Photosynthesis: An Overview

My AP Biology Thoughts Unit 3 Cellular Energetics

Welcome to My AP Biology Thoughts podcast, my name is Shriya Karthikvatsan and I am your host for episode # called Unit 3 Cellular Energetics: Overview of Photosynthesis. Today we will be discussing what exactly Photosynthesis is, its importance to life, and the processes that make up it.

Segment 1: Introduction to Photosynthesis

• We’re going to start off by discussing exactly what photosynthesis is, its importance, and a brief overview of the different stages of it
• Photosynthesis is when light energy is captured by photosynthetic molecules that are broken down in cellular respiration to obtain energy (ATP)
• Essentially, glucose molecules (or other sugars) are constructed from water and carbon dioxide, and oxygen is released as a byproduct
• Also, the carbon in CO2 is used to make carbs and other organic molecules that the organism requires to survive
• The process of producing the organic molecules is called carbon fixation where the carbon in CO2 is “fixed” and incorporated into sugars to be used to build the organic molecules
• Photosynthesis is important because photosynthetic organisms such as plants, algae, and bacteria play a key role
• They introduce chemical energy and help fix carbon by utilizing light energy, meaning they can produce their own food and are therefore called photoautotrophs
• Since humans and other organism cannot convert carbon dioxide to organic compounds, they rely on the autotrophs for these compounds and to receive energy
• Also, photosynthesis is important because it produces oxygen as a byproduct which affects the Earth’s atmosphere and removes carbon dioxide from the atmosphere, preventing a gas buildup that would be detrimental to us
• Photosynthesis simplified can be divided into two stages: the light-dependent reactions and the Calvin Cycle
• The light-dependent reactions occur in the thylakoid membrane and require light energy
• The Calvin Cycle, or light-independent reactions, takes place in the stroma and doesn’t require light
• In the next segment, we are going to go more in depth about these two processes and the specific significant parts of a plant involved in them

Segment 2: More About Photosynthesis

• Okay to start we are going to go over the important parts of a plant involved in photosynthesis you should know
• Photosynthesis itself takes place in the chloroplast of a plant which contains chlorophyll which is the pigment that absorbs different wavelengths of light from the energy source
• The chloroplasts are surrounded by a double membrane and have a third inner membrane called the thylakoid membrane where light-dependent reactions take place
• The stroma is the fluid and space in the chloroplast
• Here is a diagram of both parts of photosynthesis