Essay questions Flashcards
(Chp 1)
Describe the concept of homeostasis. Explain how negative feedback and positive feedback loops effect the homeostatic condition. Use examples to explain your answer.
homeostasis is the ability of an organism to maintain a constant internal environment even though there are changes in the external environment (ex: cardiac output and blood pressure must be properly controlled or organ systems will begin to malfunction). Negative Feedback: Designed to oppose the change that has occurred in the body so you can return to homeostasis. Negative feedback systems protect homeostasis (ex. Body temperature: If you get hot, you sweat to cool off. If you get cold, you shiver to heat up. When blood sugar is low, homeostasis will bring it back up. When blood sugar is high, homeostasis will bring it back down). Positive Feedback: Amplifies the homeostatic situation. Take you away from homeostasis for the purpose of eventually returning you back to homeostasis (ex. childbirth: contractions start & positive feedback kicks in to make contractions stronger to thin cervix then dilate).
(Chp 1)
Describe the four physiological themes discussed in the book that apply to all living organisms.
Theme 1: Structure and Function are Closely Related
Molecular Interactions: the ability of individual molecules to bind to or react with other molecules is essential for biological function.
Compartmentation: allows cells, tissues, and organs to specialize and isolate functions by dividing space into compartments forming organelles, body cavities, & hollow organs.
Theme 2: Living Organisms Need Energy
Growth, reproduction, movement, homeostasis, etc require the input of energy. The sum of all the chemical reactions in the body that are associated with energy transformation is known as metabolism.
Theme 3: Information Flow Coordinates Body Functions
Gene transfer from generation to generation. Proteins are produced by transcription and translation within the single organism. Cell to cell communication involves neurotransmitters, hormones, paracrine and autocrine regulators, and action potentials. In chemical communication, some molecules will cross membranes and others must bind to receptors in the membranes
Theme 4: Homeostasis Maintains Internal Stability
Maintaining a relatively stable internal environment even though the external environment is variable.
(Chp 2)
Explain chemical bonding in terms of covalent, ionic, and hydrogen bonds as well as discuss Van der Waals forces.
Bonding involves the interaction of valence electrons between 2 or more atoms.
Covalent bonds
- strong bonds
- share valence electrons
- take most energy to make & break
- include:
- nonpolar bonds: share electrons equally
- polar bonds: electrons pulled toward another atom
Ionic bonds
- 1 or more valence electrons transferred to 2nd atom, forming ions.
Hydrogen bonds
- weak bonds
- hydrogen gains + charge when forms polar covalent bond
Van der Waals Forces
- weak nonspecific forces between nucleus of atom & electrons of nearby atom allowing atoms to pack closely together and occupy minimum amounts of space
(Chp 2)
Describe dehydration synthesis and hydrolysis. Give examples of each type of reaction.
Dehydration synthesis
- condensation
- 2 monosaccharides covalently bonded together
- producing maltose, sucrose, or lactose
- ex H+ & OH- removed, producing H2O
- requires specific enzymes to catalyze reactions
Hydrolysis
- digestion reaction to free up sugars for energy
- reverse of dehydration
- requires specific enzymes to catalyze reactions
- polysaccharides hydrolyzed into disaccharides, then to monosaccharides
- split H2O molecules provides atoms to complete molecular structure of the products
- H+ added to one monosaccharide & OH- to the other
- split H2O molecules provides atoms to complete molecular structure of the products
(Chp 2)
Explain what a lipid is. Be able to describe triglycerides, ketone bodies, phospholipids, steroids, and prostaglandins.
Lipids
- diverse group of molecules that differ greatly in chemical structure
- primarily of hydrocarbon chains and rings that are nonpolar
- insoluble in polar solvents (such as H20)
Triglycerides
- fats and oils
- Formed by condensation of glycerol and 3 fatty acids.
- Fatty acids consist of a nonpolar hydrocarbon chain with a carboxyl end.
- include Saturated Fatty Acids & Unsaturated Fatty Acids
Ketone bodies
- four carbon acidic molecules that are converted in the liver by free fatty acids.
