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1) Functions of sub-cellular structures in animal cells.
Nucleus = Contains genetic material – controls activities of cell.
Cytoplasm = Where most chemical reactions occur; contains enzymes.
Cell membrane = Holds cell together and controls what goes in and out.
Mitochondria = Aerobic respiration occurs.
Ribosomes = Protein synthesis occurs.
2) Functions of sub-cellular structures in plant cells.
Cell wall = Made of cellulose; strengthens cell.
Large (permanent) vacuole = Contains cell sap; supports cell.
Chloroplasts = Contains chlorophyll; where photosynthesis occurs.
3) Functions of sub-cellular structures in bacteria.
Chromosomal DNA = Controls cells activities and replications.
Plasmid DNA = Small loops of extra DNA.
Flagellum = Long tail that helps it to move.
4) Describe how sperm cells are adapted to their function.
Acrosome = Stores enzymes to digest through membrane of egg cell.
Haploid nucleus = Fertilise egg cell.
Mitochondria = Provide ATP to swim to egg.
Long tail = Swim to egg.
Streamlined shape to help swim faster to egg.
5) Describe how egg cells are adapted to their function.
Nutrients in cytoplasm to feed embryo.
Haploid nucleus.
After fertilisation, membrane hardens to stop more sperm getting in.
,Shad Ahmad Biology
6) Describe how ciliated epithelial cells are adapted to their function.
Cilia (hair-like) beat to move substances along surface of the tissue.
7) Milli, Micro, Nano and Picometer…
Milli = 10-3 m
Micro = 10-6 m
Nano = 10-9 m
Pico = 10-12 m
8) What is the equation for magnification?
Total magnification = Eyepiece lens magnification x Objective lens magnification
9) Explain the mechanism of enzyme action.
Lock and key mechanism – The complementary substrate has to fit into active site of enzyme, to
form an enzyme-substrate complex. If the substrate’s shape doesn’t match the active site’s shape,
then the reaction won’t be catalysed.
When active site is denatured, the shape of it changes, so it no longer matches with the specific
substrate.
10) Explain the effects of temperature, substrate concentration and pH on enzyme activity
Temp = Higher temp increases rate. If it gets too hot, it passes optimum so bonds of the enzyme
break, which denatures the active site, so the substrate won’t fit.
Substrate conc = The higher the substrate conc, the faster the reaction. After optimum, all active
sites are used up, so a higher conc makes no difference.
pH = All enzymes have an optimum pH (often neutral pH 7). Anything too high or low with decrease
rate.
,Shad Ahmad Biology
11) Core Practical: Investigate the effect of pH on enzyme activity.
If starch is present, iodine solution changes from browny-orange to blue-black.
- Drop of iodine solution into every spot of spotting tile.
- Heat water to 35°C (water bath).
- Add amylase and buffer solution (pH 5) to boiling tube.
- Put boiling tube in water for 5 mins.
- Add starch solution to boiling tube.
- Continuously sample to record how long it takes for amylase to break down all the starch, by using
a dropping pipette to take a fresh sample from boiling tube every 10 secs and drop into a spot.
When iodine solution remains browny-orange, starch is no longer present.
- Repeat experiment with buffer solutions of different pH values.
Rate = 1000/time
12) Explain the importance of enzymes as biological catalysts in the synthesis of carbohydrates,
proteins and lipids and their breakdown.
13) Core Practical: Investigate the use of chemical reagents to identify starch, reducing sugars,
proteins and fats.
Test for sugars = Add Benedict’s reagent
(blue) to sample and heat. If test is positive,
it forms a coloured precipitate. The higher
the conc of reducing sugar, the further the
colour change goes.
Test for starch = Add iodine solution. If starch is present, goes from browny-orange to blue-black.
Emulsion Test for Lipids =
Biuret Test for Proteins = Add potassium hydroxide to make solution alkaline. Add copper sulfate
(blue) – if there’s protein, it turns purple.
, Shad Ahmad Biology
14) Explain how the energy contained in food can be measured using calorimetry.
-Weigh small amount of dry food, then put it on a needle.
- Add set volume of water to boiling tube.
- Measure temp of water, then set fire to the food using a Bunsen burner flame.
- Hold burning food under boiling tube until it goes out. Keep relighting the food until it can’t catch
fire again.
-Measure temp of water again.
15) Explain how substances are transported into and out of cells, by diffusion, osmosis and active
transport.
Diffusion = Net movement of particles from area of high conc to area of low conc.
Osmosis = Net movement of water molecules across a partially permeable membrane from a high
water conc to a low water conc.
Active transport = Movement of particles across a membrane against a conc gradient (from low to
high conc) using ATP (from respiration).
16) Core Practical: Investigate osmosis in potatoes
Measure masses of same sized potato cylinders.
Put three in each solution (have different concs of sucrose).
Remove cylinders and dry with a towel to remove water from surface.
Weigh them again and record results.
17) Calculate percentage gain and loss of mass in osmosis
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