Photosynthesis Basics

Study Notes

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create food (glucose) and oxygen.
The process occurs in two phases: the light-dependent phase (light phase) and the light-independent phase (dark phase).
The light phase occurs in the thylakoid membranes of chloroplasts, where light energy is absorbed by chlorophyll and used to split water molecules, releasing oxygen, hydrogen ions, and electrons.
The dark phase occurs in the stroma of chloroplasts, where carbon dioxide is reduced to glucose using the energy from the light phase.
Photosynthesis keeps the oxygen concentration in the atmosphere and water constant.
Photosynthesis keeps the level of carbon dioxide constant in the atmosphere and water.
Photosynthesis provides food for heterotrophic organisms.

Light intensity: At low light intensity, the rate of photosynthesis is low. The rate increases with light intensity until it reaches a maximum point where it plateaus.
Temperature: At low temperatures, the rate of photosynthesis is low. The rate increases with temperature until it reaches an optimum point. At higher temperatures, the rate decreases due to enzyme denaturation.
Carbon dioxide concentration: At low carbon dioxide concentration, the rate of photosynthesis is low. The rate increases with carbon dioxide concentration until it reaches the optimal point. At higher concentrations, the rate remains constant.

A greenhouse is a structure used to grow plants by providing optimal conditions of light, temperature, and carbon dioxide for maximum growth.
Optimum light intensity and temperature increase the rate of photosynthesis and stimulate plant growth.
Carbon dioxide levels inside a greenhouse decrease due to photosynthesis.
Farmers can pump carbon dioxide into a greenhouse to increase the rate of photosynthesis.

ATP (adenosine triphosphate) is a molecule that stores and transports energy within cells.
When a cell needs energy, ATP is broken down, releasing energy.
This energy is used to produce essential molecules like proteins and fats, and for processes like muscle contraction and movement of substances across cell membranes.

Cellular respiration is the process by which living organisms release energy from food.
There are two main types of cellular respiration: aerobic and anaerobic.
Aerobic respiration occurs in the presence of oxygen and produces carbon dioxide and water.
Anaerobic respiration occurs in the absence of oxygen and produces either lactic acid (in animals) or carbon dioxide and ethanol (in plants and yeast).
Aerobic respiration releases a larger amount of energy than anaerobic respiration.

Yeast and fungi respire anaerobically and are used in various industrial processes.
They are used to produce alcoholic beverages like beer and wine through fermentation.
Yeast cells are also used to cause bread to rise during baking.
The fermentation process is also used to produce cheese.

An experiment can be conducted to demonstrate that living organisms produce carbon dioxide during cellular respiration.
A snail is placed in a sealed jar with limewater.
Carbon dioxide exhaled by the snail reacts with the limewater, turning it milky.
This indicates the production of carbon dioxide by the living organism.