5.2.1 - PHOTOSYNTHESIS

Question 1

Describe the relationship between photosynthesis and respiration

Answer 1

• Photosynthesis used by plants to make their own food (glucose)
• Respiration used by living cells to release energy from glucose
• Energy is stored in the glucose until released by repiration
• Animals can’t make their own food, so they eat plants to obtain glucose and respire this glucose

Question 2

What is the equation for photosynthesis?

Answer 2

6CO₂ + 6H₂O + Energy —> C ₆H₁₂O₆ (glucose) + 6O₂

Question 3

State the components of the chloroplast

Answer 3

• Stroma (cytoplasm-like feature)
• Thylakoids (fluid-filled sacs)
• Lamellae (bits of thylakoid membrane linking grana together) | singular = lamella
• Grana (stacks of thylakoids) | singular = granum
• DNA
• Double membrane
• Chlorophyll

Question 4

What are chloroplasts

Answer 4

Small, flattened organelles found in plant cells
Location for photosynthesis

Question 5

Describe the functions of chlorophyll

Answer 5

• One of the chloroplasts many photosynthetic pigments (e.g. chlorophyll a, chlorophyll b + carotene)
• Absorbs light energy needed for photosynthesis (found in thylakoids membranes, attached to proteins)

Question 6

What is a photosystem?

Answer 6

The protein and pigment in thylakoid membranes (pigments)

Question 7

Describe the components of a photosystem

Answer 7

• Contains TWO types of photosynthetic pigments: PRIMARY and ACCESSORY pigments
• Primary pigments: reaction centres where electrons are excited during the light-dependent reaction
• Accessory pigments: make up light-harvesting systems (surround reaction centres + transfer light energy to them to boost energy available for electron excitement to take place

Question 8

State and describe the two photosystems used by plants to capture light energy

Answer 8

• Photosystem I (PSI) - absorbs light best at a wavelength of 700nm
• Photosystem II (PSII) - absorbs light best at 680nm

Question 9

Define metabolic pathway

Answer 9

A series of small reactions controlled by enzymes (e.g. respiration + photosynthesis)

Question 10

Define phosphorylation

Answer 10

Adding phosphate to a molecule (e.g. ADP is phosphorylated ATP)

Question 11

Define photophosphorylation

Answer 11

Adding phosphate to a molecule using light

Question 12

Define photolysis

Answer 12

The splitting (lysis) of a molecule using light (photo) energy

Question 13

Define hydrolysis

Answer 13

The splitting (lysis) of a molecule using water (hydro)

Question 14

Define decarboxylation

Answer 14

The removal of carbon dioxide from a molecule

Question 15

Define dehydrogenation

Answer 15

The removal of hydrogen from a molecule

Question 16

Define redox reaction

Answer 16

Reaction that involves oxidation + reduction
OILRIG

Question 17

Describe the involvement of coenzymes in photosynthesis

Answer 17

• Coenzyme - molecule that aids the function of an enzyme
• Work by transferring a chemical group from one molecule to another
• Coenzyme used in photosynthesis is NADP
  ^— Transfers hydrogen from one molecule to another - means it can reduce (give hydrogen to) or oxidise (take hydrogen away from) a molecule