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Bio 1010 Cell Bio Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the 3 components of the cell theory?

A

(1) All organisms are composed of one or more cell(s)
(2) The cell is the structural unit of life
(3) Cells can only arise from existing cells

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2
Q

What is the difference between TEM and SEM Microscopes?

A

Both are electron microscopes, TEM is a transmission EM that examine the internal structure of a cell/specimen, wheres as an SEM (scanning EM) creates a 3D image of the specimen/cell by scanning the surface

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3
Q

What makes a prokaryotic cell differ from a eukaryotic cell?

A

Prokaryotes do not have membrane-bound organelles, and in fact instead of a nucleus have a “region” of their DNA known as the nucleoid (circular DNA).

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4
Q

Explain why cells cannot grow infinitley in size (why are they so small)?

A

They are small because of the necessary surface-to-volume ratio: as volume increases, SA begins to decrease, posing a problem as the membrane serves as a way for gas, food, and waste exchange.

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5
Q

What is the nuclear lamince?

A

The structure surrounding the nuclear envelope, providing stucture for the nucleus.
It disintegrates during mitosis.

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6
Q

What is the function of the nucleolus?

A

It is the smaller region found in the nucleus, that makes ribosomes (the small and large subunits).

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7
Q

What are the 3 places ribosomes can be found?

A

(1) In the cytosol (free ribosomes)
(2) Bound to membranes of the ER or nucleus
(3) Mitochondria (structurally different from first 2)

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8
Q

What are some of the functions of the smooth ER?

A
  • Lipid synthesis
  • Detoxifying the cell (i.e. a lot of smooth ER in the liver)
  • Storing Ca Ions
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9
Q

What is the function(s) of the rough ER?

A

Primarily responsible for making proteins-to be on membrane, exported out of cell, or to be sent to other organelles.

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10
Q

Where do the proteins made in the ER go after? and how do they get there?

A

They are transported via vesicles, created in the lumen of the ER, to the Golgi Apparatus.

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11
Q

What are the compartments of the Golgi called? Explain the Cisternal Maturation Model.

A

The compartments of the Golgi are called cisternae, there are usually 7 of them. They start by collecting vesicles from the ER to form cistern #1 (this side is called the CIS cisternae). From there, the cistern begins moving down the line to the TRANS side, as the last cisternae becomes recycled (breaks apart into vesicles, carried to designated location).

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12
Q

Explain the function of the Golgi Apparatus

A

The Golgi modifies porteins sent in from the ER, by adding sugars, or trimming proteins, etc.
The Golgi residence enzymes are what aid in this.

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13
Q

How does the lysosome often form? What is its function?

A

The lysosome commonly comes from a vesicle that buds off from the trans side of the golgi.
The lysosome acts as a stomach of the cell, by breaking down polymers into their monomers for uses elsewhere in the cell. It can also break down entire organelles.
It does this via hydrolytic enzymes (recall polymers break down via hydrolytic reaction) in which only work in low pHs.

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14
Q

What is Autophagy?

A

Autophagy is the process of breaking down damaged or old cellular components, such as organelles or large proteins, so their monomers can be re-used.
This often happens via the lysosome.

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15
Q

What are the 3 main components of the cytoskeleton? List them in order of increasing size.

A

(1) Microfilaments
(2) Intermediate filaments
(3) Microtubules

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16
Q

Describe the structure of a microfilament, and what is it primarily composed of.

A

Microfilaments are rope-like structures that make up part of the cytoskeleton. They are made exclusively of a protein called actin (or g-actin, as it is a globular protein).

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17
Q

What protein do microfilaments often associate with? What is the function of their interaction?

A

They associate with the motor protein: Myosin.
This interaction has a few main functions:
(1) Muscle contraction/general contraction- the myosin can pull actin close, or keep it relaxed
(2) Cytokinesis via contraction- The microfilaments form a belt around the cell (in the extracellular matrix) and the myosin can pull on this belt, squeezing the cells to form into 2
(3) The microfilaments can act as a railway for myosin to walk on, myosin can attach the the microfilaments, as well as another structure (vesicles, organelles) to move them around the cell

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18
Q

Where are microfilaments typically found?

