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BIOL 107 > Quiz #7 > Flashcards

Quiz #7 Flashcards

1
Q

What are two inhibitors of cellular respiration?

A

cyanide

dinitrophenol

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2
Q

How does cyanide inhibit cellular respiration?

A

cyanide ions act as an irreversible enzyme inhibitor binding to the iron atoms of cytostome c oxidase complex (Complex IV)

no electron transport

no H+ pumping

no ATP synthesis

note that all electron flow through the chain will stop if Complex IV is inhibited

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3
Q

How does dinitrophenol inhibit cellular respiration?

A

makes mitochondria inner membrane permeable to H+

therefore no H+ gradient forms (in extreme case)

no flow back through ATP synthase

no ATP made

electron transport chain continues

energy dissipates as heat

DNP “uncouples” electrons transport
and formation of the H+ gradient, called an uncoupler

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4
Q

Why are alternative metabolic processes used?

A

although essential for many organisms, oxygen is very toxic

cellular respiration generates a lot of ATP from glucose, but if oxygen is unavailable for cellular respiration, an organism that uses an electron transport chain has two options: Die or use a secondary metabolic pathway

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5
Q

What are two ways to make ATP from organic molecules without oxygen?

A

Continue to use electrons transport chain, but use a different terminal electron acceptor, some prokaryotes that live in anaerobic conditions can perform anaerobic respiration

Use glycolysis to make ATP (recall this part of pathway does not require oxygen). The oxidizing agent is NAD+ but without the electron transport chain, NADH will quickly build up. To continue using glycolysis, NAD+ must be regenerated

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6
Q

What is alcohol fermentation?

A

pyruvate is converted to ethanol in two steps, with release of CO2

alcohol fermentation by yeast is used in brewing, winemaking, and baking

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7
Q

What is lactic acid fermentation?

A

pyruvate is reduced by NADH, forming lactate as an end product, without release of CO2

lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt

human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce

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8
Q

How are nerve cells in the brain affected by low levels of oxygen?

A

these are the first to die if deprived of oxygen

cannot make ATP unless O2 is present

cannot maintain proper ion balance and membrane potential

leads to cell damage, cessation of nerve function, death to organism

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9
Q

How is glycolysis regulated?

A

phosphofructokinase (PFK) is the key enzyme in the control of glycolysis

PFK activity is inhibited allosterically by high levels of ATP in cells

AMP (adenosine monophosphate) stimulates PFK to be more active, when ATP is used by reactions in the cell, there are various possible products

Citrate, the first product in the Krebs Cycle, inhibits PFK, citrate formation is fed by glycolysis

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10
Q

What is cell division and growth in eukaryotes and prokaryotes?

A

cell division by binary fission or mitosis produces two genetically identical cells

the process of cell division and segregation of chromosomes to daughter cells is more complicated in eukaryotes than prokaryotes

this is partly due to the fact that eukaryotes have much more DNA and multiple chromosomes

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11
Q

What processes are involved in cell division?

A

A reproductive signal “tells” the cell to divide, may originate from either inside or outside the cell

DNA replication, each daughter cell receives an identical copy of the complete instructions to perform all cellular functions

DNA segregation, the replicated DNA gets distributed to the new cells

Cytokinesis, the cytoplasm (or cytosol) divides to form two new cells each with its own cell membrane (a cell wall, if parent had one)

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12
Q

What is generation time?

A

time required for cells to divide

is determined by type of organism, level of nutrients, temperature

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13
Q

What does the graph of dividing cell populations look like?

A

slope constantly increases because of exponential growth

log plot gives straight line (easier to compare)

these graphs represent an ideal, theoretical situation, that assumes unlimited nutrients and no waste build up

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14
Q

What are the stages of cell growth?

A

Lag Phase

Log Phase

Stationary Phase

Death Phase

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15
Q

What is the lag phase in cell growth?

A

can last minutes to days

depends on species and physiological history of the starting cells

little to no cell division occurs

but cells may have a lot of metabolic activity (growing in volume, synthesizing enzymes, proteins, RNA, etc.)

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16
Q

What is the log phase in cell growth?

A

cells begin to divide

cell number doubles at a rate characteristic of the organism

growing population uses up nutrients, excretes waste product

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17
Q

What is the stationary phase of cell growth?

A

growing population uses up nutrients, excretes waste products

because of this, metabolic rate of cells decreases

cells die at a rate approximately equal to the rate of cell division

18
Q

What is the death phase of cell growth?

A

more cells die than divide

causes aren’t always clear

cells lysis due to damaged cell walls

toxicity from waste products

19
Q

What is DNA Replication in prokaryotes?

A

two regions of the DNA molecule play important roles in its replication

ori (origin): the site on DNA molecule where its replication is initiated
ter (terminus): the site where replication ends

prokaryotic DNA synthesis occurs at the same time as other metabolic processes in the life cycle, this is different from eukaryotes, which separate DNA replication from other stages of life

20
Q

What is DNA segregation in prokaryotes?

