Notes and summaries on Topic 1 : Cells of the Biology GCSE AQA 9-1. Includes notes on eukaryotes and prokaryotes; subcellular structures, differentiation and specialisation of muscle, nerve, sperm, palisade, root hair, xylem, and phloem cells; microscopy and how to use microscopes and different kin...
Prokaryotes: Prokaryotic cells include bacteria. They are 10-100 times smaller than eukaryotic
cells and are unicellular organisms. Prokaryotes such as bacteria have no nucleus, just a loop
of DNA. They also have a cell wall, cytoplasm and a slime capsule, and, inside the cell
membrane, there are no other membrane-bound structures. Apart from the loop of DNA, they
have other DNA loops that exist as plasmids. These plasmids code for very specific features
such as antibiotic resistance and can contain antibiotic DNA that they can pass on to other
strains of bacteria. Some prokaryotes have flagella but so do some eukaryotic cells, so this
cannot be a difference between them. Prokaryotic cells’ cell walls are not made of cellulose.
Eukaryotes: Eukaryotic cells include plant and animal cells. They are a lot larger and are
complex, multicellular organisms. Plant and animal cells are around the same size, but plant
cells are slightly bigger. Eukaryotes have a nucleus that contains DNA as well as mitochondria,
which prokaryotes don't have. Eukaryotes and prokaryotes both have ribosomes, which are the
sites of protein synthesis.
Subcellular structures of eukaryotic cells:
Nucleus -Contains DNA and controls cell’s activities
Cytoplasm -Where chemical reactions take place
Cell membrane -Controls what (substances) pass in and out of the cell
Mitochondria -Site of aerobic respiration to transfer energy
Ribosomes -Site of protein synthesis
Chloroplasts -Contain chlorophyll and where photosynthesis for glucose happens
Cell wall -Made of cellulose and strengthens the cell
Permanent vacuole -Contains cell sap and quite large, keeps cell rigid
, Animal cells -these include:
Muscle cell:
Pulls on bone for movement -contract and relax
Has fibres -protein filaments- that slide over each other and contract to move
Glycogen granules store lots of glycogen to transfer to the mitochondria to transfer energy for
the cell
Contains lots of mitochondria for aerobic respiration
Nucleus
Striated (striped) muscle cells work together in tissues called muscles.
Smooth muscle cells form one of the layers of tissues in the digestive system and contract to
squeeze food through your gut.
Nerve cell (neuron):
Carries electrical impulses to allow us to respond to our environment
Receives impulses through dendrites
Electrical signal carried through axon, which carry electrical impulses faster than through many
cells so that’s why it’s long
Axon has myelin sheaths which insulate and prevent the signal being lost
Transmits impulses through axon terminals
Synapses at the end of the cell to pass the signal on to the next cell
Nucleus
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