biology notes

The basic which you need to know..hope it helps

HideShow resource information
  • Created by: monica
  • Created on: 10-01-10 14:48
Preview of biology notes

First 286 words of the document:

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 and fats into small soluble substances that can
be absorbed into the blood.
What are enzymes?
Enzymes are biological catalysts - catalysts are substances that
increase the rate of chemical reactions without being used up. Enzymes
are also proteins that are folded into complex shapes that allow smaller
molecules to fit into them. The place where these substrate molecules fit
is called the active site.
If the shape of the enzyme changes, its active site
may no longer work. We say the enzyme has been
denatured. They can be denatured by high
temperatures or extremes of pH.
Temperature and enzymes
As the temperature increases, so does the rate of
reaction. But very high temperatures denature
The graph shows the typical change in an
enzyme's activity with increasing temperature.
The enzyme activity gradually increases with
temperature until around 37ºC, or body
temperature. Then, as the temperature continues
to rise, the rate of reaction falls rapidly, as heat
energy denatures the enzyme.
pH and enzymes
Changes in pH alter an enzyme's shape. Different enzymes work best at
different pH values. The optimum pH for an enzyme depends on where it
normally works. For example, intestinal enzymes have an optimum pH of

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

­ 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
reactions involved in the process happen in tiny objects inside the cell
cytoplasm, called mitochondria.…read more

Page 3

Preview of page 3

Here's a taster:

The enzymes in the stomach work best in
acidic conditions - in other words, at a low pH.…read more

Page 4

Preview of page 4

Here's a taster:

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 acids are make urine, which is stored in the
broken down bladder temporarily
Water enters the body through food and drink. It is also a product of
aerobic respiration in cells.…read more

Page 5

Preview of page 5

Page 6

Preview of page 6

Here's a taster:

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 of the blood.
1. Urea
This process occurs in the liver.
Urea is produced as a waste product.
Urea is poisonous. Its released into the bloodstream by the liver,
Kidneys filter it out of the blood and it does excrete from the body in
2.…read more

Page 7

Preview of page 7

Here's a taster:

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 a type of cell division called meiosis. They contain a single
set of chromosomes, whereas body cells contain two sets of
chromosomes.…read more

Page 8

Preview of page 8

Page 9

Preview of page 9

Page 10

Preview of page 10

Here's a taster:

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.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »