Unit 4 -- The Carbon Cycle

Factors impacting photosynthesis

Temperature CO2 concentration Light intensity Light wavelength

Cuticle

A thin layer on the top of the leaf that protects from water loss and entry of pathogens

Upper epidermis (leaves)

A transparent layer of cells below the cuticle of the leaf. They allow light through the leaf for photosynthesis (given their transparent nature) and protect the cells beneath. These cells do not contain chloroplasts.

The geological carbon cycle

Carbon dioxide within the atmosphere is influenced by the reservoir of carbon in the oceans and bodies of water -- through process of diffusion, carbon is cycled between the two locations. When carbon dioxide enters the water, it dissolves and reacts with water. This process results in a carbonate that combines with Ca2+ to form calcium carbonate, which is used within the shells of marine organisms. When these organisms die, they may become part of the sediment on the ocean floor. This sediment turns into limestone, a significant carbon reservoir on the earth. This process can also occur with plants and land animals. Generally, however, land animals and plants that decompose result in carbon being stored in soil. The weathering of terrestrial rock and minerals also result in land carbon. Another method allowing carbon to reeneter the atmosphere is through eruption of volcanoes. Carbon dioxide as a result of subduction can be released through hydrothermal vents and eruptions.

The biological carbon cycle

Carbon's entrance into the food web (and thus usage in organic compounds) is primarily conducted through autotrophs. The majority of autotrophs use photosynthesis to acquire this carbon dioxide, and do so through two key methods -- capturing CO2 from the air and bicarbonate ions from the water. These are used to make organic compounds. The carbon moves to heterotrophs when they consume these organic molecules. Both autotrophs and heterotrophs use a process known as cellular respiration to acquire the energy within carbon-containing molecules, which releases the carbon within as carbon dioxide.

Guard cells

Cells found within the lower epidermis of the leaf that contain chloroplasts. Control the opening and closing of stomata

Vascular bundle (xylem)

Dead hollow tubes within the vascular bundles of the leaf. Transport water and minerals to the leaves and provide general support

Palisade layer

Densely packed layer of cells in the upper half of the leaf. They are the primary layer responsible for photosynthesis.

Vascular bundle (phloem)

Living cells in the vascular bundles. Transport products of photosynthesis out of the leaf.

Spongy layer

Loosely packed layer of cells on the bottom half of the leaf. A site of photosynthesis, but due to their lesser density/location they do not receive as much light as the palisade layer.

Chlorophyll

Found in the thylakoid sacs, chlorophyll is a green pigment that is responsible for absorption of light. Optimum light wavelengths for chlorophyll are ~420nm and ~662nm (blue and red, respectively).

Limiting factors

If the line increases, the LF is the x axis variable. If the line is not increasing, the LF is something else. If a second line is found higher, the LF is that which is changed.

Chloroplast structure

Inner membrane Outer membrane Granum -- refers to the stacks that compose the thylakoid Stroma -- site of light independent reactions, site of glucose production Thylakoid -- site of light dependent reactions, where sunlight is converted to chemical energy Thylakoid space Thylakoid membrane -- location of chlorophyll, light absorption

Glycolysis

Occurs in the cytoplasm. Involves the process of glucose being split into two pyruvic acids. Uses two ATP and creates four more, as well as two NADH.

Electron transport chain

Occurs in the inner mitochondrial membrane. Uses NADH and FADH2 produced in previous steps of respiration, and produces a significant amount of ATP.

Mitochondria structure

Outer membrane Intermembrane space Inner membrane -- electron transport chain Cristae Matrix -- site of Kreb's cycle

Stomata

Small holes in the lower epidermis. The site of gas exchange.

Anthropogenic effects upon the carbon cycle

The burning of fossil fuels results in carbon dioxide entering the atmosphere. Due to global demand for these resources, elevated levels of atmospheric CO2 have occurred. Deforestation is also a significant contributor to increasing atmospheric CO2 levels, given that trees sequester carbon.

Cellular Respiration

The controlled release of energy from food in cells. Equation: C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP

Photosynthesis

The conversion of light energy into chemical energy (sugars, starch) Equation: 6CO2 + 6H2O -> C6H12O6 + 6O2

Carbon Cycle

The organic circulation of carbon from the atmosphere into organisms and back again. The carbon cycle can be understood as two key subcycles: - the rapid carbon exchange among living organisms - the long-term cycling of carbon through geologic processes

Anaerobic fermentation

The process of breaking down pyruvate in the cytoplasm in the absence of oxygen. Occurs as either: Alcohol fermentation in yeast Lactic acid fermentation in human muscle cells

ATP production from cell respiration

Theoretically, a production of 38 ATP would occur from a single molecule of glucose, this does not occur under most circumstances. Newer sources estimate a yield of 30-32 ATP.

Lower epidermis

Transparent layer of cells on the bottom of the leaf. Contain stomates. Primarily for protection.

Light independent reactions

Use ATP and NADPH to convert carbon dioxide into carbohydrates through process of the calvin cycle. Occurs in the stroma.

Light dependent reactions

Use light energy and water to make ATP and NADPH, producing oxygen as a byproduct. Occurs in the thylakoids of the chloroplast

Alcohol fermentation

Uses pyruvate to produce ethanol and carbon dioxide.

Lactic acid fermentation

Uses pyruvate to produce lactic acid but no carbon dioxide.

Kreb's Cycle

second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. Occurs in the mitochondrial matrix. Produces two ATP, 6NADH, 2FADH2, and 6 CO2.

Air spaces

used for gas exchange in the leaf; found mostly within the spongy layer.