June 25: Phis 206 Human Physiology - Cell Structure, Protein Synthesis, and Metabolism - Chapter 3

Flashcards based on lecture notes covering cell structure, protein synthesis, and metabolism.

Functions of plasma membranes

Regulating the passage of substances into and out of cells, detecting chemical messengers, linking adjacent cells, and anchoring cells to the extracellular matrix.

Membrane Structure

Double layer of lipid molecules containing embedded proteins; major lipids are phospholipids, which are amphipathic.

Integral membrane proteins

Closely associated with the membrane lipids and cannot be extracted without disrupting the lipid bilayer; they are amphipathic.

Peripheral membrane proteins

Not amphipathic and do not associate with the nonpolar regions of the lipids in the interior of the membrane; located at the membrane surface.

Specialized types of membrane junctions

Desmosomes, tight junctions, and gap junctions.

Desmosomes

Hold adjacent cells firmly together in areas subject to considerable stretching, such as the skin.

Tight junctions

Form barriers that limit the movement of material between cells, such as in the epithelium lining the gut and bladder.

Gap junctions

Consist of protein channels linking the cytosols of adjacent cells, allowing small molecules and ions to pass between cells.

Primary function of the nucleus

Storage and transmission of genetic information; synthesis of proteins.

Nuclear envelope

Barrier composed of two membranes surrounding the nucleus, containing nuclear pores for movement of molecules.

Nucleolus

Densely staining filamentous region without a membrane; associated with specific regions of DNA that contain the genes for forming ribosomal RNA.

Ribosomes

Protein factories of a cell, comprised of protein and RNA; synthesize protein molecules from amino acids using genetic information.

Endoplasmic Reticulum

Extensive network of membranes; rough form has ribosomes and is involved in packaging proteins; smooth form synthesizes lipids and detoxifies molecules.

Golgi apparatus

Series of flattened membranous sacs that modify and sort proteins arriving from the rough endoplasmic reticulum.

Endosomes

Membrane-bound structures involved in sorting, modifying, and directing vesicular traffic in cells.

Mitochondria

Participate in chemical processes that transfer energy from nutrient molecules to ATP molecules via cellular respiration.

Lysosomes

Organelles containing digestive enzymes that break down bacteria, debris from dead cells, and damaged cell organelles.

Peroxisomes

Consume molecular oxygen, removing hydrogen from organic molecules and producing hydrogen peroxide, which they also destroy to prevent toxic effects.

Vaults

Cytoplasmic structures composed of protein and vault RNA; potentially involved in transport of molecules between the cytosol and the nucleus.

Cytoskeleton

Filamentous network that maintains and changes cell shape; includes actin filaments, intermediate filaments, and microtubules.

Actin filaments

Composed of monomers of G-actin, determining cell shape, cell movement, cell division, and muscle contraction.

Intermediate filaments

Composed of twisted strands of proteins like keratin and desmin, contributing to cell shape and anchoring the nucleus.

Microtubules

Hollow tubes composed of tubulin, maintaining cell shape and forming spindle fibers during cell division.

Centrosome

Region of the cell that radiates microtubules and contains centrioles, regulating the formation and elongation of microtubules.

Cilia

Hair-like extensions on cell surfaces containing microtubules, producing movements to propel substances along the epithelium.

Ligand

A molecule or ion that is bound to a protein.

Binding site

Region of a protein to which a ligand binds; may contain several sites for different ligands or multiple sites for the same ligand.

Chemical specificity

The ability of a protein-binding site to bind specific ligands.

Affinity

The strength of ligand-protein binding.

Saturation

The fraction of total binding sites that are occupied at any given time.

Allosteric modulation

Occurs when a protein has two binding sites and the noncovalent binding of a ligand to one site alters the shape of the second binding site.

Covalent modulation

The covalent bonding of charged chemical groups to some of the protein’s side chains.

Catabolism

The breakdown of organic molecules.

Anabolism

The synthesis of organic molecules.

Enzyme

Protein catalyst that lowers the activation energy and makes biological reactions proceed at a faster reaction rate.

Substrates

Reactants in the case of enzyme-mediated reactions.

Metabolic Pathways

Multienzyme pathways that are the basis of cellular metabolism.

Cellular Metabolism

The transfer of energy released from the breakdown of fuel molecules to ATP.