Topic 2 digestion (from 2.27) Flashcards
What is the purpose of digestion?
Break down large insoluble molecules of food into small soluble molecules for absorption into bloodstream
What is mechanical digestion and where does it occur?
- physically breaking down food
- chewing, churning etc. in mouth, stomach
What is chemical digestion and where does it occur?
- enzymes
- mouth, stomach and small intestines
What is the alimentary canal?
Channel through which food flows through body from mouth to anus
What is the function of the mouth?
- mechanical digestion - teeth chew food to break it down
- amylase enzymes in saliva digest starch into maltose
What is the function of the oesophagus?
- muscular tube to move food to stomach
- via peristalsis
What is the function of the stomach?
- mechanically digested by churning actions
- chemically digested by protease enzymes which break down proteins into amino acids
- hydrochloric acid is present to provide optimum pH and kill bacteria
- ph 2
What is the function of the pancreas?
- produces the digestive enzymes (amylase, protease and lipase)
What is the function of the small intestine (duodenum) ?
- to mainly digest but also absorb broken down food molecules
- duodenum = first section of small intestine
- > where food finishes being digested by enzymes secreted from the pancreas and intestine walls
- > bile is released in the duodenum
- bile = made in liver + stored = gall bladder - bile emulsifies fats providing a larger surface area on which lipase can act (so digestion more efficient)
- also neutralise stomach acid
What is the function of the ileum?
- second section of small intestine
- where absorption of digested food molecules takes place
- contains lots of white blood cells + important in immune response
- long and lined with villi to increase the surface area over which absorption can occur
What is the function of the large intestine?
- water absorbed from remaining food in colon to produce faeces
- faeces stored in rectum + removed through anus
What is peristalsis?
Contraction of muscle in intestine wall behind bolus that pushes bolus through
What organ produces bile?
Liver
Where is bile stored?
Gall bladder
What is egestion
Where food that is unable to be absorbed leaves alimentary canal as faeces
Where is amylase located and what does it do?
- salivary glands/pancreas
- breaks down starch to maltose
Where is maltase located and what does it do?
- small intestine
- breaks down maltose to glucose
Where is protease located and what does it do?
- stomach/pancreas
- breaks down protein to amino acids
Where is lipase located and what does it do?
- pancreas
- acts in duodenum
- breaks down lipids into fatty acids and glycerol
What is an enzyme?
Speeds up reaction without being used itself
Biological catalyst
What is the pH of the mouth?
6.5
What is the pH of the stomach?
2
What is the pH of the duodenum?
7.5
What is assimilation?
- movement of digested food molecules into cells and processing/storing them
- the liver is important as stores some of glucose absorbed as glycogen
- also converts some of absorbed amino acids into useful proteins
How is the small intestine adapted for absorption?
- has lots of villi
- increases surface area so molecules can enter bloodstream quickly
How does a villus’ structure relate to its function?
- Villi give ileum large sa -> absorption
- Cells w microvilli increase sa for active transport / diffusion
- Large capillary network -> blood supply that constantly carries absorbed products away (maintains concentration gradient for fast diffusion)
- Lipids are absorbed into lacteal to go to lymphatic system
- Epithelium (wall) thin -> decreases diffusion distance
What is absorption?
Absorption is the movement of small digested food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol)
