Chapter 3 Flashcards
1
Q
What is cytology
A
The study of cells
2
Q
What are cells
A
The basic living, structural and functional units of the body
3
Q
What are the 3 main parts of the cell
A
Plasma membrane
Cytoplasm
Nucleus
4
Q
Describe the plasma membrane
A
- Outer surface of cells
- Separates the internal environment from the external environment
- a barrier that is selective
- regulates the flow of materials that go in and out of the cells
- communicates with other cells
5
Q
Describe the cytoplasm
A
Consists of the all the contents in between the plasma membrane the the nucleus
Two components: cytosol and organelles of the cell
6
Q
What is the cytosol of the cytoplasm?
A
Fluids, consisting of intracellular fluid, water, dissolved solutes, and suspended particles
7
Q
What are the organelles of the cytoplasm
A
Cytoskeleton, ribosomes, endoplasmic reticulum, golgi complex, mitochondria
8
Q
Describe the Nucleus
A
Houses the cell’s DNA, contains the chromosomes, genes, and proteins
- controls cell structures and functions
9
Q
What is the concept of selective permeability
A
Permeability permits the passage of substances through it, while being selective means allowing some contents to pass through but not others
10
Q
The plasma membrane has a _______ _______ that is selectively permeable
A
Lipid bi-layer
11
Q
The plasma membranes lipid bi-layer is permeable to:
A
Non polar molecules
O2,CO2, and steroids
12
Q
The plasma membrane’s lipid bi-layer is moderately permeable to:
A
Small, uncharged polar molecules
H2O, urea
13
Q
The plasma membrane’s lipid bi-layer is impermeable to:
A
Ions, large uncharged polar molecules
Glucose
14
Q
Describe the lipid bilayer interior
A
Non polar and hydrophobic
Contains fatty acid tails filled with phospholipids and glycolipids that move around randomly providing small gaps of spaces briefly
15
Q
Explain transmembrane proteins
A
Channels or carriers that increase the plasma membranes permeability for ions and uncharged polar molecules that cannot pass the membrane bilateral without assistance
They are selective, allowing only specific molecules or ions to cross
16
Q
What is the concentration gradient?
A
- The difference in concentration of a chemical from one place to another
(ions or molecules containing more concentration in either the extracellular fluid or cytosol)
17
Q
What is the electrical gradient ?
A
The difference in electrical charges between two regions across the plasma membrane
18
Q
What is membrane potential ?
A
The charge difference
19
Q
The plasma membrane creates a difference in the distribution of + and - charged ions between the two sides. The inner surface is more __ charged and the outer surface is more __ charged.
A
- and +
20
Q
The concentration and electrical gradients move substances across the membrane from a place with ____ concentration to where it is ______ concentrated to reach equilibrium
A
More to less
21
Q
What is the electrochemical gradient ?
A
The combined influence of the concentration gradient and the electrical gradient on the movement of a particular ion
22
Q
What is the difference between an active process and a passive process
A
Active process require cellular energy (usually ATP) to drive the substance uphill against its concentration or electrical gradient
passive processes move substances down its concentration or electrical gradient using its own kinetic energy
23
Q
What are the two main types of active processes
A
Active transport and transport in vesicles
24
Q
What is the difference between active transport and transport in vesicles
A
Active transport - cells use energy to move a substance across the membrane against its concentration gradient with transmembrane proteins that act as carriers
Transport in vesicles- substances move in and out of cells in vesicles that are formed from then plasma membrane created by ATP supplied energy
25
What are the two types of active transport
Primary and secondary active transport
26
What is the process of primary active transport
Energy is obtained from the hydrolysis of ATP to change the carrier proteins shaped and “pump” a substance across the membrane against the concentration gradient
27
Describe the secondary active transport process
Energy that is stored in an ionic concentration gradient is used to drive other substances across the membrane against the concentration gradient
28
What kind of process is the sodium-potassium pump
Primary active transport
29
How does the sodium potassium pump work
- maintains a low concentration is Na+ in the cytosol by pumping the sodium out into the ECF and pulling the K+ in against their concentration gradient
