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physiology exam 1
Terms in this set (64)
open loop system
the output is not measured and there is no mechanism to adjust the input (ex. system that controls eyelid; input is the approaching object and output is the closing of the lid) the system responds to the input
closed loop system
input and output (just as in open loop) and feedback; the output/response of a loop influences the input
the body's attempt to maintain a constant (within a range) internal environment despite changes to its environment
-sense changes in an internal parameter
-a control mechanism activated
-negative feedback that make the necessary adjustment to the internal parameter
overall purpose of homeostasis
many pathological conditions are due to a disturbance of homeostasis, for ex. it's not being maintained either as the condition itself or as a result of a condition
a decrease in function in response to a stimulus- most biological systems are negative feedback systems (ex. control of hormone secretion by the HP axis; hormone 1 controls secretion of hormone 2 and hormone 2 controls secretion of hormone 3; the secretion of follicle-stimulating hormone decreases as the amount of circulating estrogen increases
output of the system stimulates the system in such a way as to further increase the output. without counter-balancing or "shut down" reaction or process, a positive feedback mechanism has the potential to produce a runaway process
the feedback is used to increase the size of the input
most often associated with pathological conditions
role of the sensor
detects deviation (fall or rise) from set point
role of the integrating center
the fall or rise is sent to integrating center where it determines response needed to correct
role of the effector
what determines the atomic number
number of protons = atomic number; nucleus contains protons (+1 charge) and neutrons (no charge)
which electrons participate in bond formation
bonding/valence electrons are in the outermost shell and can participate in chemical reactions and form bonds; electrons in orbitals or shells around the nucleus (- charge)
how are electrons shared between molecules in covalent, ionic, and hydrogen bonds?
covalent bonds = electrons shared (strongest)
ionic bonds = electrons taken/transferred
hydrogen bonds = attraction (NOT BONDS) between hydrogen (partial positive) and partial negative (weakest)
which bond is broken by enzymes?
which bonds under physiological conditions are broken under temperature and pH?
what is a polar bond?
a covalent bond in which the electrons are shared unequally. molecules like phosphate, oxygen, and nitrogen tend to form polar bonds with other molecules like hydrogen
in a single water molecule (H2O), what kind of bonds form between the oxygen and the two hydrogens?
covalent bonds form between O and H within a single water molecule. hydrogen bonds between O and H of different water molecules occur.
what is a hydrophobic bond?
hydrophobic bond is a nonpolar bond that causes the molecule to avoid interacting with water molecules
match hydrophilic and hydrophobic with polar and nonpolar
hydrophilic = polar
hydrophobic = nonpolar
if a hormone forms a bond with a protein, what happens to the shape of the protein?
it goes through a conformational change
match acids and bases as a proton donor or proton acceptor
acids are proton donors (release H+) and bases are proton acceptors (absorb H+)
definition of pH
a numerical measure of the acidity or alkalinity of a solution, usually measured on a scale of 0 to 14. neutral solutions (such as pure water) have a pH of 7, acidic solutions have a pH lower than 7, and alkaline solutions have a pH higher than 7
how much H+ is present in acids vs bases?
Acidic solutions have higher concentrations of hydrogen ions (H+) and basic solutions have lower concentrations of hydrogen ions (H+).
how does a buffer work?
Buffers help maintain homeostasis (constant pH) by resisting changes in the pH of body fluids. Buffers are either weak acids or bases.
If you add a small amount of H+ to a buffer what happens to the pH? Why don't strong acids act as a buffer?
Buffers release H+ ions when pH rises and eliminate H+ ions when pH drops. Strong acids cannot act as buffers because they ionize completely.
examples of monosaccharides
simple sugars such as glucose, fructose, and galactose
examples of disaccharides
2 monosaccharides joined covalently such as sucrose or table sugar (glucose + fructose)
what is the structure of phospholipids?
they form the plasma membrane bilayer, micelles, and cholesterol.
polar head (phosphate group) and nonpolar tails (lipids)
What bonds hold disaccharides together?
covalent bonds (glycosidic linkage)
are polysaccharides polymers?
yes, they're complex carbohydrate polymers
Is a protein a polymer?
yes, proteins are polymers made up of amino acids
is DNA a polymer?
yes, DNA is a polymer made up of nucleotides
what are the basic repeat units found in DNA?
The basic repeating unit is a nucleotide which is composed of 3 groups: a 5-carbon sugar (ribose or deoxyribose), a nitrogen-rich base (cytosine, guanine, adenine, thymine in DNA or uracil instead of thymine in RNA), and phosphate.
b. What is base pairing and what is the major bond type that allows base pairing?
Base pairing is due to hydrogen bonding between specific types of bases.
A-T & G-C
How does RNA differ from DNA in structure?
