BIOLOGY A - (3.5.1 - 3.5.4) ENERGY TRANSFERS BETWEEN ORGANISMS

3.5.1 PHOTOSYNTHESIS

3.5.1 PHOTOSYNTHESIS

Name the 2 stages in photosynthesis

1. LDR - Light dependent reaction

2. LIR - Light independent reaction

Where do both reactions occur

In chloroplasts

Where does LDR occur within chloroplast

Thylakoid membranes

Where does the LIR occur within a chloroplast

The stroma

What does the LDR create that is essential for use in the LIR

ATP and reduced NADP

What are the 4 main stages of the LDR

1. Photoionisation of chlorophyll

2. Photolysis

3. Chemiosmosis

4. Production of ATP and reduced NADP

What happens during the photoionisation of chlorophyll

Light energy absorbed by Chlorophyll

Absorbed energy results in electrons becoming excited and raising an energy shell to leave (break free) of the chlorophyll

Therefore what has happened to the chlorophyll and what are some of the released electrons used for

It has been ionised

Released electrons used to make ATP and reduced NADP in chemiosmosis

What are the stages in photolysis (light energy splitting water)

Water is split to release oxygen, hydrogen ions and electrons

The electrons are passed along a chain of electron carrier proteins

The hydrogen ions (protons) are accepted by NADP to make it reduced NADP (NADPH)

The oxygen is either used for respiration or diffuses out of the leaf via stomata

What does Photolysis split one molecule of H₂ O into

½ O₂ + 2e^- + 2H⁺

What happens during chemiosmosis Pt 1 (Up to the movement of protons into thylakoid lumen)

Electrons that gained energy + left chlorophyll move along electron carrier proteins embedded in Thylakoid membrane

The series of proteins that carry electrons embedded in membrane are called electron transfer chain

The electrons release energy at each protein

That energy is used to pump protons across thylakoid membrane (protons also received from photolysis of water)

This results in higher concentration of protons in the thylakoid membrane

What happens during chemiosmosis Pt 2

Due to protons being in higher concentration on inside of lumen, they diffuse out via facillitated diffusion through ATP synthase protein (enzyme)

The ATP synthase uses proton chain to catalyse reaction of ADP + Pi to make ATP

Some protons that travel across thylakoid membrane are recycled into process again

Others are picked up by NADP as well as 2 electrons to form NADPH

Why is chemiosmosis known as such

Because H⁺ ions move down conc gradient from higher to lower conc

What is the LIR also known as

The Calvin cycle

Where does the calvin cycle occur

In the stroma

What enzyme does the stroma contain

RuBisCo

Why is this stage temperature sensitive

Because it involves enzymes which can denature

What 3 ingredients does the Calvin cycle use

CO₂

reduced NADP (NADPH)

ATP

What does 6 turns of Calvin cycle result in

Synthesis of hexose sugar (Glucose)

What are the 3 stages in the Calvin cycle

Fixation

Reduction

Regeneration

What is TP the general term for

Any 3 carbon sugar with a phosphate attached to it

What is G-3P

A specific 3 - carbon sugar molecule with a phosphate group

Go over the CALVIN CYCLE DIAGRAM FROM COGNITO MENTALLY

Go over the CALVIN CYCLE DIAGRAM FROM COGNITO MENTALLY

Explain what happens during carbon fixation

CO₂ reacts with (5C) compound RuBP (using enzyme RuBisCo) to form unstable (6C) compound

This (6C) compiund splits into 2 x GP molecules

Explain what happens during the reduction (of GP)

GP reduced into triose phosphate (TP)

This uses energy from the hydrolysis of ATP

This also requires protons and electrons from NADPH (reduced NADP)

The resulting NADP is returned to the LDR to be reduced again

Explain what happens during regeneration (of RuBP)

Most TP is used to regnerate RuBP using ATP

The rest of the TP (1/6 Carbon atoms) can be used to make useful organic substances

This means that 6 turns of the calvin cycle are required to produce one molecule of a hexose sugar such as glucose

What are the 3 limiting factors of photosynthesis

Temperature

Light intensity

CO₂ Concentration

What does it mean when the graph for a specific limiting factor of photosynthesis plateaus

That another of the 3 limiting factors has become the limiting factor

What 3 techniques do agricultural practices use to help stimulate maximum rate of photpsynthesis

Artifical lighting

Heating

Paraffin burners (to release more CO₂ )

What must farmers consider when deciding the extent to which each technique is used

The cost effectiveness

3.5.2 RESPIRATION

3.5.2 RESPIRATION

What are the 4 main steps in Aerobic respiration and where do they occur

Glycolysis (Cytoplasm)

Link Reaction (Mitochondrial matrix)

Krebs cycle (Mitochondrial matrix)

Oxidative phosphorylation (Mitochondrial cristae)

What does respiration produce

ATP

What is the first stage in AEROBIC and ANAEROBIC respiration

Glycolysis

What are the 3 main steps of Glycolysis

1. Phosphorylating glucose to glucose phosphate (using ATP)

2. Production of triose phosphate

3. Oxidation of triose phosphate to produce pyruvate with a net gain gain of ATP and reduced NAD

How is NAD different to NADP

NADP simply contains one extra phosphate group

What type of reactions does NAD usually work in

Catabolic (breaking down) reactions

What type of reactions does NADP usually work in

Anabolic (building up) reactions such as LDR

What are NADP and NAD both

Coenzymes or “helper molecules”

What happens when phosphorylating glucose using ATP

The energy that was locked up in the ATP bond is transferred to new molecule so glucose phosphate = a high energy and highly reactive

Why do the 2 TP molecules end up with 4 phosphates (2 EACH) altogether rather than one after glucose phoshpate splitsB

Because a free floating inorganic phosphate from the cell’s cytoplasm attaches to each TP molecule on top of the one that is already there

Explain the oxidation process of Triose phosphate to produce pyruvate and how we end up with a net gain of ATP and reduced NAD (NADH)

Each triose phosphate molecule loses hydrogen atoms. The helper molecule NAD grabs these hydrogens and turns into reduced NAD (NADH)

Phosphate groups are handled and released from the carbon chain

The removed phosphate groups attach to ADP (adenosine diphosphate) to create ATP

Due to 4 phosphates provided from the 2 TP molecules, 4 ADPs are able to be transformed into 4 ATPs leading to a net gain of 2 ATP molecules from the start of the process