- 3 Na+ in the cytosol bind the the pump protein which triggers the hydrolysis of ATP -> ADP + P (the phosphate group attached to the pump protein to change the proteins shape)
- when the shape changes, the Na+ gets expelled into the ECF, and allows K+ on the ECF side to bind to the protein
- when K+ is binded to the protein, it triggers the release of the phosphate group, counteracting the protein shape to its original, releasing the K+ into the cytosol
This process works nonstop to maintain equilibrium of the concentrations of Na+ and K+ on each side as they often leak back to original places by passive processes and 2ndary active transport
30
Different concentrations of Na+ and K+ in cytosol and ECF maintain a normal ________ _______ and for cells to generate electrical signals such as _________ ________
Cell volume
Action potentials
31
Explain the process of secondary active transport
- stored energy in an ionic concentration gradient is the source of this process
- the energy stored in Na+ or H+ concentration gradient drives other substances (that cannot cross) across the membrane
- Na+ or H+ is established by primary active transport from the hydrolysis if ATP
- due to the sodium-potassium pump, concentration of Na+ is high, and stores potential energy,
- secondary transport proteins harness the potential energy and provide routes for Na+ to leak back in from ECF and the stored potential energy converts to kinetic energy
- kinetic energy is used to transport other substances against its concentration gradient
- the protein acts as a carrier binding to Na+ and other substances, changes it shape and allows both substances to cross the membrane
32
What are vesicles
Small membranous spherical sacs, allows substances to enter and leave cells through these
33
What is the difference between symporter and antiporter
Symporter’s move 2 substances in the same direction
Antiporter’s move 2 substances in opposite directions
34
What is the active process of transport vesicles
Vesicles import materials from cells, and release the materials into ECF
35
What are the two types of transport vesicle processes ?
Endocytosis and exocytosis
36
What is the difference between endocytosis and exocytosis
Endocytosis- materials move into a cell by the vesicles that are formed from the plasma membrane
Exocytosis- materials move out of the cell by fusion with the plasma membrane’s vesicle located on the inside
37
What are the 3 Endocytosis processes
Receptor-mediated, phagocytosis, and bulk-phase
38
What is the receptor-mediated Endocytosis
Cells have specific ligands, which are molecules that bind to specific receptors.
The vesicles form after a receptor protein in the plasma membrane recognize and bind to a particular particle in the ECF
39
What is step 1 of receptor-mediated Endocytosis
Binding
-on the ECF side, a LDL particle that contains cholesterol binds to a specific receptor (known as an integral membrane proteins) which are concentrated in Claritin-coated pits of the plasma membrane
- a protein called clathrin attaches to the membrane on the cytoplasmic side
- multiple clathrin molecules cluster together around the LDL receptor, causing the membrane to invaginate (fold inward)
40
What is step 2 of receptor-mediated Endocytosis
Vesicle formation
- the invaginated edges of the membrane around the clathrin-coated pit begin to fuse and pinch off
- the vesicle contains the LDL receptor complexes
41
What is step 3 of receptor-mediated Endocytosis
Uncoating
- the clathrin-coated vesicle loses its coat, becoming an “uncoated vesicle”
-clathrin returns to the plasma membrane to form coats on other vesicles
42
What is step 4 of receptor-mediated Endocytosis
Fusion with the endosome
- the uncoated vesicle fuses with another vehicle called endosome
- in the endosome, the LDL particles separate from their receptors (the integral membrane protein)
43
What is step 5 of receptor-mediated Endocytosis
Recycling of receptors to plasma membrane
- the receptors accumulate with the endosome which then pinch off, and form transport vesicle that return the receptors back into the plasma membrane
44
What is step 6 of receptor-mediated Endocytosis
Degradation in lysosomes
- other transport vesicles that also contain LDL particles pinch off and bud with a lysosome
- lysosomes contain digestive enzymes, that breakdown the large protein and lipid molecules of the LDL particle into smaller molecules like amino acids, fatty acids, and cholesterol.
- the cell uses cholesterol for rebuilding its membranes and for synthesis of steroids. And fatty acids and amino acids can be used for ATP production or to build other molecules
- these small molecules then leave the lysosome
45
What is phagocytosis?
