Chapter 15- Autotrophic Nutrition Flashcards
Autotroph
An organism that manufactures its own organic molecules such as glucose, amino acids, and fats
Organic molecules contain potential energy in form of:
organic bonds
Photosynthesis
A metabolic process where solar energy is trapped, converted to chemical energy, and then stored in the bonds of plant organic nutrient molecules.
Plants use Co2 and water to make:
glucose and oxygen
Chloroplast
Specialized organelle in plants where photosynthesis takes place. Highly organized plastid containing the chlorophyll pigment
Do photosynthetic bacteria have chloroplasts?
No, but they have membranes that function in a similar manner.
Chloroplast is bounded by:
Two membranes and contains a network of membranes called thylakoid membranes.
Chlorophyll resides within the:
thylakoid membranes
Grana
Stacks of thylaoid membranes
Stroma
fluid matrix of the chloroplast
Cofactor of chlorophyll?
Magnesium
Why is chlorophyll green?
It absorbs light in red and blue wavelengths
Two types of chlorophylls?
A and B
Photosystem
light-capturing unit of the thylakoid membrane.
What is each photosystem composed of?
A number of chlorophyll molecules. In the center is a single chlorophyll molecule coupled to other proteins that is ultimately excited by the absorbed photon.
Photosystem I: Chlorophyll A molecule is called because—
it absorbs best at 700 nm
Photosystem II= 680 nm
Net reaction of photosynthesis:
6CO2 + 12 H2O + light energy —-> C6H12O6+ 6O2+ 6H20
Light reactions
Convert solar energy into chemical energy in the form of ATP (photophosporylation) and NADH. Must take place in light.
Dark reactions
Coupled to light reactions. They incorporate Co2 into organic molecules in a process called carbon fixation.
Carbohydrates are produced by reducing CO2
Cyclic electron flow
Photons of light excite electrons in P700 PSI. the high energy electrons are transferred to NADP+ and forms NADH
P700 is left with electrol hole and is a powerful oxidizing agent
What happens when light strikes P680 in PSII
Electrons are excited and travel down the same electron carrier chain used by cyclic electron flow until they reach P700 and fill in the electron holes– this is NONCYCLIC photophosphorylation
How does P680 fill its electron holes
P680 is a strong enough oxidizing agent to oxidize water and fill its holes. Water is split into two hydrogen ions and an oxygen atom, and the electrons produced reduce P680. Oxygen atoms combine to form O2
What is the net result of noncyclic electron flow?
Productin of NADPH and ATP and the photolysis of water
Photoionization
Escape of high energy electrons from chlorophyll molecules.
What do dark reactions use? What do they produce?
They use ATP and NADPH produced by the light reactions to reduce CO2 to carbohydrates, primarily glucose.
When do dark reactions take place?
During days when light reactions are replenishing supply of ATP and NADPH. Doesn’t need direct light.
What is the source of carbon for carbohydrates production in the Calvin Cycle?
CO2
What is the product of the calvin cycle?
Three-carbon sugar phosphoglyceraldehyde (PGAL)
What must happen to produce three-carbon sugar from the calvin cycle?
It must take place 3 times
What happens during the calvin cycle?
CO2+ ribulose biphosphate (5 c sugar) which produuces an unstable six-carbon intermediate which splits to two 3-carbon molecules of 3-phosphoglyceric acid.
Acid phosphorylated by ATP and reduced by NADPH to give PGAL (glycealdehyde-3-phosphate)
Two molecules of PGAL can be converted into glucose, which can then be oxidize to provide usable energy.
What is the Calvin cycle similar to?
The Krebs cycle in revese
What happens to most of the PGAL?
It is recycled to RBP by a complex series of reactions
In 6 turns of the Calvin cycle, what is formed?
12 PGAL from 6 CO2 and 6RBP
The 12 PGAL recombine to form 6 RBP and 1 molecule of glucose, the net product.
Prime end product of photosynthesis
PGAL
What can PGAL be used as?
An immediate food nutrient combined and rearranged to form monosaccharide sugars (such as glucose) which can be transported to other cells
It can also be packaged for storage as insoluble polysaccharides such as starch.
Waxy cuticle of lead
Adaptation to reduce transpiration and conserve water. Leaves have no openings on the upper surface
Palisade
Adaptation of leaf. Layer of elongated, chloroplast-containing cells spread over a large surface area. Directly under the upper epidermis and are well exposed to light.
Spongy layer.
Adaptation of leaf. Stomata open to air spaces that contact internal moist surface called spongy layer cells.
Necessary for diffusion of gases into and out of cell, for photosynthesis and respiration.
Contain chloroplasts
Guard cells
of leaves. Surround each stomata on the lower surface of the leaves. Regulate the size of the opening.
Open stomata during day to admit CO2 for photosynthesis and clsoe them at night to limit the loss of water vapor by transpiration
Stomata
Openings in the lower epidermis of a leaf that permit diffusion of carbon dioxide, water vapor, and oxygen between the leaf and the atmosphere.
What do guard cells do during the day?
Produce glucose
What does the presence of high glucose content in the cells do?
They swell up by osmosis (turgor). Because the inner wall of the guard cell is thickened, the swelling produces a curvature of the opening between the guard cells and the stomata opening the increases.
What happens at night?
Cell turgor decreases and turgor pressure decreases.
What will happen in the stomata during a drought?
The stomata will close even during the day time to prevent loss of water by transpiration. Photosynthesis will cease because of a lack of CO2.
Vascular bundle
Veins containing xylem and phloem bring water to the leaf from roots (x) and carry manufactured food out of the leaf (p)
Specialized epidermal cells with thin-waled root hair are found in the:
What do they do?
Root. They provide an increased surface for absorption of water and minerals by diffusion and active transport.
Chemosynthesis
Use of chemical energy by bacteria to form carbohydrates. Use chemical energy rather than radiant energy from the sun.
What do nitrifying cateria do?
Oxidize ammonia and nitrites into mitrates.
The plants use this nitrate to make proteins.
The bacteria use the energy obtained from this oxidation to make glucose.
Nitrogen, sulfur and iron bacteria
Bacteria that oxidize these elements– use the small amount of energy from this oxidation to form glucose and preform vital organs.