- free fatty acids are released into the blood by the hydrolysis of triglycerides in adipose tissue
- in severe cases, increased ketone bodies in the blood, which lowers pH, can cause coma or death
Phospholipids
- A number of different categories of lipids that contain a phosphate group.
- Nonpolar end is hydrophobic, polar end is hydrophilic
Steroids
- structure of three 6-carbon rings joined to a 5-carbon ring.
- Nonpolar and insoluble in H20.
- produced by the gonads and adrenal cortex
Prostaglandins
- produced and active in most organs
- Fatty acid with a cyclic hydrocarbon group.
- part of the Eicosanoids family
- serve a variety of regulatory functions.
(Chp 2)
Explain the structure of a protein and explain primary structure, secondary structure, tertiary structure, and quaternary structure.
Proteins
- large molecules composed of long chains of amino acids.
- Each amino acid contains an amino group (NH2) at one end and carboxyl group (COOH) at the other end.
Primary structure:
- Sequence of the amino acids in the protein.
Secondary structure:
- Weak hydrogen bonds that form between the hydrogen of 1 amino acid and an oxygen of a different amino acid nearby.
Tertiary structure:
- Polypeptide chains that bend and fold to produce 3-dimensional shapes.
- formed and stabilized by weak chemical bonds between functional groups.
Quaternary Structure:
- A number of polypeptide chains covalently linked together
(Chp 2)
Describe the pH scale and discuss the concept of acids, bases, and buffers.
pH
- concentration of H+ in body fluids. pH = log (1/[H+]).
- Because of the logarithmic relationship of pH, each pH value has 10 times greater or lesser [H+] from pure water.
Acid
- molecule that can release protons (H+) to a solution.
- A proton donor.
Base
- Often a negatively charged ion that can combine with H+, and remove it from solution.
Buffers
System of molecules and ions that act to prevent changes in [H+] as acids are continually added to the body through metabolism.
(Chp 3)
Describe five cytoplasmic organelles and give examples of their function.
- Cytosol: intracellular fluid separated from extracellular fluid by the cell
membrane. Cytosol contains nutrients, proteins, ions, and waste. - Inclusions: insoluble materials including stored nutrients and structures responsible for cellular function.
- Protein Fibers: internal support system known as the cytoskeleton
- Organelles: membrane bound structures that have specific functions for the cell.
- Ribosomes: a type of inclusion that do not have membranes and therefore have direct contact with the aqueous cytosol
(Chp 3)
Describe the process of DNA replication.
- DNA helicase enzymes unzip the DNA molecule at a replication fork.
- The enzyme DNA polymerase is what adds to the complimentary bases. Adds DNA nucleotides.
- DNA polymerase can add nucleotides only to the 3’ (prime) end of the molecule. Moves 5’ to 3’.
- Because of 5’-3’ direction of DNA polymerase you get a leading & lagging strand.
- Replication along the leading strand is continuous, while replication along the lagging strand is not.
- Portions of DNA (Okazaki fragments) are created on the lagging strand.
- DNA ligase must connect the Okazaki fragments together to get a continuous strand.
- Because the 5’ ends of the lagging strand cannot be replicated by DNA polymerase, DNA gets shorter with replication. A specialized enzyme called telomerase will add DNA to the end of a molecule.
(Chp 3)
Describe the importance of cyclins and tumor suppressor genes. Explain how these are linked with cancer.
Cyclins:
- promote various stages of cell cycle
- signaling proteins.
- During the G1 phase an increase in cyclin D proteins activate cyclin dependent kinases
- Overactivity of a gene that codes for cyclin D can lead to cancer.
tumor suppressor genes:
- suppresses tumor and cancer development
- protein p53 blocks protein p21 then blocks cylins which slows down cell division.
(Chp 3)
Explain the cell cycle and how mitosis fits into the cell cycle. Describe the stages of mitosis.