A cell eating form of Endocytosis
- the cell engulfs large, solid particles (such as worn out cells, bacteria, or viruses)
46
What are the two types of phagocytosis?
Macrophage and pseudopod
47
What is a macrophage ?
A type of White blood cell found in body tissues and neutrophils
- begins when the particle binds to a plasma membrane receptor on the phagocyte causing it to extend
48
What is a pseudopod ?
Projected from the plasma membrane and cytoplasm, surrounding a particle outside the cell
- membranes fuse to form a vesicle called phagosome, which enters the cytoplasm and fuses with lysosomes.
- the lysosome enzymes then breakdown the ingested material (called residual body)
- the residual Josh either gets secreted or stored in lipofusion granules
49
What is pinocytosis
“Cell-drinking” a form of Endocytosis
50
What is the process of bulk-phase Endocytosis
- no receptor proteins involved
- Tiny droplets of solutes dissolved in ECF are brought into the cell
- plasma membrane folds inwards (invaginate) and form a vesicle that contains the droplets
- the vesicle pinches off from the plasma membrane and enters the cytosol
- the vesicle then fuses with the lysosome, where enzymes degrade the engulfed solutes into smaller molecules that leave the lysosome to be used elsewhere
51
Exocytosis releases materials from a cells by 2 types of cells, which are:
Secretory cells and nerve cells
52
What do secretory cells do?
Liberate digestive enzymes, hormones, mucous or other secretions
- wastes can be released by secretory vesicles from inside cells that fuse with the plasma membrane and release their contents into the ECF
- lost segments of the plasma membrane are used by exocytosis
53
What do nerve cells do for exocytosis ?
Release neurotransmitters
54
What is transcytosis?
A transport vehicle that moves substance into a cell by Endocytosis, across the cell; and out of the cell by exocytosis
- the vesicles fuse to the plasma membrane, and contents release into the ECF
55
What are the two main process of the passive transport process
Diffusion and osmosis
56
What is diffusion
The random mixing of particles in a solution because if it’s kinetic energy. Both solutes (dissolved substances) and the solvent undergo diffusion
57
When one solute is in a higher concentration area of a solution, the other is an area of a lower concentration . Solute molecules diffuse toward the area of _______ concentration to evenly distribute the solution
Lower (goes down the concentration gradient)
58
What are the 4 types of diffusion
Simple, facilitated, channel-mediated, and carrier-mediated
59
What are the 4 factors that influence the diffusion rate
1. Steepness of the concentration gradient (bigger the difference between the two sides of the membrane; the higher the rate of diffusion)
2. Temperature (higher the temp; higher the rate)
3. Mass of the diffusing substance (bigger the mass, the slower the rate)
4. Surface area (larger the surface area of the membrane, the faster the rate)
60
What is simple diffusion ?
When a substance moves freely through the membrane without help from membrane transport proteins
- nonpolar, hydrophobic molecules, and small, uncharged polar molecules
61
What is facilitated diffusion
Integral membrane proteins assist a specific substance (too polar or highly charged) across the membrane as a channel or carrier
62
What is the channel-mediated facilitated diffusion ?
Solutes move down it’s concentration gradient across the lipid bilayer through ionic membrane channels at certain sites
- the channels are gated integral transmembrane proteins change their shape in one way to open pores one way and close the other way
- this allows the passage of inorganic ions that are hydrophilic (such as K+, Cl-, Na+, Ca2+)
63
What is the carrier-mediated facilitated diffusion
Solutes bond to a specific carrier on one side, and get released on the other side
- when the solute binds to the carrier, the carrier changes shape
- solutes bind to the carrier in the side with higher concentration
- the concentration is equalized when solutes bind to the cell side, and exit on the ECF side and vice versa at the same time
64
What is the process of osmosis
The net movement of a solvent (water) through the selective membrane from an area of high concentration to the area of low concentration (down the concentration gradient making is a passive process)
However the solute moves uphill in the concentration gradient
- water (solvent) moved through the membrane by neighbouring phospholipid molecules in the lipid bilayer by simple diffusion OR by assistance of aquaporins - integral membrane proteins that act as a water channel
- occurs when a membrane is permeable to water but not to certain solutes
65
What are aquaporins
Integral transmembrane proteins that function as water channels
Controls the water content of cells
Responsible for the production of CSF, aqueous humour, tears, and urine concentration
66
With a U-Shape tube, when water is placed on the left side, and a solute solution is placed on the right side, osmosis occurs when:
-The membrane is permeable to water but not permeable to the solutes
- The net movement of the water goes left to right down the concentration gradient and the membrane prevents solutes on the right to go left
- due to this, the volume of fluid to the right increases and the left decreases due to the movement of water, increase the pressure (hydrostatics pressure) on the membrane forcing the water back to the left to equalize the levels of fluid.
