Chapter 6: Metabolism: Energy and Enzymes

pg. 117

What are blood clots due to?

Action of fibrin, an insoluble protein in the blood plasma. Dissolved by the enzyme plasmin, which circulates in the blood inactive form called plasminogen. 

What are organic nutrients made of?

Photosynthesizing producers such as algae, plants, and some bacteria.

What are the two forms of energy? What kind of energy does the food we eat have and why? What form of energy is food? What does this term mean?

Kinetic: energy of motion (a ball rolls down a hill or water flows over a waterfall)

Potential: stored energy whose capacity to accomplish work is not being used at the moment

Food we eat has potential energy because the energy stored in chemical bonds can be converted into different forms of kinetic energy.

Food is a form of chemical energy because it has carbohydrates, proteins, and fats.

Chemical energy is energy associated with the interaction of atoms in a molecule.

What is mechanical energy? What is an example of mechanical energy? What type of energy is it: potential or kinetic?

Energy possessed by an object as the result of its motion or position

Ex: when a moose walks.

Form of potential energy.

IF SOMETHING IS MOVING, IT’S USING MECHANICAL ENERGY!

What does energy do and not do?

It flows through the ecosystem and does not cycle within it. 

What are the two laws of thermodynamics?

1st Law: Law of Conservation of Energy states that energy cannot be created or destroyed, but it can be changed from one form to another.

2nd Law: Energy cannot be changed from one form to another without a loss of usable energy.

What do leaf cells use when they photosynthesize and what do they form?

They use solar energy, carbon dioxide, and water to form carbohydrate molecules.

What are energy-rich and energy-poor molecules? Do all captured solar energy become carbohydrates?

Energy-rich: Carbs

Energy-poor: carbon dioxide and water - lack of bonds

No!! They don’t!

What is entropy? What does this mean for the second law of thermodynamics?

Measure of disorder or randomness in a system.

In reference to the second law, every process that occurs in cells always increases the entropy of the universe

Means that each cellular process makes less energy available to do useful work in the future

What is metabolism? What about reactants and products? Example using the letters A, B, C, and D.

Metabolism: sum of all chemical reactions that take place in cells.

Reactants: substances that participate in a reaction

Products: substances that form as a result of a reaction

A+B → C+D

A and B: reactants

C+D: products

What is free energy? How to determine the change in free energy?

AKA delta G or △G

Amount of energy left to do work after a chemical reaction has happened. 

• Subtract the free energy content of the reactants from that of the products

What is a negative result in reference to free energy?

-△G. It means that the products have less free energy than the reactants. This causes the reaction to happen spontaneously. 

What does metabolism include?

ATP, or adenosine triphosphate, is the common energy currency of cells.

• Cells do not keep large storage of ATP, so they regenerate ATP using ADP (adenosine diphosphate) and inorganic phosphate. ← referred to as the ATP cycle 

• ATP Cycle is powered by breaking down of glucose and other biomolecules during cell respiration—not efficient 

• Only 39%; rest is lost to heat

What is the structure of ATP?

Nucleotide 5-carbon sugar ribose (adenosine), nitrogen-containing base adenine, and three phosphate groups.

In ATP, what do the three phosphate groups do? Why is ATP called a “high-energy" molecule?

They repel each other, creating instability and potential energy.

Called that a phosphate group can easily be removed.

What is the amount of energy that is released when ATP is hydrolyzed to ADP + inorganic phosphate? What is this unit of measurement?

7.3 kcal per mole.

• Equal to the molecular weight of a molecule, but in grams.

Two ways that ATP is coupled?

To energize a reactant or to change the shape of a reactant. Both can be achieved by transferring a phosphate group to the reactant, resulting in the  term phosphorylated.

What are most enzymes?

Enzymes can be proteins, but some are made of RNA. 

• These are called ribozymes and are involved in the synthesis of RNA and proteins at ribosomes.

What are metabolic pathways? What are substrates?

Begin with a specific reactant and end with a final product. 

• Substrates are reactants in an enzymatic reaction 

• The substrates for the first reaction are converted into products, and then they (products) serve as the substrates for the next enzyme-catalyzed reaction.

