Energy in a Cell The Need for Energy

Cell Energy Autotrophs – make their own food Heterotrophs must get energy from consuming other organisms

Autotrophs – such as plants, make food from light energy Light energy is transformed into chemical energy as chemical bonds

 All chemical bonds store energy, some more than others

 There is a LOT of energy in a carbon to carbon bond (these are in organic molecules such as sugar)  There is too much energy in a carbon-carbon bond for normal cell processes

 So…mitochondria break down organic compounds, like sugars and fats, and convert the energy into ATP or adenosine triphosphate

ATP  Composed of:  Adenine – amino acid  Ribose – 5-carbon sugar  3 phosphate groups  The phosphate groups are charged particles

ATP  It requires a lot of energy to force the phosphate groups to bond because of their same charges  All that energy becomes available when the bonds are broken between the phosphates

ATP  When ATP has the last phosphate broken off to release the energy, it becomes ADP (adenosine diphosphate)

Photosynthesis Trapping the Sun’s Energy

The Photosynthesis Equation  Word equation:  Carbon dioxide + water light > glucose + oxygen  Chemical equation:  6 CO H 2 O light > C 6 H 12 O O 2

Light and Pigments  Photosynthesis requires light-catching pigments  Chlorophyll  Accessory pigments include: xanthophyll and beta carotine

Reactions in the Chloroplast  Thylakoids – membrane sacs that contain clusters of pigment molecules called photosystems  Grana- stacks of thylakoids  Stroma – area outside the thylakoid

 Light dependent reactions happen in the thylakoids (that’s where the light- catching pigments are)  Light independent reactions happen in the stroma

NADPH  The process of capturing sunlight results in the formation of high energy electrons  These high energy electrons require special carrier molecules

NADPH NADP + is a carrier molecule. NADP + is a carrier molecule. - nicotinamide adenine dinucleotide phosphate - accepts a pair of high energy electrons along with a hydrogen ion: H +- accepts a pair of high energy electrons along with a hydrogen ion: H + - creates NADPH

Light Dependent Reactions  Requires Light  Turns ADP and NADP + into the high energy carriers ATP and NADPH

How does it work?  Light is first absorbed by pigments in Photosystem II  Absorbed light increases energy in electrons which are passed to electron transport chain  New electrons for chlorophyll come from water

 High energy electrons travel from Photosystem II to Photosystem I on the Electron Transport Chain  Electron Transport Chain drives transport H + across the membrane of the thylakoid

 Photosystem I reenergizes high energy electrons and transfers them to NADP + which becomes NADPH after picking up H +  Process creates a charge difference across the thylakoid membranes; restoring the charge balance drives ATP creation

 H + concentration is higher on one side of the thylakoid membrane than the other  Facilitated diffusion happens to correct charge imbalance

 ATP synthase helps with facilitated diffusion of hydrogen ions, but uses their passage to create ATP  Drives ATP synthesis

The Calvin Cycle  ATP and NADPH are not stable enough to store energy for long  The Calvin Cycle converts less stable, high energy molecules into high energy sugars (glucose)  Calvin Cycle is light- independent

How Does it Work?  6 carbon dioxide molecules combine with 6 5-carbon molecules  combine with six 5-carbon molecules which split creating twelve 3 carbon molecules

 3 carbon molecules are then converted to high energy form using the energy from ATP and NADPH  2 of the twelve 3-carbon compounds are converted to similar molecules and combined to form a 6-carbon sugar

 The remaining ten 3-carbon compounds are recombined into 5-carbon compounds and re- enter the cycle  Plants use 6-carbon sugars for energy for growth and repair, and to construct complex carbohydrates like cellulose

Chap 9.2: Photosynthesis (summary)  Photosynthesis happens in 2 stages; light-dependant reactions, and light-independent reactions in the chloroplast.  Light-dependant reactions - energy is passed down the electron- transport chain to form ATP

 Photolysis of water releases O 2 and restores electrons for electron transport chain. NADPH forms for use in light-independent rxs.  Light-independent reactions (Calvin Cycle) uses CO 2 to form sugar in the stroma of the chloroplast.

