5: Energy Transfers Flashcards by sophia lauren

What is the balanced symbol equation for photosynthesis?

6CO2(g) + 6H2O(l) -> 6O2(g) +C6H12O6

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How is the chloroplast structure adapted to their fucntion?

have stacks of thylakoids (grana), providing a large surface area for attatching chlorphyll, electrons and enzymes
network or proteins in grana hold chlorophyll in a orientation to absorb more light
granal membranes have ATP sunthase channels which are selectively permeable to create a proton gradient
have DNA and ribosomes to synthesise proteins

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What is oxidation and reduction?

oxidation- when a substance loses elctrons, lose H+
reduction- when a substance gains electrons, gain H+

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What is a photosystem?

funnel-like structures in the thylakoid membrane
made from accesory pigments (cluster), absorbing light energy to transfer it to primary pigment reaction centre (chlorophyll)
energy funneled tor eaction centre causes photoionisation of chlorophyll, loss of an electron

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What is the role of coenzymes?

pick up and provide hydrogen atoms to complete a reaction and make a substance

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What is the first stage of photosynthesis?

Light Dependent Reaction:
- chlorophyll / photosystem absorbs light;
- electron lost by chlorophyll in photoionisation
- splitting of water / photolysis replaces electron;
- passing of excited electrons between chlorophyll molecules in photosystems;
- electron passed from photosystem II to carriers (in thylakoid membrane);
- production of ATP in this way is called photophosphorylation;
- electron causes pumping of protons into the thylakoid;
- proton gradient used by ATPase to drive ATP production;
- electron passes to photosystem I at end of carrier chain;
- electron re-excited and emitted by photosystem I;
- electron passed to / used to reduce NADP+;
- NADPH + H+ / reduced NADP produced;
- cyclic photophosphorylation using photosystem I, electron carriers and ATPase only;

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What is the second stage of photosynthesis?

Light Independent Reaction: Calvin Cycle
- light-independent reaction fixes CO2;
- to make glycerate 3-phosphate;
- glycerate 3-phosphate / GP / phosphoglyceric acid becomes reduced;
- to triose phosphate / phosphoglyceraldehyde / glyceraldehyde 3-phosphate;
- using NADPH;
- using ATP;
- ATP needed to regenerate RuBP;
- ATP is made in light-dependent reactions;
- light causes photoactivation / excitation of electrons;
- flow of electrons causes pumping of protons into thylakoid;
- ATP formation when protons pass back across thylakoid membrane;
- electrons are passed to NADP / NADP+;
- NADPH produced in the light dependent reactions;

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What are the limiting factors of photosynthesis?

light intensity- graph increases then plateaus
CO2 concentration- graph increases then plateaus
temperature- graph increases then decreases (as enzyme denatures)

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What is the balanced symbol equation for respiration?

6O2(g) +C6H12O6 -> 6CO2(g) + 6H2O(l)

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How is the mitochondria structure adapted to their fucntion?

rod shaped organelles, 0.5-1μm
site of aerobic respiration in eukaryotic cells, synthesises ATP
organelles: matrix, cristae, ribosomes, circular DNA
double membrane structure, with an inner layer with many folds to create a high surface area

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Why is respiration important?

provides energy required for condensation ADP-> ATP
for each 30.5kJmol-1 of energy released by hydrolysis of ATP, the same energy must also be input from respiration to reform ATP
energy from condensation reaction comes from chemical energy in glucose
releases small packets of energy to prevent cell damage so minimal energy is wasted

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What substances are required for repsiration?

glucose and oxygen
ADP & ATP
co-enzymes: NAD, FAD, co-enzyme A

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What are the 4 stages of respiration?

glycolysis
link reaction
kreb cycle
oxidative phosphorylation/ electron transport chain

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What is the glycolysis stage of respiration and where does it take place?

in the cytoplasm
no O2 requires
glucose splits into 2 pyruvates (3C) sugar
2 parts: energy investment phase and energy pay off phase

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What occurs during glycolysis?

phosphorylation: glucose(6C) -> hexose-1,6-bisphosphate(6C)
- 2ATP -> 2ADP
lysis: hexose-1,6-bisphosphate(6C) -> TP(3C) TIMES 2
oxidation: 2TP(3C) -> intermediate 3C
- ADP -> ATP
- NAD -> NADH
dephosphorylation: intermediate 3C -> pyruvate
- ADP -> ATP

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What is the link reaction stage of respiration and where does it take place?

occurs in matrix of mitochondria (pyruvate moves in)
enzyme controlled reaction
pyruvate converted into acetyl CoA

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What occurs during the link reaction?

start with pyruvate (2 per glucose)
decarboxylated (remove CO2)
add enzyme CoA
oxidised as NAD converted to reduced NADH
produces acetyl coA (2C)

What is the krebs cycle stage of respiration and where does it take place?

occurs in mitochondiral matrix
involves redox reactions
2 cycles per glucose
occurs 6 times for balanced equation
TP used to generate useful organic substances

Why is the krebs cycle significant?

breaks larger molecules into smaller ones
produces H atoms, essential to reduce coenzymes for use in oxidative phosphorylation
regenerates 4C molecule w/ acetyl Co A to restart cycle
source of intermediate compounds to be used in cells in body

What occurs during the krebs cycle?

acetyl CoA (2C) joins to oxaloacetate (4C) to form** citrate (6C)**
citrate (6C) gets oxidised as NAD reduced to NADH and gets decarboxylated to form intermediate 5C
intermediate 5C gets oxidised as NAD reduced to NADH and getd decarboxylated to form intermediate 4C
intermediate 4C dephosphorylates (ADP -> ATP), is oxidised (FAD -> FADH and NAD -> NADH) to reform oxaloacetate (4C)

What is the use of TP?