A

The extracellular matrix and the cortex.

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19
Q

Describe the structure and composition of microtubules.

A

Largest of the 3 cytoskeletal components, hollow-like rods.
Composed of a protein called Tubulin, existing only in dimers of a and b tubulin. The dimers form chains called protofilaments, and when there are 13 protofilaments they form a ring, which becomes the microtubule with the hollow interior.
Since the tubulin occurs as dimers, one end of the microtubule is the B (plus end) and one is the A (minus end). The plus end is where the microtubule can be assembled or de-assembled quickly.

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20
Q

Where do the microtubules come from in the cell? Where are they mainly located?

A

Microtubules grow out of the centrosomes, which is composed of centrioles, and when centrioles are in pairs they are at right angles to eachother.
Each centriole is made of 9 triplets of microtubules. They then act as railway tracks for the cell, or as extensions of the cell (flagella or cilia).

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21
Q

What motor proteins do microtubules interact with?

A

They interact with Kinesins (walks toward plus end), and Dynin (walks toward minus end).

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22
Q

Compare and contrast Flagella and Cilia.

A

Both are extensions off of a cell containing microtubules. They both allow cells to move, flagella are typically 1-2 per cell and have a snake-like motion. Cilia usually come in large number on cells, and have a rapid back-and-forth motion.
In some cases, cilia can occur by itself and in that case it is not for mobility, but rather a cell-signalling mechanism.

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23
Q

Explain the structure of the microtubules that make up a flagellum or cilia.

A

Arranged in a 9+2 arrangement: 9 doublet microtubules, and 2 in the centre holding the structural-ring together. This is called an axoneme, and extends from an area of the centriole known as the basal body.
Note nonmotile primary cilia have a 9+0 arrangement.
These

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24
Q

Explain the role the motor protein Dynein has on cellular extensions.

A

Dynein attached it self to 2 doublet pairs of the microtubules in the flagellum/cilium, and walk toward the minus end of he microtubule. This uses ATP and causes the bending motion of the flagellum and cilliim.

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25
Q

What type of cells (animal, plant, prokaryotic, etc.) are intermediate filaments typically found in?

A

Animal cells, specifically vertebrates.

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26
Q

Explain intermediate filaments structure and how they differe from the other 2 cytoskeletal structures.

A
  • They are nonpolar, unlike the other 2 , meaning both of their ends are chemically identical (explaining their un-involvement in motility in the cell).
  • More stable, resist more tension, less prone to assemble and dissemble quickly.
  • Composed of 70+ proteins; whereas the other 2 have 1 exclusive protein that they are made of
  • rope like, similar to microfilaments
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27
Q

Explain the function of intermediate filaments.

A

They are responsible for reinforcing the shape of the cell, as well as keeping various organelles in place.
-They make up the nuclear lamina, as well as they hold the nucleus in place from the outside.

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28
Q

What are glycoproteins and glycolipids and where are they typically found in the cell?

A

They are lipids or proteins with polysaccharides attached. They are common in the extracellular matrix. (made in Golgi)

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29
Q

What is a tight cell junction?

A

When the membranes of surrounding cells ae almost “fused”, preventing any extracellular fluids to seep through (impermeable).
Helpful in intestinal cells.

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30
Q

What are desmosomes?

A

Known as anchoring junctions between cells; they fasten cells together in tight sheets, held in place in the cell by intermediate filaments.

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31
Q

What are gap junctions?

A

Also called “signalling junctions”, they are cytoplasmic channels between cells. They can allow molecules or ions to pass between cells via channels, important for food and communicating purposes.

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32
Q

How do monomers generally bond together?

A

Through a condensation reaction (also known as dehydration synthesis), where a water molecule is produce when the bond is formed.

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33
Q

Where do most of the reaction involving breaking up polymers/building up polymers take place?

A

The lysosome.

