Give one piece of evidence that supports the theory that mitochondria evolved from prokaryotic cells.
Circular DNA
What is the advantage to cells of having mitochondria?
- Able to respire aerobically;
- So make (more) ATP/ release (more)
energy
Explain how the highest blood pressure is produced in the left ventricle.
stronger contractions as it has a thicker muscular wall
Some babies are born with a hole between the right and the left ventricles. These babies are unable to get enough oxygen to their tissues.
Suggest why.
- Blood flows from left ventricle to right ventricle/ mixing of oxygenated and deoxygenated blood;
- Lower volume of (oxygenated) blood leaves left ventricle/flows into aorta/C
Suggest one advantage of using a pH meter rather than a pH indicator in this experiment.
Greater accuracy
Explain why the pH decreases when the lipase is added to the milk.
Fatty acids produced
Suggest why the pH remained constant after 2 minutes.
- No more (fatty) acids produced;
2. All triglycerides/fat//lipids/substrate used up / enzyme denatured;
Trypsin is a protease. It is produced in an inactive form inside some of the cells of the pancreas.
Name the part of a pancreatic cell that produces the inactive form of trypsin.
Ribosome
Suggest the advantage of producing trypsin in an inactive form inside cells in the pancreas.
- Does not digest protein inside cells;
2. So (pancreatic) cell/tissue/function not destroyed/damaged;
Sometimes trypsin can become activated inside a pancreatic cell. A competitive inhibitor in the cell then binds to the trypsin and stops it working.
Explain how the competitive inhibitor stops trypsin working.
- Inhibitor is a similar shape to the substrate;
- (Inhibitor) blocks active site/is complementary to the active site/binds to the active site (of trypsin);
- Substrate can’t bind to active site / no/fewer ES complexes formed;
Explain the role of the diaphragm in breathing out.
- Diaphragm moves up /becomes dome shaped;
- Reduces volume of lungs / increase
pressure in lungs; - Pressure in lungs higher than outside (air);
Use the data shown in Figure 4 to compare the change in FEV1 of people who continued to smoke with those who stopped smoking.
- FEV1 of those who have stopped smoking increased after 1 year whereas the FEV1 of smokers decreased;
- (Between years 1 and 5, FEV1 of both decreases but) the rate of decrease in FEV1 of smokers is faster than those who stopped smoking;
Smoking causes changes in the lungs and airways of smokers.
Suggest two changes in the lungs of people who continue to smoke that could explain the change in their FEV1.
- Airways are narrowed/blocked;
2. Excess mucus (in airway);
Suggest how the scientists may have treated the milk to remove lactose.
Add lactase
The scientists told the volunteers to drink the milk first thing in the morning rather than at bedtime.
Suggest why.
able to record their symptoms during the day
Suggest one instruction that the scientists would have given the volunteers about what they should not eat or drink each day, during this investigation.
Eat no other foods containing lactose
Suggest why the scientists changed the type of milk they gave each group after one week.
to compare effect of lactose on both groups;
What can you conclude from the scientists’ results in Table 3?
- Drinking (untreated) milk causes (a little) bloating;
- Drinking (small amount)of untreated milk has little/no effect on pain/diarrhoea;
- Difference is small so may not be significant
People who do not have the specific receptor protein in their cell-surface membranes may be infected with the Ebola virus but do not develop the disease (lines 1–5).
Explain why they do not develop the disease.
- Virus can’t bind (to receptor)/ can’t enter cells;
2. So can’t be replicated/ multiply;
Explain the increase in specific plasma cells and antibody in people infected with the nEbola virus.
- Antigen/glycoprotein on Ebola binds to/stimulates (a specific) B cell;
- (Binding causes) replication/cloning of B cell;
- Plasma cells/B cells release/produce antibodies;
Explain how a blood transfusion from a patient recently recovered from Ebola may be an effective treatment (lines 8–10).
- Lots of antibodies (against Ebola) in recovered patient;
- Transfusion/plasma contains antibodies;
- Antibodies (specific so) will bind with (Ebola) antigen;
- (In recipient) virus destroyed/cannot enter cell;
A high mutation rate makes it difficult to develop a vaccine (line 11). Explain why.
- (High mutation rate leads to) antigens change/antigenic variability;
- Vaccine contains specific antigen;
- Antibodies not complementary to (changed) antigen / won’t bind to (changed) antigens;
Glucose is absorbed from the lumen of the small intestine into epithelial cells.
Explain how the transport of sodium ions is involved in the absorption of glucose by epithelial cells.
- Na+ ions leave epithelial cell and enter blood;
- (Transport out is by) active transport / pump / via carrier protein using ATP;
- So, Na+ conc. in cell is lower than in lumen (of gut);
- Sodium/Na+ ions enter by facilitated diffusion;
- Glucose absorbed with Na+ ions against their concentration/diffusion gradient / glucose absorbed down an electrochemical gradient;
Oxygen and chloride ions can diffuse across cell surface membranes. The diffusion of chloride ions involves a membrane protein. The diffusion of oxygen does not involve a membrane protein.
Explain why the diffusion of chloride ions involves a membrane protein and the diffusion of oxygen does not.
- Chloride ions water soluble/charged/polar;
- Cannot cross (lipid) bilayer (of membrane);
- Chloride ions transported by facilitated diffusion OR diffusion involving channel/carrier protein;
- Oxygen not charged/non-polar;
- (Oxygen) soluble in/can diffuse across (lipid) bilayer;
