Cell And Molec Test 3 Flashcards
What are the fibers of the cytoskeleton made out of? (3)
- microfilaments
- intermediate filaments
-microtubule
What are the differences between micro filaments, intermediate filaments, and microtubules?
- microfilaments are the smallest, most simple and made of actin ~7nm
- intermediate has 9 types and is a complete structure ~10nm
-microtubules are the largest, they are a hollow tube made out of tubulin(?) ~25nm
Do prokaryotes have a cytoskeleton? Do eukaryotes?
Only eukaryotes have a cytoskeleton, prokaryotes do not
What are the 4 techniques for visualizing the cytoskeleton?
- fluorescence microscopy on fixed specimens
- live cell fluorescence microscopy
- computer-enhanced digital video microscopy
- electron microscopy
Describe how Fluorescence microscopy on fixed specimens works
Fluorescence compounds directly bind to the cytoskeletal proteins, or antibodies are used to indirectly label cytoskeleton proteins in chemically preserved cells, causing them to flow in the fluorescence microscope
Describe how live cell fluorescence microscopy works
Fluorescence versions of cytoskeletal proteins are made and introduced into living cells. Fluorescence microscopy and video of digital cameras are used to cure the proteins as they function in cells
Describe how Computer enhanced digital video microscopy works
High resolution images from a video or digital camera attached to a microscope are computer processed to increase contrast and remove background features that obscure the image
Describe electron microscopy
Electron microscopy can resolve individual filaments prepared by thin section, quick freeze dry etch, or direct mount techniques
What is the largest of the cytoskeletal components of a cell
Microtubules
What are the functions of microtubules?
- move chromosomes (main function)
- flagella movement
- “highways” for vesicles
What 2 types of microtubules are responsible for the many functions in the cell?
-cytoplasmic microtubules
-axonemal microtubules
What are the functions of cytoplasmic microtubules
-maintaining axons (axons are the long structures in nerve cells)
-formation of mitotic and meiotic spindles
-maintaining or altering cell shape
-placement and movement of vesicles
What are axonemal microtubules?
they include the organized and stable microtubules found in structures such as : cilia, flagella, and basal bodies (cilia and flagella attach to)
What is the axoneme?
A highly ordered bundle of microtubules
Describe what is shown in the graph (in my notes) (LAG PHASE ELONGATION PHASE AND PLATEU PHASE
The first part of the graph (low/start) is the lag phase which is the period of nucleation
Then, during the elongation phase, (middle part) microtubules grow rapidly causing the concentration of tubulin subunits in the solution to decline when this concentration is low enough to limit further assembly, the plateau phase (high point flat at end) is reached during which subunits are added and removed from microtubules are equal rates
What is critical concentration?
Concentration at which the rate of assembly of cytoskeletal protein subunits into a polymer is exactly balanced with the rate of disassembly
What is the goal of the The microtubule organizing center (MTOC) (idk how to ask this question)
It anchors the negative end of the microtubule so it’s bound to the MTOC so it can’t shrink or grow. It can only shrink/grow at the positive end
What happens to the microtubule when there is a high tubulin concentration
The microtubule grows, GTP-tubulin subunits are added
What happens to the microtubule when the tubulin concentration is low?
The microtubule shrinks, GTP are hydrolyzed
At what end do microtubules grow/shrink
They grow and shrink at the positive end, they anchor at the negative
Which end of the microtubule is more dynamic? Why?
Positive end because that is where GTP is added and taken away (depending on the tubulin concentration) aka where it grows and shrinks
What happens in the MTOC to the microtubules when tubulin concentration is high?
GTP-tubulin subunits are added
What happens in the MTOC to the microtubules when there is low concentration of tubulin?
Catastrophe. GTP are hydrolyzed (therefore depleting the GTP cap)
Microtubules are regulated by microtubule binding proteins. Why might they use ATP?
-drive vesicle/organelle transport
-generate sliding forces between microtubules
What are the functions of microtubule-binding proteins?
-drive vesicle or organelle transport (using atp)
-generate sliding forces between microtubules (using atp)
-regulate microtubule structure
Cells regulate _______ with great precision
Microtubules
What are microtubule-stabilizing/building proteins? (MAPS)
microtubule-associated proteins that bind at regular intervals along a microtubule wall. this allows for interaction with other cellular structures and filaments
What are the 2 microtubule stabilizing/bundling proteins (MAPs)?
