cell cycle / division Flashcards
1
Q
describe how cells are dynamic
A
- sense physical and chemical surroundings and respond in ways that affect their function / development
- proliferation: cell division, maintenance, growth, repair
- determination: irreversible, differentiation of structure / function
- modify shape, metabolism, movement, in response to environment
- senescence: controlled death due to age and damage
2
Q
how does cellular communication occur
A
- environmental signals: chemical (extra / intra cellular molecules)
- cell signalling pathways, nutrient conc. (rate of division) or intracellular signals (damaged DNA, molecular signal)
- short term: activate enzyme, adjust metabolism
- long term: gene expression, synthesis new proteins, follow up response
3
Q
what are cell signalling pathways
A
- responsible for cellular messaging , chemical signals enter cell to stimulate a receptor protein
1. reception: connection of signal molecule to receptor embedded in protein (cell membrane), conformational change, cascade of events
2. transduction: higher affinity to interact with another relay molecule, amplify message, widespread response
3. response: activation of cellular response of a protein - specificity: depends on cells collection of proteins involved, signal receptors, relay, and proteins, responsible for response
- ability for different effects to occur in different cells
4
Q
what are different type of cellular responses for adrenalin and liver cells
A
- responses can be diverse as the range of cellular activities
adrenaline:
1. G protein-coupled receptor, G-protein binds to receptor switches it on
2. conformational change, sequential activation of enzymes
3. phosphorylation of G protein
4. protein kinase phosphorylate other proteins
liver: glycogen to glucose - generating energy from stores, sequence of relay proteins produce a response
- one molecule = flood of glucose (amplification)
5
Q
how is transcription regulated
A
- simplified transduction pathway: activation of transcription factor
- protein kinase cascade: phosphorylation, activates transcription factor
- transcription factor: inhibition / activation, activate gene regulating protein
- cell signalling pathways: action of multiple transcription factors
6
Q
how is the cell cycle and gene expression regulated
A
- timing and rate is critical for normal cell growth
- controlled by internal and external signals / checkpoints with molecular ‘stop’ and ‘go’ signals
7
Q
what is the RAS pathway
A
- stimulates cell cycle
- ras gene: encodes for G protein that relays a signal received by a receptor (RTK)
- synthesis of protein stimulates cell cycle (transcription activation)
- mutation: change in amount of protein / intrinsic activity, becomes an oncogene (tumour)
8
Q
what is the P53 pathway
A
- inhibits cell cycle
- P53 gene: endorse for protein that surpasses cell cycle, specific transcription factor for a cell cycle inhibiting protein
- mutation: ‘knocks’ it out, excessive cell division of cells with damaged DNA (possible cancer)
9
Q
what is cell senescence
A
- apoptosis: controlled ‘cell suicide’ (death)
- molecular ‘death signals’ trigger cascade of ‘suicide proteins’
- receptor for death signalling molecule
- damage: nucleus (damaged DNA) or ER (excessive / misfiled proteins)
- proteases and nucleases chop up DNA, organelles and other components
- packaged and engulfed by scavenging cells
10
Q
what are the different forms of DNA / chromosomes
A
- chromatin: loose chromatin threads,
- chromosome: tightly coiled DNA and protein (histone) complex to enable accurate division
- eukaryotic cells: store genetic information in chromosomes, human somatic cells (46 pairs)
11
Q
diploid vs haploid
A
diploid: a cell possessing two copies of each chromosome
- human body cells (somatic)
- 2n = 46, 23 pairs (one from each parent)
haploid: a cell possessing a single copy of each chromosome
- human sex cells (gametes) are n = 23 (one from each pair represented)
12
Q
how are chromosomes arranged during division
A
- homologous chromosomes: occur in pairs of somatic cells, similar but not identical (genes for same characteristics but different coding)
- sister chromatids: joined at centromere, identical copies, replicate before mitosis, identical coding
13
Q
briefly list the phases of the cell cycle
A
- interphase: G1 (primary growth phase), S (genome replicated) and G2 (secondary growth phase)
- mitotic phase: prophase, pro-metaphase, metaphase, anaphase, telophase
- cytokinesis (C): division of cytoplasm
14
Q
what happens during interphase
A
- G1: cells undergo majority of growth (2n)
- S (synthesis): chromosomes replicates to produce sister chromatids attached at a centromere
- G2: mitosis will occur after this phase, chromosomes start to condense and single centrosome has been replicated, nucleus intact with prominent nucleoli (4n)
15
Q
what happens during mitotic phase
A
- prophase: chromosome formation completed, assembly of spindle apparatus commences (microtubules), RNA synthesis stops (nucleoli shrink and disappear)
- pro-metaphase: nuclear envelope breaks apart, microtubules connect kinetochores sister chromatids, non-kinetochore microtubules interact
- metaphase: distinctive, spindle has formed, centrosomes are at opposite poles, chromosomes align across cells centre / equator (metaphase plate)
- anaphase: sister chromatids pulled towards poles, kinetochore microtubules shorten, centromere move toward poles, non-kinetochore microtubules lengthen (poles move, elongation of cell)
- shortening of kinetochore microtubules: ‘flying fox’ (movement along tubules), microtubules dismantled at kinetochore, motor protein causes movement along microtubule - telophase: spindle disassembles, nuclear envelope forms around each set of sister chromatids, two genetically identical nuclei have formed
- cytokinesis: cleavage of cell into two halves, cleavage furrow forms by the constriction of a belt of protein ‘cables’ (microfilaments), division of cytoplasm to form two daughter cells (2n)
