NS1: BBCF Flashcards
Types of nerves
sensory: about sensation; can be either exteroreceptors (respond to stimuli from the outside world) or interoceptors (respond to stimuli generated within the body)
motor: carry information about motions that need to be performed
Both kinds of nerves either connect to the spinal cord (thus called “spinal nerves”) or directly enter the skull (thus called “cranial nerves”)
Types of sensory nerves
PHOTON B mnemonic
Photoreceptors respond to the visible spectrum of electromagnetic waves → vision
Hair cells respond to movement of fluid in the inner ear → hearing
Olfactory receptors respond to volatile compounds in the air → smell
Taste receptors respond to dissolved compounds in substances → taste
Osmoreceptors respond to osmolarity of the blood and maintain water homeostasis
Nociceptors respond to painful stimuli → touch
Baroreceptors respond to changes in pressure
Neural pathway
sensory nerve → afferent neuron → cerebral cortex → spinal cord → efferent neurons → interneurons → motor neurons → muscle tissue
Neural pathways in the peripheral nervous system (PNS) convey information to the central nervous system (CNS) and relay instructions.
Those that take information to the CNS are known as afferent nerves, and those that relay instructions from the CNS are known as efferent nerves.
Important neurotransmitters (4) "anyone's goddess" AN-E GDES mnemonic
Acetylcholine activates muscle contraction at the neuromuscular junction. It is used in all autonomic outputs from the brain to autonomic ganglia, and in the parasympathetic nervous system for post-ganglionic connections.
Norepinephrine is used in post-ganglionic connections in the sympathetic division of the autonomic nervous system. It also increases arousal and alertness and focuses attention.
Epinephrine stimulates the fight-or-flight response
Glutamate is an excitatory neurotransmitter and is the most common, as 90% of brain cells are responsive to glutamate.
- In contrast, GABA is the main inhibitory neurotransmitter of the CNS; alcohol acts as a GABA agonist. Glycine is another inhibitory neurotransmitter found in the spinal cord and brainstem that can work in conjunction with GABA.
Dopamine is used in reward and motor pathways; affected by Parkinson’s
Endorphins suppress pain and can produce euphoria.
Serotonin regulates mood, appetite, and sleep in the brain, with low levels associated with depressive mood disorders; also regulates intestinal movement in the gastrointestinal tract, in addition to its effects in the brain.
Two ions involved with muscle contraction
Muscle activation does require release of Ca2+ from the sarcoplasmic reticulum to cause a mechanical response in the muscle. Depolarization (shown below in the context of the entire action potential) is characterized by a rapid influx of Na+ into the neuron.
Thus, both Ca2+ release and Na+ influx are involved.
why are peptide bonds so stable
A peptide is an amide linkage between the amine group of one amino acid and the carboxylic acid group of another.
Amides are stable because they exhibit resonance stabilization between the lone pair on the nitrogen and the double-bond in the carbonyl group.
differences btwn eukaryotic and prokaryotic DNA replication / transcription
Pro: one point of replication + replication occurs in two opposing directions at once + takes place in cell cytoplasm
Euk: multiple points of origin + unidirectional replication + takes place inside cell nucleus
Pros have less polymerase types than Euk.
Eukaryotic pre-mRNAs must have their ends modified, by addition of a 5’ cap (at the beginning) and 3’ poly-A tail (at the end).
- 5’ cap assists in ribosome binding during translation
- poly A tail protects from enzymatic degradation in the cytoplasm
Many eukaryotic pre-mRNAs undergo splicing. In this process, parts of the pre-mRNA (called introns) are chopped out, and the remaining pieces (called exons) are stuck back together.
steps of transcription
Yields an mRNA copy of a gene that can then be transported to the cytosol for translation into a protein
1) Initiation: RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene. Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription.
- in euk: binding to a promoter requires the assistance of transcription factors, the most important being the TATA box
2) Elongation: One strand of DNA, the template strand, acts as a template (aka anti-sense) strand for RNA polymerase. As it “reads” this template one base at a time, the polymerase builds an RNA molecule out of complementary nucleotides, making a chain that grows from 5’ to 3’; this resultant chain is referred to as the antiparallel complement strand (aka sense strand).
