.. Flashcards
Suggest and explain two ways the cell-surface membranes of the cells lining the
uterus may be adapted to allow rapid transport of nutrients.
Membrane folded so increased/large :
area;
OR
Membrane has increased/large surfac for (fast) diffusion/facilitated diffusion/ transport/co-transport;
2. Large number of protein channels/can membrane) for facilitated diffusion;
3. Large number of protein carriers (in m for active transport;
4. Large number of protein (channels/cal membrane) for co-transport
Give the two types of molecule from which a ribosome is made.
One of RNA/ribonucleic acid(s)/nucleotide(s)/nucleic
acid(s)/rRNA/ribosomal RNA/ribosomal ribonucleic
acid
and
one of protein(s)/polypeptide(s)/amino acid(s)/
peptide(s)/ribosomal protein;
Describe the role of a ribosome in the production of a polypeptide. Do not include
transcription in your answer. (3)
mRNA binds to ribosome;
2. Idea of two codons/binding sites;
3. (Allows) tRNA with anticodons to bind/associate;
4. (Catalyses) formation of peptide bond between
amino acids (held by tRNA molecules);
5. Moves along (mRNA to the next
codon)/translocation described;
In a eukaryotic cell, the base sequence of the mRNA might be different from the sequence of the pre-mRNA.
Explain wh
1.Introns (in pre-mRNA);
2. Removal of sections of (pre-mRNA)/splicing;
In mammals, in the early stages of pregnancy, a developing embryo exchanges substances with its mother via cells in the lining of the uterus. At this stage, there is a high concentration of glycogen in cells lining the uterus.
Describe the structure of glycogen.
[2 marks]
Polysaccharide of α-glucose;
OR
polymer of α-glucose;
2. (Joined by) glycosidic bonds
OR
Branched structure;
In humans, after the gametes join at fertilisation, every cell of the developing embryo undergoes mitotic divisions before the embryo attaches to the uterus lining.
• The first cell division takes 24 hours.
• The subsequent divisions each take 8 hours.
After 3 days, the embryo has a total volume of 4.2 × 10–3 mm3.
What is the mean volume of each cell after 3 days? Express your answer in standard form.
Show your working.
[2 marks
3.3 x 10–5 OR 3.28 x 10–5 OR 3.281 x 10–5
;;
1 mark for
Evidence of 128 (cells)
Correct numerical calculation but not in standard
form gains 1 mark (0.00003281 OR 0.0000328 OR
0.000033);
Sodium ions from salt (sodium chloride) are absorbed by cells lining the gut. Some of these cells have membranes with a carrier protein called NHE3.
NHE3 actively transports one sodium ion into the cell in exchange for one proton (hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how NHE3
does this.
[3 marks]
Co-transport;
2. Uses (hydrolysis of) ATP;
3. Sodium ion and proton bind to the protein;
4. Protein changes shape (to move sodium ion
and/or proton across the membrane);
Mammals have some cells that produce extracellular proteases. They also have cells with membrane-bound dipeptidases.
Describe the action of these membrane-bound dipeptidases and explain their
importance.
[2 mark
- Hydrolyse (peptide bonds) to release amino
acids; - Amino acids can cross (cell) membrane;
OR
Dipeptides cannot cross (cell) membrane;
OR
Maintain concentration gradient of amino acids
for absorption;
OR
Ensure (nearly) maximum yield from protein
breakdown;
Describe how presentation of a virus antigen leads to the secretion of an antibody
against this virus antigen. (4)
Helper T cell/TH cell binds to the antigen (on
the antigen-presenting cell/phagocyte);
2. This helper T/TH cell stimulates a specific B
cell;
3. B cell clones
OR
B cell divides by mitosis;
4. (Forms) plasma cells that release antibodies;
Collagen is a protein produced by cells in joints, such as the knee.
Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease, a person’s immune system attacks their own cells. RA causes pain, swelling and stiffness in the joints.
Scientists have found a virus that produces a protein very similar to human collagen.
Suggest how the immune response to this viral protein can result in the development of RA.
[2 marks]
The antibody against virus (antigen) will bind
to collagen;
2. This results in the destruction of the (human)
cells/collagen;
State three comparisons of genetic diversity that the scientists used in order to classify species using advanced techniques
- The (base) sequence of DNA;
- The (base) sequence of mRNA;
- The amino acid sequence (of proteins);
Contrast how an optical microscope and a transmission electron microscope work
and contrast the limitations of their use when studying cells.
[6 marks]
TEM use electrons and optical use light;
2. TEM allows a greater resolution;
3. (So with TEM) smaller organelles/named cell
structure can be observed
OR
greater detail in organelles/named cell structure
can be observed;
4. TEM view only dead/dehydrated specimens and
optical (can) view live specimens;
5. TEM does not show colour and optical (can);
6. TEM requires thinner specimens;
7. TEM requires a more complex/time consuming
preparation;
8. TEM focuses using magnets and optical uses
(glass) lenses;
An environmental scientist investigated a possible relationship between air pollution and the size of seeds produced by one species of tree.
He was provided with a very large number of seeds collected from a population of trees in the centre of a city and also a very large number of seeds collected from a population of trees in the countryside.
Describe how he should collect and process data from these seeds to investigate whether there is a difference in seed size between these two populations of trees.
[5 marks]
Use random sample of seeds (from each
population);
2. Use (large enough) sample to be representative
of whole population;
3. Indication of what size was measured eg mass;
4. Calculate a mean and standard deviation (for
each population);
5. Use the (Student’s) t-test;
6. Analyse whether there is a significant difference
between (the means of) the two populations;
Compare and contrast the structure and properties of triglycerides and phospholipids. [5 marks]
Both contain ester bonds (between glycerol and
fatty acid);
2. Both contain glycerol;
3. Fatty acids on both may be saturated or
unsaturated;
4. Both are insoluble in water;
5. Both contain C, H and O but phospholipids also
contain P;
6. Triglyceride has three fatty acids and
phospholipid has two fatty acids plus phosphate
group;
7. Triglycerides are hydrophobic/non-polar and
phospholipids have hydrophilic and
hydrophobic region;
8. Phospholipids form monolayer (on
surface)/micelle/bilayer (in water) but
triglycerides don’t;
Mucus also contains glycoproteins. One of these glycoproteins is a polypeptide with the sugar, lactose, attached.
Describe how lactose is formed and where in the cell it would be attached to a
polypeptide to form a glycoprotein (4)
Glucose and galactose;
2. Joined by condensation (reaction);
3. Joined by glycosidic bond;
4. Added to polypeptide in Golgi (apparatus);
