Digestion and enzymes

Digestion order

Ingestion->digestion->absorption->assimilation->egestion

Digestion

Breakdown of large, insoluble food molecules -> smaller, soluble food molecules

Molecules absorbed into the blood stream and delivered to cells for respiration -> energy is released

Excretion

removal of wastes produced by cells

e.g. urea, CO2

Egestion

removal of waste food molecules after digestion

e.g. poop

absorption

uptake of digested food into the bloodstream

mechanical digestion

physical breakdown of food into smaller pieces, chemical structure of food is still the same

increases surface area that enzymes can act on

e.g. mouth and stomach

chemical digestion

Large food molecules -> smaller molecules

change of chemical structure

e.g. stomach

mouth

where food enters the alimentary canal and digestion begins

teeth

chops food into smaller pieces

mechanical digestion

saliva

moistens food so it can be swallowed

contains amylase

chemical digestion

Oesophagus

muscular tube which moves ingested food to stomach

peristalsis

contractions of muscular wall to move food

stomach

muscular walls churn food (mechanical digestion)

also contains stomach acid

gastric juices

contains hydrochloric acid and protease

chemical digestion

hydrochloric acid

drops pH in stomach

kills bacteria

stops digestion of starch

small intestine

produces intestinal juice

contains maltase

duodenum

digestive enzymes are added

bile

made in liver

stored in gall bladder

transported to duodenum via bile duct

neutralises acidity of stomach

emulsification

bile breaking fat into small droplets

increases surface area for lipase

ileum

further digestion occurs

absorption of molecules

long with large surface area to absorb molecules, folds and villi

thin lining on the wall so molecules pass through easily

dense capillary network and lacteal

absorption method

end products absorbed by passive diffusion until equilibrium

moves by active transport to accumulate

blood capillaries

transport glucose, amino acids, minerals, water-soluble vitamins from ileum to liver

lacteal

transport fatty acids, glycerol, fat-soluble vitamins from ileum to lymphatic system

large intestine

water absorbed and material becomes solid

peristalsis moves solid matter into rectum

egested through anus

metabolic reaction

chemical reactions that occur in cells, controlled by enzymes

enzymes

biological catalysts (speeds up reaction without being used up)

group of proteins

specific and only react with particular substrates

substrate

molecules an enzyme acts on

active site

where substrate attaches to and forms an enzyme substrate complex

reactions

Starch + amylase = maltose

Maltose + maltase = glucose

Protein + pepsin = amino acids

Lipids + lipase = fatty acids + glycerol

temperature

enzymes are temp sensitive

first temp rises and enzymes have more kinetic energy

if temp too high, enzyme is denatured and reaction stops

fastest rate of reaction is at the optimum temp

denatured

active site loses shape

Temperature graph

1. low temp, less kinetic energy, rate is low

2. optimum temp (37 for humans) max rate

3. high temp, enzyme denatures, active site loses shape, rate is 0

pH

most enzymes work best in neutral conditions (pH7)

extreme pH leads to enzyme being denatured

fastest rate of reaction is at the optimum pH

pH graph reaction

1. low pH denatures the enzyme, reduces rate

2. optimum pH, maximum rate

3. high pH denatures the enzyme, reduce rate

enzyme/substrate concentration

rate of reaction increases by adding more enzyme/substrate

this increases initial rate of reaction until maximum initial rate is reached

egg experiment

Heat & egg: egg goes colourless liquid -> white solid

pH & egg: colourless liquid -> white solid

both change the structure of the protein

liver experiment

A metabolically active organ

Liver & hydrogen peroxide: bubbles of oxygen, a bit exothermic

Manganese IV oxide & hydrogen peroxide: few bubbles of oxygen, exothermic

Liver & heat: liver's structure changed, doesn't react with hydrogen peroxide anymore

Manganese IV oxide & heat: no effect on it, still reacts

Amylase

made in salivary glands

works in the mouth/duodenum

acts on starch

end products maltose

protease

made in stomach/pancreas

works in stomach/duodenum

act on protein

end products amino acids

lipase

made in pancreas

works in duodenum

acts on lipids

end products glycerol and fatty acids

maltase

made in the wall of small intestine

works in ileum

acts on maltose

end products glucose

experiment temp & amylase

4 diff temps 10, 20, 40, 80

Presence of starch, iodine from yellow -> blue/black

Dimple tile, water baths, stopwatch

experiment pH & enzymes

cellulase breaks down cellulose in plant cell wall

more juice can move out of the cytoplasm/vacuole

measuring cylinder, apple, funnel