- in RNA, thymine is replaced by uracil
- Termination: Sequences called terminators signal that the RNA transcript is complete. Once they are transcribed, they cause the transcript to be released from the RNA polymerase.
what is (RNA) splicing and why is it important
only in euk
In splicing, noncoding sequences (introns) are removed and coding sequences (exons) are ligated together.
- carried out by spliceosomes (a combination of small nuclear RNAs (snRNAs) and protein complexes.)
Splicing explains why there are over 200,000 proteins in the human body, but only approximately 20,000 genes → greater diversity!
what forces keep DNA double helixes together?
hydrogen bonding btwn the two complementary strands of DNA
define the following
- DNA
- RNA
- cation
- anion
dna = deoxyribonucleic acid rna = ribonucleic acid
cation = ion w positive net charge anion = ion w negative net charge
what is the immune system made of
The immune system is comprised of the innate IS (quick but general response to threats) and the adaptive IS (slower but specific response to threats; “remembered” by the body via memory cells).
what is the innate immune system comprised of
Non cellular: anatomical barriers and signaling molecules (ie cytokiens and complement proteins)
Cellular: range of leukocytes (white blood cells, incl neutrophils, lymphocytes, monocytes and their differentiation into macrophages or dendritic cells, eosinophils, basophils, and mast cells)
what is the adaptive immune system comprised of
incl B and T cells (both of which are lymphocytes produced in the bone marrow but mature in the lymphatic system)
B cells: aka humoral immunity; recognize antigens and secrete large amounts of antibodies (immunoglobulins; Ig) in responses → Ig-A/D/E/G/M
T cells: mature in the thymus; recognize non-self or damaged self cells via interactions with major histocompatibility complex (MHC) Class I and II
what are erythrocytes
red blood cells
Responsible for carrying oxygen to the different tissues of the body + aid in carrying CO2 to the lungs for exhalation → function arises due to them holding hemoglobin (polymer of 4 proteins and iron that binds oxygen)
Created in the bone marrow in response to erythropoietin (EPO), a hormone that is released from the kidney whenever erythrocyte levels are low → during their development, they will lose their membrane-bound organelles, including their mitochondria and nucleus
- As such, they only engage in anaerobic metabolism and have a limited lifespan of only about 100 days
- Their lack of internal organelles contributes to their characteristic biconcave shape, which helps them travel more efficiently through capillaries and maximizes their surface area, which assists in gas exchange
Erythrocytes are degraded by the spleen, which is located in the left upper quadrant of the abdomen.
at blood pH (7.4), which AA’s would be most likely:
- phosphorylated
- negatively charged
The residues most prone to phosphorylation are serine (S), tyrosine (Y), and threonine (T).
Both aspartate / aspartic acid (D) and glutamate / glutamic acid (E) are acidic residues and thus likely to be negatively charged.
what makes up an AA
give examples of the interactions AA’s can have based on their R groups
The central α-carbon has four substituents: –NH2 (amino), – COOH (carboxylic acid), –H, and –R.
The –R group, or side chain, is the only part that differs between amino acids and determines their individual properties.
Polar amino acids tend to be located on the exterior of globular proteins, facing the watery environment. In contrast, nonpolar amino acids are generally buried in the interior of these proteins, protected from the aqueous cytosol or extracellular fluid.
Disulfide bonds can form between cysteine side chains, which are important for the protein’s tertiary structure. Disulfide bonds arise when one cysteine’s sulfur atom connects to another, losing the attached hydrogen atoms in the process
important bio/biochem enzymes and their functions
“KAPPA MD” mnemonic for KPPMD
Kinases transfer phosphate groups from a high-energy source (usually ATP) to their substrates, while phosphorylases transfer phosphate from an inorganic phosphate source.
Phosphorylase enzymes also add phosphate groups to their substrates, so the “general effect” of a phosphorylase on its substrate is similar to that of a kinase.
Phosphatase enzymes are involved with the removal of phosphate from a substrate.
Mutases is a specific type of isomerase. These enzymes neither add nor remove phosphate groups.
