Topic 1: Cell Biology Flashcards
Cell Theory
- Living organisms are composed of cells
- the cell is the smallest unit of independent life
- cells can only arise from pre-existing cells
Exceptions to the cell theory
Striated Muscle - composed of fused cells that are multi-nucleated
Giant Algae - unicellular organisms that are very large in size
Aseptate hyphae - lack of partitioning and have a continuous cytoplasm
functions of life
metabolism, reproduction, sensitivity, homeostasis, excretion, nutrition, and growth
rate of metabolism equation
cell mass / volume
rate of material exchange
function of a cells surface area
Magnification Equation
Magnification = image/size
how do cells organize themselves
cells -> Tissue -> Organs -> systems
Stem cells
uni-specialised cells that have two qualities:
- self renewal: they can continuously divide and replicate
- potency: they have the capacity to differentiate
generated by one’s own body
Stem Cell Therapy
replaces damaged or diseased cells with healthy ones
process of stem cell therapy
- harvest stem cells from appropriate sources
- use biochemical solutions to trigger cell differentiation
- surgically implant new cells into patient’s own tissue
- suppressing the host immune system to prevent rejection
- monitoring new cells to ensure they do not become cancerous
Differentiation
differentiation involves the expression of some genes and not others in the cell genome
activation of different genes within a cell will cause it to develop differently from other cells
active genes (eukaryotic cells)
are loosely packed as euchromatin
inactive genes (eukaryotic cells)
are packed tight as heterochromatin
Stargardt’s disease
macular degeneration, and can be treated by replacing defective retinal cells with stem cells
Parkinson’s disease
death of nerve tissue, and can be treated by replacing damaged nerve cells with stem cells
Lukemia
cancer of the blood, can be treated by replacing bone marrow with stem cells
prokaryotic cell structure
- organisms that lack a nucleus
- have a singular DNA molecule (genophore)
peptidoglycan cell wall and 70S ribosome
-Pili (attachment or bacterial conjunction) - Flagella (long whip like tail for movement)
- Plasmids (autonomous DNA molecules
Bacterial Cell Division
Asexual reproduction (binary fusion)
- circular DNA is copied
- DNA loops attach to the membrane
- Cell elongates, separating the loops
- cytokinesis occurs to form two cells
differences between prokaryotic and eukaryotic cells
- Prokaryote: DNA is naked and circular, Usually no introns, no nucleus, 70S ribosomes, reproduces via binary vision, single chromosome, smaller than eukaryotes
Eukaryote: DNA is bound to protein, DNA is linear, Usually contains introns, has a nucleus, 80S ribosomes, reproduces via mitosis and meiosis, paired chromosomes, larger than a prokaryote
organelles in Eukaryotic cells
- 80S ribosomes: responsible for protein synthesis (translation)
- Nucleus: stores genetic information (site of transcription)
- Mitochondria: site of aerobic respiration (ATP production
- Endoplasmic Reticulum: transports material between organelles
- Golgi complex: sorts, stores, modifies, and exports secretory products
- centromeres: involved in cell division (mitosis and meiosis
what organelle is only found in eukaryotic plant cells
chloroplasts: cite of photosynthesis
what organelle is only found in eukaryotic animal cells
lysosomes: breakdown of macro molecules
phospholipid bilayers
structure of phospholipids:
- polar heads (glycerol and phosphate)
- consist of two non polar tails (fatty acids)
- head is hydrophilic and tail is hydrophobic
multiple phospholipids come together to form a bilayer, where the head is facing the outside and the tails face inwards
Cell membranes
enclose the contents of a cell allowing for control of internal cellular conditions (homeostasis), composed of phospholipids and proteins
- semi permeable membranes: some materials cannot cross without assistance
- selectivity: cells can regulate the passage of certain materials
Membrane protein functions
junction, enzymes, transport, recognition, anchorage, and transduction
Draw the fluid mosaic model
things within the model
- phospholipids
- integral proteins
- cholesterol
- peripheral protein
- glycoprotein
function of the fluid mosaic model
explains various characteristics regarding the structure of cell membranes
passive transport
along the gradient, no ATP expenditure
active transport
against concentration gradient, ATP is required
Two types of passive transport
- Simple diffusion: net movement of particles from a region of higher concentration to region of lower concentration until equilibrium is reached
- facilitated diffusion: passive movement of molecules across a cell membrane via the aid of a membrane protein (carrier/channel protein)
active transport
uses ATP to move molecules against a concentration gradient
- molecule binds to a transmembrane protein pump, hydrolysis of ATP causes conformational change translocating the molecule across the membrane
osmosis
the net movement of water molecules across a semi permeable membrane from a region of low solute concentration to a region of higher solute concentration (diffusion of free water molecules)
osmolarity
measure of solute concentration which can be measured as:
- hypertonic: high solute concentration (gains water)
- hypotonic: low solute concentration (loses water)
- same solute concentration (no net flow)
biogenesis experiment
- broth was boiled to kill organisms
- control group: flask neck was kept on, and there was no growth; condensation seals the flask and no growth occurred
- experimental group: flask neck was broken, break exposed contaminants. growth occurred
- conclusion: cells only arise from pre-existing cells
law of biogenesis
demonstrated by Louis Pasteur
- broths were stored in sealed vessels that were sterilized
- bacterial growth occurred if vessel was unsealed, but did not occur if vessel stayed sealed
Stages of Mitosis
- Interphase: DNA is uncondensed, replicated (s phase) to form genetically identical sister chromatids, and cell grows in size
- Prophase: DNA supercoils, Nuclear membrane dissolves, centrosomes move to poles and spindle fibers are made
- Metaphase: centrosome spindle fibers attach to centromere of each chromosome, spindle contracts moving chromosomes to cell centre, chromosomes form a line along the equator
- Anaphase: spindle fibers continue to contract, sister chromatids separate and move to opposite sides and are regarded as two separate chromosomes
- telophase: chromosomes de-condense, nuclear membranes form around two identical chromosome sets
cytokinesis occurs - Cytokinesis: cytoplasmic division occurs to divide the cell into two daughter cells
each daughter cell contains one copy of each identical sister chromatid
daughter cells are genetically identical
cell cycle
interphase: G1, s phase, and G2 stages
M phase: period of the cell cycle in which the cell and contents divide - PMAT and cytokinesis
things that occur in interphase
DNA replication, Organelle duplication, cell growth, transcription/translation, obtaining nutrients, cellular respiration
mitotic index equation
mitotic index = cells in mitosis/total number of cells
measure of proliferative status of a cell population
Cyclins
proteins that control progression of the cell cycle
- cyclins bind to the cyclin dependent kinases
- activated complex phosphorylates proteins involved in specific cell cycle events
- after the event has occurred, the cyclin is degraded and the cyclin dependent kinase is rendured inactive
What is cancer/how does it develop
cancer are diseases caused by uncontrolled cell division resulting in abnormal cell growth (tumors)
- benign: tumors that remain in their original location
- Malignant: tumors that spread and invade neighboring tissues
mutagens: agents that change genetic material of cells
Genetics: most cancers are caused by mutations of genes
Cell death occurs through two ways
Necrosis:
- cell loses functional control due to injury, toxins, etc
- destabilization of the membranes, leading to swelling
- cells burst and releases its contents causing inflammation
Apoptosis:
- controlled event triggered by mitochondrial proteins
- cell contents are packaged into membranous protrusions
- cell fragments into apopotic bodies which are recycled
