Cellular Energetics - Unit 3

ligands

ligands

A molecule that binds specifically to a receptor site of another molecule.
- change the shape of the receptor protein

signal transduction

the transmission of molecular signals from a cell's exterior to its interior
1. signaling molecule binding to specific receptor
2. activatin of asignal transduction pathway
3. production of cellular response

cyclic AMP (cAMP)

Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells. It is also a regulator of some bacterial operons.

volatile

highly unstable; explosive

Interphase

Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases

S phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.
- single chromatid duplicated to be sister chromatids, connected by a centromere

G1 phase

The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.
- cell produces all enzymes required for DNA replication

cyclins and cyclin-dependent kinases

The proteins that participate in the functioning of the checkpoints for cell cycle control are

Cell cycle checkpoints

mechanisms that monitor the preparedness of a eukaryotic cell to advance through the various cell cycle stages
-happen at phase boundaries
-regulating two families of proteins (cyclin dependent kinases and cyclins)

Oncogenes

genes that cause cancer by blocking the normal controls on cell reproduction
-abnormal/mutated versions of normal genes

tumor suppressor genes

A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.
- can trigger apoptosis

three classes of membrane receptors

ligand-gated ion channels
catalytic (enzyme-linked) receptors
G-protein-linked receptor

ligand-gated ion channels

membrane ion channels operated by the binding of specific molecules to channel proteins

catalytic (enzyme-linked) receptors

have an enzymatic active site on the cytoplasmic side of the membrane. Enzyme activity is initiated by ligand binding at the extracellular surface

G-protein-linked receptor

A signal receptor protein in the plasma membrane that responds to the binding signal molecule by activating a G protein.

secondary messenger

method of cellular signaling whereby a hormone diffuses into a cell to activate proteins within the cell to cause a response

Regulatory molecules on enzymes

Enzyme activity can be increased by activators or decreased by inhibitors. Inhibitors can be competitive (compete with the substrate for the active site) or noncompetitive (bind elsewhere on the enzyme and alter its function).

cofactors

Non-protein molecules required for enzyme activity. These can be inorganic ions or organic molecules (coenzymes).

Compartmentalization

Enzymes are stored in specific cell parts to ensure proper conditions for their activity and prevent cellular damage.

Feedback Inhibition

End products of metabolic pathways inhibit enzymes that regulate the pathway, preventing overproduction of the product.

Coenzyme

An organic cofactor, often derived from vitamins.
essential for the proper functioning of many enzymes and play a crucial role in catalyzing biochemical reactions

cooperativitiy of hemoglobin

: Hemoglobin shows cooperative binding, meaning that when one heme group binds oxygen, the affinity of the other heme groups for oxygen increases. This enhances oxygen uptake in the lungs and release in the tissues.

allosteric regulation of hemoglobin

Though not an enzyme, hemoglobin is allosterically regulated. Oxygen binding to one subunit causes a conformational change that increases the affinity of the remaining subunits for oxygen, resulting in a sigmoidal oxygen dissociation curve, which reflects improved oxygen binding and release.

quorum sensing

The ability of bacteria to sense the presence of other bacteria via secreted chemical signals.

Life cycle of cell

interphase, mitosis, cytokinesis

G0

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly.

Cancer

A disease in which some body cells grow and divide uncontrollably, damaging the parts of the body around them.

Apoptosis

process of programmed cell death when damage is s extensive that it cannot be repaired

activator

A molecule that increases enzyme activity.

Allosteric Regulation

Regulation of enzyme activity by binding of a regulatory molecule at a site other than the active site.

Cofactor

A non-protein molecule required for enzyme activity, which can be inorganic ions or organic molecules

enzyme

A type of protein that speeds up a chemical reaction in a living thing

Inhibitor

A molecule that decreases enzyme activity.

Competitive Inhibition

An inhibitor competes with the substrate for binding to the enzyme's active site.

Noncompetitive Inhibition

An inhibitor binds to a site other than the active site, altering enzyme function without blocking substrate binding.