Energy: Respiration & Photosynthesis

All living things need energy to remain alive.

Photosynthesis is the chemical process used by chlorophyll containing cells to convert inorganic raw materials into organic compounds, using light energy. All plants have chloroplasts which contain chlorophyll and carry out photosynthesis. Cyanobacteria also carries out photosynthesis.

Lighter energy from the sun is used to drive the photosynthesis reaction. The light energy is converted into chemical energy which is stored in complex organic molecules such as carbohydrates. When an animal eats a plant it obtains this chemical energy. Thus energy is passed along the food chain.

Photosynthesis has a dual role in ecosystems; it begins food chains by capturing light energy and converting it into chemical energy and it also releases oxygen as a by product. The oxygen can then be used by all organisms in respiration. 

All living organisms depend upon photosynthesis or organisms that photosynthesise for survival.

THE PHRASES (there are two stages for photosynthesis):

Light reaction: 

Light energy is trapped by chlorophyll and is used to split up water molecules into hydrogen and oxygen.

Dark reaction: 

Carbon dioxide form the air combines with the hydrogen to form carbohydrates.

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RESPIRATION:

There are two types of respiration

Aerobic: requires oxygen and forms carbon dioxide, water and energy.

Anaerobic: occurs without oxygen and its product depends on the situation.

Respiration is the breakdown of glucose with oxygen to release energy. The energy is held in the glucose bonds, when they are broken down energy is released.

Respiration is a series of chemical reactions which releases energy from complex carbohydrates. All living things respire. Aerobic respiration is the complete breakdown of molecules such as sugars, using oxygen to form carbon dioxide and water. Anaerobic respiration occurs when there is no oxygen avaliable, or the cell has insufficient oxygen. The products of anaerobic respiration depend upon the situation. 

Stages of respiration (aerobic respiration):

The general equation for aerobic respiration shows the reactants and the final products however, the process does not occur in one step. It occurs in a series of controlled chemical reactions with about 50 different stages, each catalysed by a different enzyme. An enzyme is a chemical made by living things and its function is to control the rate of a specific chemical reaction that occurs in the body.

GENERAL EQUATION FOR AEROBIC RESPIRATION:

glucose + oxygen -> carbon dioxide + water

Respiration can be divided into two main stages:

The first stage breaks down glucose, a 6 carbon sugar, into two 3-carbon molecules called pyruvate. A small amount of energy is released at this stage. 

The second stage is the breakdown of this 3 carbon molecule, pyruvate, into a 1 carbon molecule instead, carbon dioxide. This stage uses oxygen and releases a much larger amount of energy.

There are two stages in respiration (in which this information relates to the above stages):

GLYCOLYSIS

—occurs in the cytoplasm

—2 ATP molecules are gained

—splits the 6 carbon glucose into two 3 carbon molecules (pyruvate).

—does not require oxygen.

KREBS CYCLE

-- occurs in the mitochondria

-- pyruvate is broken down into water and CO2 (one carbon) 

-- 36 ATP molecules are gained

-- oxygen is required

TERMS:

ATP -- adenosine triphosphate (one adenosine attached to three phosphate groups). This is the energy carrier of all cells.

For every glucose molecule 38 ATP molecules are produced.

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ENERGY

According to the first law of thermodynamics, energy can neither be destroyed nor created; rather, it is converted from one from into another.

Energy can take many forms:
--kinetic
--energy
--potential energy
--light
--electricity
--mechanical
--chemical
In cells the energy released in respiration comes from the carbon bonds in food molecules. If a cell is not given sufficient external food it will use any organic compound as the fuel source for respiration i.e: any carbohydrate, fat, protein etc.
The energy released by respiration can be used by the organism in several different ways. Some of the energy is released as heat and this is used to maintain body temperature. This is important for endotherms (warm-blooded animals). If a human gets cold, muscles will start to shiver, this is their way of increasing activity, respiring at a higher rate and releasing heat for the body. Heat is needed by the body for reactions as the enzymes in the body require an optimum temperature for maximum efficiency. At low temperatures the random movement of molecules decreases, reducing their chance of bumping into each other and hence having a reaction.

Use of energy by organisms:
--maintaining body temperature
--growth
--active transport
--cell maintenance
--repair
--synthesis of fats.


The released energy can also be used to cause other chemical reactions in cells to occur and for repair of damaged or old cells, or for active transport of materials across cell membranes.

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AND LASTLY, THE WORKS GIVEN FROM MY SCIENCE TEACHER.