Cells and Energy Chapter 4 Cells and Energy

4.1 Chemical Energy & ATP  When you eat, the food you intake is made of Carbs, Proteins, and Lipids. Your body takes these compounds and breaks them down to release energy from their bonds.  All of this energy is made of a substance called ATP.

4.1 Chemical Energy & ATP cont.  ATP stands for Adenosine Triphosphate and is an energy storing compound.  ATP stores energy from food and the cell then uses ATP when it needs it.  ATP is like a bank, When you need money you withdraw from a bank. When the cell needs energy it withdraws and uses ATP.

4.1 Chemical Energy & ATP cont.  The cell uses ATP by breaking it down to ADP+P.  When the bond ADP+P is broken, large amounts of energy is released.  ADP is a lower energy molecule and is converted to ATP by the addition of a phosphate.  ADP is a bank account with very little money!

4.1 Chemical Energy & ATP cont.  Different compounds release different amounts of energy.  Carbohydrates create about 36 ATP’s per molecule.  Some fats create 146 ATP’s per molecule!

4.2 Overview of Photosynthesis  Some organisms are called Producers because the produce their own food.  Photosynthesis is a process that captures sunlight to make sugars that stores chemical energy.  Most of all energy for all organisms comes initially from the sun.  Plants absorb light that looks white, but is made of a variety of colors.  G

4.2 Overview of Photosynthesis  Photosynthesis occurs in Chloroplast.  There are 2 main parts to a chloroplast: 1. The Grana are stacks of coin shaped membranes where chlorophyll is stored. 2. The Stroma is the space around the Grana.

4.2 Overview of Photosynthesis  The actual substance that collects the sunlight is chlorophyll.  Chlorophyll is a light collecting pigment found inside of Chloroplast.  The Chlorophyll in the Chloroplasts collect mostly red and blue wavelengths, and not green.  This is why most plant foliage is green, because this is the wavelength of light that is reflected.

4.2 Overview of Photosynthesis  There are 2 main reactions in photosynthesis. 1. Light Dependent Reaction- captures energy from sunlight and occurs in the Grana. 2. Light Independent Reaction- uses energy from 1 st reaction to make sugars. This occurs in the Stroma.

4.2 Overview of Photosynthesis  Photosynthesis 1. The Light Reaction occurs in the Grana. Water and sunlight are needed for this part to occur. A.) Chlorophyll absorbs energy from the sunlight.The energy is transferred along the Grana. Water molecules are broken down and oxygen is released. H 2 O H+ O2 B.) Energy is transferred to molecules that carry energy like ATP.

4.2 Overview of Photosynthesis  Photosynthesis cont. 2.The Light- Independent Reactions use energy from light reaction to make sugars. These reactions occur in the Stroma. Carbon Dioxide (CO 2 ). A.) CO 2 is used to build large molecules. Energy from the light reaction is used. B.) A molecule of simple sugar is formed (C 6 H 12 O 6 ). The plant uses this sugar for energy.

4.2 Overview of Photosynthesis  The equation for the whole process is: 6CO2+6H2O C 6 H12O 6 +6O2 (Carbon Dioxide) (Water)(Sugar) (Oxygen)

4.3 Photosynthesis in detail  The overview of photosynthesis is just that… an overview. Photosynthesis is much more complex.  Everything starts with the collection of Light.  Pigments called Photo systems I & II collect sunlight. This is the Light – Dependent part of the reaction. ( The photo part of photosynthesis).

Steps of the light reaction of photosynthesis 1) Energy is absorbed by both photosystems. The energy is given to Electrons (photosystem II). 2) Water (H2O) is broken down into H+ ions, O2, and Electrons. The O2 is given off as a waste product. This is what we breathe. The electron replaces the ones that left photosystems in step 1. (photosystem II) 3) Hydrogen ions, from the split of H2O, get pumped into the Grana of the chloroplast. The energy from the Electrons are used here. (photosystem II)

Steps of the light reaction of photosynthesis cont. 4) Photosystem I absorbs light and energizes electrons. These electrons leave the molecules (photosystem I). 5) These electrons are added to NADP+ to form NADPH. NADPH is a energy storing compound like ATP.

Steps of the light reaction of photosynthesis cont. 6) H+ ions from the water molecule break-up to flow into the Grana. There are many more H+ ions in the Grana than outside. This creates an energy gradient. The energy from this gradient is used to attach a phosphate to ADP to make ATP.

Steps of the light reaction of photosynthesis cont.  The main purpose of the light dependent reaction is to create ATP & NADPH energy molecules to be used in the light independent reaction.

Summary Of Light Reaction:  Energy is captured by pigments called Photosystems.  Water molecules are broken; O2 released & electrons replace the ones that left the Photosystems.  Energized electrons do two things: 1. Added to NADP+ NADPH 2. Transport H+ ions

Summary Of Light Reaction cont.  H+ ion flow create energy to make ADP+P=ATP.  The products of the light reaction are ATP, NADPH, & O2. O2 is given off as gas and ATP&NADPH move to the Light Independent Reaction!!!!!  The second stage of Photosynthesis is called the Light-Independent Reaction.This is where the sugar is made for the plant.

Light Independent Reaction  The Light Independent Reaction also takes place in the chloroplast, however it occurs in the Stroma not the Grana. As its name implies, there is no need for sunlight because the energy for these reactions come from the ATP& NADPH from the light reaction.

