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B3 Science Revision
•Liver and muscle cells have large numbers of mitochondria
•Ribosomes are in the cytoplasm and where protein synthesis
happen.
•Four different bases, A,T,G,C.
•Proteins are made from lots of amino acids joined together.
Each amino acid is coded by the sequence (order) of three
bases. For example, GGT.
•The genetic code needed to make a particular protein is
carried from the DNA to the ribosomes by a molecule
called mRNA.
•mRNA from DNA is called transcription
•Proteins from mRNA is called translation
Enzymes
• Proteins and made from long chains of amino acids
• Functions include structural (collagen),
• hormones (insulin), carrier molecules (haemaglobin) &
enzymes.
Enzymes are biological catalysts which catalyse
chemical reactions
Enzymes use a lock and key mechanism and will denature
which change the the shape of the active site at high
PH and high temperatures
Gene mutations may lead to the production of different
proteins, these mutations can happens spotaneously, by
radiation or chemicals
Respiration
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Aerobic Respiration
Energy is needed for :
Glucose + oxygen → carbon dioxide + water
Protein synthesis
C6H12O6 + 6O2→ 6CO2 + 6H2O
Muscle contraction
Control of body temperature in mammals
ATP
Respiratory quotient (RQ)
ATP is a substance that is used as the energy
RQ = carbon dioxide produced ÷ oxygen used
source
processes rate
in cells. ATP is produced
Usually
RQ =for
1. manyMetabolic
as
a result of respiration.
For example,
one
glucose
Themetabolic
rate is the rate
at which
energy
Anearobic respiration
During exercise,
the
muscle
cells
respire
more
than they
do at acid
rest.
molecule
can
release
enough
energy
during
Glucose
→ lactic
is
used
by
the
body.
Since
aerobic
respiration
This means:
respiration
for of
theoxygen
production
of:
needs
oxygen,
theberate
Oxygen
and glucose
must
delivered
to themconsumption
more quickly
38used
ATP as
molecules
by aerobic
respiration
Waste
carbon
dioxide
must
be removed
quickly
can
be
an estimate
ofmore
metabolic
rate.
2 ATP
by anaerobic
AchievedThe
by
increasing
the breathing
rate
and respiration
heart rate.
ratemolecules
of respiration
is
influenced
by
changes in temperature and pH. This is because
enzymes are involved in respiration, and their
activity varies with temperature and pH.
• Watson and crick best known for discovering
DNA however:
• Rosalind franklin and maurice wilkins used
xray crystallograhy to take pictures of the
DNA. The pictures showed DNA as two chains
wound in a double helix
• Erwin chargaff discovered there are equal
numbers of A and T bases and of G and C
bases in DNA
Questions
• What is a section of chromosome called?
• Explain why muscle cells have lots of mitochondria?
• Finish the sentence the order of bases in DNA is
called the base ……..
• Why is collagen needed in the artery walls?
• What other name is used to describe enzymes?
• Pepsin is an enzyme found in the stomach. It breaks
down proteins into amino acids. Draw a diagram to
explain why pepsin cannot break down starch.
• Higher tier need page 13 in the text book
Unicellular vs multicellular
An ameoba, a simple unicellular organism
Organisms can consist of one cell to many cells:
•Simple organisms may be unicellular(consist of one cell)
•Complex organisms aremulticellular(consist of many cells)
There are advantages to being multicellular rather than
unicellular. These include allowing:
•The organism to be larger
•Cell differentiation (having different types of cells with
Mitosis
different functions)
in
•The organisms•Chromosomes
to
be
more
complex
‘unzipping’ to form
nucleus are copied
•Chromatids pulled
apart
•Cromosoomes
separate
•Cell divides
single strands
New double strands
forming by
complementary base
pairing
B3 Science Revision
Meiosis
Produces gametes which are
haploid (contain one
chromosomes from each pair).
Gametes combine to form a
diploid zygote
Genes on the chromosomes
combine to control the
characteristics of the zygote.
Structure of the sperm
‘unzipping’ to form
single strands
Acrosome
New double strands
forming by
complementary
base pairing
Mitochondria
Nucleus
Tail
B3 Science Revision
Red blood cells have a large
surface area to volume ratio,
lack a nucleus and contain
haemoglobin.
Pulmonary
Vena Cava
•Haemoglobin + oxygen
vein
oxyhaemoglobin
Right atrium
Left atrium
•Arteries transport blood away
from the heart,
Valve
• they have thick muscular and
Valve
elastic walls
Right ventricle
Left ventricle •Veins transport blood to the
heart, they have a large lumen
and contain valves
Red blood cells: carry oxygen
•Capillaries exchanging
White blood cells: fight disease
materials with
Platelets: clot the blood
•tissues and are therefore
permeable
Pulmonary
artery
Aorta
Plasma: the liquid that everything
travels in the blood
1.
2.
3.
4.
5.
6.
7.
what are the three reasons why the body
needs to make new cells?
Give an advantage of being multicellular
Explain how the sperm is adapted for its job
Name the 3 parts of the blood and the job
that it does
Why is plasma a liquid?
What is one way a red blood cell is adapted
to its job?
Explain why the left ventricle has a thicker
muscle wall than the right ventricle?
Bacteria cell lack a true
nucleus, mitochondria
and chloroplasts
instead they contain a
single circular strand
of chromosome
Stem cells
Undifferrentiate dcells
that can develop into
different cells.
Two types: embyonic
(obtained from
embryos) and Adult
(obtained from a
human)
Plant growth
Animal growth
Grows
continuously
Finite size
Restricted to
meristems
Everywhere
Gain height by
cell enlargement
Cells can
differentiate
Gain height by
Cell division
Lose ability to
differentiate
Genetic engineering
• Selection of desired characteristics
• Isolation of genes resposible
Selective
• Insertion of other genes
into breeding
other programmes
These
are the steps in selective breeding:
• Replication
of organismas
Decide which characteristics are important
Choose parents that show these characteristics
http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/living_growing/new
Select the best offspring from parents to breed
genesrev4.shtml
the next generation
Repeat the process continuously
B3 Science Revision
Examples: Genes from carrots and putting them into rice,
producing insulin and becoming resistant to herbicides, frost
damage or disease to crops.
Selective breeding may lead to inbreeding due to a reduction in
the gene pool
Gene therapy: changing a persons genes in an attempt to
Tissue
culture
cure
disorders
Cloning technique used to produce dolly:
Nucleus removed from an egg cell
Egg cell nucleus replaced with the nucleus from the
udder cell.
Egg cell given an electric shock to make it divide
Embryo grows into a clone of the sheep from which
the udder cell came
• plants grown from cuttings or tissue culture
are clones. advantage - can be sure of the
characteristics
of the plant since all plants will be genetically
identical
• advantage - it is possible to mass produce
plants that may be difficult to grow from
seed
• disadvantage - if plants become susceptible to
disease or to change in environmental
conditions then all plants will be affected
• disadvantage - lack of genetic variation.
• Which part of the cell contains cellulose?
• Name three structures found in an animal cell
and not in a plant cell?
• Name one characteristic of strawberry plants
that is useful to gardeners?
• Complete the sentence: when a scientist takes
______ from one organism and puts them into
another it is called _______ _______
• Which organisms are used to make insulin?
• Why would cloning pigs be useful?
• how do many plants reproduce?
• Describe an advantage and a disadvantage of
cloning plants?