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34
Q

What is the difference between alpha and beta glucose?

A

Alpha glucose and beta glucose have alternated hydroxyl groups on the first carbon. (in alpha glucose the hydroxyl is facing down, and in beta it is facing up).

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35
Q

What is the main function of polysaccharides?

A

Our body can either harvest energy from them through eating, or they can store energy through them.

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36
Q

What is glycogen and what is its function?

A

-Glycogen is a polysaccharide composed of glucose molecules, and is the main energy storage unit for animals.
-Animals store their carbohydrates as this and break it up via hydrolysis reactions when needed.
Its a long, branched molecule.

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37
Q

What is starch, and what is its function?

A
  • Starch is a polysaccharide of glucose, and has 2 forms: amylose and amylopectin. Amylose is a non branched chain with 1-4 linkages, whereas amylopectin is slightly branched with 1-4 linkages and then 1-6 linkages for branches.
  • This is the energy storage unit for plants, and is what provides animals of their glucose content.
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38
Q

What is cellulose and what is its function?

A

Cellulose is used for structure in plant cells (i.e. plant cell walls). It is composed of beta-glucose molecules, preventing most animals from digesting it.
This allows it to serve as a source of fibre.

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39
Q

What is the bond between two monosaccharides called?

A

A glycosidic linkage.

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40
Q

What are the 3 common disaccharide and what are their monomers?

A

(1) Maltose-2 glucose
(2) Surcose- glucose + fructose
(3) Lactose- galactose + glucose

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41
Q

What is the empirical formula for a carbohydrate?

A

1:2:1 (c1:h2:o1)

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42
Q

Explain the structure of a triglyceride, and its function.

A

A triglyceride is composed of 1 glycerol molecule, bonded to 3 fatty acid chains via hydrolysis.
The bond between the glycerol and fatty acids is known as an ester linkage.
This type of fat is what makes up the visible fat on your body, for warmth and protection.

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43
Q

What is a saturated vs. unsaturated fat (fatty acid) ?

A
  • Saturated fats contain no double bonds between their carbons, whereas unsaturated fats have at least 1 or more.
  • The double bond in a fatty acid causes the tail to kink, preventing the tails from locking together as tightly. This increases the fluidity of the fat (liquid at room temp), allowing for easier breakdown than the saturated fat.
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44
Q

Where are saturated fats found? Where are unsaturated fats found?

A

Saturated fats come from mainly animals, where as unsaturated fats come mainly from plants and oils.

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45
Q

What are the 2 types of unsat fats?

A

Cis an trans, referring to the branching pattern after the double bond. Cis unsat fats are the fluid ones, that cause a kink in the chain. Trans fats, on the other hand, are almost exactly the same as saturated fats.

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46
Q

How were trans fats created?

A

Unsat fats have a relatively short shelf life, so people discovered they can be hydrogenated to form saturated fats with longer shelf lives, but trans fats were a byproduct of this.
Trans fat have a very long shelf life, and taste very good, but are terrible for human health.

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47
Q

What is the structure and function of a phospholipid?

A
  • Composed of a glycerol molecule bonded to 2 fatty acid chains, and one phosphate. This phosphate is then bonded to an r-group.
  • Component of cell membranes due to its amphipathic property.
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48
Q

What is a steroid and what is cholesterol? How are they related?

A

A steroid is a lipid composed of 4 hydrocarbon rings, and it is an amphipathic molecule.
Cholesterol is a type of steroid, in which other steroids or hormones are synthesized. It is common in cell membranes.

49
Q

What is the stucture of an amino acid?

A

A central carbon, with a carboxyl group, amino group, hydrogen, an special r-group attached.

50
Q

About how many amino acids are there and how are they classified?

A

There are about 20, divided into (1) Hyrdophobic (2) Hyrdophillic (3) Electrically charged (and also hydrophillic)
-Their classifications are based on their r-group

51
Q

What is the primary structure of proteins?

A

Chain of linear amino acids (non branched) and this dictates all further levels of folding.

