principals of organisation and the human digestive system

biology aqa gcse

What are the levels of organisation?

Cell, tissue, organ, organ system

What is a cell?

Basic building blocks and units of an organism (e.g. muscle cells)

What are tissues?

Groups of cells with a similar structure and function (e.g. muscle tissue)

What is an organ?

Groups of tissues working together to perform a specific function (e.g. stomach)

What is an organ system?

A group of organs performing specific functions (e.g. digestive system)

What are all the organs in the digestive system?

Mouth, salivary glands, oesophagus, liver, stomach, gallbladder, pancreas, small intestine, large intestine

Through which of the organs in the digestive system does food actually pass through?

Mouth, oesophagus, stomach, small intestine, large intestine

What is digestion?

Breaking down large, insoluble molecules of food into smaller, soluble molecules that can be absorbed into the blood

What is an enzyme?

A biological catalyst which speeds up the rate of reaction without being used up or changed

How do enzymes work? Explain using the lock and key theory. (4)

The active site of an enzyme is complementary to a specific substrate, which binds to the enzyme’s active site, causing a chemical reaction (e.g. substrate breaks into two smaller molecules) after which the products are released from the unchanged enzyme

Why can each enzyme only catalyse a specific reaction?

Each enzyme’s active site is complementary to a specific individual substrate, so can only bind to that substrate

How are enzymes related to metabolism?

Different enzymes catalyse different metabolic reactions (e.g. respiration) which may join together smaller molecules to form larger ones or break down larger molecules to form smaller ones

What is lipase and what does it do?

An enzyme which breaks down lipids into fatty acids + glycerol

Where is lipase produced?

Pancreas and small intestine

Where does lipase act?

Small intestine

What is carbohydrate (e.g. amylase) and what does it do?

An enzyme that breaks down carbohydrates into simple sugars (e.g. starch into glucose)

Where is carbohydrase produced?

Salivary glands, pancreas and small intestine

Where does carbohydrase act?

Mouth and small intestine

What is protease and what does it do?

An enzyme which breaks down proteins into amino acids

Where is protease produced?

Stomach, pancreas and small intestine

Where does protease act?

Stomach and small intestine

What are fatty acids and glycerol used for?

To build new lipids

What are simple sugars used for?

To build new carbohydrates, some glucose used in respiration to release energy

What are amino acids used for?

To build new proteins

Where is bile produced, stored and released into?

Produced in the liver, stored in the gall bladder, released into the small intestine

What does bile do?

Neutralises stomach acid to create optimum pH for enzymes in small intestine and emulsifies lipids by converting large droplets into smaller droplets to increase surface area for enzymes to break down lipids faster

What does it mean when an enzyme denatures?

The structure of the enzyme’s active site has changed and so is no longer complementary to the substrate and cannot bind to it

How does temperature affect enzyme activity?

As temperature increases and eventually reaches an optimum, enzymes gain kinetic energy so there are more frequent enzyme-substrate collisions, however after passing the optimum temperature enzymes begin to denature and rate of reaction reaches 0

How does pH affect enzyme activity?

Enzyme activity is at a maximum at the optimum pH but in pH reaches above or below this, enzymes denature and activity decreases, so rate of reaction reaches 0

How do you calculate rate of reaction?

change in quantity (e.g. product used or produced)/change in time