A-Level Biology – OCR Exam Questions and Mark Scheme – Revision Notes
Antibodies are made by plasma cells. Explain how plasma cells are specialised for their role -
✔✔✔-Plasma cells have a lot of ribosomes, rough endoplasmic reticulum, Golgi apparatus and
mitochondria.
As more solute is added to a solution, what happens to the solute potential and hence the
water potential? - ✔✔✔-Solute potential decreases, hence water potential decreases
Briefly outline the events of atrial systole - ✔✔✔-Left and right atria contract together; blood is
squeezed from the atria through the atrioventricular valves into the ventricles, down a pressure
gradient.
Briefly outline the events of diastole - ✔✔✔-Once ventricular contraction is complete, heart
muscle starts to relax, heart starts to fill with blood again and semilunar valves close
Briefly outline the events of ventricular systole - ✔✔✔-Ventricular blood pressure rises very
quickly to a level above the arteries; semilunar valves open and blood rushes out of ventricles
into the arteries
Cacti are succulents. What does this mean? - ✔✔✔-They store water in their stems which
become fleshy and swollen
Channel proteins and carrier proteins have what main role within the membrane? - ✔✔✔-
Transport
Define and describe exocytosis - ✔✔✔-The bulk transport of particles too large to pass through
the membrane, out of the cell. It works like a reversal of pinocytosis. A vesicle containing the
substance fuses with the plasma membrane. The fused site opens, releasing the contents of the
secretory vesicle.
Define and describe phagocytosis - ✔✔✔-The intake of solid particles into the cell by engulfing.
Pseudopodia surround the particles, the membrane fuses together, to form a vesicle.
,A-Level Biology – OCR Exam Questions and Mark Scheme – Revision Notes
Define and describe pinocytosis - ✔✔✔-The intake of liquids into the cell by engulfing. The
plasma membrane invaginates, and the membrane fuses around the substance, forming a
vesicle.
Define bulk transport and give two examples - ✔✔✔-The movement of large molecules that are
too big to pass across the plasma membrane. Endocytosis (phagocytosis or pinocytosis) brings
large molecules INTO the cell, enclosed in a vesicle. Exocytosis transports large molecules OUT
of cells.
Define the term active transport - ✔✔✔-Movement of molecules, against their concentration
gradient (using energy liberated from ATP hydrolysis) using specific protein channels or carriers
Define the term diffusion. - ✔✔✔-The net movement of a substance from an area of high
concentration to an area of low concentration. It is passive, does NOT require ATP.
Define the term epidemic - ✔✔✔-A rapid spread of disease through a high proportion of a
population (usually within a country)
Define the term facilitated diffusion - ✔✔✔-Movement of molecules from a high concentration
to a low concentration, across a partially permeable membrane, via specific channel or carrier
proteins. It is passive, does NOT require ATP
Define the term osmosis - ✔✔✔-The movement of water molecules from a region of higher
water potential to a region of lower water potential, across a partially permeable membrane
Define the term tissue - ✔✔✔-A group of cells working together to perform a particular
function
, A-Level Biology – OCR Exam Questions and Mark Scheme – Revision Notes
Define the term translocation - ✔✔✔-Transport of assimilates from source to sink (tissue that
needs them)
Describe 2 major pathways taken by water to move between cells - ✔✔✔-Apoplast - through
spaces in cell walls and between cells (mass flow...not osmosis); symplast - moves through
cytoplasm and between cells via plasmodesmata
Describe 3 adaptations of marram grass (xerophyte) and explain their importance - ✔✔✔-Leaf
rolled longitudinally trapping air inside (air becomes humid and reduces water loss from the
leaf); thick waxy cuticle on upper epidermis (reduces evaporation); stomata on lower epidermis
inside rolled leaf (protected by enclosed air space); stomata are in pits in lower epidermis which
is folded and covered by hairs (reduces air movement and hence water loss); spongy mesophyll
very dense with few air spaces (less surface area for evaporation of water)
Describe and explain how erythrocytes are adapted for their function - ✔✔✔-Very small so
have a large SA:vol (biconcave shape also ensures this) meaning oxygen can reach all regions
inside the cell; well-developed cytoskeleton allows the erythrocytes to change shape and move
through very narrow capillaries; no nucleus or organelles so more space for Hb molecules
Describe and explain how sperm cells are adapted for their function - ✔✔✔-Acrosome in head
contains enzymes to penetrate the egg follicle during fertilisation; many mitochondria to
generate ATP for flagellar movement; large haploid nucleus in head to fertilise haploid ovum
Describe and explain three features of a good exchange surface - ✔✔✔-Large SA (folded walls;
provides more space for relevant molecules to pass through); thin, permeable barriers (reduces
diffusion distance); good blood supply (keeps high concentration gradients for rapid diffusion)
Describe how a microorganism can become resistant to an antibiotic - ✔✔✔-Bacteria that
survive a treatment will be slightly resistant to the antibiotic and the antibiotic acts as a
selective force which selects the resistant individuals. When they reproduce, some of their
offspring may be more resistant, thus resistance evolves.
