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AQA GCSE Biology - Paper 1| Questions Answered 100% Correct $13.49   Add to cart

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AQA GCSE Biology - Paper 1| Questions Answered 100% Correct

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  • AQA GCSE Biolog
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  • AQA GCSE Biolog

What are the two main differences between active transport and diffusion? - ANSWER Active transport uses energy whereas diffusion doesn't. Active transport goes against the concentration gradient whereas diffusion goes along it Adaptations of Exchange Surfaces - ANSWER 1) Large surface area - lo...

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  • August 28, 2024
  • 37
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers
  • AQA GCSE Biolog
  • AQA GCSE Biolog
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KenAli
AQA GCSE Biology - Paper 1| Questions
Answered 100% Correct

What are the two main differences between active transport and diffusion? - ANSWER Active
transport uses energy whereas diffusion doesn't. Active transport goes against the
concentration gradient whereas diffusion goes along it



Adaptations of Exchange Surfaces - ANSWER 1) Large surface area - lots of substances
can diffuse at once
2) Lots of blood vessels - to get stuff into and out of the blood quickly
3) Thin membrane - short distance for substances to diffuse
4) Often ventilated - air moves in & out



Give two ways that the villi in the small intestine are adapted for absorbing digested food -
ANSWER 1) A single layer of surface cells
2) A very good blood supply to assist quick absorption



Explain how the leaves are adapted to maximise the amount of carbon dioxide that gets into
their cells - ANSWER 1) The exchange surface in a leaf is covered in stomata which the
carbon dioxide diffuses through

2) The leaf has a flattened shape which increases the area of its exchange surface, therefore
it's more effective
3) The walls of the cells inside the leaf act as another exchange surface

4) The air spaces inside the leaf increase the area of the exchange surface which increases
the chance for carbon dioxide to enter the cells



What affects the rate of diffusion? - ANSWER Concentration gradient - the steeper the gradient,
the faster the rate

Temperature - the higher the temperature, the faster the rate (the particles have more
energy thus move around faster)

,Surface area - the larger it is, the faster the rate
Diffusion distance - the shorter the distance, the faster the rate




Examples of active transport - ANSWER Plants = Root hairs absorb minerals and water. Each
branch of a root will be covered in tiny hairs, therefore increasing the surface area for the
absorption of minerals and water. The concentration of minerals is usually higher in the root
hair cells than in the soil around them, therefore they can't use diffusion for this process.

Animals = Glucose is taken in from the gut and from kidney tubules.



How are alveoli in the lungs specialised to maximise the diffusion of oxygen and carbon
dioxide? - ANSWER -an enormous surface area
-a moist lining for dissolving gases
-very thin walls
-a good blood supply



How do fish respire? - ANSWER -Water enters the fish through the mouth and passes out
through the gills

-During this process, oxygen diffuses from the water into the blood in the gills and
carbon dioxide diffuses from the blood into the water



How are fish adapted for gas exchange? - ANSWER -Each gill is made up of lots of gill
filaments which create a large surface area for the exchange of gases
-Gill filaments are covered in lamellae which increase the surface even more

-The lamellae have lots of blood capillaries to speed up diffusion
-The lamellae have a thin surface layer of cells to minimise the diffusion distance

-Blood flows through the lamellae one way and water flows over in the opposite direction
which maintains a higher concentration gradient between the blood and the water

-The concentration of oxygen in the water is always higher than that in the blood to
maximise the amount of oxygen diffusion from the water into the blood

,Microscopy Practical - Preparing the Slide - ANSWER 1) Add a drop of water to the middle of a
clean slide


2) Cut up an onion & separate it out into layers. Use tweezers to peel off some epidermal
tissue from the bottom of one of the layers
3) Using the tweezers, place the epidermal tissue into the water on the slide

4) Add a drop of iodine solution - a stain used to highlight objects in a cell by adding colour
to them

5) Place a cover slip on top - stand the cover slip upright on the slide, next to the water
droplet. Then, carefully tilt & lower it so it covers the specimen. Try not to get any air bubbles
under there - there'll obstruct your view



Microscopy Practical - Using a Light Microscope - ANSWER 1) Clip the slide you've prepared
onto the stage
2) Select the lowest-powered objective lens
3) Use the coarse adjustment knob to move the stage up to just below the objective lens

4) Look down the eyepiece. Use the coarse adjustment knob to move the stage
downwards until the image is roughly in focus

5) Adjust the focus with the fine adjustment knob, until you get a clear image of what's on the
slide



Microscopy Practical - Drawing Observations - ANSWER 1) Draw what you see under
the microscope using a pencil with a sharp point

2) Make sure your drawing takes up at least half of the space available & that it is drawn
with clear, unbroken lines
3) Your drawing should not include any colouring or shading
4) If you are drawing cells, the subcellular structures should be drawn in proportion
5) Include a title & write down the magnification that it was observed under
6) Label the important features of your drawing using straight, uncrossed lines

, What happens during binary fission? - ANSWER 1) The circular DNA & plasmid(s) replicate
2) The cell gets bigger & the circular DNA strands move to opposite poles of the cell
3) The cytoplasm begins to divide & new cell walls begin to form

4) The cytoplasm divides & two daughter cells are produced. Each daughter cell has one copy
of the circular DNA, but can have a variable number of copies of the plasmid(s)



What is binary fission? - ANSWER A type of simple cell division used by prokaryotic cells
to reproduce & split into two


What conditions do bacteria need to divide? - ANSWER 1) Warm environment
2) Lots of nutrients



What is the mean division time? - ANSWER The average amount of time it takes for one
bacterial cell to divide into two



How do you make an agar plate? - ANSWER Hot agar jelly is poured into shallow Petri dishes.
When the jelly's cooled & set, inoculating loops can be used to transfer the microorganisms to
the culture medium. Alternatively, a sterile dropping pipette & spreader can be used to get an
even covering of bacteria. The microorganisms then multiply



Investigating the Effect of Antibiotics on Bacterial Growth - Method - ANSWER 1) Place paper
discs soaked in different types of antibiotics on an agar plate that has an even covering of
bacteria. Leave some space between the discs

2) The antibiotic should diffuse into the agar jelly. Antibiotic-resistant bacteria that aren't
affected by the antibiotic will continue to grow on the agar around the paper discs, but non-
resistant strains will die. A clear area will be left where the bacteria have died - an inhibition
zone

3) Make sure you use a control - a paper disc that has not been soaked in an antibiotic. Instead,
soak it in sterile water so you can be sure that any difference between the growth of bacteria
around the control disc & around one of the antibiotic discs is due to the effect of the
antibiotic alone

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