Chapter 4 Cells and Energy

Ashley Fisher

PhotosynthesisIs the process whereby organisms convert light energy into chemical bond energy of glucoseIt occurs in the Chloroplasts of plant cells

All cells need chemical energy to survive• The chemical energy used for most cell processes is carried by ATP• Think of ATP as a wallet filled with money:

Just like a wallet carries money that you can spend, ATP carries chemical energy that cells can use. Cells use ATP for functions such as building molecules and moving materials by active transport. The energy carried by ATP is released when a phosphate group is removed from the molecule. ATP has 3 phosphate groups, but the bond holding the third phosphate group is unstable & easily broken. The removal of the 3rd phosphate involves a reaction that releases energy, when the phosphate is removed, energy is released and ATP becomes ADP, a lower energy molecule.

ATP – Temporary energy storage molecule

energy is release to allow reactions to happen, such as changing the shape of a protein

ATP is a readily usable form of chemical energy. By breaking off the 3rd phosphate (ATP = adenosine triphosphate),

Chemosynthesis:

Organisms who use chemical energy instead of light energy to make energy storing carbon based molecules.

(Not all organisms have access to light and photosynthesis, such as organisms that live in the deep ocean.)

Animals/plants use energy from sunlight…• The energy from sunlight comes from ATP• ATP is made from the breakdown of sugars• Photosynthesis: is the process that captures energy from sunlight to

make sugars that store chemical energy. Therefore, the energy for all organisms begins as sunlight.• Chlorophyll: is a molecule in chloroplasts that absorbs some of the

energy in visible light.• Chloroplasts: where photosynthesis takes place in plants

There are two stages to photosynthesis:1. Light Dependent Reactions• Energy is captured from sunlight• Energy is transferred to electrons on an electron transport chain

pg103• Water molecules are broken down, they provide energy for transport• The products are oxygen, NADPH, and ATP• Energy from NADPH and ATP are used later to make sugar.2. Light –Independent Reactions (Calvin Cycle)- do not need sunlight- can take place anytime energy is available. The energy source is ATP and NADPH formed during the light-dependent reactions.

The Calvin cycle uses CO2, ATP, and NADPH to make simple sugars. Creates a 6 carbon sugar such as glucose.

Cellular Respiration: pg 107

Cellular Respiration: releases chemical energy from sugars and other carbon based molecules to make ATP when oxygen is present. • Cellular respiration is aerobic- meaning it needs oxygen to take place.• Cellular respiration takes place in the mitochondria, because in the

mitochondria is where most of the cell’s ATP is made.Mitochondria CAN NOT directly make ATP from food• Food broken down into glucose molecules• Glycolysis- splits glucose molecules into two 3-carbon molecules and

makes two molecules of ATP. Glycolysis takes place in the cytoplasm and does not need oxygen, therefore it is anaerobic.• However, glycolysis is necessary for cellular respiration. The products

of glycolysis are broken down in the mitochondria to make more ATP.

Cellular Respiration: Coverts sugar into ATP using oxygenGlycolysis: splits glucoseThe Krebs Cycle: transfers energy to the electron transport chain, which produces most of the ATP in eukaryotic cells.The Krebs has two stages• Breaks down carbon based molecules and• transfers energy to electron carriers – the electron carriers provide

energy to the electron transport chain. ATP is produced by the electron transport chain.

Photosynthesis and cellular respiration are two major processes of carbon cycling in living organisms.

One similarity between photosynthesis and cellular respiration is both convert light energy into chemical energy.

Photosynthesis vs. Respiration• Think of Photosynthesis like baking a cake. The plant takes raw

material (CO2 and H20) and uses light energy to make Glucose (and releases O2 in the process)

Respiration is the process whereby organisms break down glucose to provide energy to all life processesBreaks down glucose (sometimes with O2 and others without it), transfers energy to a small energy transferring compound called ATP• Think of Respiration like burning the cake. Energy is released from the

bonds of glucose to be stored as ATP.

All plants (photosynthetic organisms) undergo both Photosynthesis (only in the presence of light) and Respiration (all of the time)

All living organisms must go through respiration 24/7

Process Energy Transformations

Photosynthesis CO2 and H2O are transformed using the energy from sunlight to create C6H12O6 and O2. The captured and used energy is stored in the chemical bonds of glucose (C6H12O6)

Cellular Respiration O2 and C6H12O6 are broken down with a small amount of invested energy to form CO2 + H2O and a large amount of ATP which is the energy storage molecule of living things

Energy in

Energy in

Energy out

Energy outRespiration

Photosynthesis

Energy transformations involved in photosynthesis are related to energy transformations involved in cellular respiration…• They are, in essence, the reverse of each other. The products of

photosynthesis become the reactants for cellular respiration, and the opposite is true.• Again, one bakes the cake and the other one breaks it down to

release the energy