Summary Of Light Independent Rx (The Calvin Cycle)  The Calvin Cycle is the light independent reaction, named after the scientist that founded it. It has 4 steps: 1) Carbon dioxide (CO2) are added to 5-carbon molecules making 6- carbon molecules 2) The 6 carbon molecules are split into (2) 3-carbon molecules. ATP & NADPH are used to do this. 3) All 3 carbon molecules enter the Calvin Cycle. Two of them eventually leave and bond together to form Glucose.

Summary Of Light Independent (The Calvin Cycle cont.) 4) The other 3 carbon molecules are recycled into5-carbon molecules & go back to start of process.  In summary, ATP & NADPH are used to take 3- carbon compounds and bond them together to make Glucose sugar= (C 6 H 12 O 6 )

4.4-Cellular Respiration - Plants use photosynthesis to gain energy. Animals gain energy by consuming food. The food, however, is not a direct source of energy. Plants and animals break down molecules from food to produce ATP.  Cellular Respiration is the process of releasing chemical energy from sugars & other organic compounds to make ATP.

4.4-Cellular Respiration cont.  Cellular Respiration is an Aerobic Process. This means that it needs oxygen in order to work.  All Cellular Respiration occurs in the Mitochondria which is why they are called the “Power house of the Cell”.

Cellular Respiration cont.  Once food is absorbed from the body, molecules of carbohydrates, proteins, & lipids are used to make energy.  Glucose, specifically, is broken down first in a process called Glycolysis.  Glycolysis occurs in the cytoplasm and is the 1 st step in cellular respiration.  Glycolysis is an Anaerobic process that breaks Glucose (C 6 H 12 O 6 ) down into (2) three carbon compounds. Two ATP’s are made in this process.  Once Glycolysis is over, the products move into the Mitochondria for more ATP production.

Cellular Respiration  Cellular Respiration is a mirror image of photosynthesis. Photosynthesis= 6CO2 + 6H2O C 6 H12O 6 +6O 2 Respiration= C 6 H12O 6 +6O2 6CO2+6H2O  Photosynthesis builds up an energy molecule in Glucose & Cellular Respiration breaks that molecule back down and makes ATP’s with it.  As we said earlier, Glycolysis is the 1 st step in Cellular Respiration. It happens in the cytoplasm. The products of Glycloysis are sent to the Mitochondria to continue respiration.

Cellular Respiration cont. Stage 1: Krebs's cycle 1) 3 carbon molecules from Glycolysis are broken down ATP as well as other energy compounds are made CO2 is given off. 2) Energy is transferred to 2 nd stage of cellular respiration.

Cellular Respiration cont. Stage 2: Electron Transport Chain 3) Energy is transferred to a chain of proteins in the inner membrane of the Mitochondria. 4) A large number of ATP molecules are made. O2 enters process & is used to make H2O. Water and Heat are released.

Glycolysis Summary  Glycolysis is an ongoing process in the cell cytoplasm  It is Anaerobic, which means it doesn’t require oxygen.  4 ATP’s are made through each cycle of Glycolysis, but Glycolysis needs 2 ATP’s to get started so net 2 ATP’s  Pyruvate is the end product of Glycolysis  If O2 is present after Glycolysis, the Pyruvate is sent to the Mitochondria for the 1 st step in cellular respiration

Krebs's Cycle summary  1 st stage of Cellular Respiration.  Must have O2 to happen ( Aerobic).  CO2 is given off as waste, high energy electrons are transferred.  Citric Acid is formed as an intermediate molecule. It is eventually broken down into simpler carbon compounds.  Products are: CO2, two ATP, and other molecules that store energy.

Electron transport summary  2 nd stage of Cellular Respiration.  Electrons from the Krebs cycle enter electron transport.  Electrons are used to pump H+ ions across mitochondrion membrane just like in photosynthesis  Flow of H+ ions are used to make ATP.  O2 picks up electrons & H+ ions to form water as by- producer.  34 ATP’s made… which means you get a total of 38 ATP’s ( 2 ATP’s Glycolysis, 2 ATP’s Krebs's 34 ATP’s electron transport) from the complete breakdown of Glucose.

Comparing Photosynthesis and Cellular Respiration PhotosynthesisCellular Respiration A)OrganelleChloroplastMitochondria B) ReactantsCO2 & H2OC 6 H12O 6 & O2 C) ReactionsCalvin Cycle in Stroma builds sugar Krebs's Cycle in Mitochondria builds sugar D)ProductsC 6 H12O 6 &O2CO2 &H2O

Fermentation  Remember when we talked about the products of Glycolysis entering the Mitochondria for Cellular Respiration? This only happens if OXYGEN IS PRESENT!!!  If there is no oxygen, the product of Glycolysis enter another anaerobic process called Fermentation.

Fermentation cont.  Fermentation does not produce any ATP’s, but does allow Glycolysis to continue.  Fermentation can only occur for a short time because the By-Product is Lactic Acid.  Lactic Acid is the substance that causes muscles to burn.  Once oxygen is available again, your cells will return to Cellular Respiration.

Fermentation cont.  Fermentation, although only an emergency process for us, is important in the making of many foods. Things such as cheese, yogurt, bread, and beer all need fermentation to me made.