Paper 1 Flashcards
What is translocation
Translocation is the transport of assimilates through the plant from source to sink. (Sources and sinks can change throughout the year)
Describe the process of translocation
1) H+ is actively transported from companion cells to source cells, forming a concentration gradient.
2) H+ diffuses through proteins carrying sucrose.
3) sucrose concentration gradient pushes sucrose from the companion cell into the phloem sieve tube.
4) water from xylem enters phloem down water potential gradient
5) Mass flow moves assimilates to sinks driven by hydrostatic pressure
What do beta cells do?
They release insulin in response to rising glucose levels
How is insulin secreted
1) K+ channels are open which allow k+ to defuse out.
2) Glucose enters the cell when levels rise in the blood.
3) Glucokinase enzyme converts glucose to glucose phosphate and then ATP
4) ATP cause k+ channels to close, causing less negative membrane potential to arise.
5) Ca2+ ion channels open in response to rising potential.
6) Ca2+ causes vesicles containing insulin to release the hormone in exocytosis.
What does the pancreas contain
Exocrine tissue which is located in acini.
Endocrine tissue which is located in the islets of Langerhans
What is the role of exocrine glands in the pancreas
They contain acini which releases hormones into ducts
What is the components of the pancreas
B cells
A cells
Capillaries
Acinus cell
What does exocrine pancreatic juice contain?
Amylase: digest amylose to maltose
Trypsinogen: protease activated tripsin
Lipase: digests lipids
Sodium hydrocarbonate: alkaline
What does endocrine tissue contain
A cells : relaseing glucagon
B cells: releasing insulin
Capillaries: carry hormones into the blood stream
What is the first messenger (first and second messenger Model)
Non- steriodal hormones that bind at the surface receptors. Their binding causes the release of second messengers inside the cell.
What happens at the secondary messenger (first and Secondary Messenger Model)
The first messengers (glucagon and addrenalin) bind to a specific receptor on the cell that activates adenyl cyclase.
Adenyl cyclase hydrolyses ATP to cAMP (Secondary Messenger)
cAMP activates enzymes which activate other proteins (Cascade) turning on specific genes.
What does the endocrine system do?
It uses chemical hormones in the bloodstream to transport signals
The process of the endocrine
Endocrine glands or organs release hormones directly into the blood.
The hormones are distributed throughout the body via the blood.
Target tissue will have specific receptors for the hormone.
Peptide hormones are water soluble and bind to cell membrane receptors setting up cascades of reactions in the cytoplasm.
Steriod hormones are lipid soluble and pass through the membrane to a receptor in the nucleus to alter gene transcription.
Photosynthesis/ respiration reaction
C02 + H2O = C6H12O6 + O2
Carbon dioxide+ water = glucose+ oxygen
What are autotrophs
Autotrophs such as plants are able to form nutritional organic substances from simple inorganic substances such as carbon dioxide.
Plants turn fix carbon into monosaccharides during photosynthesis.
What is a compensation point in plants , and how often does it occur
The compensation point is when the rate of photosynthesis is equal to the rate of respiration.
It happens twice a day.
During the day photosynthesis takes over as there is more light energy, however during the night respiration is more dominant as there is little to no light energy.
What is the chloroplast
Organelle which is involved in photosynthesis in plants and algae.
Components of a chloroplast
Outer and inner membrane which is called the envelope
Granum, which are made up of lots of Thylakoids.
Intergranual lamellae that connect Granums
Stroma
What proccess occurs in the grana
Light dependant stage of photosynthesis, due to the large surface area.
What is contained in the stroma
Enzymes that catalyzes the light Independent stage
Starch grains
DNA loops
Ribosomes
Why do chloroplasts contain a large number of ribsomes
The ribosomes produce the enzymes required for photosynthesis in the chloroplast.