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level: 11.1 Overview of photosynthesis

Questions and Answers List

level questions: 11.1 Overview of photosynthesis

QuestionAnswer
Site of photosynthesis- Leaf in eukaryotic plants - Chloroplasts
Structure of the leaf adaptations- LSA: absorbs as much sunlight as possible - Leaves arranged to minimise overlapping: avoids shadowing - Thin: shorter diffusion distance - Transparent cuticle + epidermis: let light through to mesophyll cells - Many stomata: gaseous exchange, short diffusion path to MC, open + close in response to light intensity - Air spaces: lower mesophyll layer to allows rapid diffusion - Xylem and phloem
Photosynthesis word equationcarbon dioxide + water ------> (light) glucose + oxygen
Metabolic pathway meaning- A series of small reactions controlled by enzymes e.g. photosynthesis and respiration
Phosphorylation meaning- Adding phosphate to a molecule e.g. ADP is phosphorylated to ATP
Photophosphorylation meaning- Adding phosphate to a molecule using light
Photolysis meaning- The splitting (lysis) of a molecule using light (photo) energy
Photoionisation meaning- When light energy 'excites' electrons in in a molecule, giving them more energy + causing them to be released - The release of electrons causes mol to become a +charged ion
Decarboxylation meaning- The removal of carbon dioxide from a molecule
Dehydrogenation meaning- The removal of hydrogen from a molecule
Redox reactions meaning- Reactions that involve oxidation and reduction
The main stages of photosynthesis- Capturing of light energy - Light-dependent reaction - Light-independent reaction
Capturing of light energy- By chloroplast pigments such as chlorophyll
Light-dependent reaction- Some light energy absorbed is conserved in chemical bonds - During the process an electron flow is created by the effect of light on chlorophyll - Causing water to slit (photolysis) into protons, electrons + oxygen - Produces are reduced NADP, ATP + O2
Light-independent reaction- These protons used produce sugars + other organic molecules
Structure of chloroplasts- The grana - The thylakoids - The stroma
The grana- Grana are stacks of up to 100 disc like structure called thylakoids
The thylakoids- Where light-dependent reactions happen - Contains photosynthetic pigment, chlorophyll - Some have tubular extensions that join up w/ thylakoids in adjacent grana, granal lamellae
The stroma- Fluid-filled matrix - Where light-independent stage of photosynthesis happens - Within the stroma are the no. of other structure like starch grains
ATP properties that make it a good source of energy- Stores or releases only a small, manageable amount of energy at a time, so no energy wasted as heat - Easily broken down - It can be quickly re-made - Small, soluble molecule, easily transported around cell - Can make other molecules more reactive by transferring one of its phosphate groups to them (phosphorylation)
What is ATP (recap)- Cells cant get its energy directly from glucose - So, in respiration, the energy released from glucose is used to make ATP - ATP carries energy around the cell
How ATP works (recap)- ATP is synthesised via condensation reaction (catalysed by ATP synthase) between ADP + an inorganic phosphate, using energy from an energy-releasing reaction - Energy is stored as chemical energy in the phosphate bond - ATP diffuses to the part of the cell that needs energy - Here, its hydrolysed back into ADP + inorganic phosphate - Chemical energy is released from the phosphate bond and used by the cell - ATP hydrolyse catalyses this reaction - The ADP + inorganic phosphate are recycled, the process starts again
Coenzymes- A molecule that aids the function of an enzyme
How coenzymes work- Transfers a chemical group from 1 molecule to another - A coenzyme used in photosynthesis is NADP - It transfers hydrogen from 1 molecule to another - This means it can reduce (give hydrogen to) or oxidase (take hydrogen from) a moelcule
Examples of coezymes on resporaton- NAD, coenzyme A and FAD - NAD + FAD transfer hydrogen from 1 molecule to another - This means that can reduce (give hydrogen to) or oxidase (take hydrogen from) another molecule - Coenzyme A transfers acetate between molecules