UNIT 4: Enzymes and Cell Energy WHAT are ENZYMES??? Enzymes… Are CATALYSTS: __________ chemical reactions that would otherwise happen too ________ to support life. Catalysts _____________ make reactions happen that couldn’t happen by themselves. Are PROTEINS. Their amino acid sequences determines their ____________, which are important for their functions. Are _____________________ during the reaction—the same enzyme can be used repeatedly AND, BECAUSE of its shape, an Enzyme… Is specific to the _________ it catalyzes. The reactants (called ____________) fit perfectly into a place on the enzyme called the ____________ _____________. The ___________ of the enzyme active site makes it substrate-specific. The enzyme may slightly _________ ________ (gives substrates a squeeze in a process called ___________ ______) that allows the reaction to happen. Finally, the products are __________ from the active site, and the enzyme can be reused over and over again for more reactions. Only functions in ____________ pH and temperature ranges, where it has the proper shape. changing the temperature or pH (__________) may change an enzyme’s shape It may no longer __________________ its substrates, and therefore not function. An enzyme that has lost its proper shape and does ______________ is said to be denatured. HOW do Enzymes Work? TEMPERATURE PRODUCTS MADE (ENZYME FUNCTION) 37°C ENZYME WORKS BEST AT THIS CONDITION DENATURED ENZYME Favorable chemical reactions involve reactants going through an __________, awkward transition state. Unfavorable states are considered _______ energy and favorable states are considered _____ energy. The amount of energy required to overcome the transition state is called the activation energy Enzymes work when the _________ _____, or squeeze provided by the enzyme, makes the transition state more favorable In other words, an enzyme __________ the activation energy of a reaction

CHEMICAL ENERGY AND LIFE Enzymes work by making this transition phase more stable. In other words, enzymes lower the activation energy of a reaction. A chemical reaction that might otherwise occur once every thousand years can happen in milliseconds with the help of the proper enzyme. CHEMICAL ENERGY AND LIFE ENERGY is the ______________________________. Cells require energy for ____________ reactions, _____________ transport, _____ ___________, and maintaining _________________. We obtain energy from __________, but energy ultimately comes from the sun. Glucose is the preferred energy source, but we can obtain it from _____________, ________ and even ____________ CHEMICAL ENERGY in food is stored in __________ _________ as _______________ energy. When bonds are broken, energy of _____________ is released. Some is lost as _________, but some portion of it can be converted into a usable form in the bonds of ________. We use ATP energy to “pay for” ______________ reactions ATP is a better form of energy because it contains ___________ packets of energy than glucose If we released the energy from food molecules (like glucose) all at once, it would be ____________ and ________________ ATP, _____________________ is a ______________ composed of: ___________, a nitrogen base _________, a ____ carbon sugar _________________ groups Potential energy is stored in the ___________ _______________________ ATP is like a rechargeable ____________ ATP = “charged” (3 phosphates), ________ PE ADP = “uncharged” (2 phosphates, _____________ _________________), ______ PE

METABOLIC PATHWAYS: CELLULAR RESPIRATION AND PHOTOSYNTHESIS METABOLISM: the sum of all __________________________ in an organism. METABOLIC PATHWAYS: a series of sequential reactions in which the ____________ of one reaction is the ______________ for the following reaction. TWO major metabolic pathways in life: CELLULAR RESPIRATION ____________ molecules (like glucose) broken down to release ___________ for cell use PHOTOSYNTHESIS ___________________ from sun is converted to ________________ in the form of glucose The relationship between these two pathways results in the ___________________________ within an organism as well as within an ecosystem. Plants and other organisms that can make their own food are known as ________________ Humans and other organisms that have to obtain food are known as ________________ CELLULAR RESPIRATION CELLULAR RESPIRATION - AEROBIC (requires O2) ENERGY PRODUCTION (pp. 228-232) Cellular respiration is the breakdown of ____________ in the presence of ________ to “make” _____. The oxygen required for cellular respiration is __________ into the ________, ___________ into the _________, and is delivered to the ______________ of the body cells by _________________. The glucose needed is obtained through _________. The glucose is transported in the blood and enter the body cells via ____________________ by ______________________. Remember that this happens even in autotrophs like plants, too! (Plants DO require oxygen, but they produce more than they need) OVERALL EQUATION: Two major parts: Glycolysis Oxidative Respiration. Oxidative respiration can be further divided into two parts: the Krebs Cycle & the Electron Transport Chain KEY PLAYERS: Glucose, a six-carbon monosaccharide ATP, the final energy molecule Pyruvic acid, a three-carbon product of glycolysis O2 gas, the final electron acceptor of the ETC Electron Carriers: NADH and FADH2, carry high-energy electrons CO2 gas and H2O