Dehydrogenase enzymes are oxidoreductases, or enzymes that catalyze oxidation- reduction reactions.
what is the function of aldosterone
steroidal hormone released from the adrenal cortex in response to low blood pressure
Function: increase sodium reabsorption in the distal tubule and collecting duct via upregulation of sodium-potassium pumps along the lining of the nephron, pumping three sodium ions OUT of the nephron lining (and toward the blood) for every two potassium ions it pumps IN (toward the nephron and away from the blood)
- ultimately increases the gradient that favors water reabsorption, thus increasing blood pressure
how do cells “get old” ?
As cells undergo mitosis, the telomeres, the portion of the DNA on the ends of the chromosomes, gets progressively shorter.
- Eventually the DNA loses its telomeres entirely and is unable to reproduce; this loss in division indicates that the cell is no longer able to function properly and will be subjected to apoptosis.
what is apoptosis
Apoptosis is defined as programmed cell death, which generally plays a fundamental role in proper development and health maintenance.
In embryonic development, apoptosis plays a major role in defining the boundaries of organs and tissues. → eg. destruction of skin btwn fingers, thus eliminating the webbed structures that are initially there
Common causes of apoptosis:
- failure for a cell to pass the appropriate mitotic checkpoints
- cell-internal signaling after mitochondrial dysfunction
- lysosomes bursting (autolysis), and as a response to external signaling pathways that may be dysregulated in various disease processes
- uncontrollable division (cancer)
- no division at all (senescence)
what is sterilization vs disinfection
Sterilization refers to completely removing all living microorganisms and viruses from the surface of an inanimate object → eg. autoclaving, UV radiation, filtration
Vs. Disinfection refers to the removal of most microorganisms, especially pathogenic microorganisms → eg. bleach, 70% ethanol
why is the mitochondria so fucking important
Mitochondria is the motherfucking powerhouse of the cell binch
why? bc it’s the place where CAC, beta-oxidation of FA, and oxidative phosphorylation of the ETC occur (specifically in the mitochondrial matrix)
The structure of mitochondria can be subdivided into the outer membrane, the intermembrane space, the inner membrane, and the mitochondrial matrix (innermost part of each mitochondrion)
- protein complexes are embedded in the inner membrane as part of oxidative phosphorylation, such that the ETC causes a buildup of protons in the intermembrane space, and the resulting proton gradient is used to power the activity of ATP synthase
Mitochondria are also unique in that they are self-replicating organelles. They contain their own DNA (mitochondrial DNA, or mtDNA), which is circular in structure and inherited maternally, and undergo binary fission.
what is fertilization (just the event)
takes place in the fallopian tubes (aka oviduct) when a sperm ell encounters a secondary oocyte
1) The sperm cell passes through the corona radiata, a layer of follicular cells surrounding the oocyte, and the zona pellucida, a layer of glycoproteins between the corona radiata and the oocyte.
2) This triggers the acrosome reaction, in which digestive enzymes are released that allow the nucleus of the sperm cell to enter the egg.
3) The secondary oocyte completes meiosis II (bc it was paused in metaphase II), creating a second polar body and a mature ovum.
4) Then, the haploid nuclei of the sperm cell and the ovum merge, creating a diploid one-cell zygote.
what is crossover in chromosomes
literally arms of the chromosome crossing over at a chiasmata; involves only one arm per chromosome though (not both!)
- promotes genetic diversity
- results in recombinant DNA that is another source of variation in sexual reproduction, in addition to the variability inherent to the process
single crossover: arms cross over once; results in ends of chromosome arms being swapped
double crossover: arms cross over twice; results in the middle parts of chromosomes arms being swapped
what is mitosis
asexual cell division; yields identical daughter cells (diploid, 2n)
1) Prophase prepares the cell for mitosis: the DNA condenses such that distinct chromosomes become visible, as sister chromatids (or copies of a given chromosome) join at a region known as the centromere. The kinetochore assembles on the centromere, and is the site where microtubule fibers that extend from the centrosome and form the mitotic spindle attach to pull the sister chromatids apart in later stages of mitosis. Other microtubules known as asters extend from the centrosome to anchor it to the cell membrane. Additionally, the nuclear envelope and the nucleolus disappear, and the mitotic spindle forms.
