Energy cycles and ATP synthesis- Photosynthesis

Question 1

• Why do we need energy cycles?
• How does energy flow through living organisms?

Answer 1

• Needed for metabolic reactions
• Light energy from sun converted to chemical energy in producers, energy passed to consumers and then to decomposers. All organisms release energy when respiring.

Question 2

How are respiration and photosynthesis intimately linked?

Answer 2

• Photosynthesis creates complex organic molecules for organisms to eat
• Respiration breaks these down into smaller inorganic molecules
• Energy is released from breaking bonds in inorganic molecules is used to make ATP
• Oxygen released from photosynthesis is used in respiration
• ATP produced by respiration is used to drive photosynthesis

Question 3

Plants are autotrophs, what does this mean?

Answer 3

• They use photosynthesis to create their own complex organic molecules from small inorganic molecules

Question 4

Animals are heterotrophs, what does this mean?

Answer 4

• They consume other organisms to gain organic molecules

Question 5

ATP synthesis- describe chemiosmosis

Answer 5

• ATP produced by chemiosmosis
• Diffusion of protons from region of higher conc to region of lower conc, through a partially permeable membrane
• Movement of protons down concentration gradient releases energy which is used to attach inorganic phosphate to ADP, forming ATP

Question 6

ATP synthesis- what does chemiosmosis depend upon?

Answer 6

• The creation of a proton concentration gradient

–> the energy to do this comes from excited electrons

Question 7

ATP synthesis- what are the 2 ways that electrons can be excited?

Answer 7

• Electrons present in pigment molecules like chlorophyll excited by absorbing light from the sun
• High energy electrons are released when chemical bonds are broken in respiratory sunstrate molecules

Question 8

ATP synthesis- where do electrons go when they’ve been excited?

Answer 8

• They pass into the electron transport chain and are used to generate proton concentration gradient

Question 9

ATP synthesis- what are electron transport chains?

Answer 9

• They’re made up of a series of electron carriers

—–> each one has a progressively lower energy level

Question 10

ATP synthesis- explain what happens in electron transport chains

Answer 10

• As excited electrons move from one carrier to the next in the chain, energy is released

—–> this energy is used to pump protons across the membrane, creating proton concentration gradient

—> this gradient maintained due to impermeability of the membrane to hydrogen ions

Question 11

ATP synthesis- how do protons move through the membrane down the proton concentration gradient?

Answer 11

• Move through hydrophilic membrane channels
• ATP synthase acts as a channel protein that provides a hydrophilic channel for ions to diffuse down
• The flow of protons through these channels provides energy used to synthesise ATP