Essential Cell Biology: Chapter 14

Cell Respiration

Process by which cells harvest the energy stored in food molecules; usually accompanied by the uptake to O2 and the release of CO2.

Oxidative Phosphorylation

Process in bacteria and mitochondria in which ATP formation is driven by the transfer of electrons from food molecules to molecular oxygen.

Electron-Transport Chain (respiratory chain)

A series of membrane-embedded electron carrier molecules that facilitate the movement of electrons from a higher to a lower energy level, as in oxidative phosphorylation and photosynthesis.

ATP Synthase

Membrane-associated enzyme complex that catalyzes the formation of ATP from ADP and inorganic phosphate during oxidative phosphorylation and photosynthesis.

Chemiosmotic Hypothesis

The mechanism for generating energy that was first propose din 1961. It linked the chemical bond-forming reactions that synthesize ATP with the membrane transport processes that pump protons.

Chemiosmotic Coupling

Mechanism that uses the energy stored in a transmembrane proton gradient to drive the energy-requiring process, such as the synthesis of ATP or the transport of a molecule across a membrane.

Mitochondria

Membrane-enclosed organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells.

Matrix

Large internal compartment within a mitochondrion.

Outer Membrane

Contains many molecules of a transport protein called porin, which, forms wide aqueous channels through the lipid bilayer. It is permeable to molecules (less than 5000 daltons) and small proteins.

Inner Membrane

Impermeable to the passage of ions and most small molecules, except where a path is provided by specific membrane transport proteins. It is the site of oxidative phosphorylation and contains the proteins of the ETC, proton pumps, and ATP synthase required for ATP production.

Cristae

A series of infoldings that make up the inner mitochondrial membrane. These worlds greatly increase the surface area of the membrane.

Chlorophyll

Light-absorbing green pigment that plays a central part in photosynthesis.

Respiratory Enzyme Complex

Set of proteins in the inner mitochondrial membrane that facilitates that transfer of high-energy electrons from NADH to water while pumping protons into the inter membrane space.

NADH Dehydrogenase Complex

The first respiratory complex in the ETC that accepts electrons from NADH in the form of a hydride ion which is then converted into a proton and two high-energy electrons.

Cytochrome c Reductase

Cytochrome c Oxidase

Protein complex that serves as the final electron carrier in the respiratory chain; removes electrons from cytochrome c and passes them to O2 to produce H2O.

Electrochemical Gradient

Driving force that determines which way an ion will move across a membrane; consists of a combined influence of the ion's concentration gradient and the membrane potential.

Redox Reaction

A reaction in which electrons are transferred from one chemical species to another. An oxidation-reduction reaction.

Redox Pair

Two molecules that can be interconverted by the gain or loss of an electron; for example, NADH and NAD+.

Redox Potential

A measure of the tendency of a given redox pair to donate or accept electrons.

Quinone

Small, lipid-soluble, mobile electron carrier molecules found in the respiratory and photosynthetic electron-transport chains.

Iron-Sulfur Center

Metal complex found in electron carriers that operate early in the electron-transport chain; has a relatively weak affinity for electrons.

Cytochrome

Membrane-bound, colored, heme-containing protein that transfers electrons during cellular respiration and photosynthesis.

Cytochrome c

A small protein that accepts electrons from the cytochrome c reductase complex and transfers them to the cytochrome c oxidase complex, has a redox potential of +230 mV.

Photosynthesis

The process by which plants, algae and some bacteria use the energy of sunlight to drive the synthesis of organic molecules from carbon dioxide and water.

Chloroplast

Specialized organelle in algae and plats that contains chlorophyll and serves as the site in which photosynthesis takes place.

Carbon Fixation

Process by which green plants and other photosynthetic organisms incorporate carbon atoms from atmospheric carbon dioxide into sugars. The second stage of photosynthesis.

Stroma

In a chloroplast, the large interior space that contains the enzymes needed to incorporate CO2 into sugars during the carbon-fixation stage of photosynthesis; equivalent to the matrix of mitochondria.

Thylakoid

In a chloroplast, the flattened dislike sac whose membranes contain the proteins and pigments that convert light energy into chemical energy during photosynthesis. They are arranged in stacks called grana.

Thylakoid Space

The space inside each thylakoid that is connected with that of other thylakoids.

Light Reactions

In photosynthesis, the set of reactions that converts the energy of sunlight into chemical energy in the form of ATP and NADPH.

Dark Reactions

In photosynthesis, the set of reactions that produce sugars from CO2; these reactions, also called carbon fixation, can occur in the absence of sunlight.

Glyceraldehyde 3-Phosphate

A three carbon sugar that is exported to the cytosol where it is then used to produce sucrose and a large number of other organic molecules in the leaves of a plant.

