Week 1: Cells, Plasma Membranes & Transport Flashcards
(21 cards)
What are the eight characteristics of ALL cells?
- Plasma membranes
- DNA, as hereditary material
- Genetic code is the same in all cells of the organism
- RNA
- Proteins determine structure + function in ALL cells
- Ribosomes, as the synthesisers of proteins
- All cells need energy/use ATP
- All cells are derived from other cells (by mitosis, meiosis or binary fission)
When was the first primordial cell?
Approx 3 - 3.5 billion years ago = very small cell, with a simple internal structure.
What evidence is there that all living organism evolved from one cell?
- Too strong resemblence among living cells
- Common cell components (amino acids, sugars, nucleotides & fatty acids) can be made in vitro from simple organic molecules (C, N + O)
- Fossil evidence
What is the LECA (Last Eukaryotic Common Ancestor)?
The hypothetical last common ancestor of ALL eukaryotes that have existed
- a symbiotic combination of ancestral + bacterial lineage
What are the eleven characteristics of Prokaryotes?
- Simple structure
- Small - generally < 10 micrometres
- Basic shaped
- Can divide/replicate rapidly under optimum conditions - divide every 20 mins
- May have a peptidoglycan cell wall outside the plasma membrane
- Simple compartment of cytoplasm containing all the organelles
- Replicate/divide by binary fission
- Use a wide variety of substances as food
- Aerobic or anerobic metabolism, dependent on species
- Can occupy a large range of ecological niches, dependent on species
- Can exchange genetic information between species using Horizontal Gene Transfer
What are the basic prokaryotic cell shapes?
- Give examples
- Spherical e.g. Coccus
- Rod e.g. Bacillus, Coccobacillus
- Spiral e.g. Vibrio, Spirillum, Spirochete
What is a Monomorphic bacteria?
Bacteria that has one form
What is a Pleomorphic bacteria?
Bacteria that have the ability to alter their morphology, biological functions + reproductive modes in response to environmental conditions.
What is the Periplasmic Space?
The space between the plasma membranes in Gram Negative bacteria that is filled with Periplasm (= a concentrated gel-like matrix)
Whats the difference between Gram Positive and Gram Negative bacteria?
Gram - positive: have a mesh of peptidoglycan above the plasma membrane, below the capsule and have Lipotiechoic acid
Gram - negative: have a layer of peptidogylcan in the perisplamic space between two PM, they also can have porins and have endotoxins/lipoolysaccharides (LPS) on the outer membrane that can cause an immunological response
What is a therapeutic use of cell walls?
Cell walls provide ligands for cell attachment/adherence to other surfaces which provide good therpuetic targets
What are the steps of BInary Fission?
- Cell elongates + the DNA is replicated
- Cell wall + plasma membrane begin to grow inwards
- Cross-wall forms completely around the divided DNA
- Cells separate, cytokinesis
What ecological niches do Eubacteria occupy?
Soil, water + large organisms (e.g. humans)
What ecoclogical niches do Archaebacteria occupy?
Bogs, oceans, salt brines + hot acid springs
What is Horiztonal Gene Transfer?
= the exchnage of genetic infomation between bacterial cells of different species (conjugation)
- can enhance natural selection advantage, E-coli has acquired 1/5 of its genome through this process
- the donor cell attaches to the recipient cell through a pilus (F-pili) + transfers DNA
What internal structures do ALL bacteria have?
- Plasma membrane
- Cytoplasm
- Ribosomes (70s)
- Nuclear region containing DNA
What internal structures MAY some bacteria have?
- Pilus
- Capsule cell wall
- Inclusions
- Plasmid
- Flagella, Cilia
- Fimbriae
What are the seven characteristics of Eukaryotes?
- A nucleus
- Genetic infomation that is encoded in DNA
- DNA that is sperarted from the cytoplasm
- Membrane-bound organelles in the cytoplasm with specialised functions
- Extensive internal membranes
- Cytoplasmic fibres (e.g. the cytoskeleton) - gives the cell structural support
- Make up a wide range of organisms (e.g. unicellular protists, fungi, plants + animals)
What is the Fluid Mosaic Model?
The accepted hypothesis for the structure of the plasma membrane - there is a bilayer of phospholipids with hyrdophillic heads + hydrophobic tails, that contains imbedded proteins, carbohydrates + cholesterol.
Why was the Fluid Moasic Model hypotheised before it could be visualised?
- Cells swell in hypotonic (less salty) solutions + shrinks in hypertonic (more salty) solutions
- Cells contents escape if they’re mechanically ruptured
- Compartmentalisation is needed for the biochemical activity of cells -> acidity varies between environments/cell components
What proof is there for the Fluid Mosiac Model?
- Visualisation through electron microscopy (1960s) using an osmium stain that shows membranes
- Freeze fracture (1990s) visualises the membrane internally so shows that proteins span the membrane
