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Homeostasis and how it is maintained Negative feedback
Negative feedback and positive feedback *Negative* = Main mechanism used to maintain
homeostasis.
Acts opposite of variable to return body to homeostasis.
*Positive* = Response in the same direction as change (Moves variable further away from
normal set point value)
Components of a feedback loop Sensors -> Integrating Center -> Effectors
CH. 2 Nonpolar and polar covalent bonds, hydrogen bonds, ionic bonds *Nonpolar* =
Electronegativity of the atoms are equal
*Polar* = Pair of electrons is unequally shared between two atoms.
*Hydrogen* = A weak bond resulting from an electrostatic attraction between a proton in one
molecule and an electronegative atom in the other.
*Ionic* = Complete transfer of valence electrons between atoms. Generates 2 oppositely charged
ions. The metal loses electrons to become a positively charged cation, whereas the nonmetal
accepts those electrons to become a negatively charged anion.
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Which types of molecules are hydrophilic and which are hydrophobic Hydrophilic
=Carbohydrates, Polar & Ionic molecules
Hydrophobic = Lipids, Nonpolar molecules
Ampipathic = contains both Philic & Phobic properties
Acids, bases, buffers, and pH Acids - Release H+ when dissolved in water
Bases - Accept or remove H+
Buffers - Can both accept and donate hydrogen ions
- Absorb H+ if body fluid pH too acidic
- Release H+ if body fluid pH too basic
pH = -log [H+]
Characteristics and functions of carbohydrates, lipids, proteins, and nucleic acids *Carbs*
- Polar, Hydrophilic / Energy source, part of cell membrane
*Lipids* - Nonpolar, Hydrophobic (sometimes ampipathic) / Composed primarily of hydrogen
and carbon atoms
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*Proteins* - Polymers of amino acids with peptide bonds / Receptors, carrier proteins, enzymes,
hormones (ex. insulin,) contractile proteins (actin and myosin,) antibodies, structural proteins
*Nucleic Acids*- Polymers of nucleotides / DNA, RNA, Storage and expression of genetic
information
Cell structure: plasma membrane, nucleus, and organelles -Phospholipid bilayer,
selectively permeable, fluid mosaic model (moveable)
-Nucleus contains genetic information
Cell-to-cell adhesions: Tight junctions, Gap junctions, Desmosomes
Tight junctions - Impermeable barrier between epithelial cells lining lumens
- Solutes can only go through the cells but not around them
Gap junctions - Channels that allow cells to communicate or exchange nutrients
Ex. Cardiac muscle, smooth muscle, bone, some neurons
Desmosomes - Keeps tissues from tearing apart when mechanically
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stressed. (Like a spot weld)
- Found in skin, heart, uterus
CH. 3/21 Anabolic versus catabolic reactions Anabolic = Involves the production of larger
molecules from smaller reactants.
Catabolic = Involves breakdown of larger molecules into smaller ones.
Endergonic versus exergonic reactions Endergonic = Requires energy
Exergonic = Releases energy
Types of chemical reactions: 1. Hydrolysis and condensation reactions
2. Phosphorylation and dephospho rylation reactions
3. Oxidation-reduction reactions
Hydrolysis and condensation reactions *Hydrolysis* - Water reacts with molecules,
breaking the bonds that link a molecule together.
*Condensation* - Reverse of Hydrolysis; Joining together two or more smaller molecules to
form a larger one.