Module 2 Flashcards
Ultrastructure
Everything inside a cell
Maginification equation
I AM
Magnification definition
How many times bigger an object appears than in real life
Resolution definition
The ability to distinguish 2 adjacent objects next to each other
Light microscope
Uses lights to see large organelles, max magnification x1500 but has low resolution and low magnification
transmission electron microscope (TEM)
Fires a beam of electrons through thin specimens, helps to visualise very small organelles inside a thin sample
Scanning electron microscope (SEM)
Scans a focussed beam of electrons over a surface to create a 3D image
Max res= 10nm
Max mag= x100,000
Laser scanning confocal microscope
Used on Thick samples of tissues that’s been stained with fluorescent dyes, shows organelles at different depths and layers
Sectioning and problems
Sample cut and preserved in wax
Problems= the cut could b too thick/ thin and not representative of a real cell
Staining and problems
Coloured chemicals that bind to certain pads of cells. Too much stain distorts image
Features of eukaryotic cells
Organelles are membrane bound, have a proper nucleus
Function of internal membranes
Sort and compartmentalise contents of a cell into organelles increasing efficiency
Nucleus
Contains chromatin- DNA wrapped around histone proteins and is surrounded by a nuclear envelope and contains nuclear pores
Nucleolus
Produces RNA and ribosomes which are passed thru nucl envelope and nucl pore to the ER
RER
Studded w ribosomes for protein synthesis
SER
Continuous with RER lacks ribosomes and is for lipid synthesis
Golgi apparatus
Stack of membrane bound sacs called cisternae receives proteins from ER thru transition vesicles and MODIFIES and PACKAGES them into secretion vesicles- exocytosis
Lysosomes
Contains enzymes- lysozyme which breaks down material
Mitochondria
Double membraned, site of aerobic respiration
Permanent vacuole
Membrane bound, maintains cell stability by pushing the cytoplasm against the membrane (turgid), filled w water/ sap
Plasma membrane
Found in all cells, controls the entrance/ exit of molecules
Cell wall
Extra cellular provides support. Cellulose in plants and chitin in fungi/ protoctista
Ribosomes
Not membrane bound, some free in cytoplasm others are bound to ER, made up of rRNA and proteins, site if protein synthesis
What is the Cytoskeleton
Network of microfillaments and microtubules
What are microfillaments
Strands of actin that act as tracks for things to move in cells
What is microtubules
Hollow protein tubes
What are Centrioles
Made of microtubules arranged in 9 TRIPLETS to form a cylinder and found in pairs near the nucleus helps during cell division
Function of Microfilaments
Give cell shape, anchor organelles, resist tension
Function of Microtubules
Move organelles
Function of cytoskeleton
Structural support for animal cells shape, moves components within the cells, allows transport of vesicles and molecules around the cell, cell division- pulls daughter chromosomes to opposite poles, allows cilia, flagella and sperm to move
Structure and function of cilia
Hair like structures that wave back and forth only in eukaryotic cells
Function of flagella
Whip back and forth to create a propeller like motion only in prokaryotic cells
Prokaryotic vs eukaryotic cells
- smaller than eukaryotes
- both have ribosomes, prokaryotes are smaller not attached to any membranes
- eukaryotes have membrane bound organelles prok don’t
- eukaryotes have tails, prok have flagella
- prok have pili euk have cilia
- euk has dna contained in a nucleus, prok has free dna in the cytoplasm
- prok have plasmids euk don’t
Carbohydrates
Alpha glucose has H on top, beta has OH on top
Glycosidic bond forms from removal of water
What happens to Starch
Broken down into glucose when energy is needed
What is amylose and amylopectin
Amylose= long straight chain of alpha glucose
Amylopectin=long branched chain of alpha glucose
Water
Polar molecule, hydrophilic and hydrophobic
Cohesion- water molecules stick due to h bonds results in surface tension used in transpiration stream
Density- ice less dense than water, h bonds expand protects aquatic life underneath
High specific heat capacity- takes lots of energy to raise by 1 degrees, maintains stability in organisms
High heat of vaporisation- lot of energy needed to convert water into vapour results in cooling effect
What are triglycerides and phospholipids
Triglyceride: 1 glycerol 3 fatty acid tails
Phospholipids: 1 phosphate head 1 glycerol 2 fatty acid tails
Bond between glycerol and fatty acids
Ester bond formed by removal of h2o
Saturated vs unsaturated
Saturated = straight Unsaturated= double c=c and has kinks
Features of triglycerides
Fatty acid tails broken for energy
Insoluble: tails are hydrophobic, glycerol faces outwards (hydrophilic)
Features of phospholipids
Forms the phospholipid bilayer
Head hydrophilic tail hydrophilic
Function of cholesterol
Strengthens cell membrane and helps maintain fluidity of cell membrane
Structure of DNA
Phosphate head, deoxyribose sugar and base
How many rings for each base
Angels are pure and have 2 wings (AG purines and have 2 rings
CT pyrimidines and have 1 ring
structure of RNA
Phosphate head, ribose sugar and base (AUCG) NO T
Nucleotide bond
Phosphodiester bond forms between sugar and phosphate head to form sugar phosphate backbone and is caused by a condensation reaction
How is dna formed from 2 single polynucleotide strands
Hydrogen bonds occur from complementary base pairing AT forms 2 h bonds CG forms 3
Two strands are anti parallel first ones js 5’ to 3’ the template is 3’ to 5’
This results in the double helix
Semi conservative replication
Dna helicase unzips dna by breaking h bonds
Each original strand acts as a template free nucleotides bind to template by complementary base pairing
DNA polymerase reforms sugar phosphate backbone and strands twist to form double helix
Semi conservative as 1 strand is old and 1 strand is new
Genetic code
Base triplets= codons
>non overlapping
>degenerate- multiple combinations of triplets code for same amino acid
> universal same codons code for same amino acids in all organisms
Transcription
Dna helicase unwinds a section of DNA breaking h bonds
RNA polymerase lines up free RNA nucleotides along template strand by complementary base pairing no T, U instead
mRNA strand is formed
RNA polymerase reforms h bonds and double helix reformed
mRNA leaves nuclear pore and attaches to ribosome
Translation
mRNA attatches to ribosome
tRNA carries free bases to ribosome, they attach themselves to the mRNA via complementary base pairing
This forms amino acids and they form peptide bonds
After amino acids are bonded tRNA leaves and picks up more free nucleotides and process repeats
This continues until the stop codon is reached and a polypeptide is formed
