Metabolic Pathways and Enzymes Cellular reactions are usually part of a ________________, a series of linked reactions Illustrated as follows: E 1 E 2 E 3 E 4 E 5 E 6 A → B → C → D → E → F → G Letters A-F are reactants or ____________, B-G are the _______________ in the various reactions, and E 1 -E 6 are ___________________.

Enzymes – ________________ the rate of chemical reactions Substrates – molecules ________________ with enzymes Only one small part of an enzyme, called the _______________, reacts with the substrate(s). Active site may undergo a slight change in ____________ in order to fit with the substrate The enzyme is ________________ by the reaction (active site returns to its original state), and it is free to act again. E1 E2 E3 E4 E5 E6 A → B → C → D → E → F → G

Induced Fit Model Because the enzyme must undergo a slight change in shape to fit with the substrate, this is known as the _________________________.

Energy of activation (Ea) - the energy that must _____________ to cause molecules to react with one another Enzyme ____________the amount of energy required for reaction to occur Enzymes allow reactions to take place at ________________ – otherwise, reactions would not be able to occur at _____________ body temperatures Activation Energy

Energy of activation (Ea) When no enzyme is present – more energy required When an enzyme is added – less energy required

Enzymatic Reaction Substrate is broken down into smaller products Substrates are combined into a larger product

Every reaction in a cell requires a specific enzyme. Enzymes are named for their substrates: SubstrateEnzyme Lipid________ Ureas_________ Maltose__________ Ribonucleic acid____________ activity.html Enzyme Names

Factors Affecting Enzymatic Speed _____________________

Temperature and pH: As the temperature _______, enzyme activity ______________. If the temperature is too high, enzyme activity declines rapidly because the enzyme is ________. When enzyme is denatured, its _______________ and it can no longer attach to the substrate. Each enzyme has an _____________________ at which the rate of reaction is highest. Change in pH can alter the ______________ of the enzyme, and can eventually cause enzyme to ________________.

Rate of an enzymatic reaction as a function of temperature and pH

Rates and concentration: Reaction rate depends on the number of enzyme-substrate ______________ that can be formed. When all available enzymes and active sites are filled, the rate of activity _____________ further.

Substrate concentration Enzyme activity increases as ________________________ increases because there are more collisions between substrate molecules and the enzyme. Enzyme concentration Enzyme activity increases as __________________________ increases because there are more collisions between substrate molecules and the enzyme.

Overview of Cellular Respiration Makes ATP (potential energy) from glucose (chemical energy) Releases energy in 4 reactions Glycolysis, Transition reaction, Citric acid cycle (Kreb’s cycle), and Electron transport system An ________________ process that requires O 2 If oxygen is not available (______________), glycolysis is followed by _________________ Coupled Reaction

The four phases of complete glucose breakdown

Where does each step occur? Outside the mitochondria Step 1 - _____________________ Inside the mitochondria Step 2 - ____________reaction (matrix) Step 3 – __________________ (matrix) Step 4 – _________________________ (cristae)

Structure of mitochondria: Has a ________________________, with an intermembrane space between the two layers. ___________ are folds of inner membrane The _______, the innermost compartment, which is filled with a gel-like fluid.

It is an _________________________, or redox reaction for short. Oxidation is the _________ of electrons; hydrogen atoms are removed from glucose. ________________________is the gain of electrons; oxygen atoms gain electrons. Remember _______ (oxidation is loss, reduction is gain) Reaction that Occurs in Cellular Respiration

Enzymes involved: NAD + Nicotinamide adenine dinucleotide Accepts ______ to become NADH FAD Flavin adenine dinucleotide (sometimes used instead of NAD +) Accepts ________ to become FADH 2

Step 1. Glycolysis Occurs in the cytoplasm (outside the mitochondria) Glucose  _______________ molecules. Universally found in all organisms Does _______ require oxygen (anaerobic). Main energy source for prokaryotes

Glycolysis Summary Inputs: _______ Outputs: __________ ___ATP (net gain) When oxygen is available, ___________ enters the mitochondria, where it is further broken down If oxygen is not available, _____________ occurs

Occurs in the __________ of the mitochondria Is the transition between _________and the citric acid cycle. _______________ (made during glycolysis) is converted to acetyl CoA, and CO 2 is released NAD + is converted to NADH + H + The transition reaction occurs ________ per glucose molecule. Step 2 - Transition Reaction

Transition reaction inputs and outputs per glucose molecule Inputs: ____________ Outputs: ______________ ml

Step 3 - Citric Acid Cycle (aka Kreb’s Cycle) Occurs in the ____________ of the mitochondria. C 2 acetyl group is converted to a C 6 citrate. Each acetyl group gives off __________ molecules. NAD+ accepts electrons ____________ FAD accepts __________________. Results in a gain of ____________ per every turn of the cycle; there are two cycles per glucose, so a net of 2 ATP are produced. The citric acid cycle produces ______________ per molecule of glucose.

Citric acid cycle

Citric acid cycle inputs and outputs per glucose molecule Inputs: _____________ Outputs: __________

Step 4 - Electron Transport System (ETS) ______________ oxygen (aerobic) Located in the ______________of mitochondria _________________________ carry electrons picked up during glycolysis, transition reaction, & citric acid cycle and enter the ETS. The ETS consists of: –________________________________ that pump H + –_________________________ that transport electrons –__________________ - H + flow through it, making ATP H+ flow through from _________________________ For every 3 H + that flow through, one ______ is made

Overview of the electron transport system

hill.com/sites/ /student_view0/chapter9/animations.ht ml

Energy Yield from Glucose Metabolism Per glucose molecule: –_____________ take electrons to the ETS  __________ATP from each –2 FADH 2 take electrons to the ETS  ______ATP from each Electrons carried by NADH produced during glycolysis are shuttled to the electron transport chain by an organic molecule

Accounting of energy yield per glucose molecule breakdown

Fermentation Occurs when oxygen is _________ available. During fermentation, the ______________ formed by ___________ is reduced to lactic acid. Fermentation uses _________ and regenerates _____________________ Occurs in _______________ bacteria, fungus, & human muscle cells. LYSIS.HTML

Advantages and Disadvantages of Fermentation Fermentation can provide a __________________ in muscle cells, even when oxygen is in limited supply. Lactate, however, is _____________ to cells. Initially, blood carries away lactate as it forms; eventually lactate builds up, lowering cell pH, and causing ____________________________. Oxygen debt occurs, and the liver must reconvert ______________________________.

Fermentation inputs and outputs per glucose molecule Inputs: ______________ Outputs: ___ lactate or ___alcohol & 2 CO 2 ____ADP ____ ATP (net gain)