2442247
Edexcel
Additional
Science
Biology
Topic 1
- Cells and
Microscopy
- plant cells
- cell membrane
rigid cell walls large
vacuole chloroplasts
mitochondria
nucleus cytoplasm
- cell membrane
rigid cell walls large
vacuole chloroplasts
mitochondria
nucleus cytoplasm
- Animal Cell
- cell membrane
mitochondria
cytoplasm nucleus
- cell membrane
mitochondria
cytoplasm nucleus
- Bacteria Cell
- chromosomal DNA
plasmids flagellum
cell wall
- chromosomal DNA
plasmids flagellum
cell wall
- Microscopes
- light
microscopes
invented
1590s
- Electron
microscopes
invented
1930s
- magnification
= Length of
image/ length
of specimen
- magnification
= Length of
image/ length
of specimen
- Electron
microscopes
invented
1930s
- light
microscopes
invented
1590s
- plant cells
- DNA-
Deoxy-
ribo-
nucleic
Acid
- 4 Bases
- Adenine
Thymine
Guanine
Cytosine
- Pairings:
A+T G+C
- Adenine
Thymine
Guanine
Cytosine
- A DNA molecule has 2 strands
coiled together; the shape of a
double helix
- Base pairs are joined by weak
hydrogen bonds
- 3 bases = 1 codon/ 1 triplet for a
specific protein
- 3 bases = 1 codon/ 1 triplet for a
specific protein
- Base pairs are joined by weak
hydrogen bonds
- Rosalind
Franklin and
Maurice
Williams-
worked out
DNA had a
helical
structure
- They beams
of x-rays onto
crystalised DNA
and looking at
patterns the
x-rays formed
when they
bounced off
- James Watson and Francis Crick
used RF's and MW's ideas, along
with knowledge of the pairs to
make a DNA Model
- James Watson and Francis Crick
used RF's and MW's ideas, along
with knowledge of the pairs to
make a DNA Model
- They beams
of x-rays onto
crystalised DNA
and looking at
patterns the
x-rays formed
when they
bounced off
- Extracting DNA
- Chop Onion
- In beaker =
detergent +
salt
- water bath-
60 degrees- 15
minutes
- Beaker -> Ice
- Cold -> blender
- cool-> filter
- +ice cold
alcohol = DNA
- +ice cold
alcohol = DNA
- cool-> filter
- Cold -> blender
- Beaker -> Ice
- water bath-
60 degrees- 15
minutes
- In beaker =
detergent +
salt
- Chop Onion
- 4 Bases
- Protein Synthesis
- Trans-
cription
- DNA unzips and one strand is
used as a template to form mRNA
(base pairing ensures it's an exact
match)
- Thymine is replaced with Uracil
- The mRNA molecule moves out of
the nucleus and joins with a
Ribosome
- TRANS-
LATION
- The ribosome reads the mRNA 1
codon at a time. Molecules called
tNRA then bring back to the
ribosome amino acids that match
- The ribosome sticks the amino
acids into a chain; this is called a
POLYPEPTIDE
- this results in a protein, with its
own no. and sequence of acids
- this results in a protein, with its
own no. and sequence of acids
- The ribosome sticks the amino
acids into a chain; this is called a
POLYPEPTIDE
- The ribosome reads the mRNA 1
codon at a time. Molecules called
tNRA then bring back to the
ribosome amino acids that match
- TRANS-
LATION
- Thymine is replaced with Uracil
- DNA unzips and one strand is
used as a template to form mRNA
(base pairing ensures it's an exact
match)
- Trans-
cription
- Mutations
- BAD
- Cause a genetic
disorder- cystic
fibrosis./ change a
proteins shape
- Cause a genetic
disorder- cystic
fibrosis./ change a
proteins shape
- GOOD
- produce new
characteristics that
is beneficial e.g.
genes in bacterial
plasmids can make
them resistant to
anti-biotics
- produce new
characteristics that
is beneficial e.g.
genes in bacterial
plasmids can make
them resistant to
anti-biotics
- Neutral
- some mutations are
neither harmful or
beneficial e.g. they
don't affect a
proteins function
- some mutations are
neither harmful or
beneficial e.g. they
don't affect a
proteins function
- BAD
- Enzymes
- enzymes are
catalysts produced
by living things. a
catalyst is a
substance which
increases the speed
of a reaction
without being
changed or used up
in the reaction.
