transport

Question 1

what is the fluid mosaic model

Answer 1

the phospholipid bilayer is very small so we use the fluid mosaic model to describe what is going on in the membrane

Question 2

intrinsic proteins

Answer 2

can be carrier molecules or channels
transport substances that cant diffuse accross the membrane
can also be receptors for hormones and neurotransmitters, or enzymes for catalyzing reactions

Question 3

extrinsic proteins

Answer 3

may be free on the membrane surface or bound to an intrinsic protein
extracellular side- act as receptors for hormones or neurotransmitters or are involved in cell recognition
cytosolic side- involved in cell signalling or chemical reactions, can dissociate from the membrane and move into the cytoplasm

Question 4

cholesterol

Answer 4

C27H46O
type of lipid
controls membrane fluidity- more cholesterol, less fluid, less permeable membrane
keeps membrane at normal body temp

Question 5

simple diffusion

Answer 5

phospholipid bilayer is hydrophobic so water free
hydrophobic molecules such as fats will pass straight through

Question 6

channels

Answer 6

always open allowing diffusion accross the membrane

Question 7

carrier proteins

Answer 7

shape changed by the presence of a molecule which causes them to open like a gateway

Question 8

facilitated diffusion

Answer 8

passive process (no ATP needed)
uses proteins to transport molecules
ions and polar molecules

Question 9

concentration gradient

Answer 9

the steeper the concentration gradient, the faster diffusion takes place
both simple and facilitated diffusion allow molecules to move down their concentration gradient

Question 10

osmosis

Answer 10

diffusion of water
net movement of water molecules from a region of low water concentration, through a partially permeable membrane
process of which cells exchange water with their environment

Question 11

water potential

Answer 11

net movement of water is determined by difference in water potential between two solutions
tendancy of water molecules in a system to move
solutions have a lower water potential than pure water

Question 12

solute potential

Answer 12

the greater the amount of solute the lower the water potential
this is because water molecules bind to the solute molecules, reducing the number of water molecules that are free to diffuse

Question 13

isotonic solution

Answer 13

solute concentration is balanced with the concentration inside the cell
water still moves but the rate is the same in both directions

Question 14

hypotonic solution

Answer 14

solute concentration is lower than the concentration inside the cell
water moves into the cell
causes cell to shrivel
without a cell wall the cell can explode

Question 15

hypertonic solution

Answer 15

solute concentration is higher than the concentration inside the cell
water moves out of cell
can cause cell to shrivel

Question 16

active transport

Answer 16

movement of molecules or ions into or out of a cell from an area of low concentration to an area of high concentration

Question 17

atp in active transport

Answer 17

released during respiration
respiration is glucose+oxygen=carbon dioxide+water+atp
decrease rate or respiration-decrease atp-decrease active transport

Question 18

digestion

Answer 18

break large insoluble food molecules into smaller soluble molecules
absorb soluble food molecules
rest is waste and is removed from the body
mechanical/chemical digestion

Question 19

salivary glands

Answer 19

near the mouth
secrete amylase via a duct into the mouth

Question 21

oesophagus

Answer 21

adapted to transport food from mouth to stomach
thick muscular wall
peristalsis-muscular contractions push food down

Question 22

stomach

Answer 22

muscular sac, inner layer produces enzymes
stores and digests food, especially proteins
glands in stomach produce mucus to prevent lining digestion
mechanical digestion and chemical digestion

Question 23

small intestine

Answer 23

long muscular tube
produces enzymes in walls for digestion
inner walls folded into villi for large surface areas
surface area is further increased by microvilli
absorbtion of digestion products to blood

Question 24

gall bladder

Answer 24

bile
breaks down lipids into small droplets
raises pH

Question 25

large intestine

Answer 25

absorbs water food-drier/thicker-faeces

Question 26

pancreas

Answer 26

large gland below the stomach secretes pancreatic juice containing enzymes

Question 27

rectum

Answer 27

final section of intestines stores faeces before egestion via anus

Question 28

steps of carbohydrate digestion

Answer 28

amylose is a carbohydrase that hydrolyses starch into maltose maltose is then hydrolyses into glucose by the enzyme maltase maltase is a disaccharide which is found in cell surface membranes of the epithelial cells lining the small intestine sucrase and lactase are also found in epithelial cells and hydrolyse sucrose and lactose this allows the absorbtion of monosaccharides into epithelial cells of the small intestine which pass them into blood stream the lining of the small intestine has microvilli which increases surface area substantially allowing more membrane bound disaccharidases to fit into membrane and more absorbtion takes place

Question 30

steps of protein digestion

Answer 30

happens in stomach by protease enzymes a protease enzyme called and endopeptidase hydrolyses peptide bonds within proteins, creating smaller sized chunks this enzyme is secreted along with hydrochloeic acid, meaning the pH in the stomach is low and therefore acidic the partially digested food moves from the stomach into the small intestine fluid secreted by the pancreas travels to the small intestine and helps neutralise the acidic mixture and increase the pH this pancreatic juice contains endopeptidases and exopeptidases lastly there are dipeptidase enzymes found within the cell surface membrane of epithelial cells in the small intestines. these enzymes hydrolyse dipeptides into amino acids which are released into the cytoplasm of the cell

Question 31

endopeptidases

Answer 31

hydrolyse peptide bonds within polypeptide chains to produce dipeptides

Question 32

exopeptidases

Answer 32

hydrolyse peptide bonds at the ends of polypeptide chains to produce dipeptides

Question 33

emulsification in lipid digestion

Answer 33

in the stomach, solid lipids are turned into a fatty liquid consisting of fat droplets- not digestion when the fatty liquid arrives in the small intestine, bile whoch has been made in the liver and stored in the gall bladder is secreted the bile salts bind to the fatty liquid and breaks the fatty droplets into smaller ones via emulsification emulsification helps to increase the surface area of the fatty droplets for action of digestive enzymes

Question 34

digestion in lipid digestion

Answer 34

takes place in the lumen of small intestine lipase enzymes break down lipids to monoglycerides and fatty acids lipase enzymes are produced in the pancreas and secreted into the small intestine by the pancreas

Question 35

absorbtion in lipid digestion

Answer 35

tryglycerides are digested into monoglycerides and fatty acids after digestion, monoglycerides and fatty acids associate with bile salts and phospholipidsto form micelles micelles are needed because they transport the poorly soluble monoglycerides and fatty acids to the surface of the microvilli where they can be absorbed

Question 36

4 features of an efficient gas exchange surface

Answer 36

large surface area short diffusion pathway steep diffusion gradient good supply of blood

Question 37

a villus

Answer 37

huge surface area- further increased by microvilli thin walls tk decrease diffusion distance move to ensure contact with glucose products well supplied with blood vessels to carry away absorbed products

Question 38

absorbtion of glucose fructose galactose and amino acids

Answer 38

sodium is actively transported from the epithelial cell into the blood sodium concentration is now greater in the small intestine than the epithlial cell so diffuses into the cell as sodium enters it carries glucose with it through a cotransport protein glucose moves from a high concentratikn in the cell to a low concentration jn the blood via facilitated diffusion there is no ATP needed tk transport glucose however ATP is need fkr the active transport of sodium ions