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Summary Edexcel iGCSE Biology
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Full set of iGCSE Biology notes in line with the specification written by a student studying in the University of Oxford.
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Brian Chan Monday, 5 September 2022The nature and variety of living organisms
1.1 understand how living organisms share the following characteristics: they require nutrition, respire,
excrete their waste, respond to their surroundings, move, control their internal conditions, reproduce, grow
and develop.
Movement: change position
Respiration: cells release energy
Sensitivity: respond to surroundings/stimuli
Homeostasis: control internal conditions (temperature/water content)
Growth: get bigger and develop
Reproduction: make offspring through sexual/asexual reproduction
Excretion: gets rid of waste material produced by metabolic reaction
Nutrition: consumes chemical materials as food (plants are autotrophies that photosynthesise; others are
heterotrophies)
1.2 describe the common features shown by eukaryotic organisms: plants, animals, fungi and protoctists
Eukaryotic: has a nucleus with a distinct membrane
Plants:
• Multicellular
• Have chloroplasts; can photosynthesise
• Have cellulose cell walls
• Store carbohydrates as sucrose or starch
• maize, peas
Animals:
• Multicellular
• Don’t have chloroplasts
• No cell walls
• Usually have nervous co-ordination
• Store carbohydrates as glycogen
• horse, mosquito
Fungi:
• Multicellular or single-celled
• Most have mycelium body; made from hyphae
• Hyphae contains lots of nuclei
• Cell walls made of chitin
• Most feed by saprotrophic nutrition; excrete extracellular
enzymes to dissolve food, and absorb nutrients
• Don’t photosynthesis, so they don’t have chloroplasts
• Store carbohydrates as glycogen
• yeast (single-celled), Mucor (multicellular)
Protoctists:
• Single-celled
• Microscopic
• Usually aquatic
• Some are similar to plant cells (contain chloroplasts), some are similar to animal cells
• chlorella (plant-like), amoeba (animal-like)
• Some are parasitic: Plasmodium causes malaria.
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,1.3 describe the common features shown by prokaryotic organisms such as bacteria
Prokaryotic: no nucleus, nuclear material in cytoplasm, too small to contain mitochondria
Bacteria:
• Single-celled
• Microscopic
• Don’t have a nucleus
• Cell structure includes cell wall, cell membrane, cytoplasm, plasmids
• Have a circular chromosome of DNA
• Some can photosynthesise (have chloroplasts)
• Most feed off other living (parasitic)/dead organisms
• E-coli: causes food poisoning
• Lactobacillus: used in the production of yoghurt from milk
1.4 understand the term pathogen and know that pathogens may include
fungi, bacteria, protoctists or viruses
Pathogen: microorganism that causes disease
Viruses:
• Small particles
• Parasitic; can only produce in living cells
• Apart from reproduce, they don’t carry out any
other characteristics of living organisms
• Infects every type of organisms
• Variety of shape and size
• Don’t have a cellular structure; has a protein
coat that surrounds RNA or DNA
• Influenza virus: causes flu
• HIV: causes AIDS
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,Brian Chan (JH2) Monday, 21 February 2022
Cells
2.1 describe the levels of organisation in organisms: organelles, cells, tissues, organs and systems
Organelle: chloroplast or mitochondria
Cell: guard cell, neurone
Tissue: retina, muscle
Organ: heart, leaf
System: circulatory system, respiratory system
2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, mitochondria,
chloroplasts, ribosomes and vacuole
2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts,
ribosomes and vacuole
Nucleus: contains the genetic information located in the
DNA which forms the chromosomes.
Cytoplasm: thick water liquid for metabolic reactions that
holds organelles and enzymes.
Cell membrane: boundary that keeps the cytoplasm and
the organelles inside; controls the material entering and
leaving the cytoplasm (diffusion/active transport)
Cell wall: cellulose cell wall protects the plant cells; chitin
for fungi; a polymer of sugars and amino acids for
bacteria.
Mitochondria: for aerobic respiration.
Chloroplasts: for photosynthesis. (root cells do not have them).
Ribosomes: for synthesis of proteins (including enzymes).
Vacuole: Watery solution called cell sap which give the plant cell rigidity.
2.4 know the similarities and differences in the structure of plant and animal cells
Animal cells do not have cellulose cell wall, chloroplasts and large vacuoles.
2.5B explain the importance of cell differentiation in the development of specialised cells
Cell differentiation: process involving the development of newly formed cells into more specialised and
distinct cells as they mature.
As new cells are produced in embryo, specific genes are switched on and off inside the cell. This cause a
cell to begin differentiating into a specialised cell.
It is possible for the initial pathway of development to be switched when the cell is at a stage called
totipotent stem cell. When cell become stuck on a fixed pathway of development, they can only become a
specific kind of cell.
Our body maintain a small population of stem cells in most organs to produce new cells when adult tissue
cells are damaged or killed. Our bone marrow contains stem cells which divide to produce new RBC and
WBC.
2.6B understand the advantages and disadvantages of using stem cells in medicine
Stem cells in medicine: stem cell therapy to form tissue.
Some cell types are not capable of self-renewal (non-stem cells e.g. tissues). As these tissues cannot be
regenerated or replaced, stem cells are used to treat these injured and diseased organs. The stem cells are
injected into the damaged area where they divide to form fully differentiated replacement cells which
restore the organ function.
1
, Advantages Disadvantages
Medical benefits in therapeutic cloning to heal Ethical issues in the use of therapeutic stem cells
diseases and chronic illnesses. Use adult cells and involving the destruction of human embryos and
chemically trigger them to become stem cells umbilical cords of new-borns. Create an embryo
(induced) which could be used for themselves. specifically to produce stem cells for patient.
Potential in discovering treatments and cures for Uncertainties regarding long-term effects. If the
diseases such as Parkinson's disease and cancer. stem cells do not respond to body chemical signals
naturally, they can continue to reproduce and lead
to cancer.
Ability to test potential drugs and medicine without Rejection by patient's body as certain stem cells are
the use of animals or human simulation. obtained from embryos instead of their own cells.
Reduced risk of rejection as patient's own cells can Difficulty in controlling differentiation of pre-
be used. specialised cells into desired.
Future: induced stem cells are developed from adult cells removed from the patient, a whole replacement
organ is grown outside in tissue culture and transplanted into the patient. This can reduce the risk of
rejection by the patient’s immune system.
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