What are the steps of cell signaling?
Reception
Transduction
Response
What happens during reception? (cell signaling)
- Receptors on or in the cell bind to a ligand/signaling molecule
- causes change in shape of the receptor
- this is the initial transduction of the signal
What happens during transduction? (cell signaling)
- cascades of molecular interactions
- signals are transmitted from receptors to relay molecules
What happens during response? (cell signaling)
- response occurs in nucleus or cytoplasm
- may turn off or on genes (regulates protein synthesis)
- Other responses include cell division
What are the two types of signaling and how are they different?
Paracrine signaling
- short distance
- cells are touching
Endocrine signaling
- long distance
- uses hormones which travel via the circulatory system
What does a hydrophilic ligand do?
- bind to receptors on the plasma membrane, on the cell surface
- cannot diffuse through the membrane
What does a hydrophobic ligand do?
- can diffuse through the plasma membrane
- bind to internal receptors
How are cell signals amplified?
- Phosphorylation cascades enhance signals
- activates protein and secondary messengers
- stays active for a long enough time to process more molecules
What are G-protein coupled receptors?
- transmembrane receptor
- works with the help of a G protein
- G proteins bind GTP
What are tyrosine kinase receptors?
- membrane receptors
- catalyze transfer of phosphate groups from ATP to other proteins
- Can trigger multiple signal transduction pathways at once
What are ligand gated ion channels?
- acts as a gate that opens and closes when a receptor changes shape
- when open, lets through ions
What is negative feedback?
- brings the system back to its stable state
What is positive feedback?
- increases the change, brings it further away from the initial state
What are the steps of interphase? Describe each one.
G0 - Gap Phase - cell is not preparing to divide/not dividing
G1 - Gap 1 - Cell grows
S - Synthesis - DNA replication occurs, creates two identical sister chromatids for each chromosome
G2 - Gap 2 - Cell grows
M - Mitosis
What are the phases of mitosis in order?
Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
What happens during prophase?
- chromosomes begin to condense
- spindle fibers emerge from the centrosomes
- nuclear envelop breaks down
What happens during metaphase?
- Mitotic spindle is fully developed
- chromosomes are lined up at the metaphase plate (line directly between the centrosomes)
- centrosomes are at opposite poles
- each sister chromatid is attached to a spindle fiber
What happens during anaphase?
- cohesion proteins binding chromatids break
- the now chromosomes are pulled toward opposite poles
- non-kinetochore spindle fibers lengthen, elongating the cell
What happens during telophase?
- chromosomes begin to decondense
- mitotic spindle breaks down
- nuclear envelop material surrounds each set of chromosomes
What happens during cytokinesis?
- The cytoplasm separates into two identical daughter cells
- Animal cells –> cleavage (cleavage furrow appears and the cell splits)
- Plant cells –> cell plate (vesicles fuse into a plate which fuses with the cell wall)
What do cyclins and cyclin-dependent kinases do?
- drive the events of the cell cycle
- cyclin bonds to a cdk to activate it
- cdk activity rises and falls with changes in cyclin concentration
What is apoptosis and when may it be used?
Apoptosis = programmed cell death
It may be used to eliminate unwanted/damaged cells
What is the purpose of cell division in prokaryotes?
- asexual reproduction for unicellular organisms
What is the purpose of cell division in eukaryotes?
Development, growth and repair
