biology paper 1 stuff Flashcards
What is the difference between steroid and non-steroid hormones?
Steroid hormones: Able to bipass the lipid component of the phospholipid bilayer, binds to receptors in nucleus or cytoplasm to act as a transcription factor and switch genes on or off.
Non-Steroid hormones: Unable to pass the lipid component of the phospholipid billayer and will bind to complimentary receptors on the surface membrane to trigger a cascade of reactions inside the cell via secondary messengers.
What are the essential hormones produced by the adrenal cortex?
glucocorticoids , mineralocorticoids , androgens
How can the pancreas act as an exocrine gland?
Secretes enzymes into a duct including amylase and lipases, secrets pancreatic secretions into the gut and is alkaline
How is insulin secretion controlled ( Hint: ATP and Ca2+ )
Glucose will enter the cell via a glucose transporter and be metabolised into ATP.
ATP binds to K+ channels, they close and depolarisation occurs.
This triggers Ca2+ voltage gated channels to open which trigger secretory vesicles with insulin to bind to the membrane and be released via exocytosis .
How does adrenaline work via the secondary messenger model? hint = YLYL
Adrenaline will bind to its complimentary receptor, adenylyl cyclase is activated
This enzymes converts ATP into cyclic AMP which activates other enzymes that convert glycogen into glucose.
How can adrenaline cause different effects on different tissues?
Different tissues will have different adrenaline receptors which will either decrease or increase the cyclic cAMP levels that will trigger different secondary messengers
Why does insulin still secrete with no further glucose intake?
Glucose levels are still high, insulin is still secreted as there is still ATP present and Ca2+ voltage gated channels are still open.
How does auxin trigger growth of a plant towards light?
Auxin is produced at the tip of the plant and will move to the darker side via diffusion which stimulates cell elongation.
Stem elongation results from binding to receptors and causing PH lvls to fall , this is the optimun temperature to keep the walls flexible
Growth occurs in the darkest side of the plant
Why does the hand cover the eye in response to light?? MUSCLEE
Receptors will detect light which stimulates an action potential across the sensory neurone
Relayed to the motor neurone
Motor neurone will communicate with the effector through a neuromuscular junction and the neurotransmitters travel through synaptic transmission
Depolarisation of the skeletal muscle cell leads to contraction
Where in a chloroplast does the light independent stage occur?
The granum (Stacks of thykaloids)
What is the difference between spatial and temporal summation?
Spatial: The summination of action potential from the firing of multiple presynaptic terminals
Temporal: Rapid discharges of a presynaptic neurone added together
Why do muscle fibres have a small range of resting lengths?
Because they constantly need to have an overlap of actin and myosin for muscle contraction and powerstrokes
Why do plants need to respond to the enviroment?
To cope with changing stimuli and things such as herbivory to maximise photosynthesis agd germination of seeds
How does stomatal closure prevent growth?
LEss CO2 = less photosynthesis which is caused by water stressors to reduce the amount of water lost
What happens when transpiration occurs and how does this encourage water to go up the plant?
Water potential will decrease inside the leaf which causes a low hydrostatic pressure
Encourages water to move up the roots via osmosis
Water will move via a high to low water pressure gradient through the action of cohesion and adhesion
= capillary action
How are xerophytes generally adpapted to preventing water loss?
Less stomata , less surface area, sunken stomata and thick waxy cuticle all reduce the water potential gradient
How is exudation of a solution evidence for phloem loading?
Shows a presence of a pressure gradient
How does a respirometer measure the rate of respiration?
As your organism respires, the CO2 will be absorbed by KOH. The O2 produced will be absorbed by the respiring organism, the gas volume will decrease, and the food colouring will be drawn in.
Rate: Difference in distance/the time taken
Why do the glass beads and the living organism have to be the same volume?
A difference in volume would allow more or less oxygen to be absorbed which will alter the results. Same volume= A control variable as the apparatus works on volume and pressure changes.
What does phenolphthalein do?
An indicator which will turn pink when placed in an alkaline solution but will turn colourless in aN acidic Solution.
WHAT ARE the purpose of coenzymes like NAD and FAD?
They provide e- and H+ for the electron transport chain in chemiosmosis and are present in both respiration and photosynthesis,
The more reduced NAD and FAD produced means the more e- transported for chemosis meaning more efficent respiration and photosynthesis,
Why might ATP not produce the theoretical yield?
ATP is required to transport pyruvate to the Krebs cycle in the mitocondria for the link reaction from the cytoplasm
Not all H+ is used in ATP production, for example may be used for chemiosmosis.
Why is anaerboic repsiration in yeast cells not reversable?
CO2 is lost as a bi-product therefore the decarboxylase enzymes can not reverse the reaction
Why does the reverse of anaerobic respiration occur in the liver and not the actual respiring cells?
Hepatocytes are adapated to tolerate low pH levels and have enzymes to metabolise the reaction and have a sufficent O2 supply
