Biology: Dna and ca Channels Essay

Biology –

Microscopes –
Magnification = degree to which the size of an image is larger
Resolution = degree to which it is possible to distinguish between two objects close together
Resolution of human eye – 200um

Light microscope =
Light passes from under stage – condenser lens – specimen – objective lens – eye piece lens
Magnification up to x1500
Resolution of 200nm

Actual size = image size / magnification

Electron microscope =
Resolution of 0.2nm
Use magnets instead of lenses

Transmission electron microscope (TEM) =
Electrons pass through sample – move through dense parts more slowly – 2D image

Scanning electron microscope (SEM) =
Electrons bounced off sample – 3D image – higher magnification

Prokaryotes –
No true nucleus
1-5 um
Haploid
Asexual reproduction
Fungi and protozoa

Bacteria –
Cell wall – Peptidoglycan

Gram + = purple – thick peptidoglycan layer teichoic acids and lipoteichoic acids
Gram - = pink – thin peptidoglycan layer (outer membrane) LPA

Peptidolgycan synthesis –
Composed of alternating NAM and NAG with a B1,4 glycosidic bond joining
3rd AA from one chain binds to 4th AA of second side chain

Teichoic acids – polymers containing glycerophosphate or ribitol phosphate residues – NAM
Negatively charged – transports cations into cell

Lipopolysaccharide – endotoxin
Lipid A – core – polysaccharide
Immunogenic

Replicate by binary fission

Organelles –
Nucleus = largest organelle
Nuclear envelope – two membranes with fluid between them
Contains nuclear pores

Endoplasmic reticulum =
Consists of series of flattened membrane bound sacs called cisternae
Rough ER – transports proteins made on attached ribosomes
Smooth ER – makes lipids
Also Ca storage

Golgi apparatus =
Stack of membrane bound flattened sacs
Receives proteins from ER and modifies them

Mitochondria =
2 membranes separated by fluid filled space
Inner membrane highly folded to form cristae

Lysosomes =
Spherical sacs surrounded by single membrane
Contain digestive enzymes

Cell membrane –
Partially permeable phospholipid bilayer
Hydrophobic layer by phospholipid tails
Hydrophilic layer by phospholipid heads
Cytoskeleton –
Network of protein fibres
Actin fibres and microtubules (tubulin)

Movement of substances –

Diffusion:
Movement of molecules from a region of high conc to region of low conc
Rate affected by temp, conc, stiring, SA, thickness, size of molecule

Large or charged molecules must be carried across membrane

Active transport:
Movement of molecules across membranes using ATP to drive protein pumps
Phago = solid pino = liquid

Osmosis:
Movement of water by diffusion across a partially permeable membrane

Solute = solid that dissolves in a liquid
Solvent = a liquid that dissolves solids
Solution = a liquid containing dissolved solids

Too much water = turgid (plant), haemolysed (animal)
Too little water = plasmolysed (plant), crenated (animal)

Hypotonic = low solute, high water hypertonic = high solute, low water
Isotonic = no net movement of water

Water –
Polar = the O pulls electrons away from the H

Solvent = H attracted to negative ion and the O is attracted to the positive ion
Ice floats = ice is less dense, molecules more spread out, forms insulating layer, water below doesn’t freeze
Temp stability = many H bonds require a lot of energy to break – fairly stable
Transport = very cohesive so molecules stick together
Cooling = high latent heat of evaporation – a lot of energy used up when water evaporates

Carbohydrates –
Energy source or structural

Starch – main energy storage in plants
Amylose (1,4) – straight coiled shape
Amylopectin (1,4 & 1,6) – branched shape

Glycogen – main energy storage in animals
Similar to starch but is more branched

Cellulose – component of cell walls in plants
B glucose (1,4) with

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