BISC 101 up to Midterm #2 Flashcards
What are the three domains of life?
Bacteria, Archaea, Eukarya
What are the four main types of macromolecules in the cell?
Lipids, Carbohydrates, Nucleic Acids, and Proteins
Is a C-H bond polar covalent or non-polar covalent?
Non-polar covalent
Is a O-H bond polar covalent or non-polar covalent?
Polar covalent
When salt (sodium chloride) dissolves in water, two ions are formed. What are the ions, and what are their charges?
Na+ (sodium), Cl- (Chloride)
What are the names and functions of eukaryotic organelles?
Nucleus - control center, stores genetic information
Ribosomes - site of protein synthesis
Do plant cells have mitochondria?
Yes, plants require oxygen for cellular processes (i.e. when they need energy from cellular respiration, therefore they have mitochondria)
What is the main function of the plasma membrane?
To provide structure and support for the cell; also to selectively allow certain molecules to pass through into the cell
What are the components of the plasma membrane?
The plasma membrane is made up of a phospholipid bilayer, as well as proteins, carbohydrates, and many other things
Amphipathic
Compounds that contain both hydrophilic and hydrophobic elements
Hydrophobic
Usually non-polar, not attracted to water
Hydrophilic
Usually polar, attracted to water
Polar
A compound carrying a partial positive charge on one end and a partial negative charge on the other; usually hydrophilic
Non-polar
No charge on the compound; usually hydrophobic
How does the structure of the phospholipid bilayer make it ideal for its function (forming a selectively permeable bilayer in water?)
In water, the hydrophobic tails will face and interact with each other, while the hydrophilic heads will face outwards (towards the solution); more stable - hydrophobic tails don’t interfere with interactions; prevents large, charged/polar molecules from passing through easily (cannot get through hydrophobic tails)
Why does CO2 cross the membrane easily, but Na+ does not?
CO2 is uncharged, while Na+ is
Are cell membranes and phospholipid bilayers the same thing?
No, cell membranes contain carbohydrates, proteins and more, while phospholipid bilayers are just phospholipids
What is meant by membrane “fluidity”?
Membrane is a mosaic of phospholipids and proteins; overall structure is dynamic and fluid
What is the difference between active and passive transport?
Active transport requires energy (usually (but not always) ATP), while passive does not (diffusion is a form of passive)
What is the difference between diffusion and facilitated diffusion?
Facilitated diffusion requires protein carriers, while passive does not
Between DNA and RNA nucleotides, which carbon has a different group attached?
2’ Carbon; OH in RNA, H in DNA
Describe the difference between the 5’ end and the 3’ end of the nucleotide
5’ end = unlinked phosphate
3’ end = unlinked 3’ carbon in sugar
How many rings do pyrimidines have? Which bases are pyrimidines?
One ring; Cytosine (C), Uracil (U), Thymine (T)
How many rings do purines have? Which bases are purines?
Two rings; Adenine (A), Guanine (G)
Antiparallel
Strands run in opposite directions (i.e. on strand runs 5’ –> 3’ while the other runs 3’ –> 5’)
Why can’t a purine-purine or pyrimidine-pyrimidine pair exist?
Too much space with pyrimidine-pyrimidine; too little space with purine-purine
Which base pair is more difficult to pull apart? (A-T or C-G)
C-G because it has 3 H-bonds, while A-T only has 2
Why can’t adenine and cytosine (A-C) or guanine and thymine/uracil (G-T) pair?
Different number of H-bonds, still results in alteration of DNA structure
What are the main structural differences between DNA and RNA?
RNA contains U instead of T; RNA is single stranded; RNA can have up to quaternary structure (DNA has only secondary)
What are the different levels of structure in DNA?
Primary –> Sequence of nucleotides
Secondary –> Two antiparallel strands twist into double helix; stabalized by H-bonding and hydrophobic interactions
What are the different levels of structure in RNA?
Primary –> Sequence of nucleotides
Secondary –> Hairpins (when single strand folds back on itself to form double-helix “stem” and single-stranded “loop”
Tertiary –> Folds that form distinctive 3-D shape
Quaternary –> Associations between RNA molecules
Transcription
The process of copying hereditary information in DNA to RNA
Translation
The process of using the information in nucleic acids (i.e. RNA) to synthesize proteins
What is the difference between genotype and phenotype?
Genotype = the sequence of bases in DNA Phenotype = product of the proteins produced by DNA
What does “reading frame” mean?
