Food and Digestion

Nutrients role

Assist in tissue function and repair, and help organs function normally.

Carbohydrates function & sources

Key energy source; found in whole grains, fruits, and vegetables.

Proteins function & sources

Build, repair, and maintain muscle; make hormones/enzymes. Found in meat, eggs, beans, nuts.

Fats function & sources

Energy source and vitamin/mineral absorption aid. Found in eggs, olive oil, avocado.

Vitamins function & sources

Support basic bodily functions; found in fruits.

Minerals function & sources

Support and regulate basic bodily functions (e.g., calcium in milk, iron in red meats).

Dietary Fibre function & sources

Assists healthy digestion and lowers cholesterol; found in oats, whole grains, fruits, vegetables.

Water function

Keeps body hydrated for cell function; makes up 60% of the body.

Macronutrients

Carbohydrates, Lipids, and Proteins.

Carbohydrate polymer and monomer

Polymer: Starch. Monomer: Glucose.

Fats and Oils polymer and monomer

Polymer: Lipids. Monomer: Fatty acid and glycerol.

Protein polymer and monomer

Polymer: Polypeptides. Monomer: Amino Acids.

Enzymes definition

Biological catalysts that speed up chemical reaction rates and break down polymers to monomers.

Enzyme characteristics

Form of chemical digestion, essential for absorption, and specific to one kind of substrate.

Amylase enzyme

Produced in saliva; breaks down starch into glucose.

Protease enzyme

Produced in stomach; breaks down protein into amino acids.

Lipase enzyme

Produced in pancreas; breaks down fats and oils into fatty acids and glycerol.

Ingestion

Food taken into the body through eating.

Digestion

Food broken down into smaller molecules both physically and chemically.

Absorption

Small digested molecules taken into the bloodstream and transported to cells.

Assimilation

After absorption, small digested molecules are used up by the body.

Egestion

Undigested food residues expelled from the body as feces or waste.

Mouth digestion

Performs physical digestion via teeth and chemical digestion via saliva.

Saliva

A mix of water, ions, enzymes (amylase), and mucus.

Bolus

A rounded mass of food formed through chewing and saliva mixing.

Oesophagus function

Carries bolus and liquid to the stomach using peristalsis.

Peristalsis definition

Longitudinal and circular muscle contractions used to move food through the digestive system.

Stomach physical digestion

Muscles contract to move food, breaking bolus into smaller pieces and increasing surface area.

Stomach chemical digestion

Pepsin and HCl digest food; pepsin breaks protein into amino acids.

Chyme

Liquid substance formed after food digests in the stomach for several hours.

Stomach protection

A mucous membrane lines the stomach wall protecting it from danger.

pancreas

Produces digestive enzymes and regulates blood sugar levels via insulin and glucagon.

Liver and gallbladder role

Liver produces bile, gallbladder stores it, and bile is released into duodenum to neutralise chyme.

Small intestine function

Produces amylase, protease, and lipase to complete digestion and absorb nutrients via villi.

Villi and microvilli

Folds on the inner wall of the small intestine that increase surface area for absorption.

Large intestine function

Absorbs excess water and carries undigested food (~15m long, 6cm diameter).

Anus function

Relaxation of muscles allows stool to exit the body.

Homeostasis

Regulation of conditions in the body for a stable internal environment.

Feedback loops

Stimulus > Sensor > Control Centre > Effector > Feedback > Stimulus.

Negative feedback

Maintains homeostasis by returning the body to its original state and reducing environmental changes.

Body hot response

Sweat glands produce sweat for evaporative cooling; blood vessels dilate to radiate heat.

Body cold response

Shivering generates heat; blood vessels contract to prevent heat loss at skin.

Insulin

Released by pancreas to tell cells to absorb glucose from the blood.

Glucagon

Released by pancreas to tell cells to break down glycogen into glucose.

Glycogen definition

A stored form of glucose made up of many glucose molecules.

Hyperglycemia definition & causes

Abnormally high blood glucose state caused by not eating enough, low insulin, or high GI foods.

Hyperglycemia symptoms

Lack of energy, excessive thirst, irritability, frequent urination, lack of concentration.

Hypoglycemia definition & causes

Abnormally low blood glucose state caused by not eating enough, excess insulin, or over-exercise.

Hypoglycemia symptoms

Sweating, headache, dizziness, hunger, lip/finger numbness, lack of concentration.

Diabetes definition

Chronic condition where pancreas cannot produce enough insulin or body cannot use it effectively.

Type 1 diabetes

Autoimmune disease where pancreas makes insufficient insulin; requires genetics and lifestyle.

Type 2 diabetes causes & risk factors

Pancreas overworked or cells insulin-resistant. Risk: family history, age >45, lack of exercise, overweight.

Type 2 diabetes prevention

Balanced diet, physical activity (2.5h/week), weight loss, and medication to increase insulin.