- A MAP called Tau
- MAP2
What is the function of A MAP (Tau)?
They cause microtubules to form right bundles in axons
What is the function of MAP2?
they promote the formation of looser bundles in dendrites
What are dendrites?
short branched extensions of nerve cells (neurons) that receive signals from other neurons
Describe what the 2 regions of MAPs such as Tau and MAP2 each do
One region binds to the microtubule wall, and the other extends at right angles to allow for interaction with other proteins
What controls the spacing of the microtubules in a bundle?
The length of the extended “arm” of the MAP
What are +-TIP proteins?
- (+- end tubulin interacting proteins) are stabilizing proteins that “capture” and protect the growing positive end
-they decrease the likelihood that microtubules will undergo catastrophic subunit loss
What are 3 microtubule destabilizing/severing proteins?
- Stathmin/Op18
-Catastrophins
-proteins such as Katanins
How does Stathmin (or OP18) destabilize/sever microtubules?
-it binds to tubulin heterodimers and prevents their polymerization
How do catastrophins destabilize/sever microtubules?
at the end, they act on the microtubules and promote the peeling of du units from the ends
How do katanins (proteins) destabilize/sever microtubules
They sever the microtubules
What is “The Mesh” ?
-a network of microtubule connectors that stabilize individual kinetochore fibers of the mitotic spindle where the chromosome attaches
- yellow “lines” in the given photo
Each mesh structure holds 2 microtubules together, why?
Because the clathrin is a part of the mesh structure (in its turmeric state)
What is the smallest of the cytoskeletal filaments?
Microfilaments
Microfilaments have many roles, what do they include? What is the best known role they carry out?
- BEST KNOWN : their role in muscle contraction
also known for : - cell migration
- ameoboid movement
- cytoplasmic streaming
- development and maintenance of cell shape (they push out the edges of the cell)
- structural core of microvilli
What is actin?
- a very abundant protein in the cell, it is a building block for all microfilaments
Once actin is synthesized, it is folded into a globular shaped molecule. What does this allow it to do?
It allows the actin to bind to ATP or ADP
Since microfilaments do not anchor themselves at one end, where do they shrink/grow
There is general shrinkage at the negative end and general growth at the positive end
When the myosin fragment S1 binds to the actin in microfilaments, a “pattern” is created - describe why this is
The myosin segment binds to the actin and creates an “arrow” pattern, where the arrow will point to the negative end creating the “pointed end” and the other end is referred to as the “barbed end”
Which is not dynamic: microtubules or microfilaments
Microtubules are more dynamic
I’m terms of length, which is more stable: microtubules or microfilaments?
Microfilaments are more stable in terms of length
Explain “tredmilling” in terms of microfilaments.
-since they gain G-actin monomers at the positive end while simultaneously they lose monomers at the negative end, the net change in length is zero.
-the actin monomers start at plus end and are displaced progressively more towards the negative end until depolymerization causing it to detach
When is the ONLY time “tredmilling” in microfilaments occurs?
In a test tube/in vitro
What are 3 specific drugs that affect polymerization of microfilaments?
- Cytochalasins
- Latrunculin A
- Phalloidin
How do Cytochalasins affect the polymerization of microfilaments?
- the prevent the addition of new monomers to existing microfilaments
- cytochalasins are fungal metabolites
How does Latrunculin A affect the polymerization of microfilaments?
- hides actin monomers and prevents their addition to microfilaments
- a toxin
How do Phallodin affect the polymerization of microfilaments?
- stabilizes the microfilaments and prevents their depolymerization
- can alter and even kill the cell
Cells can precisely control where actin assembles and the structure of the resulting network, how?
- they use a variety of actin-binding proteins in order to control the actin
- control occurs at the nucleation, elongation and severing of microfilaments
What are the most stable, and least soluble cytoskeletal components?
- intermediate filaments are both the most stable and least soluble
What is an example of an intermediate filament (very abundant)
- keratin, an important component of structures that grow from skin in animals; giving structure to the skin
How many different classes of intermediate filament proteins are there?
- 6
Which of the 6 classes of intermediate filament proteins is the most stable?
