The Biology course is very similar to the Human
Biology course we have already covered. Because of this the notes I post will
be very similar.
The Nature and
Variety of Living Organisms:
Characteristics
of living organisms:
•
Require nutrition
•
Respire
•
Excrete their waste
•
Respond to external stimuli
•
Move
•
Control their internal
conditions
•
Reproduce
•
Grow and develop
Features of
plants:
•
Multicellular organisms
•
Their cells contain
chloroplasts and therefore they photosynthesise
•
Have cellulose cell walls
•
Store carbohydrates such as
starch or sucrose
•
Examples include maize, peas,
beans etc…
Features of
animals:
•
Multicellular organisms
•
Their cells don’t contain
chloroplasts and so don’t photosynthesise
•
Have no cell walls
•
Usually have nervous
coordination
•
Are able to move from one place
to another
•
Often store carbohydrates such
as glycogen
•
Examples include humans,
houseflies and mosquitos
Features of
Fungi:
•
Cannot photosynthesise
•
Organised into mycelium made
from thread like structures called hyphae which contain many nuclei.
•
Some are single celled.
•
Cell walls made of chitin
•
Fed by extracellular secretions
of digestive enzymes on to food material and absorption of the organic product.
•
May store carbohydrates and
glucagon
•
Examples include yeast.
Features of
Bacteria:
•
Microscopic single celled
organisms
•
Lack a nucleus but contain
circular chromosomes of DNA called plasmids. Also has cell wall, membrane and
cytoplasm.
•
Most feed of other organisms.
Some photosynthesise.
•
Examples include pneumococcus,
lactobacillus bulgaricus etc…
Features of
Protoctists:
•
Microscopic single celled
organisms
•
Examples include amoeba,
chlorella and plasmodium.
Features of
Viruses:
•
Smaller than bacteria;
parasitic; only reproduce inside living cells.
•
Wide variety of shapes and sizes;
no cellular structure.
•
Have a protein coat and contain
one type of nucleic acid, DNA or RNA.
•
Examples include influenza, HIV
and tobacco mosaic.
Features of
pathogens:
•
Something that causes diseases.
•
Can be fungi, bacteria,
protoctist, or virus.
Structures and
functions in living organisms:
Levels of
organisation:
Specialised cells that perform similar functions
are grouped together as tissues:
There are many
types of tissues:
1. Bones -
collection of cells that secrete calcium salts.
2. Muscle - these can
be voluntary, involuntary or also cardiac.
3. Blood - collection of red and white blood cells.
4. Nervous tissue -
makes up the brain, nerves and spinal cord.
5. Epithelium - these are tissues that line organs. They can be both
squamous or ciliated.
Tissues that perform the same function are
grouped together to form organs. e.g. Heart.
Organs that perform the same function are
grouped together to form organ systems. e.g. The circulation system
Organ systems are grouped together to form
organisms. e.g. Humans.
Cell Structure:
The main differences between a plant cell and an
animal one is the lack of certain organelles such as a permanent vacuole, cell
wall and chloroplasts. Apart from this plant cells also have a more regular
structure.
The Functions of
the parts of the cell:
Nucleus: contains chromosomes (46 in humans) which carry the genetic
information. It controls the activity of the cell by controlling which proteins
the cell will synthesise.
Cytoplasm: this
is where chemical reactions occur.
Cell membrane:
this controls what substances can pass in and out of the cell. It is
selectively permeable.
Cell wall: this
protects the cell and helps support itself.
Chloroplasts:
these are needed for photosynthesis to take place in plants.
Mitochondria: this carries out
some of the reactions in respiration.
Vacuole: filled
with cell sap which contains nutrients. It is also used for cell structure and
support.
Biological
Molecules:
Carbohydrates:
1. Contain the elements Carbon, Hydrogen and Oxygen.
2. Are split into groups polysaccharides (e.g. starch), disaccharide
(e.g. sucrose) and monosaccharides (e.g. glucose).
3. The test for starch involves iodine. If it changes colour from
red-orange to blue-black then starch is present.
4. The test for glucose involves Benedict's Reagent. If, when placed in
heat, the solution turns from blue to brick-red then glucose is present.
Protein:
1. Contain the elements Carbon, Hydrogen, Oxygen and sometimes Sulfur.
2. Made of subunits called amino acids.
3. The test for protein involves the use of a biuret solution (Sodium
Hydroxide and Copper Sulphate). If the solution goes from blue to pink-purple
then protein is present.
Lipids:
1. Contain the elements Carbon, Hydrogen and Oxygen.
2. Made of a molecule of Glycerol and three fatty acids.
3. The test for lipids involves the use of ethanol. If when mixed the
solution goes cloudy then lipid is present.
Enzymes are biological catalysts meaning that they are organic molecules
that speed up reactions but remain unchanged. The lock and key model is used to
describe the actions of enzymes. Enzymes have an active site which the
substrate (reagent) fits into. After the enzymes catalyses the reaction it's
then free to go elsewhere. Because of the varying shapes of the enzymes and
substrates, only one type of enzyme can "fit" a substrate, they are,
therefore, specific. Enzymes are used to catalyse metabolic reactions.
Enzymes are affected by temperature. The rate of
reaction increases as temperature increases as there is more kinetic energy supplied
which means more collisions occur between the enzymes and substrates. However,
after the optimum temperature the rate of reaction falls as the enzymes are
being denatured which means the active site is changed. Enzymes are also
affected by pH. If the optimum pH is not reached the active site is once again
changed.
Experiment to
show enzyme activity with temperature:
1. Place test tubes of amylase and another with starch in a water bath.
2. After five minutes mix.
3. Take sample and test with iodine.
4. Do this every thirty seconds until the iodine turns blue-black.
5. Repeat the experiment changing the temperature of the water bath to
20, 30, 40, 50, 60 °C
The movement of
substances into and out of cells:
Diffusion - the next movement of particles
from an area of high concentration to low concentration down a concentration
gradient.
Osmosis - the movement of water molecules from an area of high water
potential to an area of low water potential through a partially permeable
membrane.
Active transport - the movement of particles against a concentration gradient using
energy from respiration and carrier proteins.
The movement of substances into and out of cells
can be through diffusion, osmosis and/or active transport.
The movement of substances in plants is essential
to create turgid (firm) cells which are needed for support. Without turgid
cells, the plants would wilt.
Factors affecting
rate of movement:
1. A high concentration gradient will increase the rate of movement.
2. A high temperature will increase the rate of movement as there is
more energy meaning more kinetic energy is present. This means the particles
move faster.
3. A large surface area to volume ratio will increase the rate of
movement as there is more area for the particles to move across.
Experiment for diffusion:
1. Cut potassium permanganate agar jelly cubes into cubes of length
0.5, 1, and 2 cm.
2. Place cubes of jelly at the same time into three beakers containing
75ml hydrochloric.
3. Record the amount of time it takes for the jelly to go from the dyed
purple colour to colourless.
Experiment for
osmosis:
1. In three test tubes, pour in one 10ml of distilled water, one 10ml
0.85% salt solution and one 10ml 3% salt solution.
2. Add 1ml of fresh blood to each test tube and shake.
3. Look at the sample of each under a microscope.
4. No red blood cells should be seen in test tube one as lysis has
occurred. Normal red blood cells should be shown in test tube two and shrunken
red bloods cells should be present in test tube three (flaccid and
plasmolysed).
Experiment for both
diffusion and osmosis:
1. Fill visking tubing with a substance.
2. Place in beaker containing the substance but in different
concentrations.
3. The amount of substance in each should change.
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