2) In metaphase, the chromosomes line up at the middle of the cell along an imaginary line that is known as the metaphase plate.
3) In anaphase, the sister chromatids are separated and pulled to opposite sides of the cell by shortening of the microtubules attached to the kinetochores.
4) Telophase can be thought of as the opposite of prophase, as a new nuclear envelope appears around each set of chromosomes and a nucleolus reappears within each of those nuclei. The process of mitosis is completed by cytokinesis.
what is meiosis
sexual reproduction; takes place in sex cells; two stages that yield four daughter cells, each of which only has one copy of each chromosome (haploid, n)
In prophase I of meiosis, homologous chromosomes (i.e., the maternal and paternal copies of a given chromosome) pair up with each other in a process known as synapsis, forming tetrads. Crossover happen.
In metaphase I, homologous pairs, which take the form of tetrads, line up at the metaphase plate in random orientation.
In anaphase I, the homologous pairs are separated, and one member of each pair is pulled to each side of the cell.
In telophase I, each pole now has a haploid number of chromosomes. Cytokinesis occurs, forming two haploid daughter cells
In meiosis II, we observe same steps as mitosis (ie prophase, metaphase, anaphase, and telophase).
- mitotic division of two haploid daughter cells generates four total haploid daughter cells
what is troponin
Troponin is a complex of three proteins (troponin I, troponin C, and troponin T) required for muscle contraction in skeletal muscle and cardiac muscle, but not smooth muscle.
what is glucose
body’s main source of fuel under most circumstances
broken down by glycolysis
- breakdown promoted by insulin
- breakdown inhibited by glucagon
what is insulin
peptide hormone released by the beta cells of the pancreas in response to high blood glucose levels
function is to reduce blood glucose levels by promoting the transport of glucose into cells via insulin receptors, which activate membrane-bound glucose transporters.
promotes glycolysis
promotes glucose storage
promotes formation of triglycerides
promotes protein synthesis
inhibits gluconeogenesis
what is glucagon
peptide hormone released by the alpha cells of the pancreas, and its mechanism and function are essentially the opposite of insulin
released in response to low
glucose levels
inhibits gluconeogenesis and gluconeolysis
inhibits glycolysis
inhibits glucose storage
inhibits formation of triglycerides
inhibits protein synthesis
what are other hormones (besides glucagon and insulin) that can affect blood glucose levels?
Cortisol (the main example of a class of hormones known as glucocorticoids) is released by the adrenal cortex. It is associated with long-term responses to stress and increases blood glucose levels.
Epinephrine, which is released by the adrenal medulla and plays a major role in the fight-or-flight response to immediate stress, also raises blood glucose levels
Growth hormone can increase blood glucose levels due to its antagonistic effects on insulin (thus promotes its production)
what are fatty acids
two essential features:
- a long hydrocarbon chain (typically 4-30 carbon atoms long, usually linear and with an even number of carbons) → hydrophilic tail
- a terminal carboxylic acid group → hydrophobic head
saturated (no C=C pi bonds) vs. unsaturated (1 or more C=C pi bonds)
The lipid synthesis mechanism of the body can theoretically supply the body with near-sufficient fatty acid structures. However, the fatty acids linoleic acid and α-linolenic acid cannot be synthesized from precursors in the body, and are thus considered the essential fatty acids.
functions of FA
Constituents of complex membrane lipids → eg. mitochondria’s phospholipid bilayers
Stored fat in the form of triglycerides (esters of 3 fatty acids joined together with glycerol, a 3-C triol)
precursors for the synthesis of bioactive lipids → eg. diacylglycerol
– At physiological pH (pH 7.4), the carboxyl group is ionized, rendering fatty acids negatively charged. (Recall that this prevents most FAs from entering mitochondria’s membrane)
how does structure affect the melting point of FAs
The melting point of fatty acids increases as the length of the carbon tail increases.
In addition, unsaturated fatty acids will have lower melting points than saturated fatty acids with the same number of carbon atoms. As a general rule, unsaturated fatty acids are liquids at room temperature while more saturated fats are solids.
