B3: Digestive System & Enzymes

Topics covered: White/Black - Organisation in living Organisms Yellow - Human Digestive System Red - The Chemistry of Food Blue - Food Tests Purple - Enzymes Green - Factors affecting Enzyme Action

Organ System

Group of organs with related functions working together to perform body functions. (Circulatory System, Respiratory System)

Organ

Structure made up of a group of tissues, working together to perform specific functions.

Tissue

Group of cells with similar structures, working together to perform a shared function (Epidermal Tissue - Covers surfaces and protects them)

Cell

Basic structural and functional unit of a living organism.

Tissues Found in the Stomach and their Role

Muscular Tissue - To churn food and digestive juices that break down food

Glandular Tissue - To produce the digestive juices that break down food

Epithelial Tissue - Covers the outside of the stomach

Heart (Organ System, Functions, Other organs in that System)

Circulatory & Cardiovascular System

The system pumps blood and hormones around the body

The heart pumps and oxygenates blood

Arteries, veins and capillaries are also involved

Brain (Organ System, Functions, Other organs in that System)

Nervous System

The system carries electrical signals, allowing the body to react

The brain processes information and sends out impulses to coordinate response

Nerves and the Spinal chord are involved

Lungs (Organ System, Functions, Other organs in that System)

Respiratory System

The system takes in oxygen and transports it

The lungs allow air to move in and out of the blood

The trachea, diaphragm, nose and mouth are also involved

Physical Digestion

Breaking large pieces of food into smaller pieces of food (teeth)

Chemical Digestion

Breaking large, insoluble molecules into smaller soluble molecules to increase surface area

Mouth

Digestion begins here. The smell of food triggers salivary glands in your mouth to secrete saliva. Mechanical digestion takes place as chewing breaks food into pieces.

Oesophagus

Carries food to the stomach. It is a long muscular tube. Food is pushed through the oesophagus and into the stomach by means of a series of contractions called peristalsis.

Liver

Processes absorbed food and detoxifies the blood. Makes bile.

Gallbladder

Stores excess bile, before it is released into the small intestine.

Stomach

Contains hydrochloric acid which kills off any excess bacteria. Produces protease enzymes. The muscular walls contract to churn food.

Pancreas

Produces digestive enzymes secreted into the small intestine

Large Intestine

Connects the small intestine to the rectum. Highly specialised organ, responsible for processing waste.

Small Intestine

Produces amylase, protease, and lipase that continue digestion. Soluble products of digestion are absorbed through the walls.

Rectum

Received stool from the large intestine

Uses of proteins in the body

Used to make structural components, hormones, antibodies and enzymes

15-16% of your body mass is proteins

Build up all of the cells and tissues in your body

Structure of Proteins

Long chains make amino acids in different orders. The chains are coiled into specific 3D shapes that enable other molecules to fit into the protein. Made up of Carbon, Hydrogen, Oxygen, and Nitrogen.

Word Equation for the digestion of Proteins

Protein —-(protease)—→ Amino Acids

Uses of lipids in the body

The most efficient source of energy and energy store in your body. Important in cell membranes, as hormones, and in your nervous system. Insulate organs.

Structure of lipids

Made up of Carbon, Hydrogen, and Oxygen. Insoluble in water. Made up of 3 molecules of fatty acids joined to a molecule of glycerol. Different combinations affect state.

Word equation for the digestion of Lipids

Lipids —-(lipase)—→ Fatty acids + Glycerol

Uses of carbohydrates in the body

Provide us with the fuel that makes all the reactions in life possible. They contain the chemical elements Carbon, Hydrogen, and Oxygen

Structure of carbohydrates

All carbohydrates are made out of units of sugar. Glucose and Sucrose are known as simple sugars, and some carbohydrates contain only one of these. Complex carbohydrates such as starch or cellulose are made up of long chains of sugar units bonded together.

Word equation for the digestion of carbohydrates

Carbohydrase + Carbohydrates —→ Sugar Molecules

Stacrh —-(amylase)—> Maltose —-(maltase)—> Glucose

Testing for Glucose

Add Benedicts Solution and heat

Positive result - Brick Red

Negative result - Blue

Testing for Starch

Add Iodine solution

Positive result - Blue black

Negative result - Yellow orange

Testing for Protein

Add Biuret reagent and shake after each drop

Positive result - Lilac

Negative result - Blue

Testing for Lipids

Shake with ethanol then add to water

Positive result - White emulsion

Negative result - No emulsion

Enzymes

Enzymes are biological catalysts. This means that they speed up the rate of a biological reaction but they are not used up in the process. Each type of enzyme has a very specific shape. Only specific molecules will fit into this shape. The molecule has to be complementary. The molecules fit together like a lock and key.

Process of an enzyme working

Enzymes break down ‘substrates’

The substrate bonds to the active site of the enzyme, forming an enzyme-substrate complex

When the complex is formed, the substrate is broken down

Activation Energy

The energy needed for a chemical reaction to take place (enzymes lower the activation energy)

Active Site

The special site in the structure of an enzyme where the substrate binds.

Catalyst

A substance that changes the rate of a chemical reaction without being changed itself.

Complementary

The word used to describe molecules that fit together like pieces of a jigsaw.

Enzyme Denaturation

If the temperature gets too high, or the pH is too high/low for that particular enzyme, the shape of the enzyme’s active site changes. The enzyme is denatured.

Consequence of Enzyme Denaturation

Bonds within the enzyme will break. The active site will change state and the substrate is no longer complementary.

Enzyme Temperature Practical

The enzyme tested worked best around 40 degrees C. Above 40, the enzyme would begin to fail and denature. This would be the same for most enzymes in the body, as the average body heat is 37 degrees C.

Enzyme pH Practical

The enzyme tested had an optimum pH of around 7. This would not be the same for all enzymes in the body, as different places in the body have different pH levels. (e.g Enzymes in the stomach have an optimum pH of 2)