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bio > DAT Photosynthesis and Cell Div. > Flashcards

DAT Photosynthesis and Cell Div. Flashcards

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Biology 101 flashcards
1
Q

Photosynthesis:

A

biological process done by
photoautotrophs (plants, some bacteria and protists);
captures energy from sunlight and converts it to chemical
energy stored in the form of glucose
* Takes place in the chloroplast
* Overall Reaction: 6CO2 + 6H2O → C6H12O6 + 6O2

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2
Q

Chloroplast:

A

organelle that is only found in
photoautotrophs; contains chlorophyll (light absorbing
pigment with a porphyrin ring that has an Mg atom in the
center; similar structure to hemoglobin)

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3
Q

Chloroplast Structure (external to internal):

A
  1. Outer membrane (smooth)
  2. Intermembrane space
  3. Inner membrane (smooth)
  4. Stroma (cytoplasm of chloroplast)
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4
Q

Stroma Structure

A

a. Stroma lamellae: connect thylakoids together
b. Thylakoids: membrane bound flattened disks
found in the stroma
i. Thylakoid membrane: contain chlorophyll
ii. Thylakoid lumen: space enclosed by
thylakoid membrane
iii. Granum: stack of thylakoids

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5
Q

Photosynthesis includes…

A

light dependent and independent rxns

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6
Q

Light-Dependent Reactions:

A

include cyclic and noncyclic
photophosphorylation using chlorophyll found in
photosystems

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7
Q

Photosystems (PS):

A

(PS): large chlorophyll containing
proteins found in the thylakoid membrane.

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8
Q

Action Spectrum

A

plots wavelengths of light that are
most effective at causing photosynthesis

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9
Q

Red/blue light:

A

highest rate of photosyn

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10
Q

Green light:

A

lowest rate of photosynthesis (chlorophyll
reflects green wavelength of light instead of absorbing
it; this is why plants are green)

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11
Q

Noncyclic Photophosphorylation

A
  1. Sunlight hits PS II → photons from light excite
    electrons (boosts electrons to higher energy level)
  2. High energy electrons passed to primary electron
    acceptor
  3. Primary electron acceptor passes electrons through
    the electron transport chain (ETC), pumps protons
    (H+) against concentration gradient from stroma ➞
    thylakoid lumen (creates an electrochemical
    gradient)
  4. Protons flow through ATP synthase down their
    concentration gradient, catalyzing the conversion of
    ADP to ATP
    a. This ATP is used to power photosynthesis.
    Cellular respiration still occurs to produce
    energy in plants.
  5. Electrons (now low-energy) arrive at PS I ➞ photons
    from sunlight re-excite electrons to higher energy
    level
  6. Electrons are passed to an electron acceptor and
    travel down another ETC
  7. NADPH is formed by combining high energy
    electrons with NADP+
    a. NADPH transports high energy electrons to the
    Calvin cycle for glucose production
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12
Q

Photolysis:

A

splitting of water by light that occurs in PS II.

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13
Q

Cyclic Photophosphorylation

A

Steps: occurs in the stroma
lamellae; only involves PS I
1. Electrons in PS I get excited by sunlight to a high
energy state
2. Electrons get recycled passed back to the first ETC,
allowing more pumping of H+ and making more
ATP instead of NADPH (replenishes the ATP used in 3 phases of Calvin cycle

(1. Carbon fixation: taking carbon from an inorganic
source (CO2 in atmosphere) and converting it to an
organic compound (glucose)
a. Done by autotrophs (plants, photosynthetic
organisms, chemoautotrophic prokaryotes)
2. Reduction (steps that use up ATP and NADPH from
light reactions)
3. Regeneration: intermediates are regenerated so
cycle can continue)

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14
Q

Important Steps of Calvin Cycle:

A
  1. RuBisCo (most abundant enzyme on Earth)
    combines CO2 with RuBP, forming a 6 carbon
    intermediate (carbon fixation phase)
  2. 6 carbon molecule is broken into two 3-carbon
    phosphoglycerate (PGA) molecules
  3. PGA is phosphorylated to G3P (using ATP and
    NADPH during the reduction phase)
  4. Most G3P is converted back to RuBP (requires ATP)
    and remaining G3P is used to make glucose
    (regeneration phase)
    a. 1 molecule of glucose is produced with 6 turns
    of the cycle (1 cycle produces 2 G3P molecules,
    so 6 cycles produce 12 G3P. 10 are used to
    reform RuBP, and the remaining 2 are used to
    make glucose)
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15
Q

Photorespiration:

A

an undesirable process which reduces
the efficiency of carbon fixation, forming useless
byproducts. Occurs when RuBisCo binds O2 instead of CO2

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16
Q

C2 (type of photosynthesis)

A

photorespiration; product = useless 2 carbon molecule
* Takes place in all plants
* Some plants have no way to stop C2 and
photosynthesize less efficiently

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17
Q

C3: normal photosynthesis

A
  • Takes place in all plants in the mesophyll cells
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18
Q

C4:

A

prevents photorespiration by physically separating light
and dark reactions

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19
Q

CAM:

A

minimizes water loss via temporal separation instead
of spatial (common in plants in dry environments e.g.
cactus)

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20
Q

Stomata

A

pores found on bottom of leaves for gas
exchange. In most plants, stomata are always open for
continuous exchange of CO2 and O2, allowing water to
escape easily in certain environments

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21
Q

what do CAM plants do differently

A

only open their stomata at night so that
CO2 can enter and less water is lost. However, there
is no sunlight at night, so there is no ATP/NADPH
from the light reactions to power the Calvin Cycle

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22
Q

Cell division

A

how cells replicate to increase their number.