- class 5 (V)
Class I intermediate filaments are _____
- acidic keratins
Class II of intermediate filament proteins ___
- are basic or neutral keratins
What 2 classes make up tonofilaments? Where are the tonofilaments found?
-protien classes I and II
- found in epithelial surfaces covering the body and lining it’s cavities
Class III of intermediate filament proteins include ___
- vimentin (connective tissue), desmin (muscle cells) and glial fibrillary (GFA)
Class 5 (V) includes ____
- nuclear Kamins A, B, and C, that form a network along the inner surface of the nuclear membrane
Class 6 (VI) of intermediate filament proteins ____
- neurofilaments in the nerve cells of embryos are made of nestin
What is intermediate filament testing?
-animal cells can be distinguished based off of what types of intermediate filaments they contain
What are nucleotide triphosphates (NTP)?
- (rna) an umbrella term for : ATP, GTP, UTP, and CTP
What are deoxynucleotide triphosphates?
- (dna) dATP, dGTP, dCTP, dTTP
What is an allosteric site?
- a binding site distinctively different from the active site, that allows molecules to either activate or inhibit enzyme activity
What is a holoenzyme?
A complete enzyme including a cofactor, the enzyme, and once the substrate binds it is functional
Explain how the intermediate filament is assembled in vitro
2 intermediate filament proteins go through coiling, creating a coiled-coil dimer of 2 intertwined polypeptides.
Then, the coiled-coils line up (lateral alignment) creating a tetrameric protofilament of 2 aligned coiled-coil dimers.
They are then assembled in a staggered pattern (like bricks) into a long rope-like filament. The final structure consists of 8 protofilaments (16 coiled dimers) in staggered overlaps.
Which of the following is both flexible and can withstand tensile forces : microtubules, microfilaments, or intermediate filaments
- intermediate filaments
How do the microtubules and microfilaments work to support the cytoskeleton?
The microtubules resist bending when a cell is compressed while the microfilaments serve as contractile elements that generate tension
The nuclear lamina (on the inner surface of the nuclear envelope) disassembles when? When do they reassemble?
They disassemble at the onset of mitosis, and then reassemble afterward
Are intermediate filaments considered a static structure?
No. They are not static, they are dynamically transported and remodeled
What are Plakins?
- linker Proteins
What role does Plakins have in the cytoskeletal structure?
- the Plakins proteins connect the intermediate filaments, microfilaments, and microtubules
What is an example of a Plakin (name of it)
-plectin
Where is plectin found in the cytoskeleton?
At sites where intermediate filaments connect to microfilaments and microtubules
What are the 2 microfilament associated (actin binding) proteins? (Motor molecules)
- myosin I - monomer
- myosin II - filament (specialized)
What are the 3 microtubules associated proteins? (Motor molecules)
- cytoplasmic dynein
- axonemal dynein (specific to only flagella and cilia)
- kinesin
What is the function of myosin I and II ?
Myosin I helps with motion along the actin filaments
Myosin II I’d the thick filament of muscle cells
What is the function of cytoplasmic dynein? (MT associated motor molecule)
Responsible for movement towards the minus end of the microtubule (towards the MTOC)
What is the function of axonemal dynein?
Activation of sliding in Flagellar microtubule
What is the function of kinesin (MT associated motor protien)
Responsible for motion towards the positive end of the microtubule (AWAY from the MTOC)
What uses the motor proteins (such as kinesin and cytoplasmic dynein) for movement?
Vesicles
What is the structure of myosin I?
1 heavily coiled chain making up the “tail” which is attached to the “head” which is made up of an ATP binding site and an Actin binding site
-OOC -> heavy chain -> actin binding site -> ATP binding site -> NH3+
What is the structure of myosin II?
2 heavily coiled chains about each other (tail) connected to 2 “heads” therefore having 2 ATP binding sites and 2 Actin binding sites
Where is myosin II usually used? (What body cells)
- muscle cells - used for contraction
What allows the Dynein/Kinesin to move along the microtubule? (What is the energy source)
- ATP hydrolysis
What are the 3 proteins that make up thin filaments?
- F-actin
- tropomyosin
- troponin
Which 2 proteins are very sensitive to calcium?
- tropomyosin and troponin
What 3 component make up troponin ?
