CHAPTER 8

CELLULAR ENERGY

• SECTION 8.1 – HOW ORGANISMS OBTAIN ENERGY• MAIN IDEA – All living organisms use

energy to carry out all biological processes.

• QUESTIONS: What is energy?• Why do living things need energy?• How do humans obtain energy?

• TRANSFORMATION OF ENERGY• Chemical reactions and processes in your

cells are continuous, even when you don’t think you are using any energy. –Macromolecules are assembled and

broken down, substances are transported across cell membranes and genetic instructions are sent.•All require energy–Energy is the ability to do work.

• LAWS OF THERMODYNAMICS

•1st law of thermodynamics is the law of conservation of energy, which states that energy can be converted from one form to another, but cannot be created nor destroyed.

• AUTOTROPHS AND HETEROTROPHS• Autotrophs make their own food

using energy from the sun.–Convert light energy from the

sun into chemical energy.• Heterotrophs need to eat food to

obtain energy

• METABOLISM• Metabolism is all of the chemical

reactions in a cell.• ATP: THE UNIT OF CELLULAR ENERGY• Adenosine triphosphate (ATP) is the

most important biological molecule that provides chemical energy.

• ATP STRUCTURE• ATP is a multipurpose storehouse of chemical

energy that is used by cells in a variety of reactions.–Most abundant energy carrier molecule in

cells & found in all types of organisms.• ATP is a nucleotide made up of a adenine

base, a ribose sugar, and 3 phosphate groups.

• QUESTION: What macromolecule group does ATP belong in?

• ATP FUNCTION• ATP’s function is to release energy when

the bond between the 2nd and 3rd phosphate groups are broken–Forms adenosine diphosphate (ADP)

and a free phosphate group•Energy is released

• SECTION 8.2 – PHOTOSYNTHESIS• MAIN IDEA – Light energy is trapped and

converted into chemical energy during photosynthesis.

• QUESTIONS: What is the benefit of photosynthesis for humans?• How does photosynthesis benefit plants?

• OVERVIEW OF PHOTOSYNTHESIS• Photosynthesis is a process where light energy is converted

into chemical energy.• Chemical equation for photosynthesis is:

light

6CO2 + 6H2O C6H12O6 + 6O2 • Photosynthesis occurs in 2 phases:– Phase 1 – light dependent reactions – where light energy

is absorbed and converted into chemical energy in the form of ATP and NADPH

– Phase 2 – light independent reactions – where the ATP and NADPH that was made in phase one are used to make glucose.• After glucose is produced it can be joined with other

simple sugars to form larger molecules like starches• Can also make proteins, lipids, and nucleic acids.

• PHASE 1 – LIGHT REACTIONS• Chloroplasts capture light energy in photosynthesis.– Mainly found in the cells of leaves.• Disk-shaped organelles that contain 2 main

compartments essential for photosynthesis.– Thylakoids – flattened, saclike membranes that are

arranged in stacks called grana» Light dependent reactions take place within the

thylakoids.– Stroma are fluid filled spaces outside the grana.» Light independent reactions in phase 2 take place here.

• Pigments are light absorbing colored molecules that are found in the thylakoid membranes of the chloroplasts.– Different colored pigments absorb specific wavelengths of light.• Chlorophylls• Carotenoids

• PHASE 2: THE CALVIN CYCLE• In the Calvin Cycle energy gets

stored in organic molecules like glucose.

• SECTION 8.3 – CELLULAR RESPIRATION• MAIN IDEA – Living organisms obtain

energy by breaking down organic molecules during cellular respiration

• QUESTION: Is air the same as oxygen?

• If it is not the same, how is air different from oxygen?

• OVERVIEW OF CELLULAR RESPIRATION• Organisms obtain energy by a process called cellular respiration.– During cellular respiration electrons are collected from carbon

compounds, like glucose, and use that energy to make ATP.• ATP is used to provide energy for cells to do work.

• Equation for cellular respiration is the opposite of the equation for photosynthesis.

• C6H12O6 + 6O2 6CO2 + 6H2O

• Cellular respiration has 2 parts:– Glycolysis• Anaerobic process (does not require oxygen)

– Aerobic respiration (Requires oxygen)• Includes:– Krebs Cycle– Electron transport

• GLYCOLYSIS• Glycolysis is the process where glucose is

broken down in the cytoplasm.–2 ATP molecules are required to start

the reactions.–Produces:•2 molecules of ATP and 2 molecules of NADH for each molecule of glucose that is broken down.•2 pyruvate molecules

• KREBS CYCLE• The 2 pyruvate molecules are

transported to the mitochondria.• In the mitochondria with the help of

oxygen the pyruvate is broken down into:–6 CO2

–2 ATP–8 NADH–2 FADH2

• ELECTRON TRANSPORT• Electron transport is the final step in the

breakdown of glucose.• Electrons move along the mitochondrial

membrane from one protein to another.• The electron transport produces:–32 ATP

• In eukaryotes one molecule of glucose yields 36 ATPS under ideal conditions.

• PHOTOSYNTHESIS AND CELLULAR RESPIRATION

• Photosynthesis and cellular respiration are 2 important metabolic pathways that cells use to obtain energy.

• Photosynthesis products are oxygen and glucose, but these are the reactants for cellular respiration

• Cellular respiration products are carbon dioxide and water, but these are the reactants for photosynthesis