Biology by2 revision

Gas exchange in advanced multicellular organisms For efficient gas exchange, advanced organisms require A ventilation mechanism An internal transport system often a blood circulation system to move gases from respiratory surface to respiring cells and vice versa A respiratory pigment in the blood — to increase the oxygen carrying capacity Gas exchange in fish Water contains far less oxygen than air The rate of diffusion in water is slower Water is a dense medium compared to air so does not flow as freely, meaning it has to be pumped over the respiratory surface.

Biology by2 revision

No further reactions on carbon Ethanol and lactic acid can be broken down dioxide and water.

Biology by2 revision

A lot of energy is produced. When a molecule of glucose is broken down in the presence of oxygen, KJ of energy are produced 38 molecules of ATP. In anaerobic respiration the by products are organic compounds.

These can be broken down further in the presence of oxygen to give more energy. Far less energy is thus produced. The process is not economical as far as energy production is concerned. When a molecule of glucose is broken down in the absence of oxygen in plants, KJ are produced 2 molecule ATP.

In animals, anaerobic respiration yields kJ of energy. Substrates for Respiration Carbohydrate, mainly glucose is the main substrate inside cells. Lipids i.

Fatty acids are used when the carbohydrates are exhausted. A molecule of lipid yields much more energy than a molecule of glucose. Proteins are not normally used for respiration. However during starvation they are hydrolysed to amino acids, dearnination follows and the products enter Kreb's cycle as urea is formed.

Use of body protein in respiration result to body wasting, as observed during prolonged sickness or starvation. The ratio of the amount of carbon IV oxide produced to the amount of oxygen used for each substrate is referred to as Respiratory Quotient RQ and is calculated as follows: Respiratory quotient value can thus give an indication of types of substrate used.

Besides values higher than one indicate that some anaerobic respiration is taking place. Ethanol in beer comes from fermentation of sugar maltose in germinating barley seeds.

Sugar in fruits is broken down anaerobically to produce ethanol in wines. In the dairy industry, bacterial fermentation occurs in the production of several dairy products such as cheese, butter and yoghurt.

In production of organic acids e. Home Fermentation of grains is used to produce all kinds of beverages e. Fermentation of milk. The energy comes from breakdown of food in respiration. Carbon IV oxide is a by product of respiration and its accumulation in cells is harmful which has to be removed.

Most organisms use oxygen for respiration which is obtained from the environment. The movement of these gases between the cells of organisms and the environment comprises gaseous exchange.

The process of moving oxygen into the body and carbon Iv oxide out of the body is called breathing or ventilation. Gaseous exchange involves the passage of oxygen and carbon IV oxide through a respiratory surface. Diffusion is the main process involved in gaseous exchange.

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Gaseous Exchange in Plants Oxygen is required by plants for the production of energy for cellular activities. Carbon IV oxide is required as a raw material for the synthesis of complex organic substances.

Oxygen and carbon IV oxide are obtained from the atmosphere in the case of terrestrial plants and from the surrounding water in the case of aquatic plants. Gaseous exchange takes place mainly through the stomata.

Structure of Guard Cells The stoma stomata - plural is surrounded by a pair of guard cells. The structure of the guard cells is such that changes in turgor inside the cell cause changes in their shape. They are joined at the ends and the cell walls facing the pore inner walls are thicker and less elastic than the cell walls farther from the pore outer wall.

Guard cells control the opening and closing of stomata.Biology Revision For each of the exam boards below, there are revision notes, factsheets, questions from past exam papers separated by topic and other worksheets. GCSEs & IGCSEs. Apr 07,  · I am at a loss. I have revised so much for Biology but it is not working anymore I got an A (/ which is 88 UMS) in January for BY1 (WJEC) and in BY2 all I can muster seems to be B grades What should I do?

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Introduction. Transport is the movement of substances within an organism. All living cells require oxygen and food for various metabolic processes.

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