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UNIT 2: CELL STRUCTURE AND FUNCTION - Coggle Diagram
UNIT 2: CELL STRUCTURE AND FUNCTION
Cellular components
All cells contain:
Plasma membrane
Cytosol
Chromosomes
Ribosomes
Eukaryotic cell components
Genetic regulation
Nucleus
Where the chromosomes are
Contains nucleoli, which is where ribosomal units are made
Pores for entry regulation
The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein
Ribosomes
Used for protein and polypeptide synthesis
Protein production
The endoplasmic reticulum
Smooth
Aids in lipid synthesis
Metabolism of carbohydrates
Plays a role in detoxyfication
Rough
Aids in synthesis of secretory and other proteins from bound ribosomes
Adds carbohydrates to glycoproteins
Produces new membrane
Plays a role in intracellular transport
Golgi apparatus
Used in the modification of proteins
Synthesizes many polysaccharides
Sorts many Golgi products
Involved in the production of lysosomes
Lysosomes
These are sacs of hydrolytic enzymes that are important in intracellular digestion.
Lysosomal enzymes work best in the acidic environment inside the lysosome.
The three-dimensional shape of lysosomal proteins protects them from digestion by lysosomal enzymes
Lysosomes can use multiple methods to commence intracellular digestion
Phagocytosis is one, to which a cell engulfs another
Autophagy is another process, where the cell uses enzymes to recycle its own organelles and macromolecules
This is used in apoptosis
Vacuole
These are large vesicles from ER that are important in release of water
They are also used in digestion, storage, waste disposal, water balance, cell growth, and protection.
In plants, vacuoles take up a lot of space, allowing them to maintain a large surface area to volume ratio
Peroxisomes
These are a special metabolic unit bound by a single membrane.
It uses oxygen to break molecules
Produces hydrogen peroxide
Converts it to water.
Energy synthesis
Mitochondria
Mitrochondria specialise in energy capture and transformation.
They have a double membrane
The outer membrane is smooth
Inner membrane is full of folds (cristae)
Cristae increases surface area for ATP production
Contains enzymes important to ATP production
Enhances chemical reaction rate.
Chloroplast
They are specialised organelles found in algae and other plants.
They contain chlorophyll, the predominant pigment used to capture light.
There are many different kinds of it, but chlorophyll a is the most common.
They have a double membrane
Split into little compartments called thylakoids
Basic knowledge
Prokaryotes
Organelles are not membrane bound
DNA is found in unbound areas called nucleoid
Prokaryotic DNA are composed of one singular DNA strand
DNA is circular as opposed to eukaryotic DNA, which is linear.
Eukaryotes
Organelles are membrane bound
DNA is found in nucleus
Generally larger than proakaryotic cells
They have double membranes.
Cell size
Ratio of surface area to volume of a cell is critical
Diffusion is greatest when surface area to volume ratio is greatest
Smaller cells have a more favourable ratio
Cell membrane
Membrane structure
Hydrophobic head and hydrophillic tail
Selective permeability is a direct consequence of membrane structure
Nonpolar or small molecules move across easily.
Polar or big molecules do not.
The fluidity of the membrane is affected by:
The amount of unsaturated fatty acid tails
Cholesterol levels
Many species have variations in lipid composition to adapt to changing temperatures
Fluid mosaic model states that the membrane is fluid structure with proteins bobbing in it
Membrane proteins can be sorted into intergral and peripheral proteins.
The proteins determine most of the membrane’s specific functions.
Intergral proteins can go through the membrane.
With their ability to penetrate the hydrophobic area, can be utilised in the electron transport chain.
Peripheral proteins are loosely bound to the surface of the membrane.
Usually sits on the cytoplasmic side, and can pass on signals.
Major functions of those proteins
Passive trasnport
Diffusion
Substances diffuse down their concentration gradient
It goes from where it is more concentrated to where it is less concentrated.
No energy is needed to move molecules down the gradient.
Channel and carrier proteins are used for facilitated diffusion.
Hydrophilic molecules can use channel proteins as a tunnel.
Aquaporins are a type of channel protein.
Carrier proteins bind to the molecule and change direction.
The diffusion force will drive the change of the direction of the carrier protein’s opening.
However, the change of the protein itself requires energy.
Osmosis
Active transport