The division of RNA or DNA into a sequence of three-nucleotide codons
Does the amino acid table describe DNA or RNA bases?
RNA BASES!!!!
What are some clues that can be used to differentiate between DNA and RNA?
Presence of Thymine/Uracil (T=DNA, U=RNA); 2’ Carbon (H=DNA, OH=RNA)
Are the DNA template strand and the mRNA sequences similar or complimentary?
Complimentary
Are the DNA coding strand and the mRNA sequences similar or complimentary?
Similar (replace T in DNA with U in RNA)
Are the DNA template and the DNA coding strand sequences similar or complimentary?
Complimentary
What are the three main stages of transcription? What happens in each?
Initiation –> RNA polymerase and sigma form a holoenzyme, sigma recognizes and binds to the promoter (e.g. TATA box; promoter=upstream from transcription start site)
Elongation –> RNA polymerase begins synthesizing RNA 5’ to 3’ (moves along DNA 3’ to 5’)
Termination –> transcription stops when RNA polymerase reaches a DNA sequence that functions as a transcription-termination signal
What is the difference between “primary mRNA transcripts” and “mature mRNA”?
Mature mRNA has the introns spliced out (only exons)
What are the main difference between bacterial and eukaryotic transcription?
3 RNA polymerases in eukaryotes (1 in bacteria), complex and variable promoter structure in eukaryotes (often TATA box ~30 bases upstream), many basal transcription factors in eukaryotes (sigma only in bacteria), mRNA processing in eukaryotes
What are the three main steps in mRNA processing? What kind of organisms does this occur in?
Eukaryotes; Enzyme-catalyzed addition of 5’ cap, splicing (intron removal) by spliceosome, and Enzyme-catalyzed addition of 3’ poly(A) tail
What is the difference between a codon and an anticodon?
Codon = 3 base pair sequence on mRNA Anticodon = 3 nucleotides that form base pairs with an mRNA codon
What are the components required for translation to take place?
mRNA, tRNA (with amino acids), ribosome
What are the three main stages of translation? What happens in each?
Initiation –> mRNA binds to the small ribosomal subunit with help from initiation factors, initiator aminoacyl tRNA binds to the start codon, then large ribosomal subunit binds to complete complex
Elongation –> tRNA arrives with amino acid, ribosome forms peptide bonds, elongation factors move the mRNA through the ribosome (5’ to 3’) to allow new tRNA to arrive
Termination –> ribosome reaches stop codon, release factor (protein) free polypeptide from ribosome, ribosome falls off
What are some of the functions of proteins in the cell?
Ezymes (catalyze reactions), defence (antibodies), movement (motor and contractile proteins), signalling, structure, transport (e.g. hemoglobin)
What are the four levels of protein structure? What distinguishes them?
Primary –> Sequence of amino acids
Secondary –> α-helix or β-pleated sheet, formed by hydrogen bonding between portions of the peptide-bonded backbone
Tertiary –> most of the overall shape; result of interactions involving R-groups (H-bonds, hydrophobic interactions, Van der Waals interactions (electrical attractions), covalent bonding (disulphide bonds), ionic bonding)
Quaternary –> Interactions between multiple polypeptides
Why are enzymes important to the cell?
Enzymes bring reactants together in specific orientations and stabilize transition states (lower activation energy –> increase reaction rate of chemical processes required for life)
Substrates
Reactant molecules
Transition state
Intermediate product of a reaction (does not last, often unstable)
Enzymes are often turned off or on. Why is this ability valuable to a cell?
A higher rate of reaction isn’t always required (i.e. insulin production)
What are some functions of carbohydrates in the cell?
Structure - (e.g. cellulose, chitin, peptidoglycan) stiff, strong and durable
Display info - (glycoproteins) identify a cell as part of your body
Energy storage - carbs store and provide chemical energy in cells
What molecule is used as the “universal” energy currency in the cell?
ATP (adenosine triphosphate)
Why is ATP a good choice for the energy currency of the cell? Why isn’t glucose a good choice?
Repulsion between negative charges in phosphates provides high potential energy; glucose provides more energy than the cell can use at once, therefore ATP is more flexible and useful
What is the purpose of cellular respiration?
To produce ATP from a starting material with high potential energy (usually glucose)
What are the inputs of cellular respiration? What are the outputs?
C6H12O6 (glucose) + 6(O2) –> 6(CO2) + 6(H2O) + 36 ATP
What are the 4 processes in cellular respiration?