Fatty acids also demonstrate cis/trans isomerism.
- In cis fatty acids, the acyl groups are on the same side of the double bond, while in a trans fatty acid, the acyl groups are on opposite sides.
- Cis fats generally have higher boiling points, while trans fats have higher melting points.
nomenclature of FA
The site of unsaturation in a fatty acid is indicated by the symbol ∆ and the number of the first carbon of the double bond relative to the carboxylic acid group (–COOH), which is the highest priority carbon (i.e. #1). For example, oleic acid is a 16-carbon fatty acid with one degree of unsaturation between C9 and C10, and is labeled as 16:1Δ9.
Another form of nomenclature uses the number of carbon atoms, followed by the number of sites of unsaturation (e.g. palmitic acid is a 16-carbon fatty acid with no unsaturation and is labeled 16:0).
how does polarity affect solubility
like dissolves like
nonpolar substances will be more soluble in aprotic (hydrophobic) solvents
polar substances will be more soluble in protic (hydrophilic) solvents
– solvent examples are blood and cytosol, which are both largely made of water
what is pyruvate
how is it generated into lactate
three-carbon alpha-keto acid that is primarily involved in energy production, namely through the citric acid cycle; formed by glycolysis
The NADH produced by glycolysis is an electron carrier that can ultimately yield energy through oxidative phosphorylation. However, the NADH needs to be converted back to NAD+ for glycolysis to continue. This can happen in the electron transport chain or through fermentation. In lactic acid fermentation, which often occurs in human muscles, pyruvate is converted to lactate by lactate dehydrogenase in a reaction coupled to the conversion of NADH to NAD+.
what are some feedback loops associated with glycolysis
upregulated by low levels of ATP or high levels of AMP/ADP/inorganic phosphate
downregulated by high levels of ATP/NADH/citrate
also subjected to negative regulation, where certain products inhibit previous steps
– G6P inhibits hexokinase
how is bacteria classified by their oxygen consumption
Anaerobes: Bacteria that do not require oxygen for metabolism
- Obligate anaerobes: oxygen is toxic
- Aerotolerant anaerobes: similar to obligate anaerobes in that they cannot engage in aerobic metabolism, but oxygen is not toxic for them
Facultative anaerobes: engage in either aerobic or anaerobic metabolism, depending on the circumstances.
Obligate aerobes: require oxygen for metabolism
what are the differences btwn prokarotic cells and eukaryotic cells
both are cells, contain ribosomes, and have a membrane
pro: no nucleus or organelles; circular DNA
euk: has nucleus and organelles; linear DNA
what are buffers
In the body and in the lab, buffers are used to resist small changes in pH upon the addition of acid or base; they generally contain either a weak acid and its conjugate base or a weak base and its conjugate acid.
Thus, when a small to moderate amount of strong acid or base is added to a buffered solution, the buffer will become entirely protonated or deprotonate some of the weak acid / base; this however, does not affect the overall pH most of the time.
analogous structures
vs. homologous structures
Analogous structures: evolved independently to carry out of the same function
Homologous structures: similar evolutionary history (ie arising from the same source), even if they now have different functions
what is natural selection
mechanism through which evolution takes place; refers to the tendency of certain phenotypes to be favored in terms of reproduction → linked to fitness, which refers to the chance of reproduction within specific environmental constraints
Stabilizing selection: both extremes are selected against
Directional selection: only one extreme phenotype is selected against and the other extreme is favored
Disruptive selection: when the median phenotype is selected against
Hardy-Weinberg equilibrium
often used to model stable gene pools that satisfy the following assumptions:
1) organisms must be diploid and reproduce sexually
2) mating is random
3) the population size is very large
4) alleles are randomly distributed by sex
5) no mutations occur
6) there is no migration into or out of the population
what is genetic drift
vs. bottleneck
Genetic drift: role of chance in the absence of strong selective pressures, as well as in determining the reproductive fitness of various alleles → when no strong pressure exists for a certain allele, it may randomly happen to be reproduced more or less often
Bottleneck: occurs when some external event dramatically reduces the size of a population in a way that is essentially random with regard to most, if not all, alleles → this dramatically reduces diversity in the gene pool
