Cellular Energy and ATP lecture 6

Lecture 6 Objectives

• Identify the major energy needs of plant and animal cells
• Describe the basic structure and function of the mitochondrion
• Describe the importance of cellular compartments in energy conversion.
• Outline the mechanism of ATP synthesis and the role played by ATP in powering cellular activity.

Energy Flow

• Photosynthesis occurs only in plants
• Cellular respiration occurs in both plants and animals
• Photosynthesis uses CO2 + H2O and light energy, to generate organic molecules + O2
• Cellular respiration breaks down organic molecules and generates ATP

Adenosine Triphosphate (ATP)

• ATP is an energy carrier
• ATP's structure includes Adenine, Ribose, and a Triphosphate group

Energy Requirements of the Cell

• Energy is needed for :
• Mechanical work e.g. motor proteins
• To make new materials e.g. growth and replacement
• Transport e.g. transport of molecules across membranes
• As well as to maintain order

Mitochondria

• The site of cellular respiration is the mitochondria
• The conversion of chemical energy is shown as: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
• Mitochondria are organelles that are present in numbers from 1-1000's per cell
• The quantity depends on energy demand
• Consist of mitochondrial DNA & ribosomes
• Produces some, but not all mitochondrial proteins
• Have two membranes
• Inner and outer
• inner membrane is highly folded (cristae)
• Have two compartments that are functionally important:
• Matrix, inside the inner membrane
• Intermembrane space

Overview of Cellular Respiration

• Harvesting chemical energy from glucose occurs in three stages, each in a different location
• Compartments of the mitochondrion are essential for cellular respiration

Cellular Respiration: Glycolysis

• Glycolysis is the first stage of Cellular Respiration
• Glycolysis occurs in the cytosol
• Sugar or glucose (6 C molecule) is converted into two pyruvate molecules (2 x 3 C molecules)
• Generates 2ATP and electrons are transferred to the high energy electron carrier - NAD+ making NADH

Cellular Respiration: Pyruvate Oxidation & Citric Acid Cycle

• Second Stage of cellular respiration
• Takes place in the Mitochondrial Matrix
• Through Pyruvate Oxidation & the Citric Acid Cycle, 2 pyruvate molecules are converted to 2 Acetyl CoA molecules that enter the citric acid cycle
• Energy carrier ATP and high energy electron carriers NADH & FADH2 are outputted by this stage
• C6H12O6 + 6O2-> 6CO2 + 6H2O + Energy

Cellular Respiration: Stages 1 & 2 - Summary

• Cellular respiration starts with glucose
• Outputs include ATP and some NADH & FADH2

Cellular Respiration: Oxidative Phosphorylation

• Third stage of cellular respiration
• Occurs in the Inner Membrane of the Mitochondrion
• Has two parts
• Electron transport
• Chemiosmosis

The Inner Mitochondrial Membrane

• The inner membrane is highly folded (Cristae) and functionally important
• Intermembrane space is also functionally important

Cellular Respiration: Oxidative Phosphorylation Part 1, the Electron Transport Chain

• Electron carriers NADH and FADH2 shuttle high energy electrons to the inner mitochondrial membrane
• The Electrons then move through protein complexes embedded in the inner membrane
• Protons (H+) are pumped across the membrane as the electrons move

Cellular Resiration: Proton Gradient

• Protons (H+) accumulate in the intermembrane space
• This concentration gradient on either side of the inner mitochondrial membrane
• The mitochondrion's compartments are imporant for the process
• This accumulation of protons is crucial to the next step

Cellular Respiration: Chemiosmosis

• Chemiosmosis is the second part of oxidative phosphorylation
• The inner mitochondrial membrane contains the protein complex ATP synthase
• Protons move from a high to low concentration through ATP synthase, and this process results in ATP production from ADP
• ADP + Pi -> ATP

Summary of Cellular Respiration

• Chemical energy is converted from one form to another
• Glucose becomes ATP, an energy carrier used by the cell
• The mitochondrial structure enables the proton gradient to be established across the inner membrane, which drives ATP production
• Glucose and oxygen are consumed during cellular respiration
• Cellular respiration produces carbon dioxide, water, and ATP

Adenosine Triphosphate (ATP)

• ATP powers cellular activity and enables a controlled release of energy

Adenosine Triphosphate (ATP)

• The regeneration of ATP is essential
• The cell constantly uses and regenerates ATP

Lecture Summary

• Plant and animal cells require energy for growth and maintenance – The mitochondrion is the organelle where chemical energy is converted into a useable form (ATP)
• Mitochondrial membrane structure and compartments are essential for different stages of cellular respiration
• ATP synthesis in cellular respiration occurs in oxidative phosphorylation and requires ATP synthase and high energy electrons from earlier stages (glycolysis, pyruvate oxidation, and citric acid cycle)
• ATP, the output of cellular respiration, is the main energy carrier of the cell