mark scheme Flashcards
(16 cards)
what to include when drawing a high power diagram of a cell
- covers suitable area
- use of continuous lines
- no shading or colouring
- label clearly and don’t overlap lines
why are smaller organelles visible with an electron and not a light microscope
electrons have a shorter wavelength than light
electron microscope has a higher resolution
can distinguish between two points closer together
why is the membrane structure called a ‘fluid mosaic’ model
phospholipid and proteins can move around
unsaturated c=c bonds means membrane can float freely
phospholipid bilayer is made up of different proteins
why do sodium ions move across membrane by facilitated diffusion?
can’t pass through normally as they are charged
need energy, in the form of ATP
must pass through transport proteins
what are the advantages of using alight over electron microscope
you can observe living cells
can see mitosis taking place
what’s the difference between DNA and RNA (5)
DNA has two strands, RNA has one
DNA has hydrogen bonding, RNA doesn’t
DNA has complementary base pairing, RNA doesn’t
DNA made of deoxyribose, RNA made of ribose (extra OH group)
RNA has uracil instead of thymine
mode of action of enzyme - induced fit mechanism
active site is flexible
shape of substrate changes slightly upon entering
substrate doesn’t fit perfect
enzyme substrate complex made
what’s the structure of glycogen and how is it suitable for storage
polysaccharides are energy dense
1,6 glycosidic bonds allow glycogen to be branched and therefore compact and so can be stored in granules
non polar so insoluble - won’t dissolve and affect osmotic properties
explain how a non - competitive inhibitor acts on an enzyme to prevent it catalysing a reaction
inhibitor fits into a site other than the active site
structure changes she and bonds break
active site changes shape
substrate no longer fits/binds to active site. no longer complementary to substrate.
why do left ventricles have thicker walls
blood needs to be at higher pressure to be transported around the body
distance requires pressure, which requires more force
right ventricle only transports blood to lungs
how is the structure of the artery related to its function
small lumen / tunica intra to maintain high pressure
thick tunica media to even out flood flow
thick tunica externa to prevent bursting and maintain structure
how is an artery different from a vein
vein has less smooth muscle (not carrying g blood at high pressure)
veins lumen is much larger to reduce blood resistance
what’s the function of the SAN, AVN, bicuspid valve
SAN - pace maker of the heart - causes atrium to contract through move of excitation (electrical impulse)
AVN - helps delay impulse to allow atria to finish contracting
Valve - prevents back-flow of blood / ensures unidirectional flow of blood
how are capillaries adapted to their function
small lumen
thin wall, increase diffusion efficiency
found in bundles, increasing SA for diffusion
how are alveoli adapted for gas exchange
one cell thick squamous epithelium reduced diffusion distance
good blood supply from nearby capillaries
shape increases SA
many of them
Role of goblet cells and cilia
produce/ secrete mucous which traps pathogens/dust particles and prevents them from reaching circulatory system cilia waft a carpet of mucous up
