Chapter 5 Flashcards
Photosynthesis
light energy is used to make glucose
Solar energy is converted into chemical energy
bc energy is stored in chemical bonds
Photosynthesis is carried out by
all organisms in plant kingdom and algae in protista kingdom
Photosynthesis equation
6CO2+ 12H20 → C6H12O6 + 6H20 + 6O2
Carbon dioxide + water → sugar + water + oxygen
What type of reaction is photosynthesis?
This is a reduction reaction because carbon in co2 is gaining electrons from hydrogen in water (reduction→ the gain of electrons or protons)
Autotrophs
organisms that make their own food
Chloroplasts are
enclosed by a double membrane and contains grana (consisting of layers of membranes called thylakoids)
What happens in the grana?
light-dependent reactions occur
What happens in the stoma?
the Calvin cycle (light independent reactions occur)
When light strikes an object, it can be
reflected, transmitted or absorbed
Something that appears red
reflects red light and absorbs all other colors of light
What do photosynthetic pigments do?
absorb light energy and use it to carry out photosynthesis
Pigments
substances that absorb light in the visible spectrum
Different pigments absorb
light of different wavelengths
What can participate directly in light-dependent reactions?
Only chlorophyll (green photosynthetic pigment) can participate directly in light-dependent reactions
What assists in photosynthesis?
Other pigments called antennae (or accessory pigments )
How do antennae assist in photosynthesis?
by capturing and passing on photons of light to chlorophyll a and thus expand the range of light that can be used to produce sugar
Accessory pigments include
chlorophyll b, carotenoids, and phycobilins
Chlorophyll b
green, absorbs all the other wavelengths of light besides green
Carotenoids
yellow, orange, and red pigments and are responsible for the color of carrots
Phycoblins
red pigments and are found in red algae that live deep in the ocean where there is very little light
Red/Blue are
Yellow/Orange are
absorbed
reflected
Only light that is absorbed can be
used to power the making of sugar
2 main processes of photosynthesis are
light-dependent reactions (light reactions) and light independent reactions
Both reactions only occur when
there is light
Function of light dependent reactions is to
produce energy (atp) and protons for the light independent reactions.
Function of light independent reactions
is to make sugar (pgal)
Light dependent reactions occur in the
grana of chloroplasts within specialized membranes called thylakoids
In these thylakoids are 100s of
light-absorbing complexed called photosystems
Each photosystem consists of
chlorophyll a and the accessory pigments, chlorophyll b and carotenoids
1 of the main results of light dependent reactions is that
large amounts of ATP are produced
in chloroplasts that same way as cellular respiration
in mitochondria by ETC and chemiosmosis
Flow of light-dependent reactions (in detail)
- Chlorophyll in grana absorb light
- Electrons become energized and escape from chlorophyll molecules into ETC
- Energy from these energized electrons pumps protons across thylakoid membrane
- Creates proton gradient
- Potential energy stored in this proton is converted into ATP as protons flow through and ATP synthetase channel
Flow of light-dependent reactions (simple)
Light→chlorophyll→energized electrons →ETC →proton gradient→ atp synthetase →atp
Where does water have a role in these reactions?
Water breaks down by a process called photolysis into electrons, protons, and oxygen atoms
Water’s Role:
Electrons
Electrons replace those lost by chlorophyll in the light dependent reaction
Water’s Role:
Protons
Protons pass through ATP synthetase channel and get carried by NADP to stroma for light independent reaction
Water’s Role:
Oxygen
Oxygen is released into the atmosphere as a waste product which is the source of oxygen in the atmosphere
In short, light dependent reactions
produce atp, provide protons to the calvin cycle in light independent reactions
Sugar is produced during the
calvin cycle of the light-independent reactions
Light independent reactions
Reactions occur in stroma, function is to produce sugar or pgal
In light-independent reactions,
CO2 (which plant takes in through leaves) combines with protons and electrons carried from light-dependent reactions by NADP to produce sugar
Equation of light-independent process
CO2+H^+ (protons) + electrons = PGAL
Carbon Fixation
incorporation of CO2 into a sugar molecule
Light Independent reactions occur
in cyclical process known as calvin cycle
Large amounts of ATP are required
to keep the calvin cycle running
All necessary ATP is produced during
light dependent reactions
Essence of Light-Independent reactions
- Take place in stroma
- Pgal or phosphoglyceraldehyde, a 3-carbon sugar C(H20)n is produced
- All important enzyme require for calvin cycle is rubisco (ribulose biphosphate_
- Uses large amts of atp
Differences between cellular respiration and photosynthesis:
Occurs:
CR: occurs all the time
PS: occurs only in light
Differences between cellular respiration and photosynthesis:
redox
CR: oxidation reaction
PS: reduction reaction
Differences between cellular respiration and photosynthesis:
relies on
both rely on ETC to produce proton gradient
Differences between cellular respiration and photosynthesis:
requires:
both require O2 and release CO2
Differences between cellular respiration and photosynthesis:
proton carrier is:
CR: NAD is proton carrier
PS: NADP is proton carrier
Differences between cellular respiration and photosynthesis:
ATP is produced by:
ATP synthetase
Differences between cellular respiration and photosynthesis:
contains which cycle?
CR: contains cycle process, krebs cycle
PS: contains cyclincal process, calvin cycle
Palisade layer consists of
tightly packed cells that contain chloroplasts
Palisade layer is where
majority of photosynthesis occurs
Spongy mesophyll contains
chloroplasts and also carries out photosynthesis
Cells in spongy mesophyll are
less tightly packed and surrounded by air spaces which allow for exchange of O, CO2, and water vapor
Epidermis layer
is clear, does not carry out photosynthesis
The epidermis layer is
waterproof layer of cutin that minimizes excessive water loss
Guard cells
controls opening and closing of stomates which allows for exchange of gasses with minimum water loss