Enzymes and digestion Flashcards
Define the term enzyme
A biological catalyst that increases the rate of a chemical reaction without getting used up in the process
Describe the effect of increasing temperature on enzyme activity
Increase in temperature means molecules have more kinetic energy, so move faster and more; more likely to be a collision between enzyme active site and substrate; increased rate of reaction. If temperature becomes too high, shape of active site changes and enzyme is denatured
How does pH affect enzyme activity
If pH moves too low or too high, the enzyme active site will change shape (i.e. it denatures), meaning the substrate will no longer be able to specifically bind into an active site
What is meant by the term ‘optimum’?
The conditions which mean the rate of enzyme activity is highest, e.g. most enzymes work at an optimum temperature of 37°C in the human body)
Describe what is meant by the term digestion
The break down of large insoluble molecules into smaller soluble molecules
What is meant by the term absorption?
The movement of products of digestion into the bloodstream (usually across the villi in the small intestine)
What is meant by the term assimilation?
Incorporation of small soluble digested products into tissues, e.g. amino acids from protein digestion will be used to make new proteins
By what process does food move through the alimentary canal?
Peristalsis
Define the term peristalsis
Wave-like, rhythmic muscular contractions that squeeze food through the digestive tract
Describe the process of digestion in the mouth
Mechanical digestion by teeth to break food into smaller pieces; amylase released from salivary gland to digest starch into maltose
Describe digestion in the stomach
Mechanical digestion as stomach wall pummels and churns food; low pH (pH2 caused by hydrochloric acid) provides optimum conditions for pepsin which digests proteins into peptides
Where is bile produced and then stored?
Produced in liver, stored in gall bladder
Describe the roles of bile
Neutralises stomach acid so as not to denature digestive enzymes in the small intestine; emulsifies fats into smaller droplets so as to increase the surface area for digestion by lipase enzyme (into glycerol and fatty acids)
Describe how villi are adapted for absorption
Large surface area for absorption; thin walls (one cell thick) to decrease diffusion/active transport distance; supply of blood capillaries to maximise concentration gradients for absorption; lacteal for absorption of glycerol and fatty acids; covered in microvilli to further increase the surface area for absorption
Name three enzymes produced by the pancreas
Lipases, proteases, peptidases, maltases, amylases
