Paper 1 Flashcards
Explain how glucose produced in photosynthesis is translocated to parts of the plant where glucose is metabolised or stored.
6 marks
Phloem loads:
- Glucose is converted into sucrose in photosynthesising cells
- it travels through the apoplast pathway
- proton pump in companion cells create a H+ concentration gradient
- cotransport of H+ and sucrose into companion cell
- passive loading vis symplast pathway
- entry of sucrose decreases water potential of phloem
- water enters phloem from surrounding cells
Results in higher hydrostatic pressure
Mass flow:
- bulk transport of sucrose caused by pressure difference
- source to sink
- hydrostatic pressure gradient for source to sink explains rapid transport over long distance
Phloem unloading:
- Diffusion of sucrose form phloem to surrounding cells
- sucrose converted back to glucose which is used for respiration
- converted to starch for storage
- maintains conc gradient of sucrose between phloem and cells
- water leaves phloem to surrounding cells or xylem
- results in lower hydrostatic presssure
Evaluation treatments for type 1 diabetes (past, current and potential future)
6 marks
Past:
Insulin from animal pancreas: advantages is it kept people alive as an early treatment, disadvantage is risk of allergic reaction
Present:
Insulin that is genetically modified injections. Adv - less risk of allergic reaction, lower cost. Disadvantage - side effects of pumps e.h lumps under skin
Future potential:
Transplant of pancreatic stem cells. Adv - no need for injections, ‘reprogrammes’ immune system
Disadvantage - ethical objections to use of stem cells
Transplants - advantage is mono need for insulin injections and improved quality fo like, disadvantage is high initial costs, if there is low availability of donor tissue
Describe the role of nervous system and endocrine system in enabling water re absorption. (6 marks)
Endocrine:
- hypothalamus causes release of ADH from pituitary gland, aldosterone is released from adrenal cortex
- ADH binds to receptors on the cell membranes of collecting duct cells
- increases permeability to water
Nervous system:
- hypothalamus is part of NS
- osmoreceptors in hypothalamus detect a low w.p in blood
- ADH produced in hypothalamus
- posterior pituitary gland is an extension of hypothalamus
- aldosterone causes sodium ions to be pumped out of collecting duct
- lowers w.p of tissue fluid
- establishes a concentration gradient
- sodium ions reabsorbed from collecting duct lumen and water diffuses into collecting duct via osmosis
Similarities and differneces between formation of tissue fluid and ultrafiltration.
Similarities:
- small molecules diffuse out of blood
- occur in capillaries
- large molecules e.g proteins remain in blood
- high hydrostatic pressure in both
- many molecules e.g sugars and water are reabsorbed into capillaries
Differences:
- filtrate enters bowman’s capsule in kidney vs tissue fluid is formed into intercellular space
- molecules that are not reabsorbed form urine in the kidney but form tissue fluid is
- blood filtered through 3 layers in ultrafiltration but just one in tissue fluid is
Describe the flow of blood through the left side of the heart during the cardiac cycle and explain the role of valves and pressure differneces in the process.
Blood flow:
returns to heart via pulmonary vein - left atrium - left ventricle - aorta
Pressure differences:
Diastole
- during diastole pressure is relatively low
- pressure increases as left atrium fills with blood
Atrial systole
- pressure increase due to atrial contraction
- blood is forced into left ventricle
Ventricular systole
- further increase in pressure as left ventricle contracts
- increase in pressure cause AV valve to close
- blood is forced out to aorta
- as ventricular pressure drops, semi lunar valves loses
- pressure in ventricle drops below atrial pressure so av opens
Role of valves:
- to prevent back flow of blood
- open or close due to pressure diffferneces
- AV between atrium and ventricle
- SLV in between ventricle and aorta/ pulmonary artery
Describe the sources of ATP in muscle contraction.
There is free ATP in sarcoplasmic that is used to form phosphocreatine. ATP is required in releasing myosin head from actin filament
ATP is used in aerobic respiration:
- it only occurs if oxygen is avaliable
- oxidative phosphorylation occurs and produces a great yield of ATP
- but O2 is limited during strenuous exercise so
Anaerobic respiration is happening:
- needed in strenuous excerise
- only involves glycolysis
- ATP is formed at a substrate level phosphorylation
- net yield of 2 ATP
- cant continue indefinitely because of lactic acid build up
What is the fluid found in tubes responsible for gaseous exchange called in insects?
Tracheal fluid
Outline why animals need well developed transport systems:
They have high metabolic rate and need a large oxygen supply to meet this demand.
Diffusion woudl be too slow because the distance is too far becsue SA:V is often low
They need to remove waste from respiring cells
How do you know a transmission electron microcode has been used?
2D image, internal details and organelles visible, high magnification and resolution
What is a limiting factor?
A factor that will limit/ Capp the rate of the process if it is at a lower level or sub optimal level
Why does overwatering kill plants, use anaerobic and aerobic explanations.
Aerobic respiration requires oxygen however when a plant is overwatered there is less oxygen able to reach the root cells so anaerobic respiration must happen
Anaerobic respiration only included glycoslys becasue there is no oxygen to act as final acceptor for elections so there is no link reaction or Krebs cycle.
Pyruvate is converted to ethanal to ethanol and produces only 2 ATP
The consequences for the plant are that;
- ethanol is toxic and irreversible
- less ATP is produced so there is no active transport and root hair cells cannot take up mineral ions so plant cannot make proteins, amino acids, chlorophyll
- water is not absorbed by root hair cells to no photosynthesis becasue w.p conc gradient is not created
What synthesis enzymes
Ribosome
Compare processes happening in distal convoluted tubule and proximal convoluted tubule.
Both use active transport
Both include selective re absorption
Both involve a cotransporter
Both use sodium ions
DCT involves calcium ions
Why are adult stem cells suitable for regeneration of tissues in the kidney?
They are multipotent into any type of cell in the kidney