Cell Cycle: Interphase (non-dividing cell phases)
- G1: period of cell growth; produces mRNA for protein production and organelles
- S: If the cell is going to divide, DNA must be replicated during this phase
- G2: period of protein synthesis and final preparation for cell division
Mitosis (M Phase): results in the production of two identical diploid daughter cells as long as cytokinesis occurs.
- Prophase: Chromosomes become visible distinct structures, centrioles duplicate and move to opposite poles, nuclear envelope breaks down, and mitotic spindle forms
- Metaphase: Chromosomes line up single file along equator.
- Anaphase: Centromeres split apart.
- Telophase: Division of the cytoplasm occurs as cytokinesis begins, producing 2 daughter cells.
(Chp 5)
Explain the clathrin coated mechanism of endocytosis.
- ligand bind to receptor
- receptor ligand complex move to clathrin coated area of membrane
- membrane pinches in, where endocytosis takes place
- vesicle pinches away from membrane and lose clathrin proteins (clathrin moves back to membrane)
- the receptor and ligand start to separate from each other
- the endosome with the ligand moves to lysosome or Golgi.
- a transport vesicle with the receptors heads back to membrane
- the transport vesicle merges with the membrane, thus recycling the receptors.
- exocytosis reincorporates, incorporating receptors into membrane
(Chp 5)
Describe the steps in generating a membrane potential. Include all ions that are flowing,
which directions they are moving, and whether the inside is negative or positive.
- Within a cell: inherently have negative charge
- These fixed anions: attract positive charges in the outside of membrane.
- The cell membrane is permeable to both Na and K ions:
- both ions move according to their chemical driving force (K has a high [ ] inside, Na has a high [ ]outside)
- K leaks out of the cell and Na leaks into the cell: but there’s a greater movement of ions out than in because the cell is more permeable to K+ - As the inside becomes more negative:
- K movement: begin to slow down because positively ion, attracted to outside.
- Na movement: speed up because more attracted to inside because inside more negative.
- eventually flows become: steady, equal and opposite between K+ & Na+ (resting membrane potential) - Because the membrane is much more permeable to K: Resting membrane value is closer to equilibrium of K+
- If left unchecked, ion flow through the leak channels would alter the ion concentrations within the cell; however:doesn’t happen because run Na/K pumps.
- Na/K ATPase: pumps 3 K out, 2 Na in, maintains concentration gradient
(chp 5)
Describe the processes of diffusion, osmosis, facilitated diffusion, primary active transport,
secondary active transport, and vesicular transport. Make sure you include which processes
require energy.
Diffusion: Movement of molecules/ions/particles from higher concentration to lower concentrations that doesn’t require energy/ATP. This is a passive mechanism where molecules or ions use the inherent kinetic energy of the molecules or ions to move from one place to another.
Osmosis: diffusion of water across a membrane when you have solute concentration
differences. “Solute suck” Movement of H2O from a high [H2O] to lower [H2O] until equilibrium is reached.
Active Transport: involves moving molecules or ions from a low [] to a high [] and involves the input of energy.
primary active transport: use energy/ATP directly
secondary active transport: use energy/ATP indirectly
facilitated diffusion: Passive transport mechanism where molecules move from high to low concentration.
Vesicular Transport: macromolecules that are too large to pass through cell membranes move in and out using vesicles. Require energy.
(Chp 8)
Beginning with an AP reaching the axon terminal, describe the events that take place at the axon terminal to release NT (synaptic transmission).
- NT release is rapid because many vesicles form fusion-complexes at a “docking site”
along the presynaptic membrane. - The AP travels to axon terminal
- Ca2+ VG channels open.
- calmodulin and synaptotagmins: regulatory protein activated by Ca2+
- protein kinase: activated by calmodulin/Ca2+, necessary for release of neurotransmitter, provide energy
- phosphorylate synapsins
- NTs get excytosed
- NT (ligand) binds to specific receptor
- Chemically (ligand) regulated gated ion channels open in response to neurotransmitter
- EPSP: Na enters
- IPSP: Cl enters or K exits - Neurotransmitter is inactivated