52
Q

What is the secondary structure of proteins?

A

Secondary structure consists of small localized hydrogen bonding (stabilizing) that can lead to the alpha helix structure, or the beta pleated sheet structure.

53
Q

What is the tertiary stucture of proteins?

A
  • Stabilized 3D shaped by the bonding between the r groups.
  • Hydrophobic components will be tucked inside, as well as disulphide bridges can also form between two cysteine amino acids.
  • This stucture gives the protein functionality
54
Q

What is the quaternary stucture of protein?

A

Involves the interaction between 2 or more separate proteins to form a single functional protein (ex. hemoglobin).

55
Q

What are the cellular membranes composed of?

A

About 50% protein, 50% lipid, and some carbohydrates in the form of glycoproteins and glycolipids.

56
Q

Explain the composition of the lipid bilayer.

A

The phospholipids form a bilayer due to the amphipathic property. The heads face out, and the fatty acid tails face in, occurring in pairs so each head can face out of the stucture and also in toward the structure.
-Each of these in a pair is called a lethlet, the one facing the cytoplasm: cytoplasmic lethlet, and the one facing away from the cytoplasm is the exoplasmic lethlet.

57
Q

What are some of the things that can increase the fluidity of the membrane?

A

(1) Unsaturated fats increase the fluidity, as do especially well in cold environments as they freeze less easily.
(2) The enzyme flippase allows the lethlets to flip if necessary, since the phospholipids rarely flip over, and just move side-to-side, or switch horizontal position with eachother.
(3) Cholesterol can be imbedded in the membrane (rings facing in, OH group facing out). It affects the fluidity based on temperature: in warm temperatures it will make the membrane more rigid, and in cold temperatures it will increases fluidity.

58
Q

What is the difference between integral and peripheral membrane proteins?

A

Integral membrane proteins penetrate right through the hydrophobic region, where as peripheral membrane proteins are located on the surface of the membrane (more loosely attached) either on the extra/intra cellular side.

59
Q

What are transmembrane proteins?

A

Transmembrane proteins are a type of integral protein that spans throughout the entire membrane, where as some of the integral ones will only partway pass through the hydrophobic interior.
They tend to have an a-helices structure, and are usually asymmetric.

60
Q

How are the peripheral proteins held in?

A

On the intracellular side they are held in by the microfilaments, and on the extracellular side they are held in by the ECM.

61
Q

Where are gycolipids and glycoproteins found? What are their function?

A

They are found on the exoplasmic lethlet exclusively, and are used as a type of “flag” to identify/communicate with other cells (i.e. blood type).

62
Q

What are the 2 types of passive transport?

A

(1) Simple
basically diffusion: small non-polar molecules can pass directly through the cellular membrane, such as O2 or CO2.
(2) Facilitated Diffusion
-Channels assist larger/polar molecules to pass through the membrane (i.e. aquaporin allows water to pass through).
-Some channels allow ions to pass through either by just by diffusion(still specific to a particular ion) or by stimulus driven: changing its 3D shape.

63
Q

What is active transport?

A

Involves moving molecules against their concentration by using ATP, requiring transport proteins (i.e. sodium or potassium pumps).
-Involves a conformational change: ex. bind to 3 Na on intracellular, protein changes via ATP and Na goes into the extracellular side, where 2 K can bind and be transported to the intracellular side. This process repeats.

64
Q

What is co-transport?

A

A form of active transport where ATP is not directly assisting.
Example. The proton pump uses ATP, but then the Surcose-H+ co-transporter allows surcose to pass through as the hydrogen goes down is conc. gradient (so the proton pump only pumps hydrogen to allow it to power the other transporter).

65
Q

What are the 2 types of bulk-transport?

A
  • Endocytosis: pinocytosis and phagocytosis.
  • Phagocytosis consists of a molecule fusing with the membrane and being brought in as a vesicle, or by pseudopodium: cellular extensions composed of microfilaments gather in the molecules and form a vesicle
  • Pinocytosis uses the same mechanism but for water or other liquids.
66
Q

What is receptor-mediated endocytosis and how does it differ from normal endocytosis?

