GAS EXCHANGE & DIGESTION Flashcards
explain the surface area to volume ratio in smaller organisms ?
in small organisms the SA:VOL ratio is larger as the distance from the middle and to the edge is smaller so a shorter diffusion distance so more gas exchange occurs and more heat is lost.
explain the SA:VOL in larger organisms ?
the SA:VOL in larger organisms is smaller so a longer distanced from the middle to the edge so not as faster gas exchange , less heat is lots and the metabolic rate of larger organisms is higher so requires more frequent oxygen to cells as needed for respiration. larger organisms have an issue with getting oxygen and nutrients they need from the enviroment and this is why they develop adaptations for more frequent gas exchange as they need more efficent delivery of oxygen.
what occurs during digestion ?
a series of enzymes hydrolyse large insoluble molecules into smaller soluble ones which can be absorbed into the blood and transported around the body and used.
where does the absoption of nutrient take place and how ?
it takes place in the small intestine which has particular features which allow it to maximise the movement of substances through cells in the blood.
explain the features that the small intestine have that allow maximised movement of substances through cells in the blood.
the small intestine has internal walls folded into projections called villi. the villi have thin walls to help keep the diffusion pathway short. villi contains lots of capillaries to help maintain the concentration gradient by constantly transporting absorbed nutrients away. villi contain muscles which move and help them to mix the contents of the illeum so that the villi always have new material next to them to absorb nutrients, helps to maintain a conc gradient.
explain how epithelial cells are adapted for efficent digestion
they contain microvilli which increase surface area for diffusion further. many mitochondria which provide energy for active transport. they contain carrier proteins for active transport. they contain channel proteins for facilliated diffusion
explain the absorption & digestion of carbohydrates
So starch is broken down by the salivary glands which produces the enzyme amylase which breaks down the glycosidic bonds in starch to form maltose.
the pancreas produces the pancreatic amylase which is released into the small intestine and this breaks the glycosidic bonds to hydrolyse starch to form maltose.
In the small intestine it contains membrane bound disaccharides in the cell membrane of epithelial cells and this breaks down the glycosidic bonds and hydrolyses the disacharides into monosaccharides.
explain what the 3 membrane bound disaccharides found in the cell membrane of epithelial cells do
> maltase breaks down maltose into alpha glucose
sucrase breaks down sucrose into glucose and fructose
lactase breaks down lactose into galactose and glucose
explain the digestion of proteins
peptidases and proteases are enzymes which breakdown protein in a series of hydrolysis reactions. protein digestion only occurs in the stomach and the small intestine. the stomach produces hydrochloric acid which dentaures the protein and unfolds its 3D tertiary structure to reveal the polypeptide chains. the stomach lining produces pepsin enzyme which digests the polypeptode chains into even shorter polypeptides. in the small intestine other peptidases are made and secreted by the pancreas into the small intestine , these peptidases are membrane bound and found within the cells that line the small intestine. when the dipeptides are further broken down into amino acids they are absorbed into the blood.
what are the 3 different types of protease enzymes that break bonds in different sections of proteins.
. endopeptidases
. exopeptidases
. dipeptidases
what does endopeptidases do ?
hydrolyse bonds within a large protein to create smaller polypeptide chains.
create terminal ends for exopeptidases to work on.
what does exopeptidase do ?
hydrolyses terminal peptide bonds between the amino acids on the end of the polypeptide chain to remove individual amino acids and create smaller polypeptide chains.
what does dipeptidase do ?
its a type of exopeptitadse found in the membrane of epithelial cells lining the small intestine. they work on dipeptides to hydrolyse the peptide bonds holding them together . creating two single amino acids which can be transported through membrane into epithelial cell.
how does the digestion of lipids occur.
lipases are enzymes which hydrolyse the ester bonds in triglycerides to form fatty acids and monoglycerides. lipases are made in the pancreas and secreted into the small intestine. bile salts are produced by the liver but stored in the gall bladder which releases them into the small intestine. Bile salts help to breakdown large fat globules by emulsyfying them into smaller droplets. this speeds up the action of lipases by increasing surface area of lipids that can be exposed to the enzyme. once the lipid has been broken down by the lipase the monoglycerides and the fatty acids stay attached to bile salts and form smaller structures called micelles. these help with the absorption of fatty acids and monoglycerides into the blood stream.
