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.
What are photosytems, and where are they located
Photosytems are funnel shaped structures containing photosynthetic pigments.
Located in the thylakoid membranes
What are photosynthetic pigments
Each pigment absorbs specific wave lengths of light, that energy funnels down to a chlorophyll molecules at the primary pigment reaction center.
Types of photosynthetic pigments and the wave lengths they absorb
Chlorophyll a : green/blue and absorbs wavelengths 440 and either 680(photosytem 2) or 700(photosytem 1)
Chloroform b: yellow/green absorbs wavelengths 400-500 and 640nm
Accessory pigments: such as carotenoids and xanthophyll which absorb other wave lengths.
What is Non cyclic photophosphorylation
It uses PS2 to produce ATP and reduced NADP
Process of non cyclic photophosphorylation
1) light energy excited the chlorophyll in PS2. Electrons enter an electron transfer chain and are replaced by the photolysis of water
2) Energy is used to pump H+ ions into the thylakoid lumen.
3) electrons enter PS1 and are again excited by the light energy. They are then passed to NADP.
4) NADP accepts H+ and electrons to become reduced NADP.
5) protons pads through the ATP synthase down their gradient to produce ATP.
What is cyclic photophosphorylation
the synthesis of ATP coupled to electron transport activated by Photosystem1 solely.
Explain cyclic photophosphorylation
Light energy the electrons in chlorophyll molecules of the cells (photoionisation)
Light energy photolyses water, forming hydrogen ion and electrons, which release electrons from photoionisation and passes them down an electron transport chain.
This provides the energy for ATP synthesis in ATP synthase (ADP+Pi = ATP).
The light energy is transferred to chemical energy within the ATP bond.
The ATP produced in the LDR may he used to synthesis Glucose and ATP is used as an energy source for almost all metabolic processes.
What impacts the rate of photosynthesis
CO2 conc:
with too little CO2, RuBP can no longer react, meaning it accumulates while GP and TP levels are reduced.
Temperature:
Higher temperatures raise kinetic energy of enzymes, increasing rate of photosynthesis. Too high will mean enzymes denature
Light intensity:
Higher intensity increases rate untill another factor such as CO2 availabilit, inhibits futher increases.
What does a photosynthometers measure?
The rate of photosynthesis using the product oxygen which forms a bubble.
Volume gas collected= length of bubble xπxr2
Light intensity= 1/d2
In what way can osmosis be observed or demonstrated
Observed using onion or cheek cells under a light microscope at different water potentials.
Demonstrated using potato cores. The water potential of the potato cells can be calculated by measuring the % change in mass of the potato cores at various known water potentials (by serial dilution) and plotting on a graph.
Osmosis definition
The movement of water particles down a water potential gradient across a partially permeable membrane.
Water potential in a cell
Water potential decrease when solutes are dissolved into the solvent. Pure water has the water potential of 0kPa.
Isotonic solution (balanced)
Turgid: High water potential outside so water moves out (expands)
Plasmolysed: Los water potential outside so water moves in (shrivels)
Definition of active transport
Active transport is the movement of particles into a cell from a region of low concentration to a region of higher concentration using ATP and carrier proteins.
ATP is used directly to move partials such as in the accumulation of ions in root hair cells.
The process of active transport
Partials binds carrier proteins with a specific tertiary structure.
ATP bonds to protein and is hydrolysed to ADP +Pi releasing energy.
Proteins changes shape and carries particle to other side of the membrane.
Process can be repeated as new ATP molecule replaces ADP+ Pi and protein regains original shape
Definition of endocytosis
The membrane encloses partials to form a vesicle such as s in phagocytosis of pinocytosis for liquids
Definition of exocytosis
Internal vesicles fuse with the membrane to tease particles to the extracellular fluid such as at synapses
The link reaction
Respiration:
Occurs in the matrix of the mitochondria and produces acetyle coenzyme A from pyruvate.
