Unit 5 Cellular Energy
I. Enzymes (159) 1.Are CATALYSTS: Speed up chemical reactions that would otherwise happen too slowly to support life. Catalysts DO NOT make reactions happen that couldn t happen by themselves. 2.Are PROTEINS. Their amino acid sequences determines their, shapes which are important for their functions. 3.Are Not consumed during the reaction the same enzyme can be used repeatedly
Because of the importance of its shape, a protein also 4.Is specific to the the reaction it catalyzes. The reactants (called substrates) fit perfectly into a place on the enzyme called the active site. The shape of the enzyme active site makes it substrate-specific. The enzyme may slightly change shape (gives substrates a squeeze in a process called induced fit) that allows the reaction to happen. Finally, the products are released from the active site, and the enzyme can be reused over and over again for more reactions.
Because of the importance of its shape, a protein also 5. Only functions in narrow ph and temperature ranges, where it has the proper shape. changing the temperature or ph ( ) acidity may change an enzyme s shape It may no longer fit its substrates, and therefore not function. An enzyme that has lost its proper shape and does not function is said to be denatured.
How do enzymes work? Favorable chemical reactions involve reactants going through an, unfavorable awkward transition state. Unfavorable states are considered high energy and favorable states are considered low energy. The amount of energy required to overcome the transition state is called the Activation energy
Enzymes work when the, induced fit or squeeze provided by the enzyme, makes the transition state more favorable In other words, an enzyme lowers the activation energy of a reaction
Chemical Energy and Life ability to do work ENERGY is the. Cells require energy for metabolic reactions, active transport, cell division and maintaining homeostasis. We obtain energy from, food but energy ultimately comes from the sun. Glucose is the preferred energy source, but we can obtain it from, other carbs lipids and even protein
Chemical Energy and Life CHEMICAL ENERGY in food is stored in chemical bonds as potential energy. When bonds are broken, energy of electrons is released. Some is lost as, heat but some portion of it can be converted into a usable form in the bonds of ATP We use ATP energy to pay for unfavorable reactions
Without ATP and enzyme With ATP and enzyme
Chemical Energy and Life ATP is a better form of energy because it contains smaller packets of energy than glucose If we released the energy from food molecules (like glucose) all at once, it would be wasteful and destructive
ATP is Adenosine TriPhosphate a nucleotide that is composed of: adenine - nitrogen base ribose - 5 carbon sugar 3 phosphate groups
ATP Potential energy is stored in the - phosphate phosphate bonds ATP is like a rechargeable battery ATP = charged (3 phosphates), high PE ADP = uncharged (2 phosphates, ), adenosine disphosphate low PE
Metabolic pathways (218-221) chemical Metabolism: the sum of all reactions in a cell Metabolic pathways- series of chemical reactions in which the of product one reaction is the for reactant the next reactions.
2 major metabolic pathways in life: CELLULAR RESPIRATION organic molecules (like glucose) broken down to release energy for cell use PHOTOSYNTHESIS Light energy from sun is converted to chemical energy in the form of glucose
2 major metabolic pathways in life: The relationship between these two pathways results in the continual flow of energy within an organism as well as within an ecosystem. Plants and other organisms that can make their own food are known as autotrophs Humans and other organisms that have to obtain food are known as heterotrophs
Cellular Respiration- Aerobic (requires O 2 ) Energy Production (pp. 228-232) breakdown of glucose in the presence of oxygen to make ATP The oxygen required for cellular respiration is inhaled into the, lungs diffuses into the, blood and is delivered to the mitochondria of the body cells by. red blood cells The glucose needed is obtained through digestion The glucose is transported in the blood and enter the body cells via facilitated diffusion by. channel proteins
Do plants use cellular respiration? Do they need oxygen?
Overall Equation C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O Two major parts: Glycolysis Oxidative Respiration, further divided into Krebs Cycle Electron Transport Chain
Key Players Glucose, the starting molecule of cellular respiration Pyruvic acid, a three-carbon molecule that is the product of the breakdown of glucose during glycolysis NADH and FADH 2, which carry high energy electrons. They are forms of chemical potential energy. ATP, a form of chemical potential energy used by cells for energy-consuming processes. CO 2, the final breakdown product of glucose, generated in the Krebs Cycle. Oxygen and water. O 2 is the final electron acceptor of the electron transport chain. When it receives electrons it takes hydrogen to make water.