RNA uses ribose and uracil whereas DNA has deoxyribose and thymine
what are the three types of RNA?
mRNA, tRNA, rRNA
composition: phospholipids, lipid bilayer, cholesterol, glycolipids, proteins
function: physical barrier to separate intracellular and extracellular components / gateway for substances moving in and out of cell / communication-receptors and other proteins that recognize signaling molecules and change cell activity / enclose cell contents, control exchange of substances with environment, cell communication
composition: cytosol, inclusion bodies, organelles
function: support and suspend organelles and cellular molecules / cellular processes occur: protein synthesis, first stage of cellular respiration (known as glycolysis), mitosis, meiosis, and signaling
composition: contains digestive enzymes (activated only at acidic pH)
function: can breakdown many kinds of biomolecules (such as proteins, nucleic acids, carbohydrates, lipids) / capable of fusing with large structures such as other organelles and digesting these structures (many cellular components, like the mitochondria, are constantly being removed from the cell by lysosomes) / can recycle the components such as amino acids from proteins, etc for reuse
composition: flattened, stacked discs called cisternae
function: responsible for transporting, modifying, and delivering proteins and lipids to targeted destinations- similar to a post office / proteins synthesized in the ER are packaged into vesicles which then go to the golgi apparatus. proteins can be modified for example glycosolated- proteins are then delivered to their target destinations, lysosomes and the cell membrane. other proteins are targeted for secretion via endocytosis. the proteins can be modified for example glycosylated / the site of synthesis of glycolipids and some phospholipids
composition: contains enzymes involved in generating ATP
function: energy producing organelle (ATP generation in the mitochondrial matrix and final steps for the generation of ATP occur in the mitochondria)- initial steps of ATP generation (carbohydrate/glucose metabolism) occur outside the mitochondria
composition: large subunit and small subunit which both contain ribosomal proteins and ribosomal RNA
function: protein synthesis / found in the cytoplasm or attached to the endoplasmic reticulum
composition: contains oxidative enzymes
function: contain enzymes that reduce reactive oxygen species such as hydrogen peroxide into safer molecules like water and oxygen (the enzyme catalyzes the conversion of hydrogen peroxide to water- if not converted hydrogen peroxide can result in formation of reactive oxygen that are toxic) / breakdown of very long fatty acid chains to medium fatty acid chains, which subsequently shuttled to mitochondria where they undergo beta oxidation / (in the liver) involved in detoxification
rough (granular) endoplasmic reticulum
composition: network of tubules and flattened sacs, contains ribosomes for protein synthesis
function: produces proteins targeted to lysosomes, secretory vesicles, golgi apparatus, cell membrane / proteins made in ribosomes of rough ER are initiated on cytosolic ribosomes
smooth endoplasmic reticulum
composition: network of tubules and flattened sacs
function: synthesis of lipids, steroid hormones, and the storage and release of calcium ions
function: carry and actively transport soluble proteins, peptides or neurotransmitters / store or digest certain secreted molecules / hormones are stored in secretory vesicles for release into the bloodstream
composition: DNA, RNA, protein
function: DNA packaging / transcription regulation
composition (varies depending on cell type): protein subunits, filaments, tubules
function: primary function- gives the cell its shape and mechanical resistance to deformation (can also actively contract / involved in the uptake of extracellular material (endocytosis) / involved in segregation of chromosomes during cellular division, and the division of a mother cell into two daughter cells
villi and microvilli
villi = made up of epithelial cells which contain transport proteins
microvilli = membrane protrusions
function: increase surface area and allow for absorption (for ex. absorb amino acids)
composition: proteins (like collagen), carbs
function: "glue" that holds cells together
what is a promoter and why do you need one?
a promoter is a sequence of DNA needed to turn a gene on or off. the process of transcription is initiated at the promoter, and the promoter has a binding site for the enzyme used to make a messenger RNA molecule.
what is transcription?
Transcription is the first step in gene expression. It involves copying a gene's DNA sequence to make an RNA molecule. It's performed by enzymes called RNA polymerases, which link nucleotides to form an RNA strand (using a DNA strand as a template). Transcription produces pre-mRNA. pre-mRNA is altered in the nucleus to form mRNA, which contains the code for synthesis of a protein.
what is a nucleosome?
the nucleosome consists of DNA wound around a protein core composed of histone proteins
heterochromatin is a highly condensed region where genes are permanently inactivated
euchromatin is the part of chromosomes active in transcription
what is chromatin?
Chromatin is the ordering of nucleosomes into a more compact structure. The function of chromatin is to efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence
how does acetylation and methylation affect chromatin's structure?
Acetylation makes genes accessible / Deacetylation prevents access to genes
Methylation prevents access to genes / Demethylation allows access to genes
what is pre-mRNA?
a form of mRNA that contains introns and exons
- located on the mRNA molecule
- complementary to the nucleotide triplet in DNA
- sequentially present on the mRNA
- determines the position of the amino acid
- located in the tRNA molecule
- complementary to the codon
- individually present on tRNAs
- brings the specified amino acid by the codon
what role do mRNA, tRNA, and rRNA play in protein translation
mRNA molecules carry the coding sequences for protein synthesis and are called transcripts
tRNA molecules carry amino acids to the ribosomes during protein synthesis
rRNA molecules form the core of a cell's ribosomes (the structures in which protein synthesis takes place)
where do you find ribosomes?
They are found in the cytoplasm and on the granular (rough) endoplasmic reticulum (RER).
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