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Topic 1: Cell Biology—15 Hours for Both SL and HLSubtopic Subto IB Points to Understand
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Introductio 1.1
n to cells ● According to the cell theory, living organisms are
composed of cells.
● Organisms consisting of only one cell carry out all
functions of life in that cell.
● Surface area to volume ratio is important in the
limitation of cell size.
● Multicellular organisms have properties that emerge
from the interaction of their cellular components.
● Specialized tissues can develop by cell differentiation
in multicellular organisms.
● Differentiation involves the expression of some
genes and not others in a cell's genome.
● The capacity of stem cells to divide and differentiate
along different pathways is necessary in embryonic
development and also makes stem cells suitable for
therapeutic uses.
Ultrastruct 1.2
ure of cells ● Prokaryotes have a simple cell structure without
compartmentalization.
● Eukaryotes have a compartmentalized cell structure.
● Electron microscopes have a much higher resolution
than light microscopes.
Membrane 1.3
structure ● Phospholipids form bilayers in water due to the
amphipathic properties of phospholipid molecules.
● Membrane proteins are diverse in terms of structure,
position in the membrane and function.
● Cholesterol is a component of animal cell
membranes.
Membrane 1.4
transport ● Particles move across membranes by simple
diffusion, facilitated diffusion, osmosis and active
transport.
, ● The fluidity of membranes allows materials to be
taken into cells by endocytosis or released by
exocytosis. Vesicles move materials within cells.
The origin 1.5
of cells ● Cells can only be formed by division of pre-existing
cells.
● The first cells must have arisen from non-living
material.
● The origin of eukaryotic cells can be explained by the
endosymbiotic theory.
Cell 1.6
division ● Mitosis is division of the nucleus into two genetically
identical daughter nuclei.
● Chromosomes condense by supercoiling during
mitosis.
● Cytokinesis occurs after mitosis and is different in
plant and animal cells.
● Interphase is a very active phase of the cell cycle
with many processes occurring in the nucleus and
cytoplasm.
● Cyclins are involved in the control of the cell cycle.
● Mutagens, oncogenes and metastasis are involved in
the development of primary and secondary tumours.
Topic 2: Molecular Biology—21 Hours for Both SL and HL
Subtopic Subto IB Points to Understand
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,Molecules to 2.1
metabolism ● Molecular biology explains living processes in
terms of the chemical substances involved.
● Carbon atoms can form four covalent bonds
allowing a diversity of stable compounds to exist.
● Life is based on carbon compounds including
carbohydrates, lipids, proteins and nucleic acids.
● Metabolism is the web of all the enzyme-
catalysed reactions in a cell or organism.
● Anabolism is the synthesis of complex molecules
from simpler molecules including the formation of
macromolecules from monomers by
condensation reactions.
● Catabolism is the breakdown of complex
molecules into simpler molecules including the
hydrolysis of macromolecules into monomers.
Water 2.2
● Water molecules are polar and hydrogen bonds
form between them.
● Hydrogen bonding and dipolarity explain the
cohesive, adhesive, thermal and solvent
properties of water.
● Substances can be hydrophilic or hydrophobic.
Carbohydrate 2.3
s and lipids ● Monosaccharide monomers are linked together
by condensation reactions to form disaccharides
and polysaccharide polymers.
● Fatty acids can be saturated, monounsaturated or
polyunsaturated.
● Unsaturated fatty acids can be cis or trans
isomers.
● Triglycerides are formed by condensation from
three fatty acids and one glycerol.
Proteins 2.4
● Amino acids are linked together by condensation
to form polypeptides.
● There are 20 different amino acids in
polypeptides synthesized on ribosomes.
● Amino acids can be linked together in any
sequence giving a huge range of possible
polypeptides.
● The amino acid sequence of polypeptides is
coded for by genes.
, ● A protein may consist of a single polypeptide or
more than one polypeptide linked together.
● The amino acid sequence determines the three-
dimensional conformation of a protein.
● Living organisms synthesize many different
proteins with a wide range of functions.
● Every individual has a unique proteome.
Enzymes 2.5
● Enzymes have an active site to which specific
substrates bind.
● Enzyme catalysis involves molecular motion and
the collision of substrates with the active site.
● Temperature, pH and substrate concentration
affect the rate of activity of enzymes.
● Enzymes can be denatured.
● Immobilized enzymes are widely used in industry.
Structure of 2.6
DNA and RNA ● The nucleic acids DNA and RNA are polymers of
nucleotides.
● DNA differs from RNA in the number of strands
present, the base composition and the type of
pentose.
● DNA is a double helix made of two antiparallel
strands of nucleotides linked by hydrogen
bonding between complementary base pairs.
DNA 2.7
replication, ● The replication of DNA is semi-conservative and
transcription depends on complementary base pairing.
● Helicase unwinds the double helix and separates
and the two strands by breaking hydrogen bonds.
translation ● DNA polymerase links nucleotides together to
form a new strand, using the pre-existing strand
as a template.
● Transcription is the synthesis of mRNA copied
from the DNA base sequences by RNA
polymerase.
● Translation is the synthesis of polypeptides on
ribosomes.
● The amino acid sequence of polypeptides is
determined by mRNA according to the genetic
code.
● Codons of three bases on mRNA correspond to
one amino acid in a polypeptide.
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