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Cells (B1 and B2) (Shi Yu) (Cell structure (functions of cell structure,…
Cells (B1 and B2) (Shi Yu)
Characteristics of living organisms
Definition :
1.Movement :
An active by an organisms causing a change of position or place.
2.Respiration :
The chemical reactions in cells that break down nutrient molecules and release energy.
3.Sensitivity :
The ability to detect and respond to changes in the environment.
4.Growth :
A permanent increase in size.
5.Reproduction :
The processes that make more of the same kind of organisms.
6.Excretion :
Removal from organisms of toxic materials and substances in excess of requirements.
7.Nutrition :
Taking in of materials for energy, growth and development.
supplement :
1.Movement :
An active by an organisms or part of an organism causing a change of position or place.
2.Respiration :
The chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
3.Sensitivity :
The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.
4.Growth :
A permanent increase in size and dry mass by an increase in cell number or cell size or both.
5.Reproduction :
The processes that make more of the same kind of organisms.
6.Excretion :
Removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), toxic materials and substances in excess of requirements.
7.Nutrition :
Taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water.
Cell structure
Animals cells :
1.Nucleus
2.Nuclear envelope
3.Cell membrane
4.Cytoplasm
5.Small vacuole
Plants cells :
1.Nucleus 2.Nuclear envelope 3.Cell wall 4.Cell membrane 5.Cytoplasm 6.Chloroplast 7.Starch grain inside chloroplast 8.Large vacuole containing cell sap 9.Membrane around vacuole
All organisms are made of cells.
Compare the structure of animal cells and plant cells :
Both have :
Nucleus, Nuclear envelope, Cell membrane, Cytoplasm.
Only plants cell have :
Cell wall, Chloroplast, Starch grain inside chloroplast, Large vacuole, Membrane around vacuole
functions of cell structure
Cell membrane :
1.Encapsulate all organelles.
2.It is
partially permeable
, it can controls what goes in and out of it.
Cell wall :
1.Made of
cellulose
, it is
polysaccharides
.
2.Wrap the whole plant cell
3.It is a very strong covering to the cell, this helps to protect and support the cell. If the cell absorbs a lot of water and swells, the cell wall stops it from bursting.
4.It is
fully permeable
.
Cytoplasm :
1.It is a clear jelly.
2.It is nearly all water.
3.Many substances are dissolved in it, especially proteins.
4.Many different
metabolic reactions
(the chemical reactions of life) take place in it.
Vacuoles :
1.Surrounded by a membrane and containing a solution.
2.Contain a solution of sugar and other substances, called
cell sap
.
3.Presses outwards on the rest of the cell, and helps to keep it in shape.
4.Vesicles (vacuoles in animals) may contain nutrients or water.
Chloroplasts :
1.
Chlorophyll
absorbs energy from sunlight, and this energy is then used for making food for the plant by photosynthesis.
2.Contain starch grains.
Nucleus :
1.Is where the genetic information is stored. 2.Help the cell to make the right sorts of proteins. 3.The information is kept on the
chromosomes
, which are inherited from the organism's parents. 4.Chromosomes are made of
DNA
.
Magnification :
Objects size on Graphs / Real object size
Movement in and out of cells
Diffusion
Definition :
The net movement of molecules and ions from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement.
The substances move into and out of cells by diffuses the cell membrane.
The factors that influence diffusion :
1.Surface area. 2.Temperature.
3.Concentration gradients.
4.Diffusion distance.
Osmosis
Definition :
The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane.
Partially permeable membrane :
It have a lot of holes, the holes are big enough to let the water molecules through, but not the sugar molecules.
Water potential :
The higher concentration of solution, the water potential is lower. The lower concentration of solution, the water potential is higher.
The substances move into and out of cells by osmosis the cell membrane.
Effects of Concentration to Plant Cells :
Concentration outside higher than inside :
Plasmolysis.
It usually kills a plant cell, because the cell membrane is damaged as it tears away from the cell wall.
Concentration outside lower than inside :
Turgid
. The turgidity of its cells helps a plant that has no wood in to stay upright and keeps the leaves firm. The animal cells will bursts.
Concentration outside same to inside :
Flaccid.
The plant loses its firmness and begins to wilt.
Specialised cells
Ciliated cells :
Movement of mucus in the trachea and bronchi.
Root hair cells :
Absorption
Palisade mesophyll cells :
Photosynthesis.
Red blood cells :
Transport of oxygen.
Sperm and egg cells :
Reproduction.