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Enzymes and digestion
Enzymes are biological catalysts. There are optimum temperatures and
pH values at which their activity is greatest. Enzymes are also proteins,
and usually denatured above about 45ºC.
Enzymes are important in respiration and digestion. Aerobic respiration
releases energy from glucose. Digestion is the breakdown of
carbohydrates, proteins…

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about 8(alkali) ­ e.g. pancreatic amylase. Enzymes in the stomach have
an optimum pH of about 2(acid) - pepsin.

Aerobic respiration
Respiration is a chemical process in which energy is released from food
substances, such as glucose - a sugar.
Aerobic respiration needs oxygen to work. Most of the chemical…

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swallowed along with the food. The enzymes in the stomach work best in
acidic conditions - in other words, at a low pH.

Uses of enzymes

enzyme use

protease used to pre-digest proteins during the manufacture of baby foods

lipase used - together with protease - in biological detergents to…

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Production and removal of waste products

Waste Why is it produced? How is it removed?

carbon it is a product of aerobic through the lungs when we breathe out
dioxide respiration

urea it is produced in the liver the kidneys remove it from the blood and
when excess amino…

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The pancreas and insulin

The pancreas monitors and controls the concentration of glucose in the
blood. It produces a hormone called insulin. Insulin causes glucose to
move from the blood into cells. It lowers the blood glucose
concentration if has become too high. This can happen after eating a

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glucose they need for respiration, and the blood glucose concentration
stays normal.

The Kidneys and Homeostasis

Kidneys basically act as filters to clean the blood.
The kidneys perform three main roles:
1. Removal of urea from the blood.
2. Adjustment of ions in the blood.
3. Adjustment of water content…

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Cell division:
Chromosomes are made from DNA. Genes are short sections of DNA.
Genetically identical cells are produced by a type of cell division called
mitosis. In sexual reproduction, a male gamete fuses with a female
gamete to produce a new cell. This is called fertilisation. Gametes are
produced by…

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Mitosis is the type of cell division that leads to growth or repair. When a cell
divides by mitosis:
Two new cells form
Each cell is identical to the other one, and the cell they were formed

1. Parent cell
2. Chromosomes make identical copies of themselves
3. they…

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gametes sperm eggs

The cells that are formed by meiosis have half as many chromosomes as
the cell that formed them. Human body cells contain 23 pairs of
chromosomes, while human gametes contain 23 single chromosomes.
The main features of meiosis are:
- The chromosomes are copied
- The cell…

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Some characteristics, such as eye colour and the shape of the earlobe,
are controlled by a single gene. These genes may have different forms.
Different forms of the same gene are called alleles.

Alleles are dominant or recessive:
the characteristic controlled by a dominant allele develops if the allele


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