|
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.
|
|
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.
|
|
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
|
|
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
|
|
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.
|
|
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.
|
||
|
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.
|
|
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
|
|
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
|
|
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)
|
|
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.
|
|
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.
|
|
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.
|
|
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
|
|
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.
|
Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