67
What is osmotic pressure ?
The solution with the impermeable solute exerts a force
It is the pressure needed to stop the movement of water from the left into the right to keep the fluid volume equal
The higher the solutes concentration, the higher the solution osmotic pressure
68
What is tonicity?
The measure of a solutions ability to change the volume of cells by altering their water content
69
Osmotic pressure of cytosol is _____ to osmotic pressure of interstitial fluid. This makes cell volume _______.
Equal
Constant
70
Cells in a solution have a different osmotic pressure than cytosol, however the shape and volume of cells change. What are the 3 types of solutions?
Isotonic, hypotonic and hypertonic
71
What is an isotonic solution
NaCl .09%
- Solution where the cell maintains its shape and volume
- The concentration of solutes that cannot cross the plasma membrane are the same on both sides
- cell plasma membrane permits water to move back and forth, but is impermeable to the solutes (Na and Cl)
72
What is a hypotonic solution
Pure H2O
- solution has a lower concentration of solutes than the cytosol of the cells
- water enters the cells faster than they leave which causes the cells to swell and burst (hemolysis)
73
What is a hypertonic solution
NaCl 2%
- the solution has a higher concentration of solutes than does the cytosol of the cells
- water moves out of the cells faster than they can enter.
- this causes the cells to shrink (crenation)
74
What is the cytoplasm ?
- Cellular contents between the plasma membrane and the nucleus
- Include the cytosol and organelles
- site of all intracellular activities other than the nucleus
75
That is the cytosol
Intracellular fluid is the portion of cytoplasm surrounding organelles
- make sup 55% if the cell volume and consists of 75-90% water and dissolved/suspended components such as ion, glucose, amino acids, fatty acids, proteins, lipids, ATP and waste products
- the site of chemical reactions
76
What is the cytoskeleton
A network of protein filaments
- serves as a scaffold that determines cells shape and organize cellular contents
- aids in movement of organelles, within cells of chromosomes and whole cells
77
What are the 3 types of protein filaments
Microfilaments, intermediate filaments, microtubules
78
What are microfilaments
- The thinnest of the 3 protein filaments
- composed of actin and myosin proteins
- generate movement, provide mechanical support (strength and shape)
- involved in muscle contraction, cell division, cell locomotion, migration of embryonic cells, invasion of tissue WBC’s to fight infection, migration of skin cells during wound healing
- anchors to integral proteins
- cell extensions by microvili which increase cell surface area for absorption in the small intestine
79
What are intermediate filaments
-middle in size, very strong
- found in parts of cells subject to mechanical stress
- stabilize the position of organelles and help attach cells to one another
80
What are microtubules
- thicket if the protein filaments
- long unbranched hollow tubes
-composed of the protein tubulin
- found in the Centrosome and grow outward towards the surface of the cell
- determines cell shape and movement of some organelles
81
What is the centrosome structure and function
- structure: pair of centrioles and a pericentricular matrix
- function: builds and organize the microtubules and forms the mitotic spindle for cell division
82
What are the two types of microtubules
Cilia and flagella
83
What is the structure and function of the cilia
- structure: short, hairlike projections extend from the surface of the cell, are anchored to the nasal body below the surface of the plasma membrane
- function: sweeps foreign particles that are trapped, moves fluids along the cell surface
84
What is the structure and function of flagella
- structure: long hairlike structures
- function: move an entire cell by generating a forward motion along an axis, has a head and tail; tail rapidly wiggles giving the momentum
85
What is the structure and function of ribosomes
- structure: there are 2 subunits (small and large), made in the nucleolus then exiting the nucleus and cone together at the cytoplasm. Made up of RNA and proteins. Attach to nuclear membrane and endoplasmic reticulum, location in the mitochondria
- functions: protein synthesis for insertion in the plasma membrane or secretion from the cell