1) Pyruvate is oxidised, producing NADH, and is decarboxylated forming acetate.
2) Acetate reacts with coenzyme A to form acetyl CoA
3) Acetyl CoA is then further broken down into the Krebs cycle
Krebs cycle
Respiration
Occurs in the Matrix of the mitochondria and produces NADH, ATP, FADH and waste CO2
1) Acetyl CoA reacts with a 4c molecule producing citrate (6c)
2) the citrate molecules is decarboxylated, oxidised and dephosphorylated. Products are ATP by substrate level phosphorylation, NADH, FADH and CO2
3) the 4c molecule is remade and the cycle restarts.
Facilitated diffusion
Where large polar or charged molecules pass the membrane using protein carriers or channels.
Polar or charged molecules are water soluble and repelled by the hydrophobic tails of the phosphilids. Aqueous channels enable transport.
Large molecules can’t fit so need specialised carriers
Diffusion
Is the passive movement of molecules from an area of high to low concentration down a concentration gradient.
Small non polar molecules can move across membranes by simple diffusion.
Investigation into permeability
Using beetroot and solvents
1) make serial dilutions of solvent
2) add beetroot cell membranes to different dilutions.
3) measure pigment released into solution from cells using a colorimeter calibrated with water
Solvent concentrations that destroy membranes will cause more pigment to enter the solution and reduced light transmission.
Solvent concentrations low = 0 /10 intensity of colour Medium 1/10 High 5/10 Very high 10/10
Temperature effect on cell membranes
Low temp: causes saturated fatty acids to clump together, reducing fluidity. This is counteracted by unsaturated fatty acidss with kinks pushing lipids apart and cholesterol
High temp: allow higher kinetic energy and increases permeability. It also effects membrane movements in phagocytosis or excytosis. Also increass enzyme catalysed recations but extreme temp can cause denaturing.
Fluid mosaic model
Membranes are partially permeable barriers that allow cell compartmentalization, resulting in different conditions either side. It is a flexible structure with embed proteins.
Contains : Phospholipids Proteins Cholesterol Glycolipids/ glycoproteins
Role of the adrenal gland
The adrenal glands are endocrine glands situated above the kidneys. The cortex and medulla of the adrenal glands release hormones into the blood.
Xerophytes
Such a cacti or marram grass are adapted to living in hot, dry or icy habitats with limited water
Adaptations of a xerophyte
Thick waxy cuticle mimimising transpiration loss
Water storage swollen parenchyma
Pitted stoma reducing evaporation
Hairy curled leaves reducing surface area and creating humid environments.
Hydrophytes
Such as Lilies are adapted to live in water saturated habitats.
Open stomata and thin waxy cuticle
Large flat air filled leaves to float and capture sunlight
Air filled parenchyma
Water pathways in plants
Symplast: movement of water through cytoplasm of cells via plasmodesmata down water potential gradient
Apoplast: movement through cell walls and intercellular space. Must go through casparian strip in the endodermis.
Vacuolar: similar to the symplastic but involves vacuoles as well.
Xylem
Tissue which consists of vessels to transport water and ions as well as lignified fibers for structural support
Lignin is waterproof and strengthens walls. Kills cells making end to end columns of dead cells. Allows flexibility.
Bordered pits is gaps in lignin for redistribution of water between neighbouring vessel’s and allows water out of the xylem into living tissue.
Transpiration stream
Roots absorb water
Water potential and force gradient forms a stream of water and maintains plant shape and rigidity
Water moves by cohesion tension causing a transpiration pull
Evaporation and transportation of the stomata
Vascular bundle
Plants have a small SA:V ratio so they need specialised transport systems.
Contains: Endodermis Phloem Cambium (contains meristems) Xylem
Nervous system
CNS with brain and spinal cord, (composed of mainly grey matter with unmyelinated neurons. With spinal cord with some white matter with myelinated neurons)
Peripheral nervous system contains the sensory system and motor system ( somatic and Autonomic system)