- examples
of enzyme
catalysed
reactions
- DNA
replication
protein
synthesis
digestion
- DNA
replication
protein
synthesis
digestion
- LOCK
AND
KEY
THEORY
- enzymes have special
shapes so they can
catalyse reactions
- The enzyme has an
active site which fits the
shape of the substrate
(the molecule being
changed); the enzyme
has a specificity for their
substrate
- Enzyme
active site
= lock
- substrate
= Key
- the active site catalyses
the reaction of the
substrate, creating
products. the enzyme is
unchanged.
- temperature will affect
enzyme. increasing it will
increase the reaction to a
point; the enzymes have
more energy. once it's too
hot, the bonds holding the
enzyme breaks; the enzyme
loses its shape and doesn't
fit the substrate. The
enzyme is denatured.
- optimum
temp for
most
human
enzymes
- 37
degrees
- Factors Affecting Enzymes
- optimum
temp for
most
human
enzymes
- 37
degrees
- pH also has an effect. too high or too
low and the enzyme will denature
- substrate concentrations will increase the
rate of reaction to a point
- substrate concentrations will increase the
rate of reaction to a point
- temperature will affect
enzyme. increasing it will
increase the reaction to a
point; the enzymes have
more energy. once it's too
hot, the bonds holding the
enzyme breaks; the enzyme
loses its shape and doesn't
fit the substrate. The
enzyme is denatured.
- Enzyme
active site
= lock
- The enzyme has an
active site which fits the
shape of the substrate
(the molecule being
changed); the enzyme
has a specificity for their
substrate
- enzymes have special
shapes so they can
catalyse reactions
- examples
of enzyme
catalysed
reactions
- enzymes are
catalysts produced
by living things. a
catalyst is a
substance which
increases the speed
of a reaction
without being
changed or used up
in the reaction.
- The Human Genome Project
- 1000s of scientists collaborated to try
and find every single human gene;
about 25 000. The collaboration meant
all the genes were found quickly and
data could be made public
- Posi-
tives
- predict and prevent diseases
- develop new and better
medicines
- accurate diagnosis
- improve forensic science
- predict and prevent diseases
- Nega
-tives
- Increased stress from people
with faulty genes
- Gene-ism people with genetic
problems pressured to not
have chidren
- Discrimination from
employers and insurance
companies
- Increased stress from people
with faulty genes
- Posi-
tives
- 1000s of scientists collaborated to try
and find every single human gene;
about 25 000. The collaboration meant
all the genes were found quickly and
data could be made public
- Genetic Engineering
(GE-Genetically engineered)
- uses enzymes to cut and paste genes
- restriction
enzymes cut out
the useful gene
- lysozyme enzymes
cut a section out of
a bacterial plasmid
- the useful gene is inserted into the
bacterial plasmid and ligase enzymes join
up the ends of DNA
- the plasmid is inserted into new
bacterial cell; it is now a vector for the
gene and has recombiant DNA
- Benefits
- Reducing vitamin A deficiency.
GE rice produces BETA CAROTENE
which is used to make VA. it has
2 GE genes
- quickly and cheaply produces
human insulin for diabetics
- Increasing Crop Yield- resistant
to herbicides etc.
- Reducing vitamin A deficiency.
GE rice produces BETA CAROTENE
which is used to make VA. it has
2 GE genes
- Controversy
- reduces farmland
biodiversity
- GM crops might be
unsafe- people develop
allergies
- Genes get into the natural
environment- super weeds
that are resistant to
herbicides
- reduces farmland
biodiversity
- Benefits
- the plasmid is inserted into new
bacterial cell; it is now a vector for the
gene and has recombiant DNA
- the useful gene is inserted into the
bacterial plasmid and ligase enzymes join
up the ends of DNA
- restriction
enzymes cut out
the useful gene
- uses enzymes to cut and paste genes
- MITOSIS
- Mitosis makes new
cells for growth and
repair; it is asexual
- 1. inside the cell the
nuclear envelope breaks
and the chromosomes
duplicate into pairs
- 2. the pairs line up
along the equator of
the cell inbetween the
2 opposite poles
- 3. spindles/ cell fibres
form from the poles
and attach to the arms
of the chromosomes;
the pull the pairs apart
so each pole has its
own copy
- 4.membranes form
around each set of
chromosomes, they
become the nuclei of the
2 new cells
- .5. the cytoplasm
divides and you have 2
genetically identical
diploid daughter cells
- .5. the cytoplasm
divides and you have 2
genetically identical
diploid daughter cells
- 4.membranes form
around each set of
chromosomes, they
become the nuclei of the
2 new cells
- 3. spindles/ cell fibres
form from the poles
and attach to the arms
of the chromosomes;
the pull the pairs apart
so each pole has its
own copy
- 2. the pairs line up
along the equator of
the cell inbetween the
2 opposite poles
- 1. inside the cell the
nuclear envelope breaks
and the chromosomes
duplicate into pairs
- Mitosis makes new
cells for growth and
repair; it is asexual
- MEIOSIS
- meiosis only occurs sexual
reproduction organs- testes and
ovaries and it involves 2 divisions
- 1. the DNA duplicates into pairs of
chromosomes, each arm is identical
to the other
- 2. alike pairs line up on the equator
and share genetic codes. the
chromosome pairs are pulled apart.