Glycolysis, pyruvate processing, citric acid cycle (Krebs cycle), electron transport chain and chemiosmosis
What is are the inputs of glycolysis? What are the outputs?
Glucose, NAD+, ADP + Pi –> Pyruvate, 2 ATP, 2NADH, H+, H2O
What is are the inputs of pyruvate processing? What are the outputs?
Pyruvates, NAD+ –> Acetyl-CoA, NADH, CO2
What is are the inputs of citric acid cycle? What are the outputs?
Acetyl-CoA, H2O, NAD+, FAD –> ATP, NADH, FADH2, CO2
What is are the inputs of electron transport and chemiosmosis? What are the outputs?
NADH, FADH2, O2 –> ATP (lots), H2O
What is the purpose of photosynthesis?
To produce chemical energy (stored in the bonds of carbohydrates) by converting light energy
What is are the inputs of photosynthesis? What are the outputs?
6(CO2) + (12H2O) + Light energy –> C6H12O6 + 6O2 + 6H2O
What are the two sets of reactions in photosynthesis?
Light-capturing reactions and the Calvin cycle
What are the inputs and outputs in the light-capturing reactions of photosynthesis?
Light energy + H2O –> ATP + NADPH + O2
What are the inputs and outputs in the Calvin cycle?
ATP + NADPH + CO2 –> (ADP, NADP + Pi) + Glyceraldehyde 3-phosphate (G3P)
What are the phases of the cell cycle? What is happening in each phase?
Interphase (G1 + S + G2), mitosis and cytokinesis
G1 –> Cell grows
S –> DNA replactes
G2 –> organelles synthesizes
Mitosis and cytokinesis –> cell division
What macromolecules are involved in the cell cycle?
Nuceleic acids (Chromosomes)
Proteins (spindle fibers)
Lipids (nuclear membranes)
What are the main checkpoints of the cell cycle?
G1 –> Are conditions favourable? –> enter S phase
G2 –> Is all DNA replicated? Is all DNA damage repaired? –> enter Mitosis
M –> Are all chromosomes correctly attached to mitotic spindle? –> pull duplicated chromosomes apart
What are the two kinds of defects that cancerous cells may have?
Proteins required for cell growth active when they shouldn’t be OR tumor suppressor genes unable to shut down cell cycle
What are the stages of mitosis? What happens in each stage?
Prophase –> Chromosomes condense, spindle apparatus forms
Prometaphase –> nuclear membrane dissolves, kinetochore microtubules make contact with chromosomes
Metaphase –> chromosomes line up along cell equator
Anaphase –> Chromatids split (pulled apart by kinetochore microtubules)
Telophase –> Chromosomes pulled to opposite poles; nuclear membranes reform
What is the difference between mitosis and cytokinesis?
During mitosis, only one cell is present, while cytokinesis is the actual division of the one parent cell into two daughter cells
Why is there a difference between replication on the leading versus lagging strand?
Because the lagging strand is moving away from the replication fork, so each time the DNA unzips further, a new fragment has to be started
Why does the lagging strand get shorter every time it replicates, during normal DNA replication in eukaryotes?
Because near the end of the chromosome, there is not enough room for primase to add a new RNA primer
Why don’t bacterial cells have telomerase?
Bacteria have non-linear DNA (circular) therefore there is always somewhere for the machinery to bind, so there’s no need for telomerase
Why does telomerase need a built-in template?
To be able to DNA onto the end of a chromosome to prevent it from getting shorter
What is the difference between “food” and “nutrients”?
Food - what we eat or drink to gain energy, function properly and stay alive
Nutrients - components of food that are metabolized by the body
What is the purpose of eating?
To provide nutrients to produce energy, provide building blocks for growth and repair, and storage
What are the four steps in obtaining nutrients? What takes place during each step?
Ingestion - Taking in nutrients (food)
Digestion - The physical and chemical breakdown of food into smaller, usable parts
Absorption - Absorbing the broken down molecules to be used by cells
Excretion - Removal of any waste food material
What are the four food-getting strategies in animals?
Fluid feeders - Suck up fluid (e.g. hummingbird)
Suspension feeders - filter from fluid (e.g. baleen whales)
Deposit Feeders - Engulf deposited sediments (e.g. crabs)
Mass (bulk) feeders - Grab chunks of food with beak/mouth/other appendage (e.g. humans)
For each of the main components of the digestive tract, describe its function.