Respiration Step 1: Glycolysis sugar-splitting Glycolysis Means. Occurs in the cytosol of the cell. does not require. oxygen The splitting of glucose, or glycolysis, occurs very quickly in a 10-step process with the aid of, enzymes producing two 3-C molecules known as. pyruvic acid
Respiration Step 1: Glycolysis In addition, when the bonds of glucose are broken, the high energy electrons that are released are caught by, NADH a molecule that acts as an. electron carrier This electron energy will be converted to ATP later in the process. Glycolysis requires 2 ATP to occur, but results in the formation of 4 ATP, for a net gain of 2 ATP.
Respiration Step 1: Glycolysis REACTION: glucose + 2ATP 2 pyruvic acid + 4ATP + 2NADH
Respiration Step 1I Glycolysis releases less than ¼ of the chemical energy stored in glucose. Most of its potential energy remains bound in the pyruvic acid formed from glycolysis.
Respiration Step 1I: Oxidative Respiration O 2 In aerobic conditions, meaning is available, the pyruvic acid formed from the breakdown of glucose during glycolysis enters the mitochondria of the cell where the enzymes of oxidative respiration complete the breakdown of glucose to produce, CO 2, H 2 O and. ATP
Respiration Step 1Ia: Krebs Cycle Series of reactions that occur in the, mitochondria in which the energy stored in pyruvic acid is released in the form of high-energy electrons when bonds are broken and pyruvic acid is completely broken down to. CO 2
Respiration Step 1Ia: Krebs Cycle 2 There are only additional ATP produced in the Krebs Cycle; most of the energy released is captured in the form of electron energy, producing additional. NADH In addition, a second type of electron carrier is utilized, producing 2 filled. FADH 2
Respiration Step 1Ia: Krebs Cycle Net Energy Gain = 2ATP + 8 NADH + 2 FADH 2 Waste Generated: CO 2 (all of glucose is gone, except for its high energy electrons and Hydrogen in the electron carriers)
Respiration Step 1Ib: Electron Transport Chain (ETC) NADH the electron carriers, and FADH 2 dump their electrons. These electrons are passed along a series of molecules embedded in the inner membrane of the mitochondria of eukaryotic cells. This same process occurs in the cell membrane of prokaryotic cells cells.
Respiration Step 1Ib: Electron Transport Chain (ETC) As the electrons fall down the ETC, the energy they release is used to power an enzyme known as, ATP synthase which attaches phosphate groups to ADP to produce. ATP
Respiration Step 1Ib: Electron Transport Chain (ETC) This process is known as oxidative phosphorylation because oxygen must be present. It is the electronegativity of oxygen that pulls the electrons down the ETC. As the electrons are collected by oxygen, H 2 O is produced from oxygen. Net Energy Gain = ~ 32 ATP
STAGE WHERE # ATP Needs O 2? Wastes GLYCOYSIS CYTOPLASM 2 N - KREBS CYCLE OUTER MITOCHOND RIA 2 Y (not directly) CO 2 ETC INNER MITOCHOND RIA 30+ Y H 2 O
Alternative pathway: Anaerobic Fermentation The Krebs Cycle and ETC depend on oxygen (they are aerobic) to take electrons from the electron carriers. If no oxygen is present, NADH and FADH 2 all fill up with high energy electrons and have no where to put them, and cellular respiration comes to a halt.
Alternative pathway: Anaerobic Fermentation backup A pathway exists called anaerobic fermentation. In anaerobic conditions, the cell still uses glycolysis and generates 2 ATP and 2, pyruvic acid along with 2 full NADH The cell can empty the electron carriers by converting the 2 pyruvic acids into other chemicals.
