A-Level Biology - OCR
Antibodies are made by plasma cells. Explain how plasma cells are specialised for their role -
ANSWER✅✅✅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? - ANSWER✅✅✅Solute potential decreases, hence water potential decreases
Briefly outline the events of atrial systole - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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? - ANSWER✅✅✅They store water in their stems which
become fleshy and swollen
Channel proteins and carrier proteins have what main role within the membrane? -
ANSWER✅✅✅Transport
Define and describe exocytosis - ANSWER✅✅✅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 - ANSWER✅✅✅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
,A-Level Biology - OCR
Define and describe pinocytosis - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅Movement of molecules, against their
concentration gradient (using energy liberated from ATP hydrolysis) using specific protein channels or
carriers
Define the term diffusion. - ANSWER✅✅✅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 - ANSWER✅✅✅A rapid spread of disease through a high proportion of a
population (usually within a country)
Define the term facilitated diffusion - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅A group of cells working together to perform a particular
function
Define the term translocation - ANSWER✅✅✅Transport of assimilates from source to sink (tissue
that needs them)
Describe 2 major pathways taken by water to move between cells - ANSWER✅✅✅Apoplast -
through spaces in cell walls and between cells (mass flow...not osmosis); symplast - moves through
cytoplasm and between cells via plasmodesmata
A-Level Biology - OCR
, A-Level Biology - OCR
Describe 3 adaptations of marram grass (xerophyte) and explain their importance -
ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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.
Describe how a root hair cell plasma membrane is adapted for transport of mineral ions -
ANSWER✅✅✅Contains specialised carrier proteins to transport specific mineral ions in by active
transport
Describe how agglutinins function - ANSWER✅✅✅Agglutinins cross link pathogens by binding
specifically via their variable regions. Pathogens are clumped together (agglutinated), meaning they
cannot enter host cells and are easier to phagocytose
A-Level Biology - OCR
Antibodies are made by plasma cells. Explain how plasma cells are specialised for their role -
ANSWER✅✅✅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? - ANSWER✅✅✅Solute potential decreases, hence water potential decreases
Briefly outline the events of atrial systole - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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? - ANSWER✅✅✅They store water in their stems which
become fleshy and swollen
Channel proteins and carrier proteins have what main role within the membrane? -
ANSWER✅✅✅Transport
Define and describe exocytosis - ANSWER✅✅✅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 - ANSWER✅✅✅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
,A-Level Biology - OCR
Define and describe pinocytosis - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅Movement of molecules, against their
concentration gradient (using energy liberated from ATP hydrolysis) using specific protein channels or
carriers
Define the term diffusion. - ANSWER✅✅✅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 - ANSWER✅✅✅A rapid spread of disease through a high proportion of a
population (usually within a country)
Define the term facilitated diffusion - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅A group of cells working together to perform a particular
function
Define the term translocation - ANSWER✅✅✅Transport of assimilates from source to sink (tissue
that needs them)
Describe 2 major pathways taken by water to move between cells - ANSWER✅✅✅Apoplast -
through spaces in cell walls and between cells (mass flow...not osmosis); symplast - moves through
cytoplasm and between cells via plasmodesmata
A-Level Biology - OCR
, A-Level Biology - OCR
Describe 3 adaptations of marram grass (xerophyte) and explain their importance -
ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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 - ANSWER✅✅✅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.
Describe how a root hair cell plasma membrane is adapted for transport of mineral ions -
ANSWER✅✅✅Contains specialised carrier proteins to transport specific mineral ions in by active
transport
Describe how agglutinins function - ANSWER✅✅✅Agglutinins cross link pathogens by binding
specifically via their variable regions. Pathogens are clumped together (agglutinated), meaning they
cannot enter host cells and are easier to phagocytose
A-Level Biology - OCR
