Cells Exam Qs Flashcards
Give two ways in which pathogens can cause disease. (2 marks)
(Start if cell recognition)
- (Releases) toxins;
- Kills cells / tissues.
- Accept any reference to cell / tissue damage
Putting bee honey on a cut kills bacteria. Honey contains a high concentration of
sugar.
Use your knowledge of water potential to suggest how putting honey on a cut kills
bacteria. (3 marks)
- Water potential in (bacterial) cells higher (than in honey) / water potential in honey lower (than in bacterial cells);
- Water leaves bacteria / cells by osmosis;
- (Loss of water) stops (metabolic) reactions.
A mutation of a tumour suppressor gene can result in the formation of a tumour.
Explain how. (2 marks)
- (Tumour suppressor) gene inactivated / not able to control / slow down
cell division; - Rate of cell division too fast / out of control.
Not all mutations result in a change to the amino acid sequence of the
encoded polypeptide.
Explain why. (1 mark)
- (Genetic) code degenerate;
2. Mutation in intron.
Some cancer cells have a receptor protein in their cell-surface membrane that binds
to a hormone called growth factor. This stimulates the cancer cells to divide.
Scientists have produced a monoclonal antibody that stops this stimulation.
Use your knowledge of monoclonal antibodies to suggest how this antibody stops
the growth of a tumour. (3 marks)
- Antibody has specific tertiary structure / binding site / variable region;
- Complementary (shape / fit) to receptor protein / GF / binds to receptor
protein / to GF; - Prevents GF binding (to receptor)
Herpes simplex virus (HSV) infects nerve cells in the face, including some near the
lips. Like many other viruses, HSV can remain inactive inside the body for years.
When HSV becomes active, it causes cold sores around the mouth.
HSV infects nerve cells in the face (line 1). Explain why it infects only nerve cells. (3 marks)
- Outside of virus has antigens / proteins;
- With complementary shape to receptor / protein in membrane of cells;
- (Receptor / protein) found only on membrane of nerve cells.
HSV can remain inactive inside the body for years. Explain why this
virus can be described as inactive (2 marks)
- No more (nerve) cells infected / no more cold sores form;
2. (Because) virus is not replicating.
Suggest one advantage of programmed cell death (1 mark)
Prevents replication of virus.
What organelle is responsible for protein synthesis?
Ribosomes
What organelle is responsible for modifying protein?
Golgi apparatus
What organelle is responsible for aerobic respiration?
Mitochondria
Describe and explain how centrifuging the culture allowed the scientists to obtain a
cell-free liquid. (3 marks)
- Large / dense / heavy cells;
- Form pellet / move to bottom of tube (when centrifuged);
- Liquid / supernatant can be removed.
Give one function of lysosomes.
Break down cells / cell parts / toxins
Describe how you could use cell fractionation to isolate chloroplasts from leaf tissue. (3 marks)
- How to break open cells and remove debris;
- Solution is cold / isotonic / buffered;
- Second pellet is chloroplast.
Name two structures in a eukaryotic cell that cannot be identified using an optical
microscope. (2 marks)
Mitochondrion / ribosome / endoplasmic reticulum / lysosome / cell-surface
membrane.
Explain the difference in the structure of the starch molecule and the cellulose
molecule (2 marks)
- Starch formed from α-glucose but cellulose formed from β-glucose;
- Position of hydrogen and hydroxyl groups on carbon atom 1 inverted.
Explain one way in which starch molecules are adapted for their function in plant
cells. (2 marks)
- Insoluble;
- Don’t affect water potential;
OR - Helical;
- Compact;
OR - Large molecule;
- Cannot leave cell.