5C: organisms + digestion

edrolo 5A, 5C

organism

a living thing made of one or more cells

tissues

a cluster of cells which perform a similar function

why are cells organised into tissues?

• to carry out functions that cannot be performed by single cells alone

organ

the combination of different tissues and cells into a distinct structure that performs specific functions

system

a collection of organs and tissues that perform specific functions necessary for survival

levels of biological organisation

cell → tissue → organ → organ system → organism

digestion

• breakdown of large food molecules into smaller molecules that can cross plasma membranes and be used by the body

system responsible for digestion

digestive system

carbohydrates

provide immediate source of energy

lipids

energy storage in animals

proteins

structural components of cells, cell receptors, enzymes

vitamins

used to make enzymes

minerals

used in structural components of organisms

physical / mechanical digestion

• to be absorbed, food must be broken into smaller pieces to increase SA:V

• the process where mechanical movement of organs and tissues cause the breakdown of food into smaller pieces

examples of physical digestion

• chewing by teeth

• muscle contractions (peristalsis) of the stomach

• bile produced by the liver to break down lipids into smaller droplets

chemical digestion

• performed by enzymes and stomach acid to produce smaller molecules that are capable of being absorbed

three major types of digestive enzymes

• amylases

  • act on carbohydrates

• proteases

  • proteins

• lipases

  • act on lipids

nutrient → end product of digestion

• carbohydrates → simple sugars

• proteins → amino acids

• lipids → fatty acids + glycerol

digestive system processes

ingestion / digestion / absorption / elimination

ingestion

• food taken in through the mouth

• teeth physically break down food

• enzymes in saliva chemically break down food

• creates bolus to be swallowed

digestion

• bolus continues to be broken down physically by the muscles of the stomach and chemically by enzymes

absorption

• small molecules are absorbed by the plasma membrane of cells into the bloodstream

elimination / egestion

• undigested food that has travelled along the digestive tract and has not been absorbed is eliminated from the body as faeces