Biology B3: Organisation and Digestive System

What are the five levels of organisation in living organisms?

Cells → Tissues → Organs → Organ Systems → Organisms

What is a tissue?

A group of cells with similar structures and functions.

What is an organ?

A group of tissues working together to perform a specific function.

What is an organ system?

A group of organs working together to perform a specific function.

What is an organism?

A living being made up of organ systems.

What is the digestive system?

An organ system that breaks down food into small soluble food molecules from large insoluble food molecules for absorption.

What is the function of the mouth in digestion?

Chews food and mixes it with saliva containing amylase.

What does the oesophagus do?

Carries food from the mouth to the stomach.

What are the functions of the stomach?

Churns food with digestive juices, releases protease, and hydrochloric acid to kill pathogens.

What does the liver do in digestion?

Produces bile to neutralise stomach acid and emulsify fats.

What is the role of the gall bladder?

Stores bile.

What does the pancreas do?

Produces digestive enzymes: amylase, protease, and lipase.

What happens in the small intestine?

Digested food is absorbed into the bloodstream.

What happens in the large intestine?

Water and minerals are absorbed.

What is the function of the rectum?

Stores faeces

What is the function of the anus?

Expels faeces from the body.

What are enzymes?

Proteins that catalyse chemical reactions.(Biological catalyst)

What is the lock and key theory?

The enzyme’s active site fits only specific substrates like a key fits a lock.

What is an active site?

The part of an enzyme where the substrate binds and the reaction occurs.

What is a substrate?

The molecule that an enzyme acts upon.

What does amylase do?

Breaks down starch into glucose.

Where is amylase produced?

Salivary glands, pancreas, and small intestine.

What does protease do?

Breaks down proteins into amino acids.

Where is protease produced?

Stomach, pancreas, and small intestine.

What does lipase do?

Breaks down lipids into fatty acids and glycerol.

Where is lipase produced?

Pancreas and small intestine.

What is bile?

An alkaline substance that neutralises stomach acid and emulsifies fats.

What does emulsify mean?

Breaking fat into small droplets to increase surface area for enzymes.

What does catalyse mean?

To speed up a chemical reaction.

What does denatured mean?

When an enzyme’s active site changes shape and can no longer bind the substrate.

What causes enzymes to denature?

Extreme pH or high temperatures.

What is the optimum temperature for enzyme activity?

The temperature at which the enzyme works fastest.

What happens to enzyme activity as temperature increases?

It increases until the optimum, then decreases as enzymes denature.

What is the effect of pH on enzyme activity?

Each enzyme has an optimum pH; activity decreases outside this range.

Why do enzymes have different optimum pHs?

Because different parts of the digestive system have different pH levels.

What is the pH of the stomach?

Strongly acidic.(2)

What is the pH of the small intestine?

Close to neutral.(8)

What is the role of hydrochloric acid in the stomach?

Kills pathogens and creates the right pH for protease.

What is the role of saliva?

Lubricates food and contains amylase to begin starch digestion.