Photosystem

Large multi protein complex containing chlorophyll that captures light energy and converts it into chemical energy; consists of a set of antenna complexes and a reaction center.

Antenna Complex

In chloroplasts and photosynthetic bacteria, the part of the membrane-bound photosystem that captures energy from sunlight; contains an array of proteins that bind hundreds of chlorophyll molecules and other photosensitive pigments.

Special Pair

A chlorophyll dimer which holds its electrons at a lower energy than do the other chlorophyll molecules.

Reaction Center

In photosynthetic membranes, a protein complex that contains a specialized pair or chlorophyll molecules that performs photochemical reactions to convert the energy of photons (light) into high-energy electrons for transport down the photosynthetic ETC.

Plastoquinone

A mobile electron carrier that is part of the photosynthetic ETC that transfers the high-energy electrons to the proton pump, which uses the movement of electrons to generate an electrochemical proton gradient.

Nitrogen Fixation

Conversion of nitrogen gas from the atmosphere into nitrogen-containing molecules by soil bacteria and cyanobacteria.

NADH

Activated carrier widely used in the energy-producing breakdown of sugar molecules.

NAD+

Activated carrier that accepts a hydride ion from a donor molecule, thereby producing NADH. Widely used in the energy-producing breakdown of sugar molecule.

T/F the glucose-Na+ symport protein is bidirectional

False - unidirectional

Bacteriorhodopsin is found in

The plasma membrane of bacteria

Bacteriorhodopsin uses ____ as an energy source to perform __

Light energy

Active export of H+

Which of the following statements regarding membrane proteins is false

A. Membrane proteins can be dissociated from membranes using gentle detergent

B. Cells can restrict the movement of membrane protein

C. In transmembrane proteins that form an aqueous pore through the membrane the pore is lined with hydrophobic amino acid side chains

D. The plasma membrane is reinforced by the cell cortex. The main component of red blood cell cortex is the protein spectrin. K

C

True or False: Ion Channels stay in either the open or closed state

False

The patch clamp experiment determined that

Ion channels randomly snap between open and closed states

Linking Filaments

Pulls one channel toward another causing tilting thereby opening the ion channel

Describe the stress gated ion channels of cilia within the ear

1. Sterocilia tilt in response to sound

2. Ion channels open

3. Entry of positively charged ions can occur

Mimosa pudica

Plant whose leaflets fall down when touched,

Uses both mechanical and voltage gated ion channels to respond

Dendrites

branching extensions of neuron that receives messages from neighboring neurons

Axons

a part of a neuron that carries impulses away from the cell body

terminal branches of axon

branched endings of an axon that transmit messages to other neurons

Axons only have a

Na+ channel

Shape of the actional potential depends on the

Concentration of Na+ outside the membrane

Na+ ion channel is

Voltage gated

T/F action potentials can be propagated in multiple directions along the axon

False

What prevents an action potential from going backward?

Na+ ion channels

Relaying signal from one nerve cell to another requires conversion of electrical signal into chemical signal and back into electric signal

Where does this occur?

Synaptic structures

T/F: A symport would function as an anti port if its orientation in the membrane were revers (i.e. if the portion of the molecule normally exposed to the cytosol faced outside the cell instead

False

Passive transport of ions can be mostly driven by

A. Concentration gradients

B. Electrical charge

C. Hydrolysis of ATP

D. High energy electrons

E. Light energy

F. A & B

F

A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process.

The grape juice is contaminated with proteases (enzymes that attack some of the transport proteins in the yeast cell membrane), and the yeast cell dies. Which accounts for the cells demise?

A. Toxic buildup of CO2 inside the cell

B. Diffusion of ATP out of the cell

C. Inability to import sugar into the cell

D. Inability to take water into the cell

C

Membrane potential is governed by the permeability of a ___ to specific ____

Membrane

Ions

Which of the following organisms would you expect to have the lowest percentage of unsaturated phospholipids in their membrane

A. Antarctic fish

B. Cactus

C. Human

D. Bacteria from thermal hot springs

D

ligand-gated channels

open in the presence of a specific binding substance, usually a hormone or neurotransmitter

Ion channels that are always open are called channels.

leak

Ion Channels

A complex of protein molecules in a cell membrane that form a pore through which ions can pass.

Describe Na+ channel opening

Closed state -> add signal -> opens -> gradually inactivated -> closed

Nerve cell signaling

1. action potential reaches presynaptic nerve terminal

2. Pre-synaptic voltage-gated Ca2+ channels open in the plasma membrane, allowing Ca2+ to flow into the pre-synaptic terminal