- 3 poly peptides: TnT, TnC, TnI
What 2 proteins constitute a calcium sensitive “switch”? When does that switch activate?
- when 1 troponin complex associated with a tropomyosin
- activates contraction in striated muscle
What does the regulation of muscle contraction depend on?
- calcium
Most skeletal muscle spends time in what state : in contraction or relaxed
- more time in a relaxed state
T/F : muscle contraction and relaxation must be coordinated
True
Myosin binding sites are normally blocked by what? If this is removed, what forms?
- normally blocked by tropomyosin
- will form cross-bridges
What do tropomyosin and troponin regulate ?
- availability of myosin binding sites on actin filaments in a calcium dependent manner
When calcium concentration is low, how is interaction between the actin filament and myosin prevented?
- tropomyosin blocks the myosin binding sites on the actin filament
When calcium concentration is high, what does it bind to? What does this allow to for?
- binds to TnC
- slows for the myosin to bind because of the tropomyosin shift
Calcium levels are controlled by what?
- nerve impulses from motor neurons
Muscle contraction is regulated by what?
- calcium ions in the sacroplasm
What is the sarcoplasm ?
- cytosol of muscle cell
What is the neuromuscular junction?
- the site where a nerve contracts a muscle cell conveying a signal to contract in the form of an action potential
Where do axon terminals make contact with the muscle cells?
At the neuromuscular junction
Where is acetylcholine released from? What is this a response to?
- the axon terminals store and then release the acetylcholine in response to an action potential
How do amoebas move ?
By ameboid motion - attach the pseudo foot in front of them and move themselves towards it
How does actin aid crawling cells
The actin filament cytoskeleton pushes and contracts, slowly moving the cell
Give an example of membrane protrusion due to actin polymerization
The formation of an acrosomal process in Sea cucumber sperm (thyone)
How do cilia and flagella move?
The dynein motor proteins generate the motive force by pushing against the microtubules, to bend the flagellum and cause it to move in a whip like motion through the surrounding fluid
- referred to as flagellar or ciliary beat
The MTOC (microtubule organizing center) has other equivalent names (3)
- centriole
- centrosome
- basal body
What is the structure of a Basal body
“ 9 + 0 structure “
- 9 doublets composed of an A microtubule and a B microtubule
What is the structure of an axoneme?
“ 9 + 1 structure “ - 9 doublets around and one in the middle made of 2 microtubules (A and B)
- connected with radial spokes
Where are primary cilia used?
- sensory structures
What is the structure of primary cilia? (9 +)
- 9+0 ( no central doublet )
What can cause deafness and left-right asymmetry reversals ?
- defects in primary cilia
What does a cofactor do?
Attaches to the allosteric site of an enzyme in order to change the shape of the binding site of the substrate - once bound, you have function
What is the difference between a competitive inhibitor and a non competitive inhibitor
- A competitive inhibitor mimics the substrate and blocks it from binding
- a non competitive inhibitor binds at another site changing the shape of the binding site so the substrate does not fit
What is the optimal pH for enzymes
5.0
Increasing concentration of substrate molecules caused the rate of reaction to do what?
Rate of reaction will increase, until the active sites on all the enzymes molecules are filled (maximum reaction rate)
What are some causes of denatured proteins
- pH changes
- temperature changes
- concentration changes
What bonds are broken when a protein is denatured
- non covalent bonds (such as hydrogen bonds)
- these bonds hold the protein together in its 3D shape
Describe what happens in the ATP cycle
Energy from an exergonic reaction goes in and due to dehydration synthesis ATP is created. Then, energy is expelled during hydrolysis and goes to the endergonic reactions, splitting the ATP into ADP + P
What is chemiosmosis?
- the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient
- the formation of ATP by the movement of H+ will diffuse from a region of high proton concentration to low concentration during cellular respiration/photosynthesis
What is phosphorylation - give an example (ATP)
- the attachment of a phosphate group to a molecule or ion
- ADP + P —> ATP
- de-phosphorylation : ATP —> ADP + P
What is the cellular respiration equation (must know)
C6H12O6 + 6O2 —> 6CO2 + 6H2O + ATP
Glucose + oxygen gas —> carbon dioxide + water + energy
Using the equation for cellular respiration, label what is the reduction and which is the oxidation portion of the equation
- reduction : 6O2 -> 6H2O
- oxidation : C6H12O6 -> 6CO2
Give a quick overview of cellular respiration (steps, processes)
Glycolysis (glucose to pyruvic acid) —> Krebs cycle (produces NADH and FADH2) —> electron transport chain
- ATP is produced at each step
The inside of the mitochondria looks like wwwww (folded structure). Why is this? What is the benefit?
