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4.1 Cell Biology Cheat Sheet by

biology     aqa     gcse

Eukaryotes and Prokar­yotes

Eukaryotic cells
from eukaryotes that have a cell membrane, ctyoplasm, and genetic material enclosed in a nucleus
Prokar­yotic cells
from prokar­yotic organisms have a cytoplasm surrounded by a cell membrane,. a cell wall Mat does not contain cellulose genetic material is a DNA loop that is free in the cytoplasm end not enclosed by a nucleus. Sometimes there are one or more small rings of DNA called plasmids.

Cell Specia­lis­ation in Animal Cells Key points

As an organism develops, cells differ­entiate to form different types of cells.
As an animal cell differ­ent­iates to form a specia­lised cell it acquires different sub-ce­llular structures to enable it to carry Out a certain function.
Examples of specia­lised animal cells are nerve cells, muscle cells, and sperm cells
Animal cells may be specia­lised to function within a tissue. an organ. organ systems. or whole organisms.

Cell specia­lis­ation in Animal cells - detailed

Nerve Cells
carry electrical impulses
Muscle Cells
contract and relax + striated muscle cells work together
Sperm Cells
has genetic info from male + get to egg

with adapta­tions

Nerve Cells
1)Long axon that carries nerve impulses 2) lots of dendrites to make connec­tions 3)synapse passes impulses using special transm­itter chemicals
Muscle Cells
1)Special sliding proteins making fibres contract 2)contain mitoch­ondria required for chemical reactions 3)stores glycog­en-used by mitoch­ondria to transfer energy
Sperm Cells
1)Long tail for movement 2)middle section has mitoch­ondria (energy) for the tail to work 3)Acrosome has digestive enzymes for breaking egg’s outer-­shell 4)Large nucleus with genetic info

Cloning Plants

In the right condit­ions, a plant cell will become unspec­ialised and will undergo mitosis many times. Each of these undiff­ere­nti­ated, recently made ells will produce more cells by mitosis.
In different condit­ions, these will then differ­entiate to form tissues such as xylem, phloem, and root hair cells that are needed to form a small new plant. This new plant will be identical to the original parent.
It’s difficult to clone animals because most animal cells differ­entiate perman­ently early in embryo develo­pment and the cells cannot change back.
 

Animal and Plant cells

Key Points
Animal cell features common to all cells — a nucleus, cytoplasm, cell membrane, mitoch­ondria, and ribosomes.
 
Plant and algal cells contain all the structures seen in animal cells as well as a cellulose cell wall. Many plant cells also contain chloro­plasts and a permanent vacuole filled with sap.

Cell Specia­lis­ation in Plant cells Key points

Plant cells may be specia­lised to carry out a particular function.
Examples of specia­lised plant cells are root hair cells, photos­ynt­hetic cells, xylem cells, and phloem cells
Plant cells may be specia­lised to function within tissues, organs, organ systems, or whole organisms.

Cell Specia­lis­ation in Plant cells detailed

Root hair cells
takes up water and mineral ions
Xylem cells
is non-living and carries water from roots to leaves and shoots
Phloem cells
is living and carries dissolved food both ways

with adapta­tions

Root hair cells
1)Large surface area for water absorption 2)Large permanent vacuole to speed up water movement by osmosis 3)Many mitoch­ondria (energy) for active transport
Xylem cells
1)Are initially alive but lignin forms and cells die, forming long hollow tubes 2)The spirals of lignin make tubes strong
Phloem cells
1)Cell walls break down to form sieve plates to allow water carrying dissolved food move 2)Supp­orted by companion cells bcos internal structures and mitoch­ondria in CC transfer energy

Cell differ­ent­iation in Animal cells

In the early stages of animal and plant embryos, the cells are unspec­ial­ised. Any cell (stem cells) can become any cell required.
By birth, most cells are specia­lised to carry out a specific job, such as nerve cells, skin cells, or muscle cells. They have then been differ­ent­iated.
Most specia­lised cells can divide by mitosis, but only form the same type of cell (e.g Muscle cells divide to produce more muscle cells).
However, some differ­ent­iated cells such as RBC or skin cells cannot divide and so adult stem cells replace dead or damaged cells. (Nerve cells are not usually replaced)
 

Organelles and functions

nucleus
controls all the activities of the cell and is surrounded by the nuclear membrane. Contains genes on chromo­somes with instru­ctions for making proteins needed for new cells/­org­anisms
cytoplasm
liquid gel in which the organelles are suspended and where most of the chemical reactions needed for life take place
cell membrane
regulates what enters and leaves the cell e.g glucose and mineral ions (in)
mitoch­ondria
structures in the cytoplasm where aerobic respir­ation takes place, releasing energy for the cell
ribosomes
where protein synthesis takes place, making all the proteins needed in the cell
cell wall
is made of cellulose and streng­thens the cell and gives it support
chloro­plast
where photos­ynt­hesis takes place. It contains chloro­phyll - the green pigment in plants which absorbs the light
permanent vacuole
the space in the cytoplasm filled with cell sap. The vacuole also provides the cell with structural support, food/water storage, waste disposal, protec­tion, and growth.

Cell differ­ent­iation Key points

In plant cells, mitosis takes place throughout life in the meristems found in the shoot and root tips.
Cells produced by mitosis are geneti­cally identical to the parent cell
Many types of plants cells retain the ability to differ­entiate throughout life
Most types of animal cells differ­entiate at an early stage of develo­pment.
In mature animals, cell division is mainly restricted to repair and replac­ement. As a cell differ­ent­iates it acquires different sub-ce­llular structures to enable it to carry out a certain function. It has become a specia­lised cell.

Cell differ­ent­iation in Plant cells

Most plant cells are able to differ­entiate all through their lives. Undiff­ere­ntiated cells are formed in meristems in stems and roots. In the meristems, mitosis is constantly occurring.
Plants keep growing throughout their lives at ‘growing points’. The plant cells produced don;t differ­entiate until they are in their final position in the plat. Even then, the differ­ent­iation isn’t permanent and plant cells can switch plants, re-dif­fer­entiate and become a new type of cell.

Microscopy

An electron microscope has much higher magnif­ication and resolving power than a light micros­cope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-ce­llular struct­ures.
size of image = magnif­ication / size of real object

Culturing microo­rga­nisms (aseptic techni­ques)

pre:washed hands, disinf­ected tray, Bunsen burner, agar in water bath, lab coat
during­:fl­aming the neck of bottles, palming technique for opening lids, pre-st­eri­lised syringe and spreader, only open petri dish slightly, flaming tweezers
after:­taped petri dish lid on to stop stuff going out and in, incubated petri dish @ 25 °C so any other micro’s from growing, wash benches and hands again
In conclu­sion, the best antiseptic is bleach because it is more alkali than the others, this is shown by its average area and diameter of the clear zone.

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