6.1 DIGESTION AND ABSORPTION Flashcards
ESSENTIAL IDEA
the structure of the wall of the small intestine allows it to move, digest and absorb food
ANNOTATED DIAGRAM OF DIGESTIVE SYSTEM
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MOUTH
chewing (mechanical digestion)
saliva moistens the food to make a bolus for swallowing
salivary amylase begins chemical digestion of starch
OESOPHAGUS
a wave of muscle contractions (peristalsis) pushes the bolus into the stomach
DIGESTION ORDER
- mouth
- oesophagus
- stomach
- duodenum (S.I)
- Ileum (S.I)
- large intestine
- anus/ egestion
STOMACH
muscular contractions continue mechanical digestion
acid kills bacteria
pepsin begins digestion of proteins
DUODENUM (S.I)
bile from the liver and gall bladder neutralises acid and emulsifies fats
pancreatic amylase and lipase digest carbohydrates and fats
trypsin digest polypeptides to AA
ILEUM (S.I)
lower half of small intestine absorbs nutrients into the blood via the villi
ANUS
egestion: faeces containing undigested food, dead cells and other waste, is forced out of the anus
PERISTALSIS AND SI
a wave of muscle contractions keeps the mixture of digested and undigested food moving through the intestine
PERISTALSIS
contraction of circular and longitudinal muscles of the small intestines mixes the food with enzymes and moves it along the gut
LARGE FOOD MOLECULES BEOFRE THEY CAN BE ABSORBED NEED TO BE
digested: hydrolysis
LARGER MOLECULES ARE
large food M are usually insoluble and too large for diffusion across membranes into the blood
PRODUCTS OF DIGESTION ARE
usually soluble
small enough for absorption into the blood and later assimilation into the tissue
HYDROLYSIS
‘water splitting’
reaction used to break down large organic molecules CPL
enzymes are needed
ENZYME
globular protein that increase the rate of biochemical reaction by lowering the activation energy threshold
aka: biological catalyst
DIGESTIVE ENZYMES
released into the gut from glands and are use in catabolic reactions- they break down larger molecuels
USE OF DIGESTIVE ENZYMES
by lowering the activation energy of the reaction, the reaction does not require high temperatures
this is ideal in living things as high temperatures would cause damaged to cells and proteins
by using enzymes, reactions can occur more quickly at body temperatures
3 MAIN TYPES OF DIGESTIVE ENZYMES
amylase
protease
lipase
AMYLASE
breaks down carbohydrates
AMYLASE EXAMPLE
salivary amylase
AMYLASE SUBSTRATE
starch
AMYLASE PRODUCT
maltose
AMYLASE SOURCE
mouth
AMYLASE OPTIMUM PH
7-7.8
PROTEASE
breaks down polypeptides
PROTEASE EXAMPLE
pepsin
PROTEASE SUBSTRATE
polypeptides
PROTEASE PRODUCT
amino acids
PROTEASE SOURCE
stomach
PROTEASE OPTIMUM PH
2
LIPASE
breaks down fats and lipids
LIPASE EXAMPLE
pancreatic lipase
LIPASE SUBSTRATE
triglyceride
LIPASE PRODUCT
fatty acids and glycerol
LIPASE SOURCES
pancreas delivered to S.I
LIPASE OPTIMUM PH
7.2-7.5
PANCREAS
synthesizes 3 main types of enzymes:
amylase
lipase
protease
PANCREATIC JUICE
containing the enzymes is released into the upper region of the S.I (duodenum) via the pancreatic duct
FINAL STAGES OF DIGESTION OCCUR?
small intestine
PANCREATIC DUCT
carries pancreatic juice from pancreas to S.I
SMALL INTESTINE AND ITS LAYERS
mucosa
submucosa
muscular layer
serosa
epithelial cells
MUCOSA
inner lining, includes villi
SUBMUCOSA
connective tissue
between mucosa and muscle
MUSCULAR LAYER
inner circular and outer longitudinal muscles perform peristalsis
SEROSA
protective outer layer
EPITHELIAL CELLS
single outer layer of cells on each villus
ADAPTATIONS TO ABSORPTION
villi increases the surface area of epithelium over which absorption is carried out
VILLI- EPITHELIAL CELLS
single cell layer of epithelial cells = short path for diffusion
MICROVILLI
on the surface of each cell increases the surface area even further
VILLI-LACTEALS
allow for rapid absorption and transport of lipids
VILLI-CAPILLARIES
close to epithelium
short path of diffusion
rich supply of blood
VILLI- RICH BLOOD SUPPLY
maintains concentration gradients between lumen and blood
MEMBRANE TRANSPORT
LIPIDS
simple diffusion
non-polar and can pass freely through the hydrophobic core of the plasma membrane into the epithelial cells (down the concentration gradient)
MEMBRANE TRANSPORT
FRUCTOSE, VITAMINS
facilitated diffusion
water soluble/ hydrophilic M use channels proteins to pass phospholipid bilayer and enter the epithelial cells (down conc gr.)
MEMBRANE TRANSPORT
GLUCOSE, AA, MINERAL IONS
protein pumps use ATP to move M against conc gr into epithelial cells
MEMBRANE TRANSPORT
ANTIBODIES FROM BREAST MILK
the plasma membrane folds inwards to form vesicles to absorb larger molecules without digesting them
DIGESTION OF STARCH INTO GLUCOSE
starch consists of amylose and amylopectin
amylase breaks amylose into maltose monomers
dextrinase breaks amylopectin into glucose monomers
maltase digests maltose into glucose monomers
TRANSPORT OF THE PRODUCTS OF STARCH DIGESTION TO THE LIVER
the digested glucose is absorbed and transported to various body tissues
TRANSPORT OF THE PRODUCTS OF STARCH DIGESTION TO THE LIVER 1
glucose is co-transported with Na ions into the epithelial cells of the villus
TRANSPORT OF THE PRODUCTS OF STARCH DIGESTION TO THE LIVER 2
glucose moves by facilitated diffusion into the lumen of the villus
TRANSPORT OF THE PRODUCTS OF STARCH DIGESTION TO THE LIVER 3
glucose then diffuses a short distance into the adjacent capillaries where it dissolves into the blood plasma
TRANSPORT OF THE PRODUCTS OF STARCH DIGESTION TO THE LIVER 4
blood in the capillaries move to venules then to the hepatic portal vein which transports the glucose to the liver
TRANSPORT OF THE PRODUCTS OF STARCH DIGESTION TO THE LIVER 5
the liver absorbs excess glucose which is converted to glycogen for storage
DIALYSIS TUBING
to model absorption of digested food in the intestine
tube is semi- permeable