Past paper questions Flashcards
Tissue
group of cells with similiar structures working together to perform a function
Blood clotting process
When the skin is broken, platelets release a chemical which converts soluble fibrinogen into insoluble fibrin. This forms an insoluble mesh around the wound that traps red blood cells forming a clot
why is genetic variation improtant?
can adapt to changes in the environment and new diseases. Therefore, increasing the chances of survival of the species.
why when boiling potato sticks there is no change of mass in salt water solutions?
Because the potatoes proteins are damaged and the cell membrane becomes destroyed/damaged, so no osmosis can occur.
factors that influence the movement of molecules through membranes
temperature; surface area; concentration gradient; size of molcule; thickness across membrane; pressure; number of protein channels; number of mitochondria
describe the pathowayMolecules of carbon dioxide that are produced in muscle cells are transported to the blood.
Describe the pathway taken by these molecules of carbon dioxide
CO2 is produced in mitochondrion,
diffsues in cytoplasm
through membrane
through capillary wall
In blood:
travels in veins/arteries
travels to lungs;
to alveoli;
excreted by exhalation
how are capillaries adapted for their functions
thin wall - efficient gas exchange/diffusion
small lumen - many capillaries can fit into tissues
extensive network;
large surface for diffusion;
capillary cells have pores - allows substances to pass in and out of the blood easily
how a molecule of co2 from the atmosphere reaches the site of photosynthesis in a leaf
diffuses down a concentration gradient through the stomata. then diffuses through the spongy mesophyll cells until it reaches the palisade mesophyl cell.
adaptations of roots to absorb ions
has root hair cells;
through carrier molecule;
large SA for absorption;
roots grow continually (to find new sources of ions);
why use sodium hydrogencarbonate solution in a photosynthesis experiment
so carbon dioxide is not a limiting factor
uses in a plant of the carbohydrate produced in photosynthesis
respiration;
converted to sucrose;
used to make nectar;
used to make cellulose/lignin;
used in cell walls;
used to make starch;
stoage;
used to make amino acids;
used to make chlorophyll;
how increases in atmospheric carbon dixoide concentrations contribute to global warming
carbon dioxide is a greenhouse gas which enhances the greenhouse effect. This is when radiation is trapped in the atmosphere by greenhouse gases instead of being emitted into outer space. Causing temperatures to rise = global warming
role of mechanical digestion
breaks up food into smaller pieces without chemical change by teeth. Or muscles to mix with digestive juices. To increase surface area for enzyme action. Speeds up chemical digestion.
Or just to make food easier to swallow
what organ converts glucose to glycogen
liver
besides insulin and glucagon what other hormone influences the concentration of glucose in blood
adrenaline
why is it important that water is absorbed in the alimentary canal?
prevents:
loss of large volumes of water
loss of ions
diarrhoea
dehyration
plasmolysis how
water moves out of the cell by osmosis through a partially permeable membrane as cell contents have a higher water pot than the solution
The same gene has to be selected from each species for sequencing because ..
Allows comparison of alleles of the same gene. To show how closely related the two species are.