86
What is the endoplasmic reticulum
A network of membranes as flattened sacs (rough ER) it tubules (smooth ER) that extends from the nuclear envelope (membrane) and projects/connects through the cytoplasm
87
What is the structure and function of rough ER
Structure: folded flattened sacs on the outer surface of the ribosomes
Function: enter spaces of the plasma membrane for processing and sorting, procure secretory, membrane, and organelle proteins that get secreted by exocytosis
88
What is the structure and function of smooth ER
Structure: a network of membrane tubules that extend from the rough ER, contain unique enzymes
Function: synthesize fatty acids and steroids
89
What is the structure and function of the golgi complex
Structure: consist of cisterns (cavities) that as small, flat membranous sacs with bulging edges
Function: have different enzymes in each region that permit each area to modify, sort, and package proteins into vesicles for transport to different destinations
90
What are the 3 cisterns and their locations
1) entry (cis) face- faces the rough ER side (transport vesicles form from the ER by merging to create the entry face)
2) medial cistern - in between sacs
3) exit (trans) face - faces the plasma membrane
91
What are the steps of maturing cisterns and exchanges
1) the proteins that are synthesized by ribosomes on rough ER, cluster and form transport vesicles at the membrane surface
2) vesicles move into the entry face
3) fusion of transport vesicles create the entry face and release proteins into the lumen space
4) proteins move from the entry to the medial, and enzymes modify the proteins. Transfer vesicles bud at the edges. Some enzymes move to the entry while others move toward the exit
*5) some products that moved to the exit cistern further get modified, sorted and packaged
*6) some products as the exit are stored in secretory vesicles that deliver proteins to the plasma membrane and ECF by exocytosis
*7) other processes proteins leave the exit face in membrane vesicles that also deliver the products to the plasma membrane
8) the golgi adds new segments of the plasma membrane
*9) other proteins leave in transport vesicles, carrying the proteins to other cells
92
What are the differences between secretory vesicles, membrane vesicles, and transport vesicles
Secretory: sends proteins to the plasma membrane by exocytosis to the ECF
Membrane: proteins leave through these and get delivered to the plasma membrane to be incorporated while the Golgi adds new segments to modify and distribute to the plasma membrane as the existing ones are lost
Transport: carry proteins to other cells
93
What is the structure and function of lysosomes
Structure: are formed by the Golgi complex, they are membranous enclosed vesicles
Function: contain powerful digestive and hydrolytic enzymes that breakdown molecules once fused with vesicles that are formed by Endocytosis
94
What is autophagy
When a lysosome engulfs another organelle, digests it, and returns the contents to the cytosol to be reused (enzymes recycle the worn out cells)
- uses active transport pumps by importing H+ as it works best in acid pH, and also includes transporters and more products to assist with digestion
- organelle bring digested is enclosed by a membrane derived from the ER to create a vehicle called autophagosome that fuses with a lysosome
-involved in cell differentiation, controls growth, and tissue remodelling, helps with cell defence and and adaptation to adverse environments
95
What is autolysis
Lysosonal enzymes destroy the entire cell
- pathological conditions, responsible for tissue deterioration occurring after cellular death
- digest Endocytosis substances, transports products to the cytosol, carry out autophagy, implements autolysis, and then accomplishes extracellular growth
96
What is the structure and function of perioxisomes
Structure: contains enzymes that oxidize by removing oxygen called oxidases, from organic substances, also contains an enzyme called catalase
Function: oxidize toxic substances such as alcohol, A by product of the oxidation reaction os hydrogen peroxide (a superoxide) which is toxic, so the enzyme catalase decompose the superoxide therefore peroxisomes protect other parts of the cell
97
What is the structure and function of proteasomes
Structure: tiny barrel of 4 stacked rings of proteins that surround the core
