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3.4, 3.5 and 3.6 Cells (ORGANELLES found in eukaryotic cells. Each cell…
3.4, 3.5 and 3.6 Cells
ORGANELLES found in eukaryotic cells. Each cell type has an internal structure that suits it for its job (ultrastrucutre). Eukaryotic cells have a distinct nucleus and membrane bound organelles. Using an electron microscope you can see the structures within the cells.
CELL WALL - In plant cells. Made of microfibrils of cellulose embedded in a matrix.
Cellulose microfibrils provide the cell wall with strength against osmotic gain as it allows water to pass along it. There is a thin middle lamella layer marking the boundary between cell walls and cements cells together.
Algae have cell walls made of cellulose and/or glycoprotein.
Fungi contain a mixture of chitin (nitrogen containing ploysaccharide) or glycan and glycoproteins.
VACUOLE A fluid filled sac, in plant cells it it usually one large central vacuole. Single membrane around it called the tonoplast. Contains a solution of mineral salts, sugars, amino acids (acting as a temporary food store), wastes and pigments called anthocyanins (colour petal to attract pollinating insects) .
Supports the plants by making the cell turgid.
LYSOSOMES are vesicles produced by the Golgi Apparatus containing enzymes. Lysosomes breakdown cells after they have died (autolsis), release enzymes outside of cells (exocytosis) to destroy material around hem, and digest worn out organelles to recycle useful chemicals.
They are a key factor in an immune response:
They are abundant in phagocytic cells. Enzymes called lysozymes hydrolyse cell walls of bacteria. Lysosomes isolate enzymes from the rest of the cell before releasing them to the outside or into the phagocytic vesicle.
RIBOSOMES - They contain two sub units, large and small, which contain ribosomal RNA and protein.
80S - eukaryotic cells.
70S - prokaryotic cells, mitochondria and chloroplasts.
ENDOPLASMIC RETICULUM The ER is a continuation of the nuclear membrane spreading through he cytoplasm with tubes and sacs called cisternae.
ROUGH ER - ribosomes present and provides a large surface are to synthesise proteins and glycoproteins. Provides a pathway to transport materials like proteins through through the cell.
SMOOTH ER - lacks ribosomes on its surface and has a more tubular structure. It synthesises, stores and transports lipids and carbohydrates.
GOLGI APPARATUS - More compact than ER, contains cisternae (flattened sacs) and vesicles (hollow structures). Lipids.proteins made by ER go to Golgi where it modifies them by adding non-protein components (like carbs) and labels them so they can be sorted and sent to the correct destinations. These are transported in golgi vesicles which can move to the cell surface, fuse with the membrane and then release its contents outside of the cell.
MITOCHONDRION They have a double membrane that controls the entry and exit of material. The inner membrane is folded to form cristea (extensions) which increase the surface area for attachment enzymes and proteins or aerobic respiration. The more cristea, the higher the metabolic rate of the cell. They have a matrix of liquid containing protein, lipids, ribosomes, enzymes for aerobic respiraion, and DNA that allows mitochondria to control production of their own proteins. They are the site of ATP production.
CHLOROPLASTS - carries out photosynthesis. They have an envelope that controls what is going in and out of the organelle. They have grana stacks of thylakoids where photosynthetic pigments are found (chlorophyll). stroma is the liquid matrix where the second stage of photosynthesis occurs. Contains starch grains
NUCLEUS - contains hereditary material (genetic information, DNA, chromosomes) and controls cell activity. It acts as a control centre of the cell and contributes to protein synthesis as it manufactures ribosomal RNA ad ribosomes.
CELL SPECIALISATION All cells are specialised in different ways to perform a particular role. The types and numbers of organelles are different based on the cells function.
In an embryo all cells are identical (stem cells) but as it matures cells specialise for their specific function.
All the DNA of each cell is identical, but they change based on which gene are "switched on".
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