Physiology: Energy: Photosynthesis, Chemosynthesis and Respiration

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Animals need energy for movement, growth, reproduction, maintenance, homeostasis etc. 

Energy is used in the body in the form of ATP (adenosine triphosphate), but it usually initially obtained from the animal food. In this lecture we'd look at where the energy in food comes from and how it is converted to ATP.

Energy moves through ecosystems in the form of Carbon compounds. 

Plants use CO2 to make carbohydrates, Carbon is cycled round. 

Photosynthesis: 6CO2+6H2O->C6H12O6+6O2

Photosynthesis is the process by which plants make sugars and oxygen from carbon dioxide and water, using energy from sunlight. 

Aerobic respiration evolved because so much oxygen was being produced as a waste product; oxygen is toxic.

Chloroplasts in plants and algae: thought to result from cyanobacteria being engulfed by a primitive eukaryote and forming a symbiotic relationship. They contain the photosynthetic pigment chlorphyll. 

Algae are not plants. Chloroplasts are organelles with a double outer membrane and a watery matrix called the stroma.

A stack of thylakoids is also known as a granum. 

2 stages of photosynthesis: light stage - light energy splits water into oxygen and protons and electrons. Calvin cycle - carbon dioxide is combined with those free protons and electrons to make sugars. Calvin cycle occurs in the stroma and the light stage occurs in the thylakoids. 

Chloroplasts in animals: sacoglasson sea slugs engage in septoplasty - they absorb the chloroplasts from the algae they eat intact, then use them for photosynthesis. Several algal genes which support cloroplast function have also been found in the slug genome. (convergent evolution)

The slugs who steal chloroplasts have a different symbiotic strategy to marine…


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