each new cell now has some
chromosomes from the mum and
some from dad. mixing the alleles
creates genetic variation
- 3.. in the 2 new cells the
chromosomes line up again and
spindles form, pulling the arms of
the pairs of chromosomes apart
- 4. membranes form around each of
the 4 sets of chromosomes becoming
the nucleus
- 5. the cytoplasm splits. You now have
4 haploid daughter cells, they are
genetically different
- Gametes are another word for sex cells-
when 2 gametes combine a fertilised egg
is called a zygote
- Gametes are another word for sex cells-
when 2 gametes combine a fertilised egg
is called a zygote
- 5. the cytoplasm splits. You now have
4 haploid daughter cells, they are
genetically different
- 4. membranes form around each of
the 4 sets of chromosomes becoming
the nucleus
- 3.. in the 2 new cells the
chromosomes line up again and
spindles form, pulling the arms of
the pairs of chromosomes apart
- 2. alike pairs line up on the equator
and share genetic codes. the
chromosome pairs are pulled apart.
each new cell now has some
chromosomes from the mum and
some from dad. mixing the alleles
creates genetic variation
- 1. the DNA duplicates into pairs of
chromosomes, each arm is identical
to the other
- meiosis only occurs sexual
reproduction organs- testes and
ovaries and it involves 2 divisions
- Cloning
- cloning is a type of asexual reproduction; it
produces cells that are genetically identical to the
original
- 1. enucleate an unfertilised egg cell - remove the
nucleus
- 2. take a diploid nucleus from an adult body cell
and insert it into the enucleated egg cell
- 3. stimulate the egg cell with an electric shock;
the cell will start dividing by mitosis
- 4. when the embryo is a ball of cells, implant it
into an adult female (a surrogate)
- Uses
- help with the shortage of organs for
transplants
- study of clones could lead to a greater
understanding of the embryo and
ageing/ age related disorders
- preserve endangered species
- help with the shortage of organs for
transplants
- Issues
- closely related populations will be
wiped out by new diseases; there
may be no allele giving resistance
- cloned animals might not live as
long
- cloning often fails
- clones are often born with defects
and weak immune systems
- reduced gene pool
- closely related populations will be
wiped out by new diseases; there
may be no allele giving resistance
- Uses
- 4. when the embryo is a ball of cells, implant it
into an adult female (a surrogate)
- 3. stimulate the egg cell with an electric shock;
the cell will start dividing by mitosis
- 2. take a diploid nucleus from an adult body cell
and insert it into the enucleated egg cell
- 1. enucleate an unfertilised egg cell - remove the
nucleus
- cloning is a type of asexual reproduction; it
produces cells that are genetically identical to the
original
- Stem Cells
- cells in an embryo are all the same-undifferentiated. they are
called embryonic stem cells
- stem cells are able to divide to produce specialised cells or more
stem cells. the process of becoming specialised is called
differentiation
- in most animal cells, the ability to differentiate is lost at a early
stage; plants never lose this ability
- adult stem cells only occur in certain places like bone marrow; they
aren't as versatile- multipotent. there is a limit to what they can
differentiate into. embryonic stem cells are pluripotent
- Pro- adult stem cells are already used to
cure some diseases - sickle cell anaemia
- could be possible to use embryonic stem
cells to replace cells damaged from
injury/ disease.
- Arguments against- embryos are a
source of life
- Arguments against- embryos are a
source of life
- could be possible to use embryonic stem
cells to replace cells damaged from
injury/ disease.
- Pro- adult stem cells are already used to
cure some diseases - sickle cell anaemia
- adult stem cells only occur in certain places like bone marrow; they
aren't as versatile- multipotent. there is a limit to what they can
differentiate into. embryonic stem cells are pluripotent
- in most animal cells, the ability to differentiate is lost at a early
stage; plants never lose this ability
- stem cells are able to divide to produce specialised cells or more
stem cells. the process of becoming specialised is called
differentiation
- cells in an embryo are all the same-undifferentiated. they are
called embryonic stem cells
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