f214 photosynthesis

F214 Module 3

Chapter 1 – Photosynthesis.

a. Define the terms autotroph and heterotroph

·         Autotroph are organisms that can synthesise complex molecules like carbohydrates, lipids, proteins, nucleic acid and vitamins from inorganic molecules as a source of energy. They also use light energy and chemical energy.

·         Heterotroph are organisms which cannot make their own food. They digest complex organic molecules into simpler soluble ones which they then use to synthesise complex molecules such as lipids, proteins and nucleic acids. The chemical potential energy is released from the complex organic molecules.

b. State that light energy is used during photosynthesis to produce complex organic molecules

Summarised equation: 6 C.O₂ + 6H₂O (and light energy) makes C₆H₁₂O₆ + 6 O₂

c. Explain how respiration in plants and animals depends upon the products of photosynthesis

Oxygen needed for aerobic respiration first appeared in the atmosphere due to photosynthesis.

It allows photo-trophs and heterotrophs to release the chemical potential energy in complex organic molecules which were made during photosynthesis.

d. State than in plants photosynthesis is a two-stage process taking place in chloroplasts

Photo-autotrophs have organelles called chloroplasts where photosynthesis takes place.

There are two stages to photosynthesis: the light dependant stage and the light independent stage.

e. Explain how the structure of chloroplasts enables them to carry out their functions

·         Most chloroplasts are disk shaped and between 2-10μm long.

·         Each chloroplast has an envelope which below is an intermembrane space about 10-20nm wide.

·         The outer membrane is permeable to many small ions.

·         The inner membrane is less permeable with transport proteins embedded. It is folded into lamellae which are stacked up to form a granum.

·         The grana are attached by intergranal lamellae.

·         The stroma is a fluid filled matrix where the light dependant stage takes place due to it containing the enzymes needed.

·         The grana are stacks of flattened membrane components called thylakoids. This is where the light absorption and ATP synthase during the light dependant stage takes place.

·         Due to the inner membrane having transport proteins, it can control the entry and exit of substances.

·         The grana provide a large surface area for the photosynthetic pigments, electron carriers and ATP synthase enzyme which are needed for the light dependant reactions.

·         Photosynthetic pigments are arranged into photosystems so the maximum absorption of light energy takes place. They are held in place by the grana.

·         The fluid-filled stroma contains the enzymes needed in the light dependant reaction.

·         The grana are surrounded by stroma so products from the light dependant reaction can easily pass to the stroma where they are needed for the light dependant reaction.

·         Chloroplasts can make some of the proteins needed for photosynthesis.

f. Define the term photosynthetic pigment

·         Photosynthetic pigment

They are substances that absorb certain lengths of wavelength…