Unit 3: Cell Cycle Flashcards
Represents a self-regulated sequence of events that controls cell growth and cell division
Cell cycle
goal of cell cycle
produce 2 daughter cells, each containing chromosomes identical to those of the parental cell
2 principal phases of cell cycle
interphase & m phase (mitosis)
phospholipid bilayer; hydrophobic head & hydrophobic tail in 2 layers
cell membrane
what does the cell membrane contain?
cholesterol
cardiolipin
shingomyelin
oligosaccharides
membrane proteins
integral proteins
membrane proteins
lipid-anchored proteins & peripheral proteins
membrane proteins
several organelles are found in?
cytoplasm
organelles are suspended in a fluid-filled region called?
cytosol
T/F: The presence and abundance of the different organelles varies between different tissues and different organisms
T
Non-membrane bound organelles that are responsible for the synthesis of protein
ribosome
building block of a protein
amino acid
sequence of a ribosome
mRNA → transcription → reading of codons (translation) → synthesis of a specific protein mRNA
ribosome is made up of?
small subunit (40S) & large subunit (60S)
contains protein and rRNA which are synthesized
in the nucleolus
rubosome
where can ribosomes attach?
rough ER
cytoplasm (free floating)
perinuclear membrane
Double membrane-bound organelle
endoplasmic reticulum
Appear as folded layers that seems to be connected to the nuclear membrane
endoplasmic reticulum
responsible for protein synthesis because of the ribosomes embedded in this membrane
rough ER
double membrane folded in layers is called in such a way because of the absence of the ribosome in its membrane
smooth ER
responsible for glucose and lipid synthesis
smooth ER
network of smooth membranes consisting of flattened, disc-like cisternae with dilated rims and associated vesicles and tubules
golgi body
Where the newly synthesized protein is processed and modified
golgi body
Sorts and packs the proteins / products produced by the cell
golgi body
T/F: golgi body encloses the products and produces vesicles containing proteins which travel to the extracellular environment via endocytosis
F; exocytosis
Provides energy to the cell by producing ATPs in a process called cellular respiration
mitochondrion
Contains several enzymes and proteins embedded in its inner membrane called cristae
mitochondrion
● A type of plastid which is found in plant cell
● Contains chlorophyll located at the thylakoid membrane
● The thylakoids are stacked together to form granum
(plural grana) suspended in stroma
● Responsible for the process called photosynthesis
chloroplasts
complex structure that contains two barrel shaped centrioles surrounded by amorphous, electron dense pericentriolar material PCM
centrosome
A single membrane-bound organelle
In animal cells, vacuoles are generally small and help sequester waste products
In plant cell, this is a fluid filled structure that is made up mostly of water
vacuole
An elaborate interactive network composed of three well defined filamentous structures
○ Microtubules
○ Microfilaments
○ Intermediate filaments
cytoskeleton
Provide structural support and internal framework responsible for positioning various organelles within the interior of the cell
Provides movement of materials and organelles in cell
cytoskeleton
Found in the interior of the cell where they maintain cell shape by resisting compressive forces
microtubules
Thicken the cortex around the inner edge of a cell; they resist tension
microfilaments
Found throughout the cell and hold organelles in place
intermediate filaments
● Also known as microbodies
● Membrane bound, multifunctional organelles that carry out a diverse metabolic reactions including substrate oxidation leading to formation of hydrogen peroxide
peroxisomes
● The command center of the cell because it commands the cellular activity of the entire cell
● Made up of:
- Nuclear membrane
- Chromosomes
- Nucleolus
nucleus
● Each of these membranes contains two layers of phospholipids, arranged with their tails pointing inward (forming a phospholipid bilayer)
● It contains nuclear pores for easy transport of materials such as mRNA to the cytoplasm
nuclear membrane
● Threadlike strands of nuclear DNA with proteins called histones
● These are carrier of genetic materials that occur by pairs (with homologous chromosomes)
chromosome
T/F: In meiosis, the chromosomes condensed from chromatin to meta-chromosome becoming more visible under the light microscope
F
● Found inside the nucleus suspended in nucleoplasm
● Is an irregular-shaped nuclear structures that function as ribosome-producing organelle
nucleolus
nucleolus is more prominent during what stage?
interphase
● A rigid structure found in plants
● This provides support and protection for the cell it
surrounds
cell wall
cell wall contains
pectin
glycan
cellulose microfibrils
Expands from primary cell wall to middle lamella
Monitor and modulate the progression of cells in
response to intracellular or environmental signals
checkpoints
Internal quality control mechanisms represented by
biochemical pathways that control transition between cell cycle stages
checkpoints
checkpoints are introduced by?
