Proton Gradient

Question 1

Briefly explain the light-dependent stage of photosynthesis in relation to the proton gradient.

Answer 1

Electrons excited by light and move through carriers in thylakoid membranes - this energy pumps protons from stroma into spaces between thylakoid membranes - energy is released in chemiosmosis as protons flow down an electrochemical gradient into the stroma through ATP synthase - energy incorporated into ATP

Question 2

Briefly explain respiration in relation to the proton gradient.

Answer 2

Electrons excited by energy from food molecules - their energy made available as they move through carriers in the inner mitochondrial membrane - energy pumps protons across membrane from matrix into inter membrane space (proton gradient) - energy released in chemiosmosis in the same way - this energy incorporated into ATP

Question 3

Describe apoptosis

Answer 3

Programmed cell death and occurs, for example, during embryonic development. It operates by preventing proton gradients across cell membranes from forming

Question 4

Describe how DNP causes death.

Answer 4

DNP is a mitochondrial poison which allows electron transport but not ATP synthesis. The body oxidises fats and carbohydrates, so weight is lost, but all energy released from those molecules is converted to heat as no ATP is made. The body overheats sometimes fatally.