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23
Q

Chromatin

A

a condensed form of DNA that is wrapped
around histones. DNA is stored as chromatin, but during
cell division, it condenses even more into chromosomes.

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24
Q

Chromosomes:

A

dense packaging of chromatin, existing
during mitosis and meiosis. Chromosomes can be in
duplicated or unduplicated forms.

25
Q

Chromatid:

A

one half of a duplicated chromosome

26
Q

Sister Chromatids:

A

two duplicated chromatids that
are completely identical to one another. They can
connect at the centromere to form an X-shaped
chromosome

27
Q

Centromere:

A

region where two sister chromatids are
connected; kinetochores attach here

28
Q

n =

A

number of chromosomes in a set

29
Q

Haploid Human cells:

A

cells: n=23,

30
Q

Diploid Cells (2n)

A

have 2 sets of chromosomes: one
from the mother and one from the father. The vast
majority of human cells are diploid.

31
Q

Homologous Chromosomes

A

set of a chromosomes
(one from each parent) in a pair. Found in diploid cells.
Homologous chromosomes are similar in length, gene
position, and centromere position. They carry genetic
information for the same traits, but are not genetically
identical.

32
Q

Centrosomes

A

the Microtubule Organizing Centers
(MTOCs) of animal cells. A centrosome is composed of 2
centrioles perpendicular to each other.

33
Q

Spindle Fibers:

A

microtubules that emerge from the
centrosome. They allow chromosomes and chromatids
to be separated during specific phases of cell division.

34
Q

Mitosis:

A

nuclear division that creates a pair of diploid cells
that are genetically identical to the original cell

35
Q

Mitosis Overview:

A

prophase → prometaphase →
metaphase → anaphase → telophase and cytokinesis

36
Q

Prophase

A
  • Chromatin condenses into chromosomes
  • Nucleolus disappears
  • Mitotic spindle begins to form
  • Centrosomes begin to move towards opposite ends of
    the cell
37
Q

Prometaphase

A
  • Nucleus disassembles
  • Chromosomes condense even further
  • Each chromatid is attached to a kinetochore
  • Mitotic spindle further develops
  • Spindle fibers begin to attach to kinetochores of
    chromosomes
38
Q

Metaphase

A
  • Chromosomes are lined up across the center of the cell
    (aka metaphase plate)
  • Centrosomes have reached opposite ends of the cell
  • Mitotic spindle is fully developed
  • All chromosomes are attached to spindle fibers via
    kinetochores
39
Q

Karyotyping

A

(physical observation of a cell’s
chromosomes with a microscope)

40
Q

Anaphase

A
  • Microtubules shorten
  • Sister chromatids are pulled apart
  • Once separated, each sister chromatid is now
    considered to be an individual chromosome
41
Q

Telophase

A
  • Nucleoli redevelop
  • Two nuclear envelopes develop
  • Chromosomes decondense back into chromatin
  • Spindle fibers disappear
  • Cytokinesis occurs during telophase
  • Mitosis: the nucleus duplicates
  • Cytokinesis: the rest of the cell duplicates
42
Q

Cytokinesis:

A

physical division of the cytoplasm to form two
cells.

43
Q

Animal cells form a

A

cleavage furrow (contractile ring
formed by actin and myosin) forms; ring contracts to
separating the dividing cells into two

44
Q

Plant cells form a

A

cell plate that develops between the
two nuclei; essentially a cell wall that fuses with the
existing plant cell wall, separating the two cells

45
Q

Meiosis:

A

nuclear division in that produces four haploid
gametes that are not genetically identical to the original
cell. Gametes are an organism’s reproductive cells (sperm in
males, eggs in females).

46
Q

Cell Cycle:

A

an ordered sequence of events that occur
before and during cell division.

47
Q

Interphase:

A

Interphase: when the cell is growing and preparing for
cell division, but not actively dividing. Interphase
ensures that each daughter cell will have enough
biological material. Cells spend most of the cell cycle in
interphase.

48
Q

The phases of interphase include:

A

G1, S, G2, G0, m phase

49
Q

G1 (Gap Phase 1):

A

cell grows in size and protein
synthesis begins (preparation for cell division).
‣ Usually the longest phase of the cell cycle

50
Q

S (Synthesis Phase):

A

DNA and centrosomes are
replicated. Sister chromatids are formed.

51
Q

G2 (Gap Phase 2):

A

final preparation for mitosis. Cell
continues to grow, and organelles replicate. Cell
checks that everything is ready (e.g. chromosomes
are replicated) to proceed with mitosis.

52
Q

G0: resting phase.

A

Cells are active/functional, but
are not dividing or preparing to divide

53
Q

Cells have to divide because of functional limitations:

A

SA to volume ratio, Genome to volume ratio

54
Q

checkpoints of cell cycle

A

End of G1:, end of G2, M Checkpoint/Spindle Checkpoint

55
Q

Density dependent inhibition:

A

cells stop dividing
when the surrounding cell density reaches a
maximum. Prevents overcrowded cells from
dividing.

56
Q

Anchorage dependence:

A

cells will only divide when
attached to an external surface
a. Prevents cells from multiplying while floating
freely through the body

57
Q

p53 gene:

A

an important tumor suppressor gene that
regulates cell division
* Mutation of p53 causes the cell to divide in an
uncontrolled manner and leads to tumor formation

58
Q
A

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