midterm Flashcards
What is the internal environment of the cell?
extracellular fluid (plasma, interstitial) that surrounds each cell
What do solute, solvent, and solution mean? What are hydrophilic, hydrophobic, and amphipathic molecules?
SOLUTE: substance dissolved in a liquid
SOLVENT: the liquid in which a substances are dissolved (e.g., water)
SOLUTION: solutes dissolve in a solvent to form a solution
HYDROPHILIC have a number of polar bonds and/or ionized groups, soluble in water (e.g., carboxyl, amino)
HYDROPHOBIC are composed mostly of carbon and hydrogen, insoluble in water (bc electrically neutral covalent bonds, e.g., C-H, are not attracted to water)
AMPHIPATHIC have polar or ionized region at one site and nonpolar at another, when mixed with water form clusters with polar (hydrophilic) heads at surface of cluster and nonpolar (hydrophobic) tails oriented inward
What is organic chemistry?
chemistry of the compounds of carbon
What are the major classes of organic molecules?
carbohydrates, lipids, proteins, nucleic acids
What are the subclasses of carbohydrates?
monosachharides, disaccharides, polysaccharides
What are the subclasses of lipids?
fatty acids, triglycerides, phospholipids, steroids
What are endocrine glands? What do they do?
glands of the endocrine system that produce and secrete hormones into the bloodstream
What are proteins and what are they made out of?
complex polymers of more than 50 amino acids (folded into a characteristic shape forming a functional molecule)
What are peptides and what are they made out of?
- amides, -NHCO-
- a polypeptide with 50 or fewer amino acids, with a known biological function
What are polypeptides?
a sequence of amino acids linked by peptide bonds
What is a peptide bond?
bond formed between amino and carboxyl group (polar covalent)
What are fatty acids? What do they do?
building block of lipids, provide energy for cellular metabolism
(carbon chain w/ acidic carboxyl group at one end)
types:
- SATURATED (when all Cs are linked by single covalent bonds (animal fats))
- UNSATURATED (one or more double bonds of C (vegetable oils))
- POLYUNSATURATED (more than one C double bond (vegetable fats))
- EICOSANOIDS (derived from the polyunsaturated arachidonic acid) regulate a number of cell functions
What are triglycerides? What do they do?
a subclass of lipids, “fat”; majority of body’s lipids; found in blood and can be synthesized in liver; stored (via dehydration) in adipose tissue where they supply energy to cells (via hydrolysis) esp during fasting or exercising
(glycerol + 3 fatty acids) combine by dehydration to form triglycerides and water
What are phospholipids? What do they do?
a subclass of lipids, amphipathic (w/ polar hydrophobic end + nonpolar hydrophobic end) permits them to form the lipid bilayers of cellular membranes
(glycerol + 2 fatty acids + phosphate + small charged nitrogen molecule)
What are steroids? What do they do?
a subclass of lipids (e.g., cholesterol, cortisol from the adrenal glands, estrogen and testosterone secreted by the gonads)
(4 interconnected rings of carbon atoms, plus a few hydroxyl groups may be attached)
What is biochemistry?
organic chemistry of life and its constituents
What are monosaccharides?
a subclass of carbohydrates (e.g., glucose, fructose), the simplest sugars, stores energy for later use
5C + O form a ring on a flat plane, H and HO on each carbon lie above and below the plane
What are disaccharides?
a subclass of carbohydrates, composed of two monosaccharides (e.g., sucrose or table sugar, lactose in milk)
dehydration links monosaccharides, hydrolysis uncouples monosaccharides
What are polysaccharides?
a subclass of carbohydrates, polymers of monosaccharides (e.g., starch, glycogen or animal starch)
hydrolysis of glycogen (as during fasting) leads to release of glucose monomers into the blood, thereby preventing blood glucose from decreasing to dangerously low levels
What are glycoproteins?
Proteins covalently attached to a monosaccharide; present in plasma membranes; major components of connective tissue; also abundant in fluids like mucus where they play a protective or lubricating role
What are the subclasses of nucleic acids?
DNA (stores genetic info)
RNA (decode info sfrom DNA into instructions for forming specific proteins)
What makes the cell’s plasma membrane special? What is its structure?
- acts as selective barrier, regulating passage of substances into and out of cell
- also detects extracellular signals, links adjacent cells, and anchors proteins on cellular surface
- structure: lipid bilayer (mostly phospholipids, 25%) with embedded proteins (55%)
- also contains cholesterol (13%)
What are the different membrane junctions?
desmosomes, tight junction, gap junction
What is a desmosome?
