Hi,
I achieved all 9s in my 2022 GCSE exams. I achieved 239/252 in Geography, 172/200 in Biology, 192/200 in Chemistry and 189/200 in Physics. These notes were my main source of revision to achieve these grades, I hope they're useful. Disclaimer: due to covid and Advance Information, a small mino...
May/June 2022
GCSE Biology Notes
For each topic:
- Freesciencelessons video + Cognito video with notes
- Key Cards
- After each large topic, exampro questions, save my exams digital, and CGP practice
PAPER I
Eukaryotes and Prokaryotes
• Both animals and plants are eukaryotes
• All eukaryotic cells have DNA enclosed in a nucleus
• In fact, that is the definition of a eukaryotic cell: a cell that contains its genetic
material (i.e., DNA) enclosed in a nucleus
• Plant and animal (eukaryotic) cells also have a cell membrane and a cytoplasm
• Unlike animals and plants, bacteria are prokaryotes
• In prokaryotic cells, the genetic material is not enclosed in a nucleus, instead it is
looped freely in the cytoplasm:
,Major topic Low-stakes topic
• Another difference between prokaryotic and eukaryotic cells is that prokaryotic
cells are much smaller than eukaryotic cells (you can remember that because
bacteria are really small)
• Prokaryotes (like bacteria) may also have small rings of DNA called plasmids
which encode for a certain characteristic
• Like eukaryotes, prokaryotic cells have a cell membrane but they also have a cell
wall (note: this is not a cellulose cell wall like the eukaryotic cell wall of a plant)
• Note: prokaryotes are prokaryotic cells because almost all prokaryotes are
unicellular
• Bacteria have ribosomes but do not have mitochondria or chloroplasts
Animal and Plant Cells
• Here is an animal cell:
• The nucleus holds all the genetic material of the cell, controlling the activities of
that cell
• The cytoplasm is a gel-like solution where metabolic chemical reactions take
place
• The cell membrane controls what enters and leaves the cell
• Mitochondria are tiny organelles where aerobic respiration takes place to release
energy for the cell’s reactions
• Ribosomes are the sites of protein synthesis
• The mitochondria are tiny but the ribosomes are even smaller (that is how you
distinguish them in a diagram)
,Major topic Low-stakes topic
• Here is a plant cell:
• EVERYTHING an animal cell has, a plant/algal cell has
• Hence, plant cells also have a cell membrane, a nucleus, a cytoplasm,
mitochondria and ribosomes
• But they also have a few extra subcellular structures:
• They have chloroplasts which are organelles that contain chlorophyll to absorb
light energy needed for photosynthesis – hence, this is where photosynthesis
takes place
• They have a cellulose cell wall that strengthens the cell
• They also have a permanent vacuole filled with cell sap which helps keep the
plant turgid and rigid
, Major topic Low-stakes topic
Cell specialisation
• Most animal cells are specialised so have adaptations that help them to carry out
a particular function
• When cells become specialised, differentiation takes place
• The 3 different specialised animal cells you need to be able to explain
adaptations for are sperm cells, nerve cells and muscle cells:
• (1) Sperm cells
• The role of a sperm cell is to fertilise an egg
• One adaptation is that they contain only half the genetic material of a normal
adult cell, meaning that, when fertilisation takes place they produce a normal
body cell
• They also have a long tail that allows them to swim to the egg and fertilise it
• They have an acrosome which contains enzymes that allow it to digest through
the outer layer and cell membrane of the egg and fertilise it
• They have many mitochondria which provide energy for it to swim via aerobic
respiration
• (2) Nerve cells
• The role of a nerve cell is to carry electrical impulses around the body
• They have a long axon which allows it to carry impulses from one part of the
body to another along long distances
• The axons are covered in myelin which insulates the axon and speeds up
transmission of nerve impulses
• They also have synapses which are junctions that allow it to connect to other
nerve cells and carry the impulse from one cell to another
• Dendrites increase the surface area of the cell so other nerve cells can connect to
it
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 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 YassinY32. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £7.49. You're not tied to anything after your purchase.
