AQA As Biology Unit 3 Cells

Calculate the maximum length of the chloroplast in micrometres show your working (2)

2.53-2.66 Any lenghth diving by 30000

Describe the function of the chloroplast.(2)

Absorbs/ traps/uses light (1)for photosynthesis(2) Produces carbohydrates/Sugars/lipids/protein(Alternative mark)

(ref to January AQA 2013, Or AQA Biology As Year 1 And AS Page 82) The photograph shows part of the cytoplasm of a cell Organelle x is a mitochondrion. What is the function of this organelle?(1)

Aerobic respiration

B What is function of organelle Z(1)

Aerobic respiration/provide energy

This photograph was taken using a transmission electron microscope. This structure visible in this photograph could not have been seen using an optical light microscope, Explain why? (2)

As light microscope has lower resolution due to the wavelengths being too high

The scientists measured cell damage by measuring the activity of lysosome give one function of the lysosomes (1)

Breaks down cells(1)

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells(5)

Cell is homogenised to break down cell(1) then filtered to remove debris(2) Use isotonic solution to prevent damage to cells due to bursting via osmosis(3) Keep cold to stop cell activity(4) use buffer stock to stop denaturing of enzyme(4) Centrifuge at low speed to separate the heavier organelles (5) Respin at higher speed to get mitochondria at pellet(Any 5 from these points)

(ref to January AQA 2012, Or AQA Biology As Year 1 And AS Page 82) An Amoeba is a single-Celled Eukaryotic organism, Scientists used a transmission electron microscope to study an amoeba. This Diagram shows its structure A(I) Name Organelle Y (1)

Golgi Apparatus

Name organelle Y(1)

Golgi apparatus

(ref to January AQA 2012, Or AQA Biology As Year 1 And AS Page 82) The diagram shows a chloroplast as seen with an electron microscope Name X and Y(2)

Granum Stroma

The scientist used a transmission electron microscope to study the amoeba explain why?

Higher resolution so Shorter wavelength Can see internal structures

Describe and explain how centrifuging the culture allowed the scientist to obtain a cell free liquid(3)

Large heavier cells (1) Move to bottom of tube when centrifuged(2) Supernatant can be removed(3)

A(ii) Name to other structures which shows that the amoeba is a eukaryotic cell.(2)

Lyosomes Nucleus Endoplasmic reticulum

Rapid diffusion of substances from the lumen of the gut into the cytoplasm(1)

Microvili increase the Surface area

(ref to January AQA 2012, Or AQA Biology As Year 1 And AS Page 83) The diagram shows part of the epithelial cell from an insect's gut. The cell is adapted for the three functions below used the diagram to explain how this cell is adapted for each of these functions below. Use different feature in the diagram for your answer The active transport of substances from the cell into the blood(2)

Mitochondria respire produces ATP transport against gradient.

What does the graph show about the growth of roots? Use data in the table to explain your answer(2)

More faster mitosis division near the tip at 0.2(1) No mitosis after 1.6 So roots grow via mitosis adding new cells to tip

Describe the principles and the limitations of using a transmission electron microscope to investigate cell structure(5)

Principles: Electron beam pass through thing layer of specimen(1) Denser parts absorb more electron(2) So the denser parts look darker(3) Limitations: Takes a long time to prepare as there is a complex staining method(1) Specimens must be dead as it must be in a vacuum(2) Artefacts may be present(3)-Due to preparation-

The synthesis of enzymes (2)

Ribosomes make proteins enzymes are proteins

(Reference to Physics and Maths tutor Studying cells page 4) The student cut out thin sections of tissue to view with an optical light microscope explain why it was important the sections were thin(2)

To allow more light to pass through(1) Few layers of cells to be viewed(2)

H.Pylori cells produce an enzyme that neutralises acid suggest one advantage of the h.Pylori of producing this enzyme(2)

To stop them being damaged (1) By the stomach acid(2)