exam questions

Question 1

describe the roles of the liver and pancreas in the digestion of fats (5)

Answer 1

liver releases bile which emulsifies fats to increase the surface area and make breaking down fats into smaller dropplets more efficient
-bile neautralises stomach acid so the enzyme works best since its at an optimum ph
-the pancreas makes lipase which is an enzyme that breakks down fatty acids into glycerol so it can be absorbed into the bloodstream

Question 2

a food contains protien, describe what happens to this protien after food is swallowed (4)

Answer 2

• digested / broken down / made soluble by protease enzyme in the stomach
  -protien broken down into amino acids by protease enzyme in the stomach
  -amino acids absorbed into blood

Question 3

complete the table that shows which digestive enzyme is made where (4)
bile
amylase
lipase
protease

Answer 3

bile is made in the liver
amalyse is made in salivary glands
lipase is made in pancreas/small intestine
protease made in stomach/pancreas/small intestine

Question 4

why is it necessary to break down protiens in the digestive system (3)

Answer 4

proteins are large
  proteins (may be) insoluble
so they cannot be absorbed / cannot enter blood or cannot pass through gut lining

Question 5

describe what is meant by diffusion (2)

Answer 5

the movement of particles from a high to low concentration down a concentration gradient

Question 6

explain 1 way the lungs of mammals are specialised for gas exhchange (2)

Answer 6

alveoli provide a large surface area for efficient gsa exchange
or capillaries are 1 cell thick to provide a shorter diffusion pathway

Question 7

explain how the structure of the root hair cell is adapted to absorb different substances (6)

Answer 7

• root hair/extension provides a larger surface area to increase the rate of water and ion absorbption by osmosis and active transport
• lots of mitochondria since active transport
  requires (lots of) energy from respiration
• and the uptake of mineral ions requires energy / active transport  because ions are absorbed against a concentration gradient
• thin cell wall creates a shorter absorption pathway
  -vacuole has a high salt concentration to increase water uptake by osmosis

Question 8

explain why the root hair cell does not need choloroplasts (2)

Answer 8

 no (available) light underground

(so) roots do not photosynthesise or do not make glucose

Question 9

describe why diffusion is important to animals and plants, include examples of diffusion of named substances,animals and plants. (6)

Answer 9

importace of diffusion-   to take in substances for use in cells chemical reactions and remove waste product
examples of diffusion-  for gas exchange / respiration: O2 in / CO2 out ,   food molecules absorbed: glucose, amino acids, etc , water absorption in the large intestine ,  water and ion absorption by roots
description of processes
-partially permeable membrane ,tugor flaccid and plasmolysis for osmosis, movement of particles down a concentration gradient

Question 10

Give one feature of a reflex action

Answer 10

Fast automatic and involuntary

Question 10

what is osmosis (3)

Answer 10

• the passive movement of water particles through a partially permeable membrane from a high to low concentration

Question 11

Explain how conditioning can be used to train police horses to be calm in noisy environments (3)

Answer 11

Habituation uncanny be used to expose animals to noisy environments so the calm reaction can be automatic due to positive reinforcement

Question 12

Suggest 2 advantages of using police on horses compared to police on foot

Answer 12

1-can see more people from above, 2-intimidate criminals to move away and leave

Question 13

Give 2 advantages of using gm wheat compared to pesticides

Answer 13

-prevents the reduction of biodiversity and doesn’t kill any organisms,no bioacccumilation of pesticide doses

Question 14

Give 2 reasons why some people are concerned about the use of gm wheat

Answer 14

Concerned about the spreading of genes and disease in a-hit population.long term human health effects are unknown

Question 15

Why do we incubate agar plates when growing microrganisms

Answer 15

So bacteria has time to reproduce

Question 16

Describe 3 techniques the students should use to prevent contaminated agar when growing microrganisms (3)

Answer 16

-consistently sterilize the forceps and materials used
-work near a flame to kill off bacteria
-don’t fullly open dish to prevent spread of microorganisms

Question 17

Bacteria didn’t grow near disk soaked in sanatiser but around the edges of it. Explain why. (3)

Answer 17

Sanatiser killled bacteria and sanatiser diffused from the dish but the concentration fo sanatiser around the edges was too low to be effective

Question 18

Explain why the widespread use of anti microbial chemicals could increase the proportion of bacteria resistant to sanatiser b (2)

Answer 18

-random mutation in the bacteria causes resistant bacteria to outcompete the non resistant ones, resistant bacteria survive and reproduce then pass of resistant gene to offspring

Question 19

Explain how cleaning large forest areas effects the balance of gases in the environment (2)

Answer 19

Removal of trees leads to less co2 being removed by photosynthesis and increase of co2 emissions due to trees being burnt so less trees can undergo photosynthesis

Question 20

Explain how an increase in temperature could lead to a decrease in the human population (4)

Answer 20

Glaciers could melt and reduce biodiversity to flood land.seasonal crops are unable to grow, animals lose their habitat which leads to crop failure and starvation in the human population,inanhibitable land leads to an increase in pathogens which can spread.

Question 21

Explain how an increase of nitrate ions can lead to the death of fish in a lake. (5)

Answer 21

Increased nitrate will stimulate the growth of algae bloom which will block the light needed. This leads to less photosynthesis from underwater plans which results in the death of algae. Microrganisms will Seef on dead algae and resprire to use more oxygen which will lead to the plant sufffocating due to too much competition for oxygen