A

The vesicle process for this mechanism only occurs when specific molecules (ligand) bind to receptors on the membrane: allowing for only specific molecules to be brought in, rather than at random done by regular endocytosis.

67
Q

What does a neg vs. pos delta G (Gibbs free energy of a system) entail?

A
  • A pos delta G is an endergonic reaction is a non spontaneous reaction that requires energy, and is less stable formation
  • A neg delta G is an exergonic reaction meaning energy is released via a spontaneous reaction ending in a more stable formation
68
Q

What the efficiency of our body in making ATP?

A

About 40% (the rest is turned to heat).

69
Q

What the process by which ATP is made in all parts of cellular respiration other than in the ETC/Chemiosmosis.

A

Substrate-level phosphorylation.

70
Q

What are the products of glycolysis?

A

(1) 2 pyruvate molecules (2 3C)
(2) Net of 2 ATP
(2) 2 NADH

71
Q

What is the endosymbiont theory? What does it explain about the mitochondria?

A
  • That early in evolution a eukaryotic cell engulfed a small prokaryotic cell via endocytosis, and the prokaryotic cell had ability to make ATP so the cell did not digest it but rather kept it.
  • It explains the 2 membranes of the mitochondria (normal membrane of prokaryotic cell and the vesicle)
  • Explains the circular DNA
  • Explains the different ribosomes.
72
Q

What are the products of pyruvate oxidation? Where is is done?

A

Completed in the matrix, it begins with a pyruvate molecule (2 per glucose) and produces 1 CO2, 1 NADH, and 1 acetyl co-A molecule. (x2 for each glucose).

73
Q

What are the products of the TCA cycle?

A 
Per glucose molecule: 
4 CO2
6 NADH
2 FADH2
2 ATP
74
Q

What is the end product of the TCA cycle that combines with acetyl coA? What does it form?

A

Acetyl coA (2c) combines with end product oxaloacetate (4c) to make citrate (6c).

75
Q

What are the 2 components of oxidative phosphorylation?

A

(1) ETC

(2) Chemiosmosis

76
Q

How many complexes are in the ETC? Which ones pump hydrogen?

A

There are 4 complexes: #1,3,4 pump hydrogen via the electrons provides from NADH and FAdH2. Cytochrome Q does not pump hydrogen.

77
Q

What does the complex #4 (cytochrome oxidase) do in addition to pump H?

A

It delivers the electrons to oxygen, which forms water. At this complex the electrons have no where to go, so they need to be collected by something.

78
Q

How many hydrogens can FADH and NADH pump?

A

NADH contributes electrons at complex #1, so it can pump 3.

FADH2 contributes electrons at complex #2, so it can only pump 2.

79
Q

What does ATP synthase complex do?

A

Pumps hydrogen out of the inner membrane into the matrix, which powers the reaction to convert ADP to ATP. This hydrogen gradient creates the proton motive force.

80
Q

How many ATP are made during oxidative phosphorylation? How many total per 1 glucose molecule?

A

26 or 28, leading to a total of 30 or 32 total ATP made.

81
Q

What is the composition of ATP?

A

(1) Three phosphates
(2) Ribose sugar in centre
(3) Adenine (amino acid/nucleotide)

82
Q

What does the hydrolysis of ATP create?

A

ADP + inorganic phosphate + energy (neg delta G)

83
Q

What are the 2 main things that ATP can power?

A

(1) Transport work-triggers conformational change on membrane proteins
(2) Mechanical work-drives motor proteins (i.e. myosin).

84
Q

What does the oxidation of NADH release?

A

Becomes NAD+, and releases 2 electrons plus a hydrogen.

85
Q

What does the oxidation of FADH2 release?

A

Becomes FAD+, and releases 2 electrons and 2 hydrogens.

86
Q

What are the 2 types of direct cell signalling?

