Summary Notes designed for the International Baccalaureate Diploma Programme. These notes are detailed yet concise, with all the information to achieve a 7 in IB Biology HL or SL. These notes were made using information from the IB syllabus, Oxford IB Diploma HL Biology Textbook, Bioninja and the B...
Unit 1.1
• Cell theory states that: Cells are the smallest unit of life and only come from pre-exisiting cells.
All living things are composed of cells or cell products.
• Exceptions to this include striated muscle which share nuclei and fungal hyphae which have a
continuous cytoplasm.
• For something to be classed as alive, it must have: (MR. H. GREN)
• Metabolism • Homeostasis • Reproduction • Nutrition
• Response • Growth • Excretion
• Cells divide by mitosis when the surface area:volume ratio becomes too small as it increases
rate of material exchange.
Paramecium Chlorella
• An emergent property is a property which a collection or a complex system has, but which the
individual members do not have (e.g an ear can hear but its components can’t).
• Specialised tissues can develop by cell differentiation in multicellular organisms.
• If all genes are expressed in a cell it is totipotent (a stem cell), meaning it can differentiate into
anything by deactivating certain genes.
• Stargardt’s disease causes photoreceptor cells in your eye to degenerate, causing blindness.
• Injecting embryonic cells (totipotent cells) into the retina allows them to differentiate into healthy
photoreceptor cells and treat the disease. This also works for leukaemia in the bone marrow.
• Induced pluripotent stem cells are created by injecting transcription genes to express all of the
genes. However oncogenes are also turned on, which increase the risk of cancer.
Comparison of stem cell sources
Embryo Cord Blood Adult
Can differentiate into any Can only natural divide into Limited capacity to
Differentiation
cell type blood cells differentiate
Stem cells are not Fully compatible with the patient as the stem cells are
Compatibility
genetically identical genetically identical
Can be obtained from Easily obtained and stored. Difficult to obtain as there
Ease of Extraction excess embryos generated Though limited quantities are very few and are buried
by IVF programs. available deep in tissues
Can only be obtained by Umbilical cord is normally Adult patient can give
Ethics of Extraction
destruction of an embryo discarded. consent for extraction.
Growth Potential Almost unlimited Reduced potential (compared to embryonic cells)
Tumour Risk Higher risk of development Lower risk of development
, Unit 1.2
• Electron microscopes have a higher resolution than light microscopes,
allowing you to see the ultrastructure of cells.
• Eukaryotes have compartmentalised cell structure (organelles) to isolate
metabolic processes whereas prokaryotes do not.
• Prokaryotes replicate by binary fission. These are the cell components:
• Flagella: tail attached to the cell membrane for movement.
• Cytoplasm: where metabolic reactions take place.
• Ribosomes (70S): where translation takes place.
• Nucleotide: loop of DNA/naked DNA.
• Cell wall: made of murein
• Plasma membrane: keeps the shape of the cell.
• Mesosome: folding in the inner membrane where
respiration takes place.
• Plasmid: additional DNA for extra properties.
• Slime capsule: provides protection.
• Pili: for communication and adhesion to other bacteria.
Structure Function Microscope
Double nuclear envelope To enclose and protect DNA Nucleus
Allows entry and exit of
Nuclear pores
substances
Nucleoplasm Where the DNA is found
Where ribosomes, nucleotides
Nucleolus and some proteins are
manufactured
Ribosomes
Provides binding sites for the
Ribosomes have a small subunit binding of mRNA which allows
and a big subunit. translation of the DNA code, and
provide the enzymes necessary
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