Organisation

Animal tissues, organs, and organ systems

The digestive system breaks down complex food substances and provides a large surface area for maximum absorption of food.

The small intestine is folded and has projections called villi, these villi have their own projections called microvilli. Villi increase the surface area of the small intestine

Enzymes are biological catalysts so they speed up reactions. They are proteins that are folded into a 3D structure, each enzyme has a region called an active site

The substrate fits into the active site

How do enzymes work

1. Substate binds to the active site - the active site is complementary to the substrate

2. Enzyme catalyses the breakdown of the substrate - the fit between the enzyme and substrate is called lock and key

3. Products are released from active site - the enzyme molecule is unchanged

Production and function of bile

The heart and blood vessels

Blood

Coronary heart disease

Lifestyle and non-communicable diseases

Cancer

Plant tissues organs and systems

Factors affecting enzymes

Temperature - At low temperatures the particles have less kinetic energy and so there are fewer successful collisions

If the temperature gets too high then the enzyme will denature meaning the active site has changed shape

pH - Changing th

e pH can also change the active site of the enzyme

Enzymes involved in digestion

The heart and blood vessels

The heart is an organ that pumps blood around the body in a double circulatory system.

The right ventricle pumps blood to the lungs where gas exchange takes place. The left ventricle pumps blood around the rest of the body.

Blood enters the heart from the body through the vena cava where it flows into the right atrium and then the right ventricle, it is pushed towards the lungs through the pulmonary artery. When blood comes back to the heart it enters through the pulmonary vein into the left atrium and then the left ventricle and it leaves to go to the rest of the body aorta.

The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker. Artificial pacemakers can be used to correct irregularities in the heart rate.