Chapter 4 Energy of Life Review

What do enzymes do in cells?

Enzymes speed up chemical reactions (catalyze) without being consumed in the process.

Why does it cost energy for a cell to maintain a concentration gradient?

It costs energy for a cell to maintain a concentration gradient because it must move substances against diffusion, which tends to allow gradients to dissipate.

List three conditions that influence enzyme activity.

3 conditions that can influence an enzyme's activity are pH, temperature, & salt concentration.

What distinguishes a reaction that has reached chemical equilibrium?

A reaction that has reached chemical equilibrium has the same rate of forward & reverse reactions. This does not mean that the product & reactants are equal. It means that the "rate" of the reactions is equal.

What is the molecular structure of ATP?

ATP (Adenosine Triphosphate) is a nucleotide (adenosine) that has 3 attached phosphate groups instead of one.

What is active transport?

Active transport - molecules move from low concentration to high concentration, requiring both ATP and a transport protein.

Distinguish between an enzyme and a coenzyme.

An enzyme is a chemical catalyst that speeds a chemical reaction. A coenzyme is an organic molecule that is required for the enzymatic reaction to proceed.

What is the normal role of CFTR in humans, & how can faulty CFTR proteins cause cystic fibrosis?

CFTR is a membrane protein that sends Cl- out of the cell by active transport. This accumulation of Cl- outside the cell draws water by osmosis. A faulty CFTR protein leads to less water movement onto the lining of the lungs. The mucus in the lungs is not thinned, and therefore traps and holds bacteria.

What is an electron transport chain?

Electron transport chains are groups of proteins that accept & then pass on electrons, releasing small amounts of energy along the way. Chain 1, 3, 4 pump H+ out of mitochondrial matrix; 5 lets H+ back into matrix & generates ATP; 2 handles FADH2.

Distinguish between endergonic and exergonic reactions.

Endergonic means "absorbing energy in the form of work. Endergonic reactions require an input of energy to proceed to completion; exergonic reactions release energy.

How does an enzyme lower a reaction's activation energy?

Enzymes bring reactants into contact with each other so that less energy is required to start the reaction.

How do exocytosis & endocytosis use vesicles to transport materials across cell membranes?

Exocytosis - Golgi apparatus produces vesicles filled w/substances to be secreted. The visicles move to the cell membrain, join it and release the substance outside the cell.. Conversely, in Endocytosis, a vesicle forms as the cell membrane pinches inward, bringing substances into the cell.

What is facilitated diffusion?

Facilitated diffusion - ATP energy is still not used, but molecules need a protein passageway to cross the membrane.

What type of transport occurs when a polar molecule moves from a region of high concentration to a region of low concentration?

Facilitated diffusion.

How does ATP hydrolysis supply energy for cellular functions?

Hydrolysis of ATP breaks the bond of ATP's endmost phosphate group, releasing energy.

What would happen to a cell that was placed into a hypertonic environment?

It would shrink.

What types of substances diffuse freely across a biological membrane?

Lipids & small nonpolar molecules diffuse freely.

What is metabolism on a cellular level?

Metabolism is the sum of all chemical reactions in a cell. Metabolism takes place in sequences of biochemical reactions called pathways. It includes all reactions involving electron transfers (oxidation-reduction, or redox, reactions)

What are the roles of negative and positive feedback?

Negative and positive feedback are ways to regulate enzymes. In negative feedback the product stops the reaction, and in positive feedback the product propagates the reaction.

What are oxidation & reduction, & why are they always linked?

Oxidation is the loss of electrons from a molecule, atom, or ion, while reduction is a gain of electrons. They always are linked because they occur simultaneously. The oxidized molecule, atom, or ion will be a source of electrons, while its partner will gain those electrons in a reduction reaction. This is called a redox reaction. remember OIL RIG (Oxidation Is Loss, Reduction Is Gain - of electrons)

A concentration gradient is an example of ...

Potential energy.

Summarize the question Gabriel & his colleagues asked, & explain how their experiment helped answer the question.

Researchers were interested in understanding why such a harmful mutation to CFTR has not been removed by natural selection from the population. They hypothesized that faulty CFTR proteins give increased resistance to cholera. Their experiment showed that mice w/just 1 faulty copy of the CFTR gene had some resistance to cholera. In the human population, resisting cholera would have allowed the individuals to live a healthy reproductive life. So natural selection does not remove the faulty gene copy.

The movement of water molecules during osmosis is due to...

Simple diffusion.

How do differing concentrations of solutes in neighboring solutions drive osmosis?

Solutions with high concentrations of solutes have relatively low concentrations of water. Water always moves from a high concentration of water to a low concentration of water. Therefore, water will move by osmosis from a low concentration of solutes (high concentration of water) to a high concentration of solutes (low concentration of water).

Describe the relationship between endergonic reactions, ATP hydrolysis, & cellular respiration.

The ATP that is produced in cellular respiration can be hydrolyzed to release energy that can be used to drive endergonic reactions.

What is true regarding noncompetitive inhibition?

The active site is unable to bind substrate.

How do you think the results in figure 4.24 would have been different if, before adding cholera toxin, the researcher had added a chemical that blocked the site at which the toxin binds to CFTR?

The chemical would prevent the toxin from producing extreme water loss, and so the graph showing water loss should be evenly low for all three groups.

What are the first and second laws of thermodynamics?

The first law of thermodynamics says that energy cannot be destroyed or created, only changed in form. The second law of thermodynamics says that each time energy is converted from one form to another, some energy is always lost as heat.

Why does the amount of entropy in the universe always increase?

The second law of thermodynamics states the entropy in the universe always increases: some energy is always lost as heat, and heat is a disordered form of energy.

What is diffusion?

The spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a region where it is less concentrated.

How do proteins contribute to the function of an electron transport chain?

They become oxidized and reduced.

What is the role of an enzyme in a cell?

To increase the energy required to make a reaction occur.

Give an example of how your body has both potential and kinetic energy.

When your mitochondria break down sugars to chemical energy (in the form of ATP) you are storing potential energy. Your body converts potential energy to kinetic energy when ATP is used for membrane transport or to move your muscles.

Where in a molecule of ATP is the stored energy that is used by the cell?

Within the five-carbon ribose sugar.

Which of the following is the best example of potential energy in a cell.

a molecule of glucose

An endergomic reaction is one that is characterized ....

as needing an input of energy

What are some examples of the "work" of a cell?

cell division, biochemical reactions (such asdehydration synthesis & hydrolysis), & membrane transport.

What is simple diffusion?

simple diffusion - molecules move across the membrane without the use of a protein or ATP energy.