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Unit 1 Cell Biology - Coggle Diagram
Unit 1 Cell Biology
1.1 cell theory(1/23)
living organisms are composed of cells
cells can only arise from pre-existing cells
Cell is the smallest unit of independent life
cell theory exceptions
Striated muscle -fused cells =multunucleated
Giant Algae- unicellular in a very large size
Aseptate- lack partioning + continuous cytoplasm
Function of life
MRSHENG (metabolism, reproduction, sensitivitym homeostasis, excretion, nutrition, growth)
Cell size
SA:Volume ratio
Volume=the rate of metabolusm
Surface area=the rate of material exchange
Cells have a large SA:Vol to survive
Magnification
MIA (magnification=image/actual
Microscope
Light micro = natural colour+lower solution
Electron micro = dead spicemens + higher magnification + cross sections
Emergent Properties
Present in multicellular organisms=arise from interactions between individual cells to produce a new function
1.4 membrane transport
properties of membranes
semi-permeable(only certain things can cross)
selective (membranes can regulate material passage)
Passive transport (along the concern grad+ No ATP)
Simple diffusion: net movement of particles from a higher concern to a lower concern until quilibrium
Involbes small lipophilic molecules ex O2 CO2
Facilitated Diffusion: via the aid of membrane protein (carrier channel protein)
Involves large charged molecules(ions, glucose)
Active( against concern grad+ ATP required)
Active transport
3 Na bind to intracellular sites on the sodium-potassium pump
A phosphate group is transferred to the pump via the hydrolysis of ATP
Pump undergoes a conformational change = translocating Na accross the membrane
the change in shape expose two potassium binding site on the extracellular surface of the pump
the phosphate is releaed = pump return to its original conformation
potassium released = completed the ion changes
Symport: both molecules move the same direction
Antiport: molecules move in opp directions
Osmosis : the net movement of water molecules across a semi permeable membrane from a region of low solute to a high solute
Osmolarity: a measure of solute concerntration
Hypertonic : high solute / ani shivered /plant plasmolysed
Hypotonic: low solute / ani lysed / plant turgid
Isotonic: same solute / ani normal/ plant flaccid
Vesicular transport
Exocytosis: materials released from a vell via vesicles
Endocytosis: materials internalised within vesicle
Path way: rough ER -Golgi(vesicle) -plasma
1.6 Cell Divison
Cell cycle : an ordered set of events that culminates in cell devision
Interphase: G1, S , S2
Transcription / translation
Obtaining nutrients
Cell growth
Respiration
Organelle duplication
DNA replicaton
M phase: cell devide + consists of mitosis and cytokinesis
Tissue repair
Organism growth
Asexual reproduction
Development of embryos
Supercoiling: during mitosis, chromatin condenses via supercoiling to become tightly packed chromosomes
Mitotic Index: a measure of the proliferative status of a cell population (number of dividing cells)
cells in mitosis/ total number of cells
Cytokinesis: process of cytoplasm division
Animals(centripetal): micotubules form a concentric ring and contract towards the center
Plants(centrifugal): vesicls form at the cell centre and fuse outward to form a cell plate
Stages of Mitosis
Metaphase
centrosom spindle fibres attach to the centromere of each crhromosome
spindle fibre contract and move the chromosomes towards the cell centre
chromosomes forn a line along the equator (middle) of the cell
Anaphase
spindle fibres continue to contract
sister chromatids seperate and move to the opp sides of the cell
sister chromatis are now regared as two seperate chromosomes
Prophase (2n)
DNA supercoils and condenses (visivle chromosomes)
Nuclear membrane dissolves
Centrosomes move to polse and begin to produce spindle fibres
Telophase
chromosomes decondense( DNA forms chromatin)
Nuclear membranse form around the two identical chromosomes sets
Cytokinesis occurs concurrently
Interphase (2n)
DNA is uncondensed (chromatin)
DNA is replicated (S phase) to form genetically identical sister chromatids
Cell grows in size and organelles are duplicated( G1 G2)
Cytokinesis
Cytoplasmic division occurs to divide the cell into two daughter cells
Each daughter cell contain one copy of each idential sister chromatid
Daughter cells are identical
Cell cycle regulation
checkpoints
G1 checkpoint:
monitors potential growth conditions (nutrients)
level of DNA damage
G2 checkpoint:
minotor state of pre-mototic cell
identifies and repairs any DNA replication errors
Metaphase checkpoint
ensure proper alignment
Cyclins: proteins that control progression of the cell cycle
bind to cyclin dependent kinases(CDK)
The activated complex phosphorylates proteins involved in specific cell cycle events
After the event has occured, the cyclin is degraded and the dependent kinase is rendered inactive
cancer
Mutagens: agents that change the genetic material of cells
mutagens that cause cancer are classified as carcinogens
physical: UV
Chemical: arsenic
Biological : certain viruses
Smoking: cigarette smoke contains more than 60 known carcinogens
Genetics: cancer caused by mutations to two classes of genes
Proto-oncogenes: stimulate cell growth and proliferation = create cancer-causing oncogenes
Tumor supressor genes: repress cell cycle pregression
Cell Death
Necrosis(uncontrolled cell homicide)
cell loses functional control due to injury, toxis