- a specialized type of membrane junction, in areas subject to stretching (skin)
- a region of 20nm btwn two adjacent cells held together by cadherins, anchored by dense protein along cytoplasmic surface of membrane
What is a tight junction?
- a specialized type of membrane junction that occurs in a band around the cell’s circumference
- impedes molecular movement btwn cells, joins most epithelial cells
What is a gap junction?
- a specialized type of membrane junction involved in transmission of electrical activity
- 2-4nm gap allows CONNEXINS from two membranes join, forming 1.5 nm protein-lined channels linking cytosols of the cells
- passes small molecules and ions (e.g., Na+ and K+), and excludes large proteins
What is the granular/rough endoplasmic reticulum?
- the most extensive cytoplasmic organelle, a network of membranes w/ a flattened-sac appearance
- with ribosomes bound to its cytosolic surface
- involved in producing and packaging proteins to be secreted by the cell
What are ribosomes?
- the “protein factories” of the cell (located in cytoplasm)
- composed of 70-80 proteins and several RNA molecules
- synthesize proteins using genetic info from DNA
- bind to rough endoplasmic reticulum (or float free in cytoplasm)
- the proteins pass into the lumen of the reticulum and are then transferred to the Golgi apparatus
What is the Golgi apparatus?
- the “packaging center” of the cell
- a series of flattened sacs forming a cup-shaped structure
- modifies and sorts proteins (sent from rough endoplasmic reticulum) into secretory vesicles
- e.g., where carbohydrates are linked to proteins to form glycoproteins
What is an oligodendrocyte?
type of glial cell in the CNS that:
1) provides physical support for neurons
2) insulates neurons by supplying myelin sheath
3) forms one 1mm segment of myelin for several adjacent axons (one process = one myelin segment)
What is a Node of Ranvier?
bare portion of axon btwn myelin sheaths
What is a Schwann cell?
PNS counterpart to oligodendrocyte:
1) an entire cell = one myelin segment
2) serves as phagocyte and guides regeneration (when peripheral nerve is damaged)
What is the difference btwn transcription and translation?
DNA –> RNA (in the nucleus)
RNA –> Protein (in the cytoplasm)
What are metabolism, anabolism, and catabolism?
- the entire collection of chemical reactions in the body
- synthesis of organic molecules by cells
- breakdown of organic molecules
What is a cofactor?
substance (e.g., trace metal) that ACTIVATES ENZYME - binds to enzyme altering its conformation to conform to substrate
What is a coenzyme?
- a cofactor that is an organic molecule and participates as one substrate in a reaction, adding or removing only a few atoms (e.g., H, acetyl, methyl)
- derived from vitamins (e.g., NAD+ from niacin, FAD from riboflavin)
What does the Michaelis-Menten equation mean?
- reaction rate increases as substrate concentration increases, until all active sites on enzyme are bound (saturation occurs)
- reaction time plateaus at full saturation, despite change in substrate concentration
- reaction rate can be increased by increasing enzyme concentration (even after saturation) (semi-saturation constant is unaffected)
- reaction rate can be altered by changing properties of enzyme’s active site (e.g., affinity), resulting in change in semi-saturation constant (max rate is unaffected)
What is chemical specificity?
- shape of binding site permits only particular ligands to bind to it
- determines drug side effects (less ___, more side effects)
(shape determines proximity; greater proximity, greater force of attraction)
What is affinity?
- strength of binding btwn protein and given ligand
- increases with increased specificity and proximity:
HIGH (if oppositely charged + high specificity),
INTERMEDIATE (high specificity only),
LOW (low specificity only) - if ___ is high for a drug, then very little of the drug is required to bind, thus reducing unwanted side effects
What are components of covalent modulation?
changes shape and activity of protein by covalently binding charged chemical group to protein side chain (e.g., phosphorylation)
1) PHOSPHATE GROUP adds negative charge to region, changing the protein’s shape
2) ENZYMES accelerate rate at which substrates are converted into products
3) PROTEIN KINASE: any enzyme that mediates protein phosphorylation
4) PHOSPHOPROTEIN PHOSPHATASE: enzyme that dephosphorylates protein
phosphorylation:
protein + ATP –> phosphorylated protein + ADP
dephosphorylation:
phosphorylated protein + water –> protein + phosphate group