biol-l112 MULTIPLE CHOICE exam 2

What is the 1st law of thermodynamics?

Matter and energy cannot be created or destroyed. They can only be transferred or transformed.

What is the 2nd law of thermodynamics?

Overall entropy (disorder) increases during energy transformations.

What does entropy mean?

Disorder.

If life is ordered, how can life follow the 2nd law of thermodynamics?

Maintaining order requires energy. This process releases heat, which increases disorder in the surroundings.

Does the order found in living things violate the 2nd law of thermodynamics?

No. Living things create local order, but the overall disorder of their surroundings increases.

What does O.I.L. R.I.G. stand for?

Oxidation Is Loss; Reduction Is Gain (of electrons).

What is oxidation?

The loss of electrons.

What is reduction?

The gain of electrons.

If a molecule gives an electron to another molecule, what happens to each molecule?

The molecule losing the electron is oxidized. The molecule gaining it is reduced.

What is the net ATP yield of glycolysis per glucose molecule?

$2\text{ ATP}$.

Does glycolysis require oxygen ($O_2$)?

No. Glycolysis does not require oxygen.

What is the net ATP yield of complete aerobic cellular respiration per glucose?

About $30\text{--}32\text{ ATP}$.

Approximately how many times more ATP does aerobic cellular respiration produce than glycolysis alone?

About $15$ times more ATP.

What does glycolysis do to glucose?

It breaks one glucose molecule into two pyruvate molecules and produces a net gain of $2\text{ ATP}$.

When does fermentation occur?

When oxygen is absent and cells need to regenerate $NAD^+$ so glycolysis can continue.

What is the purpose of fermentation if fermentation itself does not yield ATP?

It regenerates $NAD^+$, allowing glycolysis to continue producing ATP.

What are the products of lactic acid fermentation?

Lactate (lactic acid).

What are the products of alcohol fermentation?

Ethanol and carbon dioxide ($CO_2$).

What is the difference between lactic acid fermentation and alcohol fermentation?

Lactic acid fermentation produces lactate. Alcohol fermentation produces ethanol and $CO_2$.

What is putrefaction?

The anaerobic fermentation of amino acids.

Is putrefaction a natural process?

Yes. It is a natural process involved in the decomposition of organic material.

What is Rubisco's job in photosynthesis?

It binds to $CO_2$ during carbon fixation

What is the problem with Rubisco?

It sometimes binds $O_2$ instead of $CO_2$.

What happens when Rubisco binds $O_2$ instead of $CO_2$?

Photorespiration occurs, wasting energy and materials.

What is the challenge plants face when opening their stomata?

water loss

What happens when stomata open versus when they close?

Open: more $CO_2$ enters, but more water escapes. Closed: water is conserved, but less $CO_2$ enters.

Why are C4 and CAM photosynthesis useful in warm, dry climates?

They help plants conserve water while maintaining photosynthesis and supplying $CO_2$ to Rubisco.

What does spatial separation mean in C4 photosynthesis?

CO₂ is taken in and processed in two different types of cells.

Which type of photosynthesis uses spatial separation?

C4 photosynthesis.

What does temporal separation mean in CAM photosynthesis?

CO₂ is taken in at night and used for photosynthesis during the day.

When do CAM plants open and close their stomata?

They open them at night to take in $CO_2$ and close them during the day to conserve water.

How do CAM plants use the $CO_2$ they take in at night?

They store it in 4-carbon acids and release it during the day.

What is the main difference between C4 and CAM photosynthesis?

C4 uses spatial separation (different places); CAM uses temporal separation (different times).

Can plants completely oxidize glucose through aerobic cellular respiration?

Yes. Plants break down glucose to release energy and produce ATP.

Do plants have mitochondria?

Yes. Plants have mitochondria and perform aerobic cellular respiration.

What molecule do plants make from glucose to store energy?

Starch.

What structural molecule do plants make from glucose to build their cell walls?

Cellulose.

What are three things plants can do with the sugars made during photosynthesis?

Use glucose in cellular respiration, store it as starch, and build cellulose for their cell walls.

In oxygenic photosynthesis, where does the released $O_2$ come from?

Water.

How is $O_2$ produced during oxygenic photosynthesis?

Light-driven reactions split water, releasing oxygen and supplying electrons for photosynthesis.

Why is water called an electron donor during oxygenic photosynthesis?

Water supplies electrons to the photosynthetic process.

When water gives up electrons during photosynthesis, is it oxidized or reduced?

Oxidized.

What does photoautotroph literally mean?

An organism that uses light energy to make its own food.

What are examples of photoautotrophs?

Plants and algae.

What element may be lacking when a photoautotroph needs to make proteins and nucleic acids?

Nitrogen.

Why do organisms need nitrogen?

Nitrogen is needed to make proteins and nucleic acids.

What is a chemoautotroph?

An organism that makes its own food using energy from chemical reactions rather than light.

What example of chemoautotrophy was discussed in Lecture 20?

Giant tube worms (Riftia) that house chemoautotrophic bacteria.

How do the bacteria associated with giant tube worms obtain energy?

They oxidize hydrogen sulfide ($H_2S$) and use the energy to make food.

