NVCC BIO 101 Exam 2

Metabolism

the totality of an organism's chemical reactions

Metabolic pathway

Begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product.

catabolic pathway

release energy by breaking down complex molecules into simpler compounds

anabolic pathways

consume energy to build complex molecules from simpler ones
- proteins are synthesized from simpler molecules called amino acids

Bioenergetics

the study of how energy flows through living organisms

Energy

the capacity to cause change

kinetic energy

energy of motion

thermal energy

kinetic energy associated with the random movement of atoms or molecules

heat

thermal energy in transfer from one object to another

potential energy

energy that matter possesses because of its location or structure

chemical energy

potential energy available for release in a chemical reaction

Thermodynamics

The study of energy transformations that occur in a collection of matter.

first law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed
- also called the principle of conservation of energy

second law of thermodynamics

Every energy transfer or transformation increases the entropy of the universe.

Entropy

- a measure of molecular disorder, or randomness
- scientists use the term "disorder" to describe how dispersed energy is in a system and how many energy levels are present

Chemical reactions

- Endergonic ("energy in")
- Exergonic ("energy out")
- Energy coupling

Endergonic

- A chemical reaction that requires the input of energy in order to proceed
- yields product rich in potential energy
- start with reactabr molecules that contain relatively little potential energy but end with products that contain more chemical energy

Exergonic

Chemical reactions that release energy
- these reactions release the energy in covalent bonds of the reactants
- burning wood releases the energy in glucose as heat and light

energy coupling

The use of an exergonic process to drive an endergonic one.

ATP (adenosine triphosphate)

main energy source that cells use for most of their work
- composed of ribose (a sugar), adenine (a nitrous base), and a chain of three phosphate groups
- ATP hydrolysis releases energy and produces ATP (adenosine diphosphate) and inorganic phosphate
- the energy released comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves

enzyme

A macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.
- most enzyme names end with -ase

catalyst

substance that speeds up the rate of a chemical reaction

activation energy

Energy needed to get a reaction started by breaking bonds in the reactant molecules

A cell does three main kinds of work

chemical, transport, mechanical

Substrate

the reactant molecule on which an enzyme acts
- the enzyme binds to its substrate, forming an enzyme-substrate complex

ATP

- is a renewable resource that is regenerated by addition of a phosphate group to ADP
- the energy to phosphate ADP comes from catabolic reactions in the cell
- The ATP cycle is a revolving door through which energy passes during its transfer from catabolic to anabolic pathways

enzyme inhibitors

Enzyme activity is often regulated by molecules that selectively inhibit enzyme function

competitive inhibitors

bind to the active site of an enzyme, competing with the substrate

noncompetitive inhibitor

bind to an alternative site on the enzyme, causing the active site to change shape and become less effective

Cofactors

nonprotein molecules that help carry out processes that are difficult for amino acids
- may be inorganic (such as metal in ionic form) or organic
- an organic cofactor is called a coenzyme

aerobic respiration

consumes organic molecules and O2 and yields ATP

Fermentation

A partial degradation of sugars that occur without the use of O2
- consist of glycolysis plus reactions that regenerate NAD for use in glycolysis

anaerobic respiration

similar to aerobic respiration but consumes compounds other than O2

cellular respiration

includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration

C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy

chemical equation for cellular respiration
* = loss of hydrogen atoms (becomes oxidized)
non * = gain of hydrogen atoms (becomes reduced)

redox reaction

the movement of electrons from one molecule to another

a molecule that gives up electrons is

oxidized

a molecule that accepts electrons is

reduced

electron carriers

proteins arranged in chains on the membrane to allow the transfer of electrons from one carrier to another.

Electron Trabsport Chain

Found on the inner mitochondrial membrane
Produces the most ATP compared to glycolysis and citric acid cycle

During cellular respiration

Electrons are transferred from glucose to oxygen and energy is released

Cells capture energy from electrons "falling" from organic fuels to oxygen

an electron loses its potential energy when it is transferred to oxygen

substrate-level phosphorylation

The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.
- glycolysis and the citric acid cycle only produce four ATP molecules by substrate-level phosphorylation
- NADH and FADH2 account for most of the energy extracted from glucose

lactate fermentation

anaerobic sugar breakdown pathway that produces ATP and lactate

alcoholic fermentation

pyruvate us converted to ethanol in two steps:
- CO2 is released from pyruvate, forming acetaldehyde
- acetaldehyde is reduced by NADH to ethanol

obligate anaerobes

use only fermentation or anaerobic respiration and cannot survive in the presence of O2

facultative anaerobes

yeast and many bacteria, can use cellular respiration in the presence of O2, or fermentation when O2 is absent

autotrophs

self-feeders that get energy and carbon entirely from nonliving sources
- producers, make organic molecules from CO2 and other inorganic molecules

Photoautotrophs

Organisms that use light as a source of energy to synthesize organic substances
- almost all plants and animals are photoautotrophs

heterotrophs

obtain energy and carbon from the organic material derived from other organisms
- consumers eat other organisms, decomposers break down and absorb energy and nutrients from nonliving remains or wastes of other organisms

plant structure

mesophyll, stomata, chloroplast

mesophyll

The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.
- chloroplasts are found inside

Stomata

Small openings on the underside of a leaf through which oxygen and carbon dioxide can move

Chloroplast

composed of a double membrane surrounding a dense fluid called the stroma
- a third membrane system, composed of sacs called thylakoids, is suspended within the stroma
- the green in leaves comes from chlorophyll

stages of photosynthesis

1. Light-dependent Reaction: chlorophyll absorbs light energy to make carrier NADPH
- H2O is split
- O2 is released as a waste product
- The electron acceptor NADP is reduced to NADPH
- ATP is generated by adding a phosphate group to ADP in a process called photophosphorylation
2. Calvin cycle: Carbon Dioxide, ATP and NADPH are used to make glucose.
- CO2 is initially incorporated into an organic molecule through a process called carbon fixation

electromagnetic spectrum

All of the frequencies or wavelengths of electromagnetic radiation

Wavelength

Horizontal distance between the crests or between the troughs of two adjacent waves

Photons

particles of light
- have a fixed quantity of light, inversely proportional to the wavelength of light

pigment

Light-absorbing molecule
- different pigments absorb different wavelengths

light reactions

The first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.

Photosysten II

functions first (numbers reflect the order of discovery) and is best at absorbing a wavelength of 680 nm

electron transfer chain

Array of enzymes and other molecules that accept and give up electrons in sequence, thus releasing the energy of the electrons in steps.

Photosystem I

One of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P700 reaction-center chlorophyll.

cellular respiration steps

1. Glycolysis
2. Pyruvate Oxydation
3. Citric Acid Cycle (Krebs Cycle)
4. Oxidative Phosphorlyation

Glycolysis

pyruvate: 2
ATP: 2 net
NADH: 2

pyruvate oxidation

Acetyl CoA: 2
NADH: 2
CO2: 2

Citric Acid Cycle (Krebs Cycle)

CO2: 4
NADH: 6
ATP: 2
FADH2: 2

oxidative phosphorylation

ATP synthase uses energy from a proton gradient
ATP: 28