Photosynthesis: Structure, Process, and External Factors

Comprehensive vocabulary flashcards covering chloroplast anatomy, the light and dark phases, external limiting factors, and the ecological importance of photosynthesis based on Grade 11 Life Sciences lecture notes.

Chloroplasts

Green disc-shaped plastids composed of an outer double membrane containing the stroma and grana, within which the process of photosynthesis takes place.

Double membrane (Chloroplast)

The outer boundary of a chloroplast that is permeable to water and carbon dioxide, allowing $H_2O$ and $CO_2$ to enter easily.

Grana

Structures in the chloroplast made up of thin flat discs called lamellae that contain chlorophyll to trap sunlight and present a large surface area for light absorption.

Lamellae

Thin, flat disc-like membranes that make up the grana and contain chlorophyll.

Stroma

The fluid-filled interior of the chloroplast that contains enzymes required for the chemical reactions of the dark phase.

Chloroplast Ribosomes

Structures located in the stroma that synthesize enzymes necessary for photosynthesis.

Starch Granule

A chloroplast structure that serves to temporarily store glucose manufactured during photosynthesis.

Light Phase

The light-dependent stage of photosynthesis taking place in the grana, where chlorophyll traps light energy, $H_2O$ is utilized, $O_2$ is released through stomata, and ATP along with $H^+$ are produced.

Dark Phase

The light-independent stage of photosynthesis taking place in the stroma that can occur in light or darkness, in which $CO_2$ from the atmosphere is combined with $H^+$ and energy from ATP to produce glucose ($C_6H_{12}O_6$).

External Factors Affecting Photosynthesis

Environmental factors that influence the rate of photosynthesis, specifically carbon dioxide concentration, light intensity, wavelength of light, and temperature.

Atmospheric Carbon Dioxide Concentration

The proportion of carbon dioxide naturally present in the atmosphere, which is approximately $0{,}03\%$.

Effect of Carbon Dioxide Concentration on Photosynthetic Rate

The rate of photosynthesis increases as $CO_2$ concentration increases; however, if $CO_2$ levels remain high over a long period, the rate levels off due to toxic (poisonous) effects or other limiting factors.

Effect of Light Intensity on Photosynthetic Rate

The rate of photosynthesis increases as light intensity increases until a certain intensity is reached, where it levels off due to other limiting factors like insufficient water or carbon dioxide.

Limiting Factors

Environmental conditions (such as insufficient water, light intensity, or carbon dioxide) that restrict the rate of photosynthesis, preventing it from increasing further and causing it to level off.

Optimum Temperature (Photosynthesis)

The temperature at which the rate of photosynthesis reaches its highest point before declining as temperatures become too high.

Provision of Food/Energy (Biological Importance)

The function of green plants trapping radiant energy to manufacture organic compounds, allowing light energy to be transferred to organisms in higher trophic levels that lack chlorophyll.

Control of Carbon Dioxide/Oxygen Levels (Biological Importance)

The maintenance of a constant atmospheric $CO_2/O_2$ ratio by photosynthesizing plants consuming harmful accumulations of $CO_2$ (from respiration, combustion, and decay) and releasing $O_2$ for cellular respiration.