A

(1) Through gap junctions

(2) Cell-cell recognition-bumping into eachother

87
Q

What is paracrine and endocrine signalling?

A

(1) Paracrine signalling is local, and is when a cell releases a signalling molecule to hit another target cell
(2) Endocrine signalling is a long distance form of cell communication, commonly involving hormones, that are released by endocrine cells into the bloodstream to hit specific target cells in another part of the body

88
Q

What are the 3 main kinda of transmembrane proteins that are involved in cell reception?

A

(1) G-protein coupled receptors (GPCRs)
(2) Receptor tyrosine kinases
(3) Ion channels

89
Q

How is a g-protein activated?

A

When a specific ligand bind to the GPCR on the extracellular lethlet the GPCR is activated, changing its shape on the cytoplasmic lethlet, allowing an inactive g-protein to bind to it, and then subsequently replace the bound GDP with a GTP, activating the g-protein.

90
Q

When a g-protein becomes activated what happens to the GDP its attached to (i.e. does it go through a reaction to become ATP or ?)

A

The GDP is not phosphorylated, but rather is just replaced with a GTP molecule.

91
Q

Once the activated g-protein is bound to the specific enzyme in the membrane, how does the signalling stop? (i.e. how does the g-protein inactivate).

A

The signalling response will only stop once the phosphate is cleaved off from the protein to become GDP. This is completed by the g-protein itself, as it has GTPase activity.

92
Q

What is a kinase?

A

Any enzyme that catalyzes the transfer of a phosphate onto a molecule.

93
Q

How is a receptor tyrosine kinase activated?

A

Once a ligand binds to each of the 2 monomers, they come together as a dimer. Once they are as a dimer it is activated, allowing each tyrosine kinase to phosphorylate the other tail end of the other monomer: takes a phosphate off an ATP and onto the amino acid tyrosine. Per dimer, 6 ATP are used.

94
Q

What does each activated tyrosine on the receptor allow?

A

Specific relay proteins to bind to it, creating conformational changes and ultimately cellular responses.

95
Q

In what case might the cell receptor be inside the cell?

A

Occurs for steroid hormones as they can readily pass through the cell membrane. From there it makes a complex and can travel to nucleus to act as a transcription factor.

96
Q

What is the basis of signal transduction?

A

A phosphorylation cascade, in each case a new protein kinase is phosphorylated by the last, ending in a molecule that can phosphorylate a different protein that can induce a cellular response.

97
Q

What role do protein phosphates play in signal transduction?

A

A protein phosphatase is an enzyme that can rapidly remove phosphates from a protein. It can do this to protein kinases, giving the ability to turn off the signal for the pathway to continue once the initial signal is gone. It also frees up the protein kinases for use for another cell signal.

98
Q

What are second messengers?

A
  • Small, non protein, water soluble molecules or ions that carry a signal from the membrane receptor to inside the cell. (Called second messengers because first messenger is the ligand).
  • They are not ALWAYS involved in signal transduction, but they are frequently
99
Q

How is cyclic AMP created?

A

In the first part of cell signalling: reception, recall that an enzyme was activated by a g-protein in some cases. This enzyme is adenylyl cyclase converts ATP to cAMP, by taking off 2 phosphates and making it into a circular form.

100
Q

If a hormone responsible for activating an adenyl cyclase enzyme is removed from the receptor, what happens to the cAMP already created by the enzyme inside the cell?

A

Another enzyme, phosphodiesterase, converts cAMP into AMP in the absence of the hormone.

101
Q

What second messenger is responsible for opening Ca channels in smooth ER?

A

IP3, travels to smooth ER where it opens calcium channels.

102
Q

Once calcium is released from the smooth ER into the cytoplasm, where does it go? Why does induce so many cellular responses in the cytoplasm?

A

Ca conc. is low in the cytoplasm, and so it can induce many cellular responses if released. It typically goes either to the extracellular, or the mitochondria.

103
Q

How is IP3 created?

