Photosynthesis and the Carbon Cycle

Vocabulary flashcards covering the mechanism of photosynthesis, chloroplast structure, stomatal regulation, leaf adaptations, and the carbon cycle.

Photosynthesis

A physiological process by which plant cells containing chlorophyll produce food in the form of carbohydrates using carbon dioxide, water, and light energy, releasing oxygen as a by-product.

Chlorophyll

The green pigment located in the chloroplasts of green plants that absorbs red and blue wavelengths of light and reflects green wavelength.

Chloroplast

A double membrane-bound, oval cell organelle containing thylakoids arranged in grana suspended in a colourless ground substance called stroma.

Thylakoids

Closely packed flattened sacs located inside chloroplasts that contain chlorophyll and are arranged in stacks called grana.

Grana

Piles or stacks of flattened thylakoid sacs situated within the colourless stroma of a chloroplast.

Stroma

The colourless ground substance in the interior of the chloroplast in which grana lie.

Stomata

Minute openings present in the epidermal layers of leaves responsible for the exchange of gases during photosynthesis.

Sugar Concentration Theory

A theory stating that guard cells photosynthesise and produce sugar during the daytime, becoming turgid and causing the stomata to open.

$K^+$ Ion Concentration Theory

A theory stating that stomatal opening and closing depends on a potassium ion gradient, where an increase in $K^+$ concentration inside guard cells causes stomata to open.

Palisade Layer

The region of mesophyll cells in leaves that acts as the centre for photosynthesis where light energy is trapped by chlorophyll.

Light-dependent Phase

A photochemical reaction taking place in the thylakoids where absorbed light energy splits water molecules into $H^+$ and $OH^-$, reducing NADP to NADPH and releasing molecular oxygen.

Hill Reaction

Another term for the light-dependent photochemical reaction phase of photosynthesis that occurs in the thylakoids of the chloroplast.

Polymerisation

The process by which several molecules of glucose are transformed immediately after formation to produce one starch molecule.

Translocation

The process of transporting soluble glucose (reconverted from starch at night) to different parts of the plant through the phloem.

Optimum Temperature for Photosynthesis

The temperature, usually up to $35\,^\circ\text{C}$, up to which the rate of photosynthesis increases with rising temperature.

Destarching

The experimental procedure of keeping a plant in darkness for $24\text{--}48\text{ hours}$ to deplete all starch from its leaves.

Carbon Cycle

A series of chemical reactions in which carbon is absorbed from the atmosphere in the form of $CO_2$, utilised by living organisms for body processes, and ultimately returned to the atmosphere.