Antibodies are made by plasma cells. Explain how plasma cells are specialised for their role -
✔✔✔-Plasma cells have a lot of ribosomes, rough endoplasmic reticulum, Golgi apparatus and
mitochondria.
As more solute is added to a solution, what happens to the solute potential and hence the
water potential? - ✔✔✔-Solute potential decreases, hence water potential decreases
Briefly outline the events of atrial systole - ✔✔✔-Left and right atria contract together; blood is
squeezed from the atria through the atrioventricular valves into the ventricles, down a pressure
gradient.
Briefly outline the events of diastole - ✔✔✔-Once ventricular contraction is complete, heart
muscle starts to relax, heart starts to fill with blood again and semilunar valves close
Briefly outline the events of ventricular systole - ✔✔✔-Ventricular blood pressure rises very
quickly to a level above the arteries; semilunar valves open and blood rushes out of ventricles
into the arteries
Cacti are succulents. What does this mean? - ✔✔✔-They store water in their stems which
become fleshy and swollen
Channel proteins and carrier proteins have what main role within the membrane? - ✔✔✔-
Transport
Define and describe exocytosis - ✔✔✔-The bulk transport of particles too large to pass through
the membrane, out of the cell. It works like a reversal of pinocytosis. A vesicle containing the
substance fuses with the plasma membrane. The fused site opens, releasing the contents of the
secretory vesicle.
Define and describe phagocytosis - ✔✔✔-The intake of solid particles into the cell by engulfing.
Pseudopodia surround the particles, the membrane fuses together, to form a vesicle.
,A-Level Biology – OCR Exam Questions and Mark Scheme – Revision Notes
Define and describe pinocytosis - ✔✔✔-The intake of liquids into the cell by engulfing. The
plasma membrane invaginates, and the membrane fuses around the substance, forming a
vesicle.
Define bulk transport and give two examples - ✔✔✔-The movement of large molecules that are
too big to pass across the plasma membrane. Endocytosis (phagocytosis or pinocytosis) brings
large molecules INTO the cell, enclosed in a vesicle. Exocytosis transports large molecules OUT
of cells.
Define the term active transport - ✔✔✔-Movement of molecules, against their concentration
gradient (using energy liberated from ATP hydrolysis) using specific protein channels or carriers
Define the term diffusion. - ✔✔✔-The net movement of a substance from an area of high
concentration to an area of low concentration. It is passive, does NOT require ATP.
Define the term epidemic - ✔✔✔-A rapid spread of disease through a high proportion of a
population (usually within a country)
Define the term facilitated diffusion - ✔✔✔-Movement of molecules from a high concentration
to a low concentration, across a partially permeable membrane, via specific channel or carrier
proteins. It is passive, does NOT require ATP
Define the term osmosis - ✔✔✔-The movement of water molecules from a region of higher
water potential to a region of lower water potential, across a partially permeable membrane
Define the term tissue - ✔✔✔-A group of cells working together to perform a particular
function
, A-Level Biology – OCR Exam Questions and Mark Scheme – Revision Notes
Define the term translocation - ✔✔✔-Transport of assimilates from source to sink (tissue that
needs them)
Describe 2 major pathways taken by water to move between cells - ✔✔✔-Apoplast - through
spaces in cell walls and between cells (mass flow...not osmosis); symplast - moves through
cytoplasm and between cells via plasmodesmata
Describe 3 adaptations of marram grass (xerophyte) and explain their importance - ✔✔✔-Leaf
rolled longitudinally trapping air inside (air becomes humid and reduces water loss from the
leaf); thick waxy cuticle on upper epidermis (reduces evaporation); stomata on lower epidermis
inside rolled leaf (protected by enclosed air space); stomata are in pits in lower epidermis which
is folded and covered by hairs (reduces air movement and hence water loss); spongy mesophyll
very dense with few air spaces (less surface area for evaporation of water)
Describe and explain how erythrocytes are adapted for their function - ✔✔✔-Very small so
have a large SA:vol (biconcave shape also ensures this) meaning oxygen can reach all regions
inside the cell; well-developed cytoskeleton allows the erythrocytes to change shape and move
through very narrow capillaries; no nucleus or organelles so more space for Hb molecules
Describe and explain how sperm cells are adapted for their function - ✔✔✔-Acrosome in head
contains enzymes to penetrate the egg follicle during fertilisation; many mitochondria to
generate ATP for flagellar movement; large haploid nucleus in head to fertilise haploid ovum
Describe and explain three features of a good exchange surface - ✔✔✔-Large SA (folded walls;
provides more space for relevant molecules to pass through); thin, permeable barriers (reduces
diffusion distance); good blood supply (keeps high concentration gradients for rapid diffusion)
Describe how a microorganism can become resistant to an antibiotic - ✔✔✔-Bacteria that
survive a treatment will be slightly resistant to the antibiotic and the antibiotic acts as a
selective force which selects the resistant individuals. When they reproduce, some of their
offspring may be more resistant, thus resistance evolves.