A

The activated g-protein from cell reception activates an enzyme that cleaves a component of the phospholipid membrane (PIP2) into IP3 and DAG. DAG functions in other pathways, where IP3 affects calcium release from the smooth ER (activates gated channel).

104
Q

What is often a response to a cell signal?

A

Activating a transcription factor.

105
Q

What prevents cells from undergoing the death pathway?

A

The ced-9 protein located on the outer mitochondrial membrane?

106
Q

What happens when a cell receives a death signal?

A

The response of the cell is to inactivate the ced-9 protein on the mitochondrial membrane. Once this protein is inactivated, it relieves the inactivation of 2 other proteins involved in the death pathway. They can activate and begin a pathway that forms nucleases and proteases, beginning apoptosis.

107
Q

What is blebbing and what is its purpose?

A

Blebbing is the formation of vesicles of a cell that is dying, to prevent surrounding cells from harm of the potentially dangerous contents of the dying cell.
Macrophages come eat these vesicles.

108
Q

What happens in the s-phases of the cell cycle?

A

DNA is replicated during this phases. Chromosomes are still in-condensed in the form of chromatin, however, there are now 96 chromosomes (23 pairs=46 1 from each parent, duplicated).

109
Q

When are the centrosomes (2 centrioles) duplicated?

A

During G2.

110
Q

What are the characteristics of prophase?

A
  • Chromosomes condense
  • Nucleoli disappear
  • Duplicated centrosomes begin moving to opposite poles of the cell, partly in aid of the microtubules extending from them
111
Q

What are the characteristics of pro metaphase?

A
  • The nuclear envelope is completely fragmented
  • The centrosome begins forming the mitotic spindle: which invades the nuclear area of the cell
  • The centromere on each of the sister chromatids now have the kinetochore protein
  • The kinetochore microtubules attached to the kinetochore, where they can jerk the chromosomes back and forth
112
Q

What are the 3 types of microtubules made in the formation of mitotic spindle?

A

(1) Astral Microtubules- smaller in shape, forming more toward the back of the cell
(2) Kinetochore Microtubules-the ones that attatch to the sister chromosomes via the kinetochore
(3) Polar Microtubules-longer in size, directed toward centre and they overlap

113
Q

What are the characteristics of metaphase?

A
  • The chromosomes are aligned along the metaphase plate; specifically, their centromere
  • Each sister chromatid has their kinetochore attached to a microtubule coming from an opposite pole.
114
Q

What are the characteristics of Anaphase?

A
  • The enzyme seperase cleaves the proteins holding the sister chromatids together; each now as their own (daughter) chromosome
  • Anaphase 1: The kinetochore microtubules pull the daughter chromosomes to the poles, doing so by shrinking at the end attached to the kinetochore, as the motor protein dyenin walks toward the minus end. Tubulin subunits are released.
  • Anaphase 2: The polar microtubules elongate the cell by sliding against each other. The motor protein kinesin walks toward the plus end, creating subunits, as they slide together.
115
Q

What are the characteristics of telophase?

A
  • The nuclear envelope re-appears around each set of new chromosomes
  • Any remaining mitotic spindle is depolymerized
  • The DNA un-condenses
116
Q

What are the characteristics of cytokinesis?

A
  • Means the splitting of the cytoplasm
  • Involves a cleavage furrow, where a belt made of microfilaments wraps around the centre of the large elongated cell and squeezes, forming the 2 daughter cells.
117
Q

Explain the G0 stage of a cell

A

A cell can go into this at the G1 checkpoint, if it does not receive the go ahead to keep dividing.
It can be in there forever (terminally differentiated) such as neuronal cells, or can be in there temporarily like most cells.

118
Q

Whats the M checkpoint?

A

Ensures that all sister chromatids are attached to a microtubule

119
Q

What is the G2 checkpoint and how is it regulated?

A

It is regulated by 2 molecules: cdk and cyclin.

  • Cdk is always in the cell, but the concentration of cyclin increases during mitosis
  • Together these molecules form MPF (Maturation promoting factor) in which promotes mitosis

Biology (6 decks)

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