Cellular Respiration

Chapter 9.3: Big Ideas  Cellular Respiration happens in 3 stages:  glycolysis,  the citric acid cycle(Krebs cycle),  the electron transport chain.

Chapter 9.3: Big Ideas (cont)  Glycolysis- breaks down glucose to make pyruvic acid and ATP to start the respiration process.

Chapter 9.3: Big Ideas (cont)  Citric Acid cycle- breaks down Acetyl-CoA and forms ATP and CO2 in the Mitchondria  Electron Transport Chain- Produces ATP and H2O

Cellular Resp. Overview Process used by cells to release energy from foods using oxygenProcess used by cells to release energy from foods using oxygen oxygen + glucose  carbon dioxide + water + energyoxygen + glucose  carbon dioxide + water + energy

Cellular Resp. Overview (cont) 6 O 2 + C 6 H 12 O 6  6 CO H 2 O + Energy6 O 2 + C 6 H 12 O 6  6 CO H 2 O + Energy Involves glycolysis and the Krebs or Citric Acid CycleInvolves glycolysis and the Krebs or Citric Acid Cycle

Glycolysis  Basically: one glucose (6- carbon sugar) is split into 2 pyruvic acid (3-carbon molecules)  2 ATP are needed to start process, but 4 ATP are produced

Glycolysis (cont)  NAD + is another high energy electron pair acceptor  2 NADH are created by glycolysis; can be used to make ATP  No oxygen needed

The Krebs Cycle and Electron Transport  Aerobic part of cellular respiration  The Krebs cycle breaks pyruvic acid into carbon dioxide and water using oxygen

The Krebs Cycle a.k.a. Citric Acid Cycle  Pyruvic acid enters mitochondrion from the cytoplasm  1 carbon is broken off as carbon dioxide; 2-carbon compound is left

 2-carbon compound binds with coenzyme A to form acetyl- coenzyme A (acetyl-coA)  Acetyl-coA attaches to a 4- carbon compound to form citric acid ( hence the name Citric Acid Cycle )

 Through various intermediate stages; 2 more carbons are released as carbon dioxide  A 4-carbon compound is left; this will attach to the next acetyl-coA and the cycle starts over

Electron Transport  A series of molecules that uses high-energy electrons to convert ADP into ATP

Electron Transport  High energy electrons are passed along the electron transport chain; at the end, there is usually an enzyme that transfers the electrons to oxygen and hydrogen to form water

 Every time a pair of electrons travels down the chain, their energy is used to send H + across the membrane.  This creates an area of high H + concentration and an area of low H + concentration

 Facilitated diffusion occurs to try to bring H + concentrations to equilibrium  The carrier molecule is ATP synthase which make an ATP for every H + that goes across the membrane  1 pair of high energy electrons = 3 ATP

The Totals  Glycolysis = 2 ATP  Krebs/Electron Trans=34ATP  Total36 ATP

Fermentation  Anaerobic way to process food to get energy  Everything starts with Glycolysis

Alcoholic Fermentation  Pyruvic acid + NADH  alcohol + CO 2 + NAD +  Yeast works on an alcoholic fermentation system

Lactic Acid Fermentation  Pyruvic acid + NADH  lactic acid + NAD +  Muscle cells can build up lactic acid when they are forced to work without enough of an oxygen supply

Photosynthesis and Cellular Respiration Photosynthesis Cellular Respiration Function Energy storage Energy release LocationChloroplastsMitochondria Reactants CO 2 and H 2 O C 6 H 12 O 6 and O 2 Products CO 2 and H 2 O Equation 6 CO H 2 O -> C 6 H 12 O 6 + 6O 2 6O 2 + C 6 H 12 O 6 - > 6 CO H 2 O