A

start separating DNA as soon as they can

FtsZ protein distantly related to eukaryotic tubulin, before DNA replication, FtsZ is distributed throughout the cytosol

immediately after DNA starts to replicate, other dynamics proteins bind to a region next to the ori and form filaments that help separate the two replicating nucleoids as they finish replication

then, FtsZ proteins start to congregate between the separating nucleoids

21
Q

What is cytokinesis in prokaryotes?

A

FtsZ proteins form a ring that “pinches” the cell membrane inwards until it separates the cytosol

as the membrane pinches in, new cell wall materials are deposited in the plane of the FtsZ ring (new barrier is termed a septum), which finally separates the two cells

22
Q

What is eukaryotic cell division?

A

mitosis and cytokinesis

they first divide the nucleus (mitosis) and then the cytoplasm (cytokinesis)

23
Q

What is eukaryotic reproductive signals?

A

unlike prokaryotes, most eukaryote cells do not simply divide whenever conditions are favorable, cells within a multicellular organism may not divide for many days, months, or years

the signals that control cell division are often related to the function of the whole organism, rather than the individual cell

24
Q

What is eukaryotic DNA replication?

A

eukaryotes have more than one chromosome, but each one replicates in a manner similar to prokaryotes, replication of DNA occurs at a specific stage of the cell cycle

replication initiates at specific sites in DNA (origins), most eukaryotic chromosomes have multiple origins of replication because they are very long

25
Q

What is eukaryotic DNA segregation?

A

more complicated than prokaryotes

there is a nuclear envelope

there are multiple chromosomes

each chromosome can be very long

replicated DNA molecules become highly condensed (packaged) in the nucleus before they segregate

completely replicated DNA molecules are initially connected to each other (as sister chromatids)

26
Q

What is a centromere?

A

a physical constriction of the duplicated chromosome, the sister chromatids are most closely attached at this site (we will discuss the function of the centromere later)

27
Q

What is eukaryotic cytokinesis?

A

refers to the division of the cytoplasm

the final stage of cell reproduction

mechanism different in animal vs. plant cells

28
Q

What are the steps involved in meiosis?

A

pairing of replicated homologues

recombination

segregation of homologues (division, completion of meiosis I)

segregation of sister chromatids (division, completion of meiosis II)

29
Q

What is interphase?

A

chromosomes are present (long, thin fibers of chromatin (DNA + proteins)), but not visible under a microscope as distinct entities

metabolic activity and growth occur throughout interphase, but the phases allow control over decisions to grow, change shape/behavior, replicate DNA, or divide

30
Q

What is G1 phase?

A

each chromosome is long and thread-like, a double-stranded helix of DNA plus associated proteins

each chromosome has centromere: specialized DNA sequence important for chromosome segregation

G1 prepares the cell for DNA replication

31
Q

What happens at the start of S phase?

A

the two strands of the helix unwind (unwinding starts at an origin)

each serves as a template for synthesis of a new strand

32
Q

What happens at the end of S phase?

A

one chromosome with 2 sister chromatids

the DNA in each chromatid consists of one “old strand” and one “new strand”

33
Q

What is G2 of interphase?

A

DNA replication is finished, now the cell prepares for chromosome segregation and cell division

when centrioles duplicate, the new one (called the daughter centriole) grows out from the older centriole (called the mother centriole)

two centrosomes (duplicated in S phase) usually stay close together, each centrosome has a pair of centrioles

34
Q

What is prophase?

A

the two centrosomes begin to separate because of microtubule growth and motor proteins pushing against opposing microtubule

nucleoli disappear

chromatin fibers become more condensed and visible

35
Q

What is prometaphase?

A

nuclear envelope starts to break down, (e.g. lamins disassemble, and membrane forms small vesicles that remain around the chromosomes)

this allows microtubules to grow into the area and make contact with kinetochores

if a microtubule plus end “hits” a kinetochore that microtubule becomes “captured”

36
Q

What is kinetochore?

A

a large structure made of ~100 different proteins, that assembles on the DNA (at the centromere), each chromatid has one kinetochore, the pair face in the opposite directions

captures microtubules and is required for proper chromosomes congression and separation of sister chromatids

37
Q

What is metaphase?

A

chromosomes congress to the “equatorial region”, forming a metaphase plate

38
Q

What is anaphase?

A

the shortest stage of mitosis

begins when cohesion proteins are cleaved

tension builds up initially due to kinetochore microtubules pulling equally in opposite directions

tension released, and chromatids more rapidly apart, with kinetochore leading the way

39
Q

What are the two different ways that mitotic chromatid segregation can occur?

A

shortening the distance between poles and chromatids (anaphase A)

movement of spindles poles (centrosomes) apart (anaphase B), depending on the cell involved, it may use either method or both

40
Q

What is telophase?

A

two daughter nuclei form in the cell

nuclear envelope starts to reform

chromosomes start to de-condense (become less visible)

division of the nucleus into two genetically identical nuclei is complete

41
Q

What is cytokinesis?

A

refers to the splitting of the cytoplasm in a eukaryote

it begins during late anaphase and continues through telophase until complete separation of daughter cells into distinct compartments

an actin-based contractile ring forms at the membrane

42
Q

Why would a cell ever divide asymmetrically?

A

to create two daughter cells that are not identical to each other (different in size, components, etc.)

BIOL 107 (11 decks)

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