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Summary Grade 9 GCSE Biology Triple Paper 1 notes
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This document has all the notes for GCSE Biology Triple Paper 1 that can get you a grade 9 + including all the required practicals.
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Major topics Low stakes topics TJNOTESGCSE Biology Notes
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:
• 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)
,Major topics Low stakes topics TJNOTES
• 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
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)
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 topics Low stakes topics TJNOTES
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
,Major topics Low stakes topics TJNOTES
• (3) Muscle cells
• The role of a muscle cell is to contract (and relax) to allow for movement
• The main adaptation of muscle cells is having lots of mitochondria to release
energy for muscular contraction using aerobic respiration
• They also have protein fibres that can change their length, allowing cell to
contract and shorten
Some plant cells also have certain adaptations to help them carry out their
function, the ones you need to be able to explain for the exam are root hair
cells, xylem cells and phloem cells:
(1) Xylem
• The role of xylem cells is to carry water and dissolved mineral ions from the
roots to the leaves
• They have very thick walls containing lignin, a chemical that strengthens the cell,
helping to support the plant and allows it to withstand the high water pressure
travelling through it
• The end walls between cells have broken down, meaning that the xylem cells
form hollow tubes with open ends, allowing lots of water and dissolved mineral
ions to travel through these cells – they also have no nucleus, cytoplasm, vacuole
or chloroplasts, allowing for more space for dissolved mineral ions and water to
flow
(2) Phloem
• The role of phloem cells are to carry dissolved sugars up and down the plant
• They are made up of vessel cells and companion cells
• Vessel cells have little subcellular structures to allow glucose to travel through it
and companion cells have lots of mitochondria in order to provide energy for the
active transport and translocation of sugars up and down the plant by
respiration
• Vessel cells also have sieve plates rather than completely closed ends, to allow
dissolved sugars to travel from cell to cell, forming a tube
(3) Root hair
• Roots have finger-like projections called root hairs which increase the surface
area of the root cells, allowing more water and mineral ions to be absorbed into
the cell by osmosis, diffusion and active transport more effectively and more
quickly
• They also have lots of mitochondria to provide energy for active transport of
mineral ions via cellular respiration
• They also have a large permanent vacuole to increase solute concentration inside
the cell, ensuring steep concentration gradient for water to diffuse across by
osmosis
,Major topics Low stakes topics TJNOTES
Microscopy
• Microscopes allow us to magnify things (image produced is larger than the real
object)
• Microscopy techniques have developed over time
The two types of microscopes:
(1) light microscopes
(2) electron microscopes
• Light microscopes are the ones used in schools and have a limited magnification,
this makes it difficult to see smaller subcellular structures like ribosomes or
things within the nucleus, for example
• They also have a limited resolution; the image is blurred so we cannot see the
finer details – but they do allow us to see individual cells and large subcellular
structures like nuclei
• Electron microscopes were developed later on and these have a much greater
magnification and resolution than light microscopes – due to this, biologists can
now see finer detail and investigate smaller subcellular structures
• Resolution is the ability to distinguish between two points so a higher resolution
means a sharper image is produced
• Microscopy techniques have developed over the years as technology has
improved – meaning we can produce microscopes with higher magnifications
and resolutions
• Because electron microscopes allow us to see in a higher mag and resolution, we
can now see smaller subcellular structures in finer detail and their internal
structures can be investigated now as well due to the development of technology
and scientific research
To calculate the magnification of an object:
𝑖𝑚𝑎𝑔𝑒 𝑠𝑖𝑧𝑒
𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 =
𝑟𝑒𝑎𝑙 𝑠𝑖𝑧𝑒
, Major topics Low stakes topics TJNOTES
Required Practical 1: Microscopy
Aim: To use a light microscope to observe, draw and label a section of plant and animal
cells. A magnification scale must be included
Apparatus:
Risks:
Iodine stain irritant
Glass coverslip/slide
Bulb could get hot
Method:
1) Place the prepared slide onto the stage and use clips to hold slide in place
2) Direct the mirror to shine light through the hole in the stage
3) Select the lowest power objective lens
4) Use the coarse adjustment knob to position it so that it almost touches the
microscope slide – ensure to look at the microscope from the side while
adjusting the position of the objective lens NOT through the eyepiece to prevent
breaking the slide
5) Look down through the eyepiece, turn the coarse focus knob to increase the
distance between the objective lens and the slide – stop adjusting when it
becomes the most focussed
6) Then, use the fine adjustment knob to bring cells into a clear focus
7) You can then use a higher power objective lens
8) Calculate the magnification of the microscope by multiplying the magnification of
the eyepiece lens by the magnification of the objective lens
9) Use a pencil to make a clear, labelled drawing of some of the cells in the image –
including labels of the nucleus, cytoplasm, cell membrane and mitochondria; and,
if it is a plant cell, we can label the vacuole and the chloroplasts as well
10)When drawing the image, ensure that it is an uninterrupted pencil line, with no
shading and have a magnification scale to indicate how big the cells are. To do
this we place a clear ruler onto the stage and look through the eyepiece to
measure how large the image is and use this on our drawing using a scale bar
and write the magnification we calculated
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