start PAYDAY RESPIRATION STEP 1: GLYCOLYSIS RESPIRATION STEP 2: OXIDATIVE REPSIRATION Glycolysis – Means _____________________. Occurs in the ________________ of the cell. does not require _____________. The splitting of glucose, or glycolysis, occurs very quickly in a 10-step process with the aid of _________, producing two ___-C molecules known as ___________________. In addition, when the bonds of glucose are broken, the high energy electrons that are released are caught by __________, a molecule that acts as an ________________. This electron energy will be converted to ATP later in the process. Glycolysis requires ___ ATP to occur, but results in the formation of ___ ATP, for a net ______ of ___ ATP. Reaction: Net Energy Gain = 2 ATP + 2 NADH Glycolysis releases less than ¼ of the chemical energy stored in glucose. Most of its potential energy remains bound in the ______________ formed from glycolysis. In aerobic conditions, meaning ___ is available, the pyruvic acid formed from the breakdown of ___________ during ___________ enters the ______________ of the cell where the _________ of oxidative respiration complete the breakdown of glucose to produce _____, _______, and ______. Reaction: 6 + +6 +6 + 2 + +2 + +30 + 2 4 STEP 2A: KREBS CYCLE Series of reactions that occur in the _______________, in which the energy stored in _____________ is released in the form of high-energy ___________ when bonds are broken and pyruvic acid is completely broken down to _______. 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 _________. In addition, a second type of electron carrier is utilized, producing 2 “filled” ________. Net Energy Gain = 2 ATP + 8 NADH + 2 FADH2 Wastes Generated = CO2 start Krebs Cycle PAYDAY 2 + 8 + 2

STEP 2B: ELECTRON TRANSPORT CHAIN (“PAY DAY”) the electron carriers, ________ and _______ “dump” their electrons. These electrons are passed along a series of molecules embedded in the inner membrane of the ______________ of ______________ cells. This same process occurs in the ________________ of ________________ cells. As the electrons “fall” down the ETC, the energy they release is used to power an enzyme known as ____________________, which attaches phosphate groups to ________ to produce _______. This process is known as _______________ phosphorylation because oxygen must be present. It is the ___________________ of oxygen that “pulls” the electrons down the ETC. As the electrons are collected by oxygen, __________ is produced from oxygen. Net Energy Gain = __~ 32 ATP_______ STAGE WHERE # ATP Needs O2? Wastes GLYCOYSIS CYTOPLASM KREBS CYCLE OUTER MITOCHONDRIA ELECTRON TRANSPORT CHAIN INNER ALTERNATIVE PATHWAY : ANAEROBIC (WITHOUT OXYGEN) FERMENTATION The Krebs Cycle and ETC depend on ______________ (they are aerobic) to take electrons from the electron carriers. If no oxygen is present, ________ and _________ all fill up with high energy _______________ and have no where to put them, and cellular respiration comes to a halt. A ____________ pathway exists called _____________ fermentation. In anaerobic conditions, the cell still uses ___________ and generates 2 ____ and 2 _____________, along with 2 full _______ 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 buildup contributes to the muscle ___________ experienced during intense exercise Some bacteria and fungi do this and are important in producing the lactic acid in ______________ and ____________ ALCOHOLIC FERMENTATION: In ___________ and some bacteria, the pyruvic acid are converted to alcohol. This is important in commercial brewing and baking. Overall, much ________ energy (only 2 ATP compared to 32) is produced by fermentation

PHOTOSYNTHESIS Photosynthesis is the metabolic pathway that provides energy for ____________________ Occurs in the chloroplasts of plants and other photosynthetic eukaryotes like _________ Occurs in _______________—photosynthetic bacteria Overall Equation: CHLOROPLASTS: Abundant in the ___________ _______________ of most plants Structure: Thylakoids-flattened ______________ ________________ arranged in stacks, where the light-dependent reactions occur Grana—stacks of ________________ Stroma—_________________ that is outside the ___________, where light-independent reactions take place. PIGMENTS: light-__________________ colored molecules act like ___________ for absorbing energy Different pigments absorb different __________________ of light Chlorophyll—most abundant pigments, absorb __________ _____________ the strongest, ___________ ____________ Accessory pigments—absorb blue and green, __________ _____________________. The pigments we see if fall leaves when ____________ production stops. Ex: Beta-carotene. Proteins that are part of the thylakoid membrane organize ___________________________ into clusters called __________________________ ENERGY CARRIERS: Chemical Energy Carrier: ____________ ___________ + ______________ + energy - _______________ High Energy Electron Carrier: _______________ ___________ + __________ ___________ _____________  __________________

STEPS OF PHOTOSYNTHESIS LIGHT-DEPENDENT REACTIONS: requires _____________ Molecules are part of the ___________ ______________ BEGINS AT PHOTOSYSTEM II… Chlorophyll in thylakoid membrane absorbs ___________ ______________ and uses it to excite and strip away electrons from __________. Water is broken apart, forming _____________ gas (_____) …NEXT TO AN ELECTRON TRANSPORT CHAIN… High energy electrons are passed to an ETC from one carrier to the next, losing energy that is used to drive the synthesis of __________. The enzyme responsible for ATP synthesis is called __________________________. AND ENDS AT PHOTOSYSTEM I ! The now low-energy electron is re-energized by another chlorophyll pigment and light in photosystem II. The energized electron is passed to ____________, a high energy electron carrier. CALVIN CYCLE (Light-independent rxns)—does not require ___________, in the stroma _______ gas is used as a source of __________ and __________ atoms to make glucose. NADPH used as a source of high energy ___________ and _____________ _______ is used as a source of ___________ (from light-dependent rxns) (returned to light-dependent rxns) 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