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Whole summary cell bioLecture 1 Essential Cell Biology
The cell
essential features
- contains biomolecules (e.g protein/RNA/DNA)
- is an autonomous unit in performing a function
- can respond & adapt to stimuli
- can (often) reproduce itself
The basic ingredients of the cell
- DNA: deoxyribonucleic acid the language of genes
o Conserved within all known cells
- 3d structure: double helical structure
o Protects against damage
o Allows double copy for repair
- proteins: form code to function
Tree of life: bacteria, archaea & eukaryotes
- prokaryotes: cells without organelles, have structure by complexes instead of organelles
o Bacteria : no nucleus or other organelles
o Archaea : no nucleus, often extremophiles
- Eukaryotes : nucleus and other organelles, sometimes multicellular life forms
the power of the lens HOTTIE <3
- Microscope: invented by Antonie van Leeuwenhoek (1632-1723)
- Talented glassworker, made microscopes with one lens with pin and candle
How do they work
- light source
- falls through couple of lenses
- condenser lens: made sure that light from lamp is concentrated on specimen
- objective: rotated to change magnification and focus
- eye piece: determines end magnification
- eye: will also effect magnification
Advanced light microscopy: fluorescence microscopy
- instead of all light, filter used to only use one
colour of photon
- light is reflected onto object
- reflecting protein is bit longer wavelength, looses a bit of energy
- can specifically look at proteins labelled with specific tag
GFP: green fluorescent protein
- Cloned from: Jellyfish: important for attracting mates, uses blue light to interact with GFP
- Using GFP, you can visualise subpopulations of cells in tissue and living cells in multicolour
,The resolution of EM (electron microscopy)
- Hardly any wavelength
How does an EM work?
- Electron gun: same as light but will radiate electrons
- Radiate into a beam onto the slide by condenser lens
- Contrast natural elements with heavy metals: more protons more
positive charge to deflect electrons
- Can not use colour: are scattered away or absorbed: electron
- We can not see electrons: use chemicals to make electrons emit green light: visible
- Microscope used under vacuum
LM vs EM
- Advantage of EM over LM:
o Superior resolution (up to 0.5 nm!, atoms!)
o Visualise the whole cell, not only a fluorescent probe (e.g. GFP).
o Huge magnification range (30x-300.000x: 104)
- Disadvantages of EM compared to LM:
o requires fixation of cells (operates under vacuum).
o Only small pieces of tissue can be imaged.
o Time-consuming method
Summary 1: cells & microscopes
- A cell is a compartment containing biomolecules (DNA, RNA, protein) that are surrounded by
membrane and can react to stimuli.
- All cells have the same basic ingredients but show huge diversity in shapes and functions
- To study the form-function relationships, microscopes are essential:
o Light microscopy
o Fluorescence microscopy
o Electron microscopy
eukaryotes
The nucleus
- Denser part: nucleolus
o Darker DNA: a lot used,
- Lighter part: chromatin stored in cell, euchromatin: used a lot
- Tightly coiled: used less
- Nuclear envelope: membrane around nucleus, protects DNA
- Nuclear pore: promotes inside outside environment
- Scaffold proteins: only found during metaphase of cell cycle
Translation of RNA to protein in the endoplasmic reticulum (ER)
- ER: looks like fishnet of connecting tubes and sheets, lot of membrane
- Continuous lumen
, What does the Golgi apparatus do?
- protein modification & protein sorting
o Modulate 3d shape by modifying different sugar chains
o Come in at cis site, gets out at trans site
o Trans Golgi network: sorting of proteins
▪ Go to different organelles
▪ Outside world
▪ Membrane: receptors
- Man: mannose - Gal: galactose
- GlcNAc: n-acethylglucosamine - NANA: N-acetylneuraminic acid
The mitochondrion: energy supply
- Double membrane: wrapped not only inner part but forms cisternae inside, increase PM
- Burning glucose yields energy in the form of (ATP) by krebs cycle
- Mitochondria contain own DNA: bacteria: symbiotic relationship
The chloroplast: energy supply in plants photosynthesis
- Used to be bacteria: symbiosis
- Plants still need mitochondria to burn the glucose provided by in photosynthesis.
Cytoplasm
- cytoplasm is not fluid, but a jelly matrix of proteins and subcellular compartments
processes of the cytoplasm
- transport
- protein synthesis
- protein break-down
- signal transduction
- membrane fusion
- ionic homeostasis
form and transport: the cytoskeleton
- intermediate: cross links and cross interacting, organelles
- actin: dynamics, quick changes
- microtubule: main structure of cell
Summary 2: organelles
- Cells in the tree of life comprise bacteria, archaea and eukaryotes.
- Only eukaryotes contain organelles and a nucleus, can form multicellular organisms
- The basic organelles and their function:
o The nucleus: store DNA and transcription of DNA to RNA.
o The endoplasmic reticulum: translation of RNA to protein and protein folding.
o Golgi apparatus: post-translational modification and sorting of proteins.
o Mitochondrion: energy supply in the form of ATP
o Chloroplast: photosynthesis
o Cytoskeleton: cell shape and transport
o Cytoplasm: multifunctional protein gel and homeostasis
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