5.6 - Photosynthesis Flashcards
What is autotrophic nutrition?
Type of nutrition where organic molecules are synthesised from inorganic molecules such as carbon dioxide and water.
E.g. photosynthesis where sunlight energy is converted to chemical energy = used to synthesise large organic molecules from small inorganic molecules.
What are two names for organisms at the beginning of the food chain and why do they have these names?
PHOTOAUTOTROPHS: Organisms that photosynthesise.
- because they use light as the energy source for autotrophic nutrition.
PRODUCERS:
They are at the beginning (first trophic level) of a good chain.
- provide energy & organic molecules to other, non-synthetic, organisms.
Give the general equation for photosynthesis:
6CO2 + 6H2O —> (chlorophyll)
C6H12O6 + 6O2
What is a photon?
A particle of light; each photon contains an amount (a quantum) of energy.
Why is photosynthesis an example of carbon fixation?
Because it is a process by which carbon dioxide is converted into sugars.
What kind of reaction is carbon fixation? (Two details)
- an endothermic reaction = requires energy
- a reduction reaction = needs electrons
Why is carbon fixation useful?
- helps regulate the concentration of carbon dioxide in the atmosphere and oceans.
Why is photosynthesis important to all organisms not just plants?
- most forms of life on Earth rely directly or indirectly on photosynthesis.
Why do plants need energy?
They need energy for things like photosynthesis, active transport, DNA replication, cell division and protein synthesis.
Who do animals need energy?
Animals need energy for things like muscle contraction, maintenance of body temp., active transport, DNA replication, cell division & protein synthesis.
How do plants respire?
They oxidise the organic molecules that they have previously synthesised by photosynthesis & stored, releasing chemical energy.
How do non-photosynthetic animals respire?
Non-synthetic organisms are organisms that cannot photosynthesise.
- they consume food
- they obtain energy from the products of digestion by respiration.
What happens in respiration?
Glucose and other organic compounds are oxidised to produce carbon dioxide and water.
Is respiration endo or exothermic?
Respiration is exothermic.
- releases chemical energy that can drive the organism’s metabolism.
Give the formula for respiration.
C6H12O6 + 6O2 → 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water)
Give the two types of respiration.
Aerobic respiration:
- using oxygen
Anaerobic respiration:
- without oxygen
Metabolic pathway definition:
a series of small reactions controlled by enzymes, e.g. respiration and photosynthesis
Phosphorylation definition:
adding phosphate to a molecule e.g. ADP is phosphorylated to ATP
Photophosphorylation definition:
adding phosphate to a molecule using light
Photolysis definition:
the splitting (lysis) or a molecule using light (photo) energy
Hydrolysis definition:
the splitting (lysis) of a molecule using water (hydro)
Decarboxylation definition:
- the removal of carbon dioxide from a molecule
Dehydrogenation definition:
the removal of hydrogen from a molecule.
Redox reaction definition:
a reaction that involves oxidation and reduction
When do plants photosynthesise and why?
Plants only photosynthesise during the day.
What is the term to describe when photosynthesis and respiration proceed at the same rate?
The plant is at its compensation point.
The time a plant takes to reach its compensation point is called the ……?
Compensation period.
Is the compensation period the same for all plant species?
No.
- the compensation period is different for different plant species.
Describe the difference in response between a shade plant and a sun plant when they are both exposed to light.
SHADE PLANTS:
- can utilise light of a lower light intensity that sun plants can.
- when exposed to light after darkness, shade plants reach their compensation point sooner
> have a shorter compensation point than sun plants.
SUN PLANTS:
- require a higher light intensity to achieve their optimum rate of photosynthesis.
What shape and how big are most chloroplasts?
- most plant chloroplasts are DISC SHAPED
- around 2-10μm long.
Describe the basic structure of chloroplasts.
> each chloroplast is surrounded by a double membrane, the envelope, with an inter membrane space of width 10-20nm between the inner & outer membrane
> outer membrane = HIGHLY PERMEABLE.
> the stroma = the fluid filled matrix
> grana = consist of stacks of thylakoids membranes
Where does the first stage of photosynthesis take place and what is this stage called?
The grana
- it is called the light-dependent stage.
How many membranes do chloroplasts have?
- the outer, inner and thylakoid
Gives three separate internal compartments:
> the intermembrane space
> the stroma
> the thylakoid space
- the outer, inner and thylakoid
Is the thylakoid membrane of each chloroplast highly permeable or slightly permeable?
Not very permeable.
Why is useful that the grana are so small and there are many chloroplasts within each cell?
It means there is a huge surface area for:
- the distribution of the photosystems that contain the photosynthetic pigments that trap sunlight energy
- the electron carriers and ATP synthase enzymes needed to convert that light energy into ATP.
Why is important that there are proteins embedded in the thylakoid membranes?
So the photosystems are held in place.
Why are the grana surrounded by stroma?
So the products of the light-dependent stage can easily pass to the stroma to be used in the light-independent stage.
What does the stroma contain?
Contains the enzymes needed to catalyse the reactions of the light-independent stage of photosynthesis, as well as:
> starch grains
> oil droplets
> small ribosomes similar to those found in prokaryote cells
What does the loop of DNA in the stroma contain?
Genes that code for some of the proteins needed for photosynthesis.
- these proteins are assembled at the chloroplast ribosomes.