What is nitrogen fixation?

The process of converting atmospheric nitrogen gas ($N_2$) into a usable form, such as ammonia ($NH_3$).

What enzyme carries out nitrogen fixation?

Nitrogenase.

What is the substrate for nitrogen fixation?

Nitrogen gas ($N_2$).

What is the product of nitrogen fixation in the reaction covered in class?

Ammonia ($NH_3$).

Why is nitrogen fixation difficult?

Nitrogen gas has a strong triple bond that is difficult to break.

Is nitrogen fixation an energy-expensive reaction?

Yes. It requires a large amount of energy.

How much ATP does nitrogen fixation require according to Lecture 20?

$16\text{ ATP}$ per $N_2$ molecule fixed.

Why is nitrogen fixation important for primary producers?

It makes nitrogen available for building proteins and nucleic acids, which are needed for growth.

What is symbiosis?

A close relationship between two different species.

What is mutualism?

A relationship in which both organisms benefit.

What are the three mutualistic relationships from Lecture 20?

Chemoautotrophs and giant tube worms; diatoms and endosymbiotic nitrogen-fixing bacteria; legumes and rhizobia.

How do chemoautotrophic bacteria and giant tube worms benefit each other?

The bacteria make food for the tube worm, and the tube worm provides the bacteria with a place to live.

How do nitrogen-fixing bacteria and diatoms benefit each other?

The bacteria provide usable nitrogen to the diatom and receive a place to live and resources from their host.

What is a diatom?

An aquatic organism that can host nitrogen-fixing bacteria inside it.

How do legumes and rhizobia benefit each other?

Rhizobia fix nitrogen for the legume, while the legume provides the bacteria with sugars and a place to live.

What are legumes, and what are examples?

Plants such as beans, peas, peanuts and soybeans.

Where do rhizobia live in legumes?

In structures called root nodules on the plant's roots.

Why is nitrogen fixation by rhizobia useful to legumes?

It supplies nitrogen the plant can use to make proteins and nucleic acids.

What is the common theme connecting all three mutualistic relationships?

Both partners benefit by providing something the other needs.

What is passive transport?

Doesn’t require energy moves from higher to lower concentration

What is active transport?

Requires energy, uses ATP or a pump to move from lower to higher concentration.

What is simple diffusion

Substance moves directly through the membrane from high to low concentration

Does simple diffusion require energy?

no, its passive

What is facilitated diffusion?

Movement of a substance from high to low concentration that does not require energy but requires a membrane transport protein.

What is the key difference between simple diffusion and facilitated diffusion?

Simple diffusion occurs directly through the membrane, whereas facilitated diffusion requires a transport protein.

 Does facilitated diffusion require energy?

no, its passive

What is the difference between facilitated diffusion and active transport?

Facilitated diffusion requires no energy and moves down a gradient, whereas active transport requires energy and can move against a gradient.

What is bulk transport?

The movement of large particles using membrane-bound vesicles, requires energy.

What is phagocytosis?

A type of bulk transport in which a cell engulfs a large particle

What is osmosis?

water moves through a semi permeable membrane toward a higher solute concentration

If water moves across a membrane toward a higher concentration of dissolved salt, what is the mechanism?

Osmosis

Does active transport or facilitated diffusion require ATP?

Active transport requires energy. Facilitated diffusion does not.

A substance moves from low concentration to high concentration using a pump. What is the mechanism?

active transport

What is osmoregulation?

The regulation of water and salt balance.

Why can excessive water entering a cell become a problem, and what is this bursting called?

Too much water entering can cause the cell to burst. lysis.

How do animal cells prevent excessive swelling from water entering?

ion pumps to maintain salt and water balance.

How do protist cells prevent excessive swelling?

They use contractile vacuoles to collect and expel excess water from the cell.

How do plant, fungal, and bacterial cells prevent bursting from water influx?

Their cell walls resist the pressure caused by water entering and limit swelling.

How do animal, protist, and plant/fungal/bacterial cells differ in preventing bursting?

How do animal, protist, and plant/fungal/bacterial cells differ in preventing bursting?

What does water follow?

Salt and sugars. 

What are halophiles?

Organisms that thrive in salty environments.

What is crenation?

The shrinking of a cell resulting from water loss.

What is the difference between cell lysis and crenation?

Lysis is cell bursting, whereas crenation is cell shrinking.

How do halophiles use a light-driven chloride pump to help prevent shrinking?

They pump chloride ions into the cell to help match the high salinity outside

Why does pumping chloride into a halophile help it retain water?

 It increases the cell’s solute concentration, reducing the tendency for water to leave the cell.

What pump creates the electrochemical gradient important for membrane excitability

sodium potassium pump

What does the sodium-potassium pump move during one cycle?

Three Na+ ions out of the cell and two K+ ions into the cell

What provides the energy for the sodium-potassium pump?

ATP hydrolysis,

Does the sodium-potassium pump move ions with or against their concentration gradients?

Against their concentration gradients, which requires energy.

What is an electrochemical gradient?

A difference in ion concentration and electrical charge across a membrane.

Why is the sodium-potassium pump important for membrane excitability?

 It maintains the ion gradients that allow cells to produce electrical signals