Biology AS Paper 2022 Flashcards
Describe the mechanism for the absorption of amino acids in the ileum (4 marks)
- facilitated diffusion of amino acids into cell when high concentration in lumen
- co-transport
- Na+ active transport from cell to blood
- Na+ diffusion gradient established
- facilitated diffusion of amino acids into blood
Which of these are hydrolysed in the ileum and a product of this hydrolysis is found in micelles?
A. maltose
B. triglyceride
C. nucleotide
D. cellulose
E. amino acid
(1 mark)
triglyceride
Which is formed by a condensation reaction between two a-glucose molecules?
A. maltose
B. triglyceride
C. nucleotide
D. cellulose
E. amino acid
(1 mark)
maltose
Which is formed by the action of DNA polymerase?
A. maltose
B. triglyceride
C. nucleotide
D. cellulose
E. amino acid
(1 mark)
nucleotide
Which gives a positive result in an emulsion test?
A. maltose
B. triglyceride
C. nucleotide
D. cellulose
E. amino acid
(1 mark)
triglyceride
Give two types of molecules from which a ribosome is made
(2 marks)
rRNA
protein
Give four structural differences between a DNA molecule and an mRNA
(4 marks)
double helix/stranded : single helix/stranded
deoxyribose : ribose
long : short
thymine : uracil
Explain why the resolution of an image obtained using an electron microscope is higher than the resolution of an image obtained using an optical microscope
(1mark)
wavelength of light rays is longer than that of electrons
How can a student determine the size of the structure?
(2 marks)
measure length of cell using ruler (cm)
divide image size by magnification to find actual size
convert answer from cm->nm by x10,000
Name two structures found in all bacteria that are NOT found in plant cells
(2 marks)
circular DNA
murrain cell wall
Name two features of HIV particles that are NOT found in bacteria
(2 marks)
reverse transcriptase
capsid
Describe how monomers join to form the primary structure of a protein
(3 marks)
monomers of proteins are amino acids
amino acids form peptide bonds with other amino acids in a condensation reaction which involves the removal of water
creates a sequence of amino acids- the primary structure of a protein
Describe one similarity and one difference between the induced fit model of enzyme action and the lock and key model of enzyme action
(2 marks)
similarity: both result in formation of enzyme-substrate complex
difference: lock and key- substrate exactly complementary to active site of enzyme
induced fit- substrate not exactly complementary to active site, active site alters shape to bind with substrate
State how enzymes help reactions to proceed quickly at lower temperatures
(1 mark)
enzyme acts as biological catalyst which provide an alternative pathway of lower activation energy
Explain a property of iron ions that enables these ions to carry out their role in red blood cells
(1 mark)
iron ions polar as they are charged (Fe2+) so associate with oxygen to form oxyhaemoglobin
What is a tumour?
(2 marks)
mass of cells produced from uncontrolled mitotic division
Describe how you would determine a reliable mitotic index from tissue observed with an optical microscope
(3 marks)
count number of cells undergoing mitosis in field of view
divide by total number of cells in field view
repeat process many times
Suggest why the number of E.coli cells per mm3 in each culture after 24 hours might be lower if the student had NOT used a sterilised pipette. Explain why
(2 marks)
bacteria other than E.coli in culture
competition for nutrients
E.coli may be outcompeted
less nutrients for E.coli, less division, less E.coli cells
Describe how composition of blood in pulmonary artery of foetus is different from composition of blood in pulmonary artery of mother
Give one reason for this difference
(2 marks)
fetal blood has more oxygen
gas exchange occurs in placenta
Explain how a foetus is protected against pathogens that infect its mother during pregnancy
(3 marks)
antibodies from mother complementary to antigens crossing placenta
binding between antibodies and antigens forms antibody-antigen complex
provides passive immunity in foetus
Suggest how vaccinating as many babies as possible protects UK population against pathogens in measles
(1 mark)
measles a virus
vaccinations achieve herd immunity
reduces transmission
Suggest how vaccinating as many babies as possible protects UK population against pathogens in tetanus
(1 mark)
tetanus is a bacteria
no herd immunity
only protects individual
Suggest why there has been a recent increase in the number of children catching measles
(1 mark)
virus has mutated