- the folds create more surface area, allowing for more ATP (energy) to be created
What structures do mitochondria have that leads us to believe they used to be their own bacteria?
- they have their own DNA, tRNA, ribosomes, and mRNA
Give an overview of the glycolysis process.
What goes in, what comes out, what is created (“ break down sugar”)
Glucose (6 carbon sugar) is split, 2 pyruvic acids are created
2 ADP + 2 P —> ATP
2 NAD+ —> 2 NADH + 2H+
How many total ATP is produced from glycolysis? How many net ATP is produced from glycolysis?
- total : 4
- net : 2 (2 are imputed to
When NAD+ gains a hydrogen, it becomes NADH. Is this a reduction or an oxidation reaction?
- reduction
Write the overall reaction of glycolysis
Glucose + 2 NAD+ + 2ADP + 2P —> 2 pyruvate + 2 NADH + 2 ATP
THIS IS DONE TWICE
In the conversion of pyruvic acid to acetyl coenzyme a, pyruvic acid is oxidized or reduced?
Oxidized
T/F : glycolysis requires O2
- false. Glycolysis occurs whether o2 is present or not
Where in the cell does glycolysis occur?
- cytoplasm
What are the folds of the mitochondria called
- Cristae
What is the prep story step in glycolysis ( Explain the process of pyruvic acid becoming acetyl CoA )
- pyruvate oxidation
- 1 carbon is removed from pyruvate making it acetyl coA (a 2-carbon chain)
- during this process, NAD+ becomes NADH
Krebs cycle is also known as what
Citric acid cycle
What is the Krebs cycle? What goes in what comes out
In - Acetyl CoA
Out - 3 NADH (x2), 1 ATP (x2), 1FADH2 (x2)
—> total: 6NADH 2ATP 2FADH2
How many NADH come from the preparatory stage? (Before Krebs cycle, after glycolysis)
- 2
After the Krebs cycle, how many net ATP, NADH, and FADH2 have been produced so far?
- 4 ATP
- 10 NADH
- 2 FADH2
What gets imputed into the ETC? (Electron transport chain)
- NADH and FADH2
How many ATP can be made in the ETC from both the NADH and the FADH2 (each)
- each NADH can produce 3 ATP
- each FADH2 can produce 2 ATP
~ going into the ETC, 10NADH are imputed giving a total of 30 ATP and 2 FADH2 are imputed giving 4 ATP
How many NET total ATP are produced during cellular respiration. How many TOTAL?
- NET : 36-38
- TOTAL : 38-40
Is the ETC is what kind of transport
Indirect active transport
What does NADH reductase do? (in the ETC)
- strips the NADH of its hydrogen
(ETC) When NADH loses its hydrogen, what/where is it transfered to ?
- hydroxyquinone
(ETC) once the hydroxyquinone posesses a hydrogen, where does it go
Gets bound to cytochrome C
Where does the ETC take place
In the mitochondrial membrane
What is the final electron acceptor?
Oxygen
(Cellular respiration) After glycolysis, of no oxygen is present what happens? (2 options)
- alcoholic fermentation or lactic acid fermentation
Is alcoholic fermentation aerobic or anaerobic respiration?
- anaerobic
What is the difference between heterolactic and homolactic ?
- homolactic : only lactic acid can be produced
- heterolactic : can produce many types of acid
What product is made from the alcoholic fermentation cycle?
- 2 ethanol which can be used to make other products
- 2 NAD+
- 2 CO2
What is the output of the lactic acid cycle?
- 2 ATP
- 2 NAD+
- 2 lactic acid molecules
Is the hydrolysis of ATP to ADP an exergonic or endergonic rxn?
- exergonic
Is the synthesis of ADP to ATP an exergonic or endergonic reaction?
