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Module 1: Cells as the Basis of Life - Coggle Diagram
Module 1: Cells as the Basis of Life
Types
Prokaryotic
No membrane-bound organelles
DNA in single chromosomes and plasmids
e.g. E.coli, cyanobacteria,
Eukaryotic
Membrane-bound organelles
DNA in multiple chromosomes in nucleus
e.g. paramecium, amoeba, multicellular organisms
Microscopes
Light microscope
Samples prepared quickly and cheaply
Up to 1500x magnification
Living cells can be studied
Electron microscope
Up to 1 000 000x magnification
Expensive, long prep time
Only non-living samples
Cell chemicals
Inorganic
Water -> transport medium, solvent, site of reactions
Mineral salts -> body processes, assist in reactions
Gases -> carbon dioxide and oxygen
Organic (C-H)
Proteins (CHON)
Structure: 20 amino acids, different combinations, form polypeptide chains, twist to form proteins
Function: growth and repair, enzymes, hormones
Carbohydrates (CHO)
Monosaccharides; one unit of sugar, quick energy e.g. glucose
Disaccharides; two units of sugar, quick energy e.g. sucrose
Polysaccharides; many units of sugar, storage and cell structure e.g. starch
Lipids (CHO)
Structure: glycerol molecule with three fatty acid chains
Function: energy storage, cell membrane structure
Nucleic acids (CHONP)
Nucleotide; sugar, phosphate, base
DNA; double strand, ATGC bases, genetic info
RNA; single strand, AUGC baes, protein synthesis
Cell membrane
Semi-permeable; allows substances in and out of the cell
Flexible; cholesterol (animals), phytosterol (plants)
Fluid mosaic model
Phospholipid bilayer
Hydrophilic phosphate head
Hydrophobic lipid tails x2
Proteins scattered through the membrane (suspended)
Adhesion; link cells, maintain 3D
Transport; passageways to allow substances to cross
Receptor; depends on cell type, receives messages for that type
Recognition / glycoproteins; identify the cell, help body differentiate body cells from foreign
Enzymes
Definition
Proteins, active site = where substrate binds to enzyme
Catalysts; lower activation energy, speed up the reaction rate
Specific; only bonds to one type of substrate for one reaction
Reusable; not used in the reaction
Models
Lock and key: enzyme and substrate bind and fit exactly
Induced fit: active site changes shape to better bind to the substrate, returns to old shape after reaction
Affecting factors
pH level: optimum pH = optimum activity, too high or too low -> low activity -> enzyme denatures
Temperature: optimum temperature = optimum activity, too cold = low activity, too hot -> denatures
Substrate concentration: activity increases to saturation point, then plateaus (working at maximum capacity)
Active transport
Up a concentration gradient (low to high concentration)
Bind to carrier proteins to cross the membrane
Endocytosis
Phagocytosis = cell membrane engulfs solid particle into cell
Pinocytosis = cell membrane engulfs liquid particle into cell
Exocytosis
Membrane-bound vesicle moves to cell membrane -> membranes fuse -> vesicle contents released to outside cell
Passive transport
Diffusion
Down a concentration gradient (high to low concentration)
In cell membrane: moves water, urea, carbon dioxide, oxygen
Osmosis
Water down a concentration gradient (not lipid soluble, moves through aquaporins)
Hypotonic = environment lower solute concentration than the cell (animal -> lysed, plant -> turgid)
Isotonic = equal concentration in and out of cell
Hypertonic = environment higher solute concentration than the cell (animal -> shrivelled, plant -> plasmolysed)
Facilitated diffusion
Down a concentration gradient
Substances can't dissolve in bilayer; need assistance
Assisted by carrier and channel proteins
Substances = larger (e.g. amino acids, sugars), charged (e.g. chloride ions)