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Exam Date: Tuesday 6th November
B2: The
Components of
Life…read more

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Topic 1: The Building Blocks of Cells
1.1 Describe the function of the components of a bacterial cell including chromosomal DNA, plasmid DNA, flagella
and cell wall
1.2 Describe the function of the components of a plant cell including chloroplast, large vacuole, cell wall, cell
membrane, mitochondria, cytoplasm and nucleus
1.3 Describe the function of the components of an animal cell including cell membrane, mitochondria, cytoplasm and
1.4 Describe how plant and animal cells can be studied in greater detail with a light microscope
1.5 Demonstrate an understanding of how changes in microscope technology have enabled us to see cells with more
and detail than in the past, including simple magnification calculations
1.6 Recall that a gene is a section of a molecule of DNA and that it codes for a specific protein
1.7 Describe a DNA molecule as: a) two strands coiled to form a double helix b) strands linked by a series of
complementary base pairs joined together by weak hydrogen bonds: i) adenine (A) with thymine (T) ii) cytosine (C)
with guanine (G)
1.8 Investigate how to extract DNA from cells
1.9 Explain how the structure of DNA was discovered, including the
roles of the scientists Watson, Crick, Franklin and Wilkins
1.10 Demonstrate an understanding of the implications of sequencing the human genome (Human
Genome Project) and of the collaboration that took place within this project
1.11 Demonstrate an understanding of the process of genetic engineering, including the removal of a gene from the
DNA of one organism and the insertion of that gene into the DNA of another organism
1.12 Discuss an understanding of the advantages and disadvantages of genetic engineering to produce GM
organisms, including:
a beta carotene in golden rice to reduce vitamin A deficiency in humans
b the production of human insulin by genetically modified bacteria
c the production of herbicide-resistant crop plants
1.13 Describe the division of a cell by mitosis as the production of two daughter cells, each with identical sets of
chromosomes in the nucleus to the parent cell, and that this results in the formation of two genetically identical
diploid body cells
1.14 Recall that mitosis occurs during growth, repair and asexual reproduction
1.15 Recall that, at fertilisation, haploid gametes combine to form a diploid zygote
1.16 Describe the division of a cell by meiosis as the production of four daughter cells, each with half the number of
chromosomes, and that this results in the formation of genetically different haploid gametes…read more

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1.17 Recall that cloning is an example of asexual reproduction that produces genetically identical copies
1.18 Demonstrate an understanding of the stages in the production of cloned mammals, including: a
removal of diploid nucleus from a body cell
b enucleation of egg cell
c insertion of diploid nucleus into enucleated egg cell
d stimulation of the diploid nucleus to divide by mitosis
e implantation into surrogate mammals
1.19 Demonstrate an understanding of the advantages, disadvantages and risks of cloning mammals
1.20 Recall that stem cells in the embryo can differentiate into all other types of cells, but that cells lose this ability
as the animal matures
1.21 Demonstrate an understanding of the advantages, disadvantages and risks arising from adult and embryonic
stem cell research
1.22 Describe how the order of bases in a section of DNA decides the order of amino acids in the protein
1.23 Demonstrate an understanding of the stages of protein synthesis, including transcription and
translation: a the production of complementary mRNA strand in the nucleus b the attachment of the
mRNA to the ribosome c the coding by triplets of bases (codons) in the mRNA
for specific amino acids d the transfer of amino acids to the ribosome by tRNA e the linking of amino
acids to form polypeptides
1.24 Describe each protein as having its own specific number and sequence of amino acids, resulting in different-
shaped molecules that have different functions, including enzymes
1.25 Demonstrate an understanding of how gene mutations change the DNA base sequence and that mutations can
be harmful, beneficial or neither
1.26 Describe enzymes as biological catalysts
1.27 Demonstrate an understanding that enzymes catalyse chemical reactions occurring inside and outside living
cells, including: a DNA replication b protein synthesis c digestion
1.28 Describe the factors affecting enzyme action, including: a temperature b substrate concentration c pH
1.29 Recall that enzymes are highly specific for their substrate
1.30 Demonstrate an understanding of the action of enzymes in terms of the `lock-and-key' hypothesis
1.31 Describe how enzymes can be denatured due to changes in the shape of the active site
1.32 Investigate the factors that affect enzyme activity…read more

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Light and Electron Microscopes
All living organisms are made up of cells. A
cell is the basic biological unit of all organisms
which contains organelles that carry out the
various metabolic functions in the cell.
Cells and their organelles are two small to be seen unaided and can only be seen under a microscope.
Magnification is how much bigger a sample appears to be under the microscope than it is in real
Overall magnification = Objective lens x Eyepiece lens
Resolution is the ability to distinguish between two points on an image i.e. the amount of detail
Light microscopes use glass lenses to refract
light and produce a magnified image of a
specimen. Light microscopy has a resolution of
about 200 nm, which is good enough to see
cells, but not the details of cell organelles.
The magnification of a light microscope =
Objective lens x Eyepiece lens
Electron microscopes use a beam of electrons
to `illuminate' a specimen. The wavelength of
electrons is much smaller than the
wavelength of light therefore much greater
magnification and resolution of the specimen.
Their invention in the 1930's revolutionised
biology allowing organelles such as
mitochondria, ER and membranes to be seen
in detail for the first time.…read more

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Plant and Animal Cells (eukaryotes)
Eukaryotic cells are cells that contain a nucleus such as plant an animal
*Nucleus ­ the `control centre of the cell', an organelle containing the
DNA organised into chromosomes.
*Mitochondria (sing. Mitochondrion) ­ double membrane spherical
organelles in which aerobic respiration occurs (oxygen and glucose
energy), the powerhouses of the cell where energy is released from
*Cell membrane ­ barrier that separates the contents of the cell and its
surroundings, it controls the movement of substances into and out of the
cell. The membrane is said to be semi-permeable only allowing some
substances through
*Cytoplasm ­ aqueous `jelly like' environment where most of the
chemical reactions take place, also contains the organelles.
Centriole ­ there are two of these in every animal cell, they help to
organise cell division during mitosis and meiosis.
Endoplasmic reticulum ­ i) rough ER ­ a series of membranes folded to
form channels attached to which are small bodies called ribosomes where
proteins are synthesis occurs ii) smooth er ­ tubular part of the er without
ribosomes involved in synthesising and transporting materials, mainly
lipids, needed by the cell.
Golgi apparatus ­ stacks of membrane bound discs that collect protein
from the endoplasmic reticulum and package and modify it before it is
used or excreted from the cell
*Vacuoles ­ membrane bound sacs involved in intracellular digestion and
the release of cellular waste products, in animal cells these are very small
and numerous filled with things like
Plant cells have some other unique structures:
*Cell wall ­ a tough outer layer made of cellulose a type of
carbohydrate. It supports the cell providing a limiting structure
allowing it to keep its shape
*Large vacuole ­ a membrane bound bubble which is filled with
sap (a watery sugar/salt mixture)
*Chloroplasts ­ organelles containing the green chlorophyll
that absorbs photons during photosynthesis to harness energy
for the cell…read more

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