- endergonic
Draw a molecule of ATP. What is the difference between this and ADP?
…
What are 4 NTPs ? (Nucleotide triphosphates)
- ATP
-GTP
-UTP
-CTP
What are the 4 deoxyribose triphosphates?
-dATP
-dGTP
-dCTP
-dTTP
Which dNTP or NTP is used the most ?
ATP
Draw an NAD+ - how does it become NADH
…
What is the function of NAD+
- it is a hydrogen carrier
What is the definition of photosynthesis
The process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water
In what organisms does photosynthesis occur
Plants, algae, and some prokaryotes
Is photosynthesis an endergonic or exergonic reaction
Endergonic - it stores energy
What is energy stored as (when using photosynthesis)
- carbohydrates
What is the formula for photosynthesis
6CO2 + 6H2O —> C6H12O6 + O2
^ light energy added
What is the definition of carbon fixation
The process by which inorganic carbon from the atmosphere is assimilated into living organisms and converted to organic compounds
When does carbon fixation occur in photosynthesis (before which process)
Before the Calvin cycle
In which organelle does photosynthesis occur
Chloroplast
What structure in the chloroplast does photosynthesis occur
Thylakoids
What are stoma?
The holes on plants that the plant can get CO2 from
What are granum
A stack of thylakoids
In the formula for photosynthesis, follow where each molecule “goes” (6CO2 - the carbon goes to which product, the oxygen goes to which product)
- 6 CO2 : Carbons go to glucose, oxygen does to water
- 12 H2O : Hydrogens go to glucose and water, oxygen is converted to oxygen gas (O2)
In photosynthesis, which part of the reaction is being reduced and which part is being oxidized
The CO2 is reduced to glucose
The water is oxidized into O2 gas
What is the function of NADP+
- it is a hydrogen carrier
- similar to NAD+
What are the 2 processes of photosynthesis?
- light reaction
- dark reaction (Calvin cycle)
Why is the Calvin cycle also called the dark reaction?
- because it happens in the absence of light
Why are plants green
Light passed through the chloroplasts, the green light is reflected back into our eyes and the rest of the colors’ lights are absorbed into the chloroplast
What wave lengths does photosynthesis mostly occur
- 400-500 and 600-700 ( purples and blues to oranges and reds )
Which photosystem splits the water? Which photosystem produces NADPH
- photosystem II splits water
- photosystem I produces NADPH
Draw NADPH
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Where does cyclic photophosphoylation take place? (PS I PSII both or neither). At what wavelength
Only photosystem I, 700nm
What is the end product of cyclic photophosphorylation
ATP only
Where does non-cyclic photophosphoylation take place? (PS I PSII both or neither). At what wavelength
Both photosystem II (680nm) and photosystem I (700nm)
What does non cyclic photophosphorylation produce
NADP, ATP, and O2
Where does the dark reaction (or light independent, or Calvin cycle) take place?
In the Stroma of the chloroplast
What enzyme does the light independent reaction require?
- RUBISCO (ribulose biphosphate carboxylase)
In the Calvin cycle (also called carbon rxn pathway, light independent, and dark cycle), what is the cleavage of P (from ATP) used for
That energy is used to fix and reduce CO2 to form a carbohydrate
What is the most abundant biological molecule on earth
RuBP
Give a summary of the Calvin cycle
- 3 5-carbon ribulose-1,5-bisP (total of 15 carbons) are carboxylated (meaning 3 carbons are added), cleaved, phosphorylated, reduced, and dephosphorylated
- this yields :
1 3-C glyceraldehyde-3-P exits as a product
5 3-C glyceraldehyde-3-P (15C) are recycled back into 3 5-C RuBP
How is the rate of photosynthesis defined?
- the rate of oxygen production per unit mass of green plant tissues or per unit weight of total chlorophyll
What are the main factors that can affect photosynthesis
- light intensity
- wavelength
- CO2 concentration
- temperature
- water supply
- chlorophyll concentration
- pollution
What is the main function of microtubules
- cell movement and intrazellularem Transport
- cell shape
What is the main function of microfilaments
- help generate the forces used in cellular contraction/basic cell movements
What is the main function of intermediate filaments?
- they are mechanical stress absorbers and an integrating device for the entire cytoskeleton
Draw a sacromere
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