Detailed notes from a student who achieved a grade 9 in Biology last year on:
Topic 1: Cell biology
Topic 2: Organisation
Topic 3: Infection and response
Topic 4: Bioenergetics
Topic 5: Homeostasis and response
Topic 6: Inheritance, variation and evolution
Topic 7: Ecology
TOPIC 1: CELL BIOLOGY
Topics:
● SECTION A: Cell structure
○ Eukaryotes and prokaryotes
○ Animal and plant cells
○ Cell specialisation
○ Cell differentiation
○ Microscopy
○ Binary fission
○ Culturing microorganisms
● SECTION B: Cell division
○ Chromosomes
○ Mitosis and the cell cycle
○ Stem cells
● SECTION C: Transport in cells
○ Diffusion
○ Osmosis
○ Active transport
, ell structure
→ SECTION A: C
Eukaryotes and Prokaryotes:
Eukaryotic cells: Prokaryotic cells:
● Complex and include all animal and plant ● Smaller and simpler compared to eukaryotic
cells ● Single-celled organism
● All eukaryotic cells have: ○ eg/ bacteria
○ Cell membrane ● 0.2 - 2.0 µm in length and 1 - 2 orders of
○ Cytoplasm magnitude smaller than eukaryotes
○ Genetic material (DNA) - enclosed in ● All prokaryotic cells have:
the nucleus ○ Cytoplasm
■ eg/ animals, plants, fungi ○ Cell membrane
and protista are all ○ Cell wall (not made of cellulose)
eukaryotes ○ Genetic material found free in
cytoplasm - chromosome is a single
DNA loop
○ Plasmids (extra small rings of DNA)
code for specific features such as
antibiotic resistance
○ Protective slime capsule
○ Flagella (protein strand that lashes
about to move)
Animal and Plant Cells:
→ All living organisms are made of cells
● Subcellular structures = different parts of a cell
● The structures of different types of cells are related to their specific function
● Plant and animal cells have similarities and differences
○ Animal cells → 10 to 30 µm long
○ Plant cells → 10 to 100 µm long
⇒ Found in animals and plant cells:
PART FUNCTION DIAGRAM
● Controls activities of cells
● Contains genetic material
Nucleus
● Surrounded by nuclear membrane
○ Average diameter = 10µm
● A liquid gel where chemical reactions occur
Cytoplasm
● Contains enzymes which control reactions
● Holds cell together
Cell membrane
● Controls passage of substances (eg/ glucose)
● Where aerobic respiration takes place
Mitochondria
● Releases energy that the cell requires
Ribosomes ● Where the protein synthesis takes place
, ound only in plant cells:
⇒F
PART FUNCTION DIAGRAM
● Rigid
Cell wall ● Made of cellulose
● Supports/strengthens cell
● A space in the cytoplasm filled with cell sap
Permanent ○ Cell sap = a weak solution of sugar and salts
vacuole ● Helps to keep cells rigid
● Supports the plant
● Found in green parts of plant
● Contain chlorophyll
○ ^ absorbs light so plant can make food by
Chloroplasts photosynthesis
● Around 3 - 5µm long
● Root cells don't need chloroplasts - they are
underground and don't photosynthesis
Cell Specialisation:
→ Cells have different structures to suit their different functions
● As an organism develops, cells differentiate t o form different types of cells
○ They differentiate to become specialised → it acquires different subcellular structures to enable it
to carry out a certain function
○ Most differentiation occurs as an organism develops
Animal cells: Plant cells:
● Differentiate at an early stage of ● Retain ability to differentiate throughout life
development ● Very specialised cells with clear adaptations
● Specialised cells used for repairing and for a particular job
replacing cells (eg/ skin and blood cells) ● Can be specialised to function within tissues,
● Can be specialised to function within tissues, organs, organ systems or whole organisms
organs, organ systems or whole organisms ○ eg/ root hair cells, photosynthetic
○ eg/ nerve cells, sperm cells, muscle cells, xylem cells, phloem cells
cells
⇒ Specialisation in animal cells:
CELL TYPE FUNCTION SPECIAL FEATURES
● Carries electrical impulses ● Lots of dendrites - make connections t o other nerve
around the body cells
● Provide rapid ● Long axon to carry nerve impulses
communication system ● Synapses = nerve endings - pass impulses to other
Nerve cell between different parts of cells using special transmitter chemicals
body ● Contain lots of mitochondria - energy needed to make
● Sends and receives signals chemicals
● Controls and coordinates ● Myelin sheath insulates impulse
actions
● Move and control our ● Smooth muscle cells contract to squeeze food through
Muscle cell
movements gut (digestive system)
, ● Can contract and relax in ● Striated muscle cells = contain special proteins that
pairs to move bones of slide to make fibres contract
skeleton ● Many mitochondria - transfers energy needed for
chemical reactions to take place as muscles relax and
contract
● Store glycogen - chemical is b roken down to be used
in cellular respiration
● Long - have space to contract
● Fertilises the ovum (egg cell) ● Long tail - helps move sperm through female
● Contain genetic info from reproductive system
male parent ● Streamlined head
● Moves through the female ● Middle section full of mitochondria - transfers energy
Sperm cell
reproductive system to to tail
reach an egg and break into ● Acrosome (head) - stores digestive enzymes which
it help break outer layer of egg
● Large nucleus - contains genetic information
pecialisation in plant cells:
⇒S
CELL TYPE FUNCTION SPECIAL FEATURES
● On the surface of plant roots ● Large SA - allows lots of water to move
● Help plant take up water/mineral ions into cell
more efficiently ● Large permanent vacuole - speeds up
Root hair cell
● Close to xylem cells movement of water by osmosis
● Mineral ions moved into root hair cells by ● Many mitochondria - transfer energy
active transport needed for active transport
● Allows plant to make food for itself ● Contain chloroplasts = specialized green
through process of photosynthesis structures
○ Contain chlorophyll - trap light
needed for photosynthesis
● Positioned in continuous layers in leaves
and outer stem to absorb as much light
Photosynthetic as possible
cell ● Large permanent vacuole
○ Helps keep cell rigid during
osmosis
○ Supports stem (forms
photosynthetic tissue)
○ Keeps leaves spread out to
capture light
● Xylem = transport tissue - carries ● Lignin builds up in spirals in cell walls -
water/mineral ions from roots to leaves causes xylem cells to die and form hollow
Xylem cell and shoots tubes which transport water/minerals
● Supports plant ● Spirals/rings of lignin withstand pressure
● Made up of xylem cells of water moving up plant
● Phloem = transport tissue - carries ● Cell walls between cells break to form
glucose made by photosynthesis around sieve plates - allow water carrying
plant dissolved food to move
Phloem cell ● Made from phloem cells ● Less internal structures to allow more
space for water
● Supported by companion cells - transfer
energy from mitochondria
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller GCSE9. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $6.55. You're not tied to anything after your purchase.