destabilization of the membranes=swelling
cell bursts and release contents=inflammation
Apoptosis (programmed cell suicide)
controlled event triggered by mitochondrial proteins
cell contents are packaged in membranous blebs
the cell fragments into apoptic bodies are recycled
1.2 Prokaryotic cells
Structure
single, circular DNA molecule + petidoglycan cell wall + 70s ribosomes
contain those followings
pili: attachment or bacterial conjugation
Flagella: long whip for movement
Plasmids: autonomous DNA molecules
Prokaryotic VS Eukaryotic
DNA
Prokaryote: DNA naked + circular
Eukaryote: DNA bound to protein + linear
Organelles
Prokaryote: No nuclues + 70 s ribosome
Eukaryote: Has nucles+ 80 s ribosomes
Reproduction
Prokaryote: Binary dission + single chromosome
Eukaryote: Mitosis + Meiosis + paired chromosome
Average size
prokaryote: smaller (1-5um)
Eukaryote: Larger (-10-100um)
Bacteria Cell Devision
Process: (DNA replication + cell growth + cytokinesis)
Circular DNA copied
DNA loops attatch to the membrane
Cell elongates seperating the loops
Cytokinesis occurs to form two cells
1.3 Membrane structure
Phospholipids Bilayers
Contain a polar head composed of phosphate
two non polar tails, composed of a fatty acid chain
phospholipids are amphipathic
Properties
bilayer held tgt by weak hydrophobic interactions between tails
Individual phospholipids can move within the bilayer(fluidity + flexibility)
Amphopathic properties restrict passage (semu-permeable)
Arrangement in membranes
phosphate heads face out to the solution
hydrophobic fatty acid tails face inwards + shielded from the polar fluids
Membrane Proteins
Transport : facilitated fiffusion + active transport
Recognition : function as markers for cellular identification
Enzymes : localizes metabolic pathways
Anchorage: attatchemnt points for cytoskeleton
Junction : join two cells tgt
Transduction: functino as receptors for peptide hormones
Fluid Mosaic Model(singer-nicolson )
Fluid: membrance compoenents can move position
Mosaic: phospholipid bilayer is embedded with protein
Membrane Models
Davson-danielli
trilaminar=distinct layers
bilayer was flanked by two protein layers(sandwich)
Falsifies by the following 1. proteins are mobile 2. not all membranes have a constant lipid : protein ratio 3. identify transmembrane proteins
Cholesterol: fundamental component of animal cell membranes+ reduce membrane fluidity + permeability to some solute+ prevents crystallization
Topic 1.5 Origin of cells
Abiogenesis: formation of living cells from non living materials
non living synthesis of simple organic molecules
assembly of organic molecules into complex polymers
formation of polymers that can self-replicate
packaging of mollecules into membrances create an internal chemistry
Miller Urey experiment
water boiled to vapour to reflect the high tempt
vapor mixed with gases(h2, ch2, nh3) to create a reducing atmosphere (no oxygen)
mixture exposedto an eletrical discharge
micture cool and left for a period 5. condensed micture was analysed
Biogenesis
Pastuer experiment
Broths were stored in sealed vessels that were sterlised
bacterial growth occured if vessel was unsealed = didn't occur if vessel stayed sealed(contamination)
Endosymbiosis: The engulfed cell remained undigested and contribute a new function to the engulfed cell
Choloplasts and mitochondira arose via endo
DNA: have naked and circular DNA
Division: occurs via fission like process
Antibiotics: show susceptibiility
Ribosomes: have 70s ribosomes
Membranes: have a double membrane
1.2 Eukaryote Cells
Organelles
80s ribosomes: protein synthesis (translation)
Nucleus: stores genetic information (transcription )
Mitochondria: aerobic respiratoin (ATP)
Endoplasmic reticulum: transport materials between organelles
Golgi: midifies secretory products
centrosomes: cell division
Only gound in specific cell types
choroplastsL photosynthesis (plant)
Lysosomes(animals): breakdown of macromolecules
Animals VS Plants
Chloroplast
Ani: No / Plant: Yes
Plasmodesmata
Ani: No/ Plant: Yes
Cell Wall
Ani: No / Plant: yes
Vacuoles
Ani: temporary / Plant: large central vacuoles
Cholesterol
Ani: present in cell membrane / Plant no cholesterol
Ani: Glucose-glycogen / Plant: Glucose-starch
1.1 Cell specialization
Stem cells
Self-renewal 2. potency
totipotent : any cell type + extra-embryonic
plutipotent : form any cell type
multipotent: differentiate into a number of vlosely related cell type
unipotent : can not differentiate but are capable of self renewal
stem cell therapy
replace damages or diseased cells
harvesting stem cells from sources
usiing biochemical solutions to trigger cell differentiation
impanting new cells into patient's tissue
suppressing the immune system (prevent rejection)
monitoring new cells
Therapeutic examples
Stargardt's disease - macular黃斑 degeneraton - replace defective retinal cells
Parkinson's disease - death of nerve tissue -replace damaged nerve cells
Leukemia- cancer of the blood-replacement of bone marrow
Ethics of stem cell use
embryo -(pluripotent) -high tumour risk- obtained from abortion -requires destruction of the embryo
umbilical cord blood-multipotent -lower risk of tumour -easily obtained and sotred- cells must be stored from birth at cost
Adult tissue-multopotent-lower risk of tumour-invasice to extract-restriction in scope
Differentiation : expression of some genes and not others in the cell's genome
Gene packaging
active genes are LOOSELY packed as Euchromatin
Inactive gens are CONDENSED as heterochromatic