past papers Flashcards
state three differences between eukaryotic and prokaryotic kingdoms
eukaryotes:
- have nucleus
- have more than one chromosome
- lack plasmids
- have organelles
give an example of a disease caused by a protoctist
- plasmodium causing - malaria
explain the role of fibre in diet
- for peristalsis
- to move food along the intestine
- because it is an indigestible material
what is a catalyst
a substance that speeds up chemical reactions
explain why some farmers limit the amount of chemical fertilisers they give to their crops
- incresed soil concentration reduces water potetial of soil
- which prevents water uptake
- so plant wilts
- it washes into river and lakes (leaching)
- and causes eutrophication
- so loss of aquatic life
- can use natural fertilisers
- which produces organic which earns more money
explain the role of bile in digestion
- neutralises stomach acid
- for optimum pH for enzymes
- emulsifies lipids
- to increase their surface area
why is the concentration of glucose in the hepatic portal vein higher than in the hepatic vein 1 hour after eating
because the liver:
- absorbs glucose
- and uses insulin
- to convert it to glycogen
- which lowers blood glucose leaving liver
why is the concentration of glucose in the hepatic portal vein lower than in the hepatic vein 5 hours after eating
- because there is less glucose coming in from food
- so no insulin is released
- and glycogen is being converted to glucose
- and the glucose is being released from the liver
why are there not exactly equal numbers of boys and girls in the world
- because each time it is random
- during fertilisation
- more Y sperm die
two adaptations of the spongy mesophyll
- gaps between cells- diffusion
- near bottom - absorption CO2
what role do lymphocytes have in the immune response
they create -specific -antibodies to -destroy -pathogens and to -clump them together
explain what happens to bacteria once they have been ingested by phagocytes
- they are broken down by - digestive enzymes - and therefore destroyed - and the products are absorbed by phagocyte
why is it important for cows to be able to break down a plant cell wall
- releases cellulose
- for glucose/energy
- for respiration
what does auxin do in the roots and the shoots
- in the shoots auxin promotes cell growth
- the the roots auxin inhibits cell growth
why does the eye contain a liquid with an enzyme that can break down cell walls
- so that it can break down pathogens
- to prevent infectiou/disease