What is the active site? What is an induced fit model?

Region of an enzyme where the substrate binds and where the chemical reaction occurs.

• The enzyme and substrate are like a key lock in this site 

• The induced fit model is when there is a change in the shape of an enzyme’s active site that enhances the fit between the active site and its substrate(s).

W'hat is the energy of activation? (Ea) Why is this important? What do enzymes influence?

Energy that must be added to cause molecules to react with one another.

• Important because it keeps molecules from spontaneously degrading within the cell. 

• Not the energy content, but the rate of the reaction

What can increase the rate of reactions? What is denaturation? What do some enzymes require?

Increasing the amount of substrate and the amount of enzyme. 

• Prevents an enzyme from binding to its substrate efficiently and can decrease the rate of reaction. Can be caused by change in pH or temperature, as well as inhibitors. — Loss of a protein’s or an enzyme’s normal shape, so that it no longer functions, usually caused by a less-than-optimal pH and temperature

• Require additional molecules like cofactors to help speed up the rate of the reactions.

What are cofactors and coenzymes? Examples of cofactors?

Cofactors: ions or molecules. 

• Inorganic ions include copper, zinc, or iron.

• Ex: NAD+ (nicotinamide adenine dinucleotide), FAD (flavin adenine dinucleotide), and NADP+ (nicotinamide adenine dinucleotide phosphate) each play a role in cell respiration or photosynthesis

Coenzymes: nonprotein organic molecules.

What are vitamins?

They are usually components of coenzymes. They are small, organic molecules that are required in trace amounts in our diet for the synthesis of coenzymes. It becomes part of a coenzyme’s molecular structure.

Ex: niacin is part of the coenzyme NAD+

How are enzymes covalently modified? What is enzyme inhibition? What is a noncompetitive inhibition?

Phosphate added to proteins: kinase

Phosphate removed from proteins: Phosphatase 

• When a molecule (the inhibitor) binds to an enzyme and decreases its activity.

• Noncompetitive inhibition is where the inhibitor binds to an enzyme at a location other than the active site and then the enzyme shape changes, and the inhibitor is unable to bind to its substrate, and no product forms.

What is an allosteric site? What is a competitive inhibitor? Are enzyme inhibitions reversible?

Site on an allosteric enzyme that binds an effector molecule; binding alters the activity of the enzyme.

• Form of enzyme inhibition where the substrate and inhibitor are both able to bind to the enzyme’s active site. Only when the substrate is at the active site will product form.

• In most cases, yes. Not damaged by inhibition

What are oxidation-reduction reactions? What is another term for this? What is the mnemonic for this?

Reactions that involve the gain and loss of electrons. 

• Oxidation is the loss of electrons and reduction is the gain of electrons.

• Redox reaction 

• OIL RIG—oxidation is loss and reduction is gain

What can oxidation-reduction reactions also apply to?

Covalent reactions

Oxidation - loss of hydrogen atoms (e⁻ + H⁺)

Reduction - gain of hydrogen atoms

When a molecule loses a hydrogen atom, it has lost an electron.

When a molecule gains a hydrogen atom, it has gained an electron.

What is a chloroplast? What is its formula?

In plants, they capture solar energy and use it to convert water and carbon dioxide.

*Hydrogen atoms are transferred from water to carbon dioxide to form glucose.

Carbon dioxide has been reduced and water has been oxidized.

6 CO₂ (carbon dioxide) + 6 H₂O (water) → C₆H₁₂O₆ (sugar) + 6 O₂ (oxygen)

What are mitochondria and cellular respiration? What is the equation for cellular respiration?

Mitochondria is in both animals and plants and they oxidize carbohydrates and use the released energy to build ATP molecules. 

Cellular respiration consumes oxygen and produces carbon dioxide and water, molecules taken up by chloroplasts. 

Equation:

C6H12O6 + 6O₂ → 6CO₂ + 6H₂O + ATP

*Glucose has lost hydrogen atoms (been oxidized), and oxygen has gained hydrogen atoms (been reduced)

When oxygen gains electrons, what does it become?

Water

What is the mole of glucose in kcal?

686