Leland Hartwell and Ted Weinert (1988 )
Defined as the failure to arrest the cell cycle before or at mitosis, resulting in aberrant chromosome segregation
mitotic catastrophe
Caused by malfunction of cell cycle checkpoints and may lead to cell death and tumor cell development
mitotic catastrophe
T/F: in mitotic catastrophe, malignant cells lose contact inhibition
T
a normal process where a cell inhibits cellular division once in contact with a cell
contact inhibition
The Cell Cycle Is Regulated by?
protein kinases
The key enzymes that control the transitions between the different states of the cell cycle, and the entry of nondividing cells into the cell cycle, are the?
cyclin-dependent protein kinases, or CDKs
T/F: Endogenous hormones such as auxin, cytokinins, abscisic acid, gibberellins and brassinosteroids as well as environmental factors all regulate progression through the cell cycle
T
T/F: Cell cycle events take place with clock-like precision
T
A group of highly conserved serine/threonine kinases
cyclin-dependent kinases(CDKs)
are among the most important core cell cycle regulators
cyclins
help to promote passage through “ Start” or the restriction point in late G1
G1-cyclins
bind Cdks at the end of G1 and commit the cell to DNA replication
G1/S-cyclins
binds Cdks during S phase and are required for the initiation of DNA replication
S-cyclins
promote the events of mitosis
M cyclins
are enzymes that phosphorylate proteins using ATP
protein kinases
T/F: The regulated activity of CDKs is essential for the transitions from G1 to S and from G2 to M, and for the entry of dividing cells into the cell cycle.
F; nondividing
2 tyrosine phosphorylation sites of cdks
one causes activation and one causes inactivation
T/F: The transition from G1 to S requires a set of cyclins ( G1 cyclins) different from those required in the transition from G2 to mitosis, where mitotic cyclins activate the CDKs
T
T/F: Specific kinases carry out both the stimulatory and the inhibitory phosphorylation
T
can remove phosphate from CDKs, either stimulating or inhibiting their activity, depending on the position of the phosphate
protein phosphatases
2 CDK important mechanisms
- cyclin synthesis & destruction
- phosphorylation & dephospho of key amino acid residues w/in the CDK protein
T/F: CDKs are inactive unless they are associated with a cyclin
T
are synthesized and then actively degraded (using ATP)
at specific points in the cell cycle
cyclins
Cyclins are degraded in the ______ by a large proteolytic
complex called the ________.
cytosol, proteasome
T/F: Before being degraded by the proteasome, the cyclins are marked for destruction by the attachment of a small protein called ubiquitin, a process that requires ATP
T
It is when the cell prepares itself for cellular division
interphase
Usually the longest and the most variable phase of the cell cycle, and it begins at the end of M phase
G1 phase
The cell gathers nutrients and synthesizes RNA and proteins necessary for DNA synthesis and chromosome replication
G1 phase
G1 phase hrs
9-12
damage checkpoint
monitors the integrity of newly replicated DNA
G1 DNA
○ Sensitive to the size of the cell, the state of the cell’s physiologic processes, and its interactions with extracellular matrix
○ Mediated by interactions between pRb and a family of E2F with target promoters
○ In normal cells, proper interaction between pRb and E2F turns off many genes and blocks cell-cycle progression
Restriction checkpoint
● DNA is replicated
● Chromosome replication is initiated at many different
sites along the chromosomal DNA → replicon
● Checkpoint: S DNA-damage checkpoint
S phase
S phase hrs
7.5 to 10 hrs