Lactic Acid Fermentation In human muscle cells, pyruvic acid is converted to lactic acid Lactic acid buildup contributes to the muscle soreness experienced during intense exercise Some bacteria and fungi do this and are important in producing the lactic acid in cheeses and yogurt
Alcholic Fermentation In yeast and some bacteria, the pyruvic acid are converted to alcohol. This is important in commercial brewing and baking. Overall, much less energy (only 2 ATP compared to 32) is produced by fermentation
Photosynthesis
Photosynthesis Photosynthesis is the metabolic pathway that provides energy for most ecosystems Occurs in the chloroplasts of plants and other photosynthetic eukaryotes like algae Occurs in cyanobacteria photosynthetic bacteria
Overall Equation: (light energy) 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2
Chloroplasts leaf cells Abundant in the of most plants Structure: Thylakoids-flattened sac-like membranes arranged in stacks, where the light-dependent reactions occur
Structure continued thylakoids Grana stacks of Stroma fluid-filled space that is outside the, grana where lightindependent reactions take place.
Pigments absorbing light- colored molecules act like antennas for absorbing energy Different pigments absorb different wavelengths of light
ENERGY & ELECTRONS http://www.mhhe.com/biosci/pae/botany/uno/graphics/uno01pob/vrl/images/0160.gif http://www.wjcc.k12.va.us/robb/atom%20animation%20resources_files/image003.gif
Chlorophyll- most abundant pigments. Absorb red and violet the strongest, and reflect. green
Accessory pigments- allows plant to absorb different wavelengths of light energy Carotenoids absorb - in region Blue & green &, reflect Yellow, orange & red Ex. β carotene In fall production of slows chlorophyll down or stops, thus bringing out the colors of the accessory pigments.
ENERGY & ELECTRONS http://www.mhhe.com/biosci/pae/botany/uno/graphics/uno01pob/vrl/images/0160.gif http://www.wjcc.k12.va.us/robb/atom%20animation%20resources_files/image003.gif
PHOTOSYNTHESIS OVERVIEW Pearson Education Inc; Publishing as Prentice Hall
PHOTOSYNTHESIS HAPPENS IN CHLOROPLASTS Proteins that are part of the thylakoid membrane organize Light absorbing PIGMENTS into clusters called PHOTOSYSTEMS http://www.science.siu.edu/plant-biology/plb117/jpegs%20cd/0076.jpg
LIVING THINGS NEED ENERGY CARRIERS Molecule that carries = ATP Molecule that carries HIGH ENERGY ELECTRONS = NADP + Images by Riedell
Frying pan image from: BIOLOGY by Miller and Levine; Prentice Hall Publishing 2006 NADP NADP + is one of the carriers that cells use to transport high energy electrons. + 2 e - + H +
LIGHT-DEPENDENT REACTIONS Requires LIGHT Molecules are part of THYLAKOID membranes
Starts at photosystem II: Chlorophyll in thylakoid membrane absorbs light energy and uses it to excite, and strip away electrons from H 2 O Water broken apart, forming oxygen gas ( ) O 2
Light-Dependent Reactions
Next to an electron transport chain: High energy electrons are passed to the electron transport chain from one carrier to the next, losing energy that is used to drive the synthesis of ATP. The enzyme responsible for ATP ATP synthase synthesis is.
Light-Dependent Reactions
Ends at photosystem I: The now low-energy electron is re-energized by another chlorophyll pigment and in photosystem I The energized electron is passed NADP+ carrier to, a high energy electron. light
Light-Dependent Reactions
PHOTOSYNTHESIS OVERVIEW Pearson Education Inc; Publishing as Prentice Hall
CO 2 Enters the Cycle Calvin Cycle Energy Input 5-Carbon Molecules Regenerated Sugars and other compounds 6-Carbon Sugar Produced See Calvin cycle animation
Calvin Cycle (Light-independent rxns) does not require, light in the stroma CO 2 gas is used as a source of carbon and oxygen atoms to make glucose. NADPH used as a source of high energy electrons and hydrogen ATP is used as a source of energy
Factors Affecting Photosynthesis Light more light, more photosynthetic activity Water needed to supply electrons. Not enough water, slow or no photosynthesis Temperature photosynthesis functions best at 0-32 C