Function: destroys unneeded, damaged or faulty proteins,myriad proteases enzymes cut proteins into small peptides then other enzymes breakdown the peptides into amino acids to be recycled into new proteins
98
What is the structure and function of mitochondria
Structure: has an internal mitochondrial membrane (folds of mitochondrial cristae surrounds the matrix), mitochondrial matrix (central fluid filled cavity, enclosed by the internal membrane), and external mitochondrial membrane with fluid filled spaces in between the membranes
Functions: generates ATP by aerobic respirations, plays a role in apoptosis
99
What is apoptosis
Genetic program of cell death
100
What is the role of the mitochondrial matrix
Has enzymes that catalyze the reaction for ATP
101
What is the role of the internal mitochondrial membrane cristae
Provided surface area for chemical reactions for aerobic cell respirations producing ATP
102
What is the structure and function of the nucleus membrane
Structure: spherical/oval shape, had a double membrane called nuclear envelope that separates the nucleus from the cytoplasm, had many nuclear pores with circular arrangements of a proteins that surround a large opening
Function: pores control the movement of substances between the nucleus and cytoplasm by passive diffusion (small ions and molecules), or active transport (large molecules like RNA and proteins)
103
What is the structure and function of the nucleoli
Structure: cluster of protein, DNA, RNA enclosed by a membrane , and genes which are arranged along chromosomes
Function: produce ribosomes, sites of synthesis and assembly of rRNA and proteins into ribosomes psi units
Control cell structures and direct cell functions (the powerhouse of the cell)
104
DNA consists of __ chromosomes, with __ each from the mom and the dad
46
23
105
1 single chromosome molecule is coiled together with _____
Proteins
106
What makes up a chromatin
DNA, Proteins, and RNA
107
What is a genome
Total genetic information carried in a cell/organism
108
Before cell division, DNA replicates and loops condense to form _______
A pair of chromatids
109
What are the 2 steps in protein synthesis
Transcription and translation
110
What are the 3 types of RNA and their functions
Messenger (directs protein synthesis)
Ribosomal (joins with ribosomal proteins to create ribosomes)
Transfer (binds to amino acids and hold in place on a ribosome till it’s a protein) - one end Carrie’s an amino acid, the opposite end contains an anticodon
111
What is the process of transcription of protein synthesis
Copies DNA to produce a specific RNA sequence (occurs in the nucleus)
The tRNA anticodon attaches to the mRNA codon
- RNA polymerase (enzyme) catalyzes transcription
- begins at the the “promoter” which is the beginning of a gene of a special nucleotide sequence
- ends at the “terminator” where an enzyme detaches
112
What is the process of translation of protein synthesis
-occurs in the ribosome
- mRNA molecule attaches to a ribosome subunit at the mRNA binding site (where information contained in the RNA gets translated into a corresponding sequence of amino acids to form a new protein
- a special (initiator) tRNA binds to the start codon (AUG) on mRNA (site translation begins and is amino acid methionine, the first amino acid in a growing peptide)
- pairing between the complementary bases (the tRNA anticodon (UAC) attaches to the mRNA codon (AUG) )
- the large ribosomal subunit attaches to the small ribosomal subunit creating the mRNA complex (creates a functional ribosome)
- the initiator tRNAc with the amino acid (methionine) fits into the “P” site of the ribosome and the anticodon if another tRNA with it’s attached amino acid pairs with the second mRNA codon at the “A” site of the ribosome
- a component of the large ribosomal subunit catalyzes the formation of a peptide bond between the methionine and the amino acids carried by the tRNA at the “A” site
- following the formation of the peptide bond, the resulting two peptide proteins become attached to the tRNA at the “A” site
- after peptide bond formation, the ribosome shifts the mRNA strand by one codon, the tRNA in the “P” site enters the “E” site and is released from the ribosome
- the tRNA in the “A” site bearing the two peptide protein shifts into the “P” site, allowing another tRNA with its amino acid to bind to a newly exposed codon at the “A” site
