Cell biology 1.1-1.5 Flashcards
What are the principles of cell theory?
> all organisms are made of cells > cells have membranes - division > cells conduct metabolic processes > cells have their own energy and genetic material
Exceptions to cell theory
- striated muscle cell
- multinuclear fusion of many cells
- cells formed without cytokinesis
- giant algae
What are the functions of a unicellular organism?
- homeostasis
- metabolism
- reproduction (of genetic material)
- growth
- nutrition
- excretion
- reaction / response
- in multicellular organisms different cells have different functions (differentiation)
Why is surface area to volume ratio important?
- volume = amount of cytoplasm and metabolism
- surface area = exchange of materials
- larger cells need more surface area → more metabolism
- too small ratio → not enough secretion → overheating
Solutions - microvilli - creating extensions - flattening into thin film - dividing cytoplasm into smaller parts
What are emergent properties?
- sharing functions between different cells (and compartments within a cell)
- more than sum of the properties
How do cell specialise?
> differentiation - the same genetic material - gene expression > more effective - same function groups = tissue
Stem cells
> capable of renewing for long time > variable potency (differentiation) > embryonic - unlimited growth potential - high tumour risk - ethical considerations > cord blood - easily obtained and stored - compatible with adult body - limited amount > adult - limited potency - compatible with tissue - difficult to obtain
Therapeutic uses of stem cells
- Stargardt’s disease
- active transport in retina cells
- retina degenerates
- no light detection
- stem cells in retina
- Leukemia
- abnormally reproducing WBC
- stem cells frozen
- chemotherapy
- stem cells reintroduced
What is the structure of prokaryotic cell?
- simplest structure
- no nucleus
- lighter
- DNA
- one chamber
- ribosomes 70s
What is binary fission?
- cell division of prokaryotes
- DNA replication
- opposite ends of the cell
- membrane elongates (cytokinesis)
How can cell perform many functions simultaneously?
- made of compartments
- higher concentration of enzymes and substances
- different pH
- compartments move
- protection from dangerous enzymes
- nucleus has chromosomes
What are the amphipathic properties?
- hydrophobic parts
- phospholipid tails
- hydrophilic parts
- phospholipid heads
- phosphate group
> arranged in double layer - hydrophilic parts on the outside
What were different phospholipid bilayer models?
Davson-Danielli model
- phospholipids sandwiched between protein layers
- good barrier
Singer and Nicolson model (fluid mosaic)
- proteins have different positions
- peripheral, integral proteins
- phospholipids and proteins move
How was Davison-Danieli falsified?
> freezing of cells and fracturing them - globular structures appeared - transmembrane proteins > structure of membrane proteins - globular, different shapes > fluorescent tagging - antibodies on proteins - scattered = movement
What are the functions of membrane proteins?
- hormone receptors
- immobilised enzymes
- active site outside
- cell adhesion
- junctions in tissue
- cell-to cell communication
- synapses
- channels for passive transport
- pumps for active transport
What is cholesterol and what is its role?
- in animals
- hydrophobic
- near neurotransmitters
- role in membranes
- stabilising
- disrupt tails = no cristalisation
- disrupts molecular motion = no liquid
- stabilising
What is simple diffusion?
- particles move from high concentration to low
- gases
- solutes in solvent
- no energy
What does semi-permeability mean?
- only some particles can move through
- plasma membrane
- only small and uncharged molecules pass
- water, O2, CO2, urea
- only small and uncharged molecules pass
What affects diffusion rate?
- concentration gradient
- surface area
- length of diffusion
Increase in diffusion rate
> surface area - villi - cristae in mitochondrion - alveoli > diffusion distance - thin membrane - single layer of cells - small diameter
What is osmosis?
- movement of solvent molecules
- semi-permeable membrane necessary
- types of solutions
- hypertonic (high solute)
- isotonic (equal)
- hypotonic (low solute)
- osmolarity - total concentration of osmotically active solutes
What is facilitated diffusion?
- molecules that are too big or charged cannot pass
- glucose
- ions
- protein transporters (glucose) or channels (channels)
- along conc. gradient
- no energy needed
How does potassium channel work?
- 4 protein subunit
- pore small
- potassium solution can’t pass
- potassium broken into ions passes
- other molecules can’t pass
- impulse (nerve cells)
- charges change
- outside (-) inside (+) —> normally the other way
- channel opens and close rapidly
- ball goes into the pore
- charges change
What is active transport?
- through pump
- needs energy (ATP)
- against gradient
How does a pump work?
> nerve impulse - potassium and sodium move, facilitated diffusion from different gradients > gradients are built up by active transport > potassium-sodium pump (cotransport) - 3 Na ions - ATP —> ADP + Pi - 3 Na ions out, 2 K ions in - let Pi detaches
How are things transported within a cell?
> from ER to Golgi apparatus
From Golgi apparatus to the membrane
in vesicles
- spheres of phospholipid bilateral
How are vesicles formed?
- plasma membrane pulled (PM moves)
- pinched off
What is endo- and exocytosis?
- endocytosis
- forming a pit
- engulfing the molecule
- vesicles is formed and pinched off
- inner layer outside
- particles are digested (fusion with lysosome)
- exocytosis
- vesicles with particle travel to PM
- bilayers of membrane fuse
- particles from vesicle are released
How are cells formed?
- from division of existing cells
Pasteur’s experiment
- swan-necked flasks
- hypothesis: pre-existing microorganisms in air can contaminate broth
- broth in flasks
- boiled / unboiled
- long / short necks
- the results showed that in boiled flasks with long necks there were no organisms
How did first cells arise?
- production of carbon compounds
- Miller-Urey experiment
- carbon compounds arose from non-organic molecules
- Miller-Urey experiment
- assembly of carbon compounds
- deep-sea vents
- hot water + inorganic molecules
- energy
- assembling carbon compounds into polymers
- deep-sea vents
- formation of membranes
- phospholipids naturally form spherical membranes (vesicles)
- amphipathic properties
- phospholipids naturally form spherical membranes (vesicles)
- mechanism for inheritance
- RNA was genetic material
- self-replicating and catalyst
- RNA was genetic material
What is the origin of eukaryotic cells?
> prokaryotic cell (doing anaerobic respiration) engulfed a different cell (aerobic)
- instead of digesting it, both cells lived in mutualism
- energy supply
during natural selection they were favoured
What are the signs that mitochondria and chloroplasts were separate prokaryotes?
- their own DNA (circular)
- 70s ribosomes
- DNA transcription
- mRNA used to synthesise proteins
- produced by division of pre-existing cells
