Fats and oils.

Name the two main types of carbohydrates.

Starch and sugar.

Describe the structure of a lipids molecule.

Up to 3 fatty acids and one molecule of glycerol.

What is the main function of lipids?

To provide energy and make up parts of the cell membrane.

What are the main functions of proteins?

For growth and repair.

What is the main function of carbohydrates?

To provide energy.

Describe how protein is digested.

Mechanical digestion from the mouth.
Protease enzymes, pepsin in stomach breaks down proteins into amino acids.

How do enzymes break down substrates

Substrates bind to active site of the enzyme
Shape of the active site and substrate are complementary
Substrate is broken down to form smaller molecules and active site is unchanged.