TP: used to produce hexose phosphates (6C), which can be used to produce starch, sucrose or cellulose, lipids for cell membranes and amino acids for protein synthesis

What is the oxidative phosphorylation stage of respiration and where does it take place?

highest no. of ATP produced
uses H from co-enzymes
takes place in cristae membrane and intermembrane space

What occurs during oxidative phosphorylation?

NADH and FADH releases H atom, which splits into an electron and proton (H+)
electrons get excited and move through the e.t.c. in redox reactions, transferring/ losing energy
energy released used to synthesise ATP and pump protons into i.m. space, creating an electrochemical gradient
H+ ions want to move in due to gradient, using ATP synthase channels which convert ADP+Pi to ATP as the channels change shape
oxygen combines with protons in ATP synthase channels and electrons in e.t.c.: O2 + 4H+ + 4e- -> 2H2O (oxygen acts as electron acceptor)
NAD & FAD go back to earlier stages in respiration

What is anaerobic respiration?

respiration without O2 present
occurs in cytoplasm (mainly glycolysis as NAD/FAD can’t be used in these stages)
if no O2, NADH & FADH can’t be reoxidised in e.t.c. as there’s an absence of O2 to pick up H and e-

How does anaerobic respiration occur in mammals?

**lactate fermentation:** - occurs in mostly muscle cells when ATP demand is high and O2 deficit - in animals and some bacteria - oxidised NAD reused in glycolysis as H carrier produces 2ATP - **pyruvate(3C) -> lactate(3C)** - lactate dehydrogenase used to reoxidise NADH to NAD

How does anaerobic respiration occur in plants and fungi:

**ethanol fermentation:** - pyruvate decarboxylated, accept H - oxidised NAD reused - **pyruvate(3C) -> ethanal(2C) -> ethanol(2C)** - uses pyruvate decarboxylase to convert pyruvate to ethanal, losing CO2 - uses ethanol dehydrogenase to convert ethanal to ethanol, reoxidising NADH to NAD

What is a respiratory substrate?

- the organic nutrients oxidised at the time of respiration - oxidation of organic nutrients occurs to obtain energy (ATP) - order of preference of organic nutrients as respiratory substrates are – carbohydrates, lipid, proteins

How does lipids act as a respiratory substrate?

- important for many tissues (e.g. muscle) - lipids are hydrolysed to fatty acids and glycerol - **glycerol is phosphorylated, converted into TP** which can then enter the glycolysis pathway - **fatty acid broken down** into 2C fragments, into** acetyl CoA** - generates **NADH, FADP & acetyl CoA** to enter the Krebs cycle - oxidation of lipids produces many 2C molecules used in oxidative phosphorylation - for the same mass, **lipids release more than 2x the energy of carbohydrates as they produce more ATP**

How does proteins act as a respiratory substrate?

- amino acids used as substrates in excess - **proteins first hydrolysed to individual amino acids**, taken to liver where amino group is removed in deamination - removed amino group converted to urea, moved by kidneys as waste - **remaining amino acid converted to an intermediate** - **no. of carbon atoms involved determines next step e.g. 3C= pyruvate**

What is biomass?

- organic material that makes/ is produced living things - mass of carbon or dry mass of tissue per given area

How is energy lost at each trophic level?

- energy always disspiated as heat loss (in respiration/ faeces) - lost as not all an organism is consumed (e.g. bones) and not all energy available for the next organism - less energy available to sustain living tissue at higher food chain level

What are the types of pyramids measuring energy transfer?

- **numbers** - **biomass-** dry mass of living material - **energy** released per unit mass

What are limitations of the pyramid of biomass?

- takes into account size of organism but it's only a snapshot of the amount of material present at a given time - changes at different times of the year - doesn't state the date of primary consumers (e.g. excretes/ not eaten/ faeces)

What do pyramids of energy represent?

- more accurate representation of flow of energy (energetics) obtained by measuring energy content material and displaying info0. as pyramids of energy - using energy valuyes determined from given area over a specified period of time for each trophic level (e.g. kJm-2yr-1)

How can the chemical energy store in dry biomass can be estimated?

using calorimetry/ bomb calorimeter

How does a bomb calorimeter work?

- determines energy content of material by burning a known mass of dry material in pure oxygenn - results in complete combustion, an accurate measure of energy content

Why is dry mass used to measure energy transfer?

- potential energy contained in sample in kJ where 4.24KJ equal to heat required to raise temp. of 1kg of water by 1°C

What is the equations required for energy released and energy for pyramid?

- energy released= mass x s.h.c x △t - energy for pyramid= H2O energy released ÷ biomass burned/ kg ÷ time

Where does primary and secondary production come from?

- **primary production-** producers - **secondary production-** consumers

What is gross primary production (GPP)?

chemical energy store in plant biomass, in a given area or volume