- the protein lengthens as the steps repeat and synthesis ends when the ribosome reaches a “stop” codon at the “A” site causing the protein to detach from the final tRNA
113
What are the 2 types of cell division
Somatic and reproductive
114
What is somatic cell division
Nuclear division (mitosis) and cytoplasmic division (cytokinesis)
-produce 2 genetically identical cells w/ the same number and kind of chromosomes as the original cells
- replace dead/injured cells and adds new ones
115
What are the two main phases of the somatic cell cycle
Interphase and mitotic
116
Describe interphase of the somatic cell cycle
Interphase is where there is high metabolic activity, where cells do most of its growing, and consists of 3 phases
-G1(replicated most organelles and cytosolic components and centrosomes begin)
-S (DNA replication and synthesis begins, 2 identical cells form at the site of cell division later)
-G2 (cell growth, enzymes and protein synthesize in preparation for cell division and replication of centrosomes complete)
117
Describe the mitotic phase of somatic cell division
Formation of 2 identical cells
consisting of nuclear division and cytoplasmic division
118
Describe nuclear division of the mitotic phase of the somatic cell cycle
Distributed 2 sets of chromosomes into 2 separate nuclei
4 stages:
1)prophase- chromatin fibers condense and shorten into paired chromatids. Tubulins in the centrosomes form mitotic spindles, the nucleus disappears and the nuclear envelope breaks down
2) metaphase- microtubules align the centrosomes of chromatid pairs at the metaphase plate
3) anaphase- centrosomes split separating the 2 members of each chromatid pair (chromosomes) which get pulled by the microtubules of the mitotic spindle (separates chromatids) and centre instead stage the arms of chromatids towards the poles on opposite ends
4) telophase- with movement, the sets of chromosomes on opposites poles begin to uncoil and revert to a “thready” chromatin form. The nuclear envelop forms around each chromatin, nucleoli reappear and the mitotic spindle breaks up
119
What is the cytokinesis process of the somatic cell division cycle
Division of cell cytoplasm and organelles into 2 identical cells
Begins in late anaphase - begins to form a cleavage furrow which completed after telophase
- actin microfilaments form contractile rings that pull the plasma membrane inward, and constrict the centre of a cell to pinch it into 2
Once this step completes, interphase begins again
120
What is reproductive cell division
The union of 2 different gamete’s (fertilization) - 1 produced from each parent
Meiosis- occurs in the gonads (ovaries/tested)c produce gametes in which the number of chromosomes is reduced by half, making them haploid cells
121
What are the 2 main stages of reproductive cell decision
Meiosis 1 and meiosis 2
122
Describe the process of Meiosis 1
During interphase before meiosis 1, chromosomes of diploid cells begin the start replicating
Meiosis 1 starts once chromosomal replication is complete
Has 4 phases:
1) prophase 1 (chromosomes shorten and thicken, nuclear envelop and nucleoli disappear, mitotic spindle forms.
2) metaphase 1 (2 sister chromatids of each pair of chromosomes pair off - synapsis resulting in 4 chromatids called tetrads that line up along the metaphase plate side by side. Parts of the chromatids of the 2 chromosomes exchange genes with one another in a proves called “cross over”. This results in genetic recombination, the formation of new combinations of genes for genetic variation)
3) anaphase 1 (each pair of chromosomes separate and pull to opposite piles of the cell by microtubules attached to centromeres, the chromatids are held by the centromere and remain together)
4) telophase 1(the sets of chromosomes on opposites poles begin to uncoil and revert to a “thready” chromatin form. The nuclear envelop forms around each chromatin, nucleoli reappear and the mitotic spindle breaks up)
123
Describe the process of Meiosis 2
Consists of 4 stages:
-prophase 2, metaphase 2, anaphase 2, telophase 2
- similar to mitosis, centromeres spirit, sister chromatids separate and pull towards opposite poles of a cell z
- each of the 2 haploid cells formed during meiosis 1 divides, and the net result is 4 haploid gamete’s that are genetically different from the starting diploid cell.