Mouth - mechanical breakdown of food, chemical breakdown of starch (salivary amylase)
Esophagus - Pass food from mouth to stomach via peristalsis
Stomach - acidic, further mechanical and chemical breakdown of nutrients (breaks down proteins via peptidase)
S. Intestine - Chemical breakdown of food (starch, proteins, lipids, carbs); absorption of nutrients (high SA –> villi and microvilli)
L. intestine - absorption of water; carries waste to rectum/anus for expulsion
In mammals, where does most of the enzymatic breakdown of macromolecules occur?
In the small intestine; enzymes from liver/pancreas (including digestive enzymes) & leftover enzymes from mouth/stomach are active in the small intestine
How does the structure of the small intestine support its function of absorbing nutrients?
High SA (villi, microvilli); small diffusion distance (1 cell only) between intestine lumen and blood
What is homeostasis?
The tendency towards a relatively stable equilibrium between interdependent elements
What is the difference between negative feedback and positive feedback?
Negative feedback = reverse the change to return to normal
Positive feedback = amplify the change to return back to normal
Endotherm
An organism that is able to self-regulate its body temperature
Ectotherm
An organism that is reliant on external sources to regulate its body temperature
What is countercurrent exchange?
Arteries and veins arranged to flow in opposite directions to maintain a constant heat gradient to preserve body heat
Why is countercurrent exchange more effective than concurrent?
Always a temperature gradient in countercurrent; only a short gradient in concurrent, so minimal heat transfer (i.e. minimal heat preservation)
What are some factors that affect the rate of transfer?
Gradient; distance between the two surfaces, surface area
Rate of transfer = ((Amount on one side - Amount on other)* surface area)/distance across
What is Fick’s law of diffusion?
Rate of diffusion = kA((P2-P1)/D)
k=diffusion constant
A=area for exchange
P2-P1=gradient (difference in partial pressures)
D= distance (thickness of barrier)
What would happen to a fish in saltwater in terms of osmoregulation? What is a general solution?
- Environment is hypotonic to fish (in terms of water)
- H2O lost by fish through osmosis
- Salts/electrolytes gained by passive transport
Drink water, but pump out ions
What would happen to a fish in freshwater in terms of osmoregulation? What is a general solution?
- Environment is hypertonic to fish (in terms of water)
- H2O gained by fish via osmosis
- salts lost via passive transport
Don’t drink water, excrete lots of water, bring in extra electrolytes (active transport across gills or eating)
What are the four steps in salt excretion in a marine animal (e.g. a shark)?
1) Na+ from epithelial cell to blood, K+ from blood/extra cellular fluid (ECF) to cell
2) Sodium (Na+), potassium (K+) and Chloride (Cl-) from blood/ECF into cell
3) Chloride (Cl-) from cell outside the shark; Potassium (K+) from cell to blood/ECF
4) Sodium (Na+) from blood/ECF to outside the shark
For each step, state whether energy is required, what type of transport occurs and what is achieved during this process.
1) Na+ from epithelial cell to blood, K+ from blood/extra cellular fluid (ECF) to cell
Yes - ATP
Primary Active
Establish a sodium gradient (high in blood/ECF, low in cell)
For each step, state whether energy is required, what type of transport occurs and what is achieved during this process.
2) Sodium (Na+), potassium (K+) and Chloride (Cl-) from blood/ECF into cell
Yes, sodium gradient
Secondary Active
Use sodium concentration gradient (move sodium down gradient) to move potassium up the concentration gradient; transport chloride into cell
For each step, state whether energy is required, what type of transport occurs and what is achieved during this process.
3) Chloride (Cl-) from cell outside the shark; Potassium (K+) from cell to blood/ECF
No
Passive
Remove chloride from cells (pump outside cell); create potassium gradient for repeat of step 1
For each step, state whether energy is required, what type of transport occurs and what is achieved during this process.
4) Sodium (Na+) from blood/ECF to outside the shark
No
Passive
Remove sodium ions from blood/cells (pump outside the body)
There are no known active transporters for water molecules. How then, is water balance maintained?
By moving salts, and using the concentration gradient to move water (i.e. cell transports solute to pull water around)
Why is oxygen necessary for animals?
Oxygen is necessary for animals to perform cellular respiration in order to generate ATP (energy)
What are the 4 components required to get gas to and from cells?
Ventilation, gas exchange, circulation, cellular respiration
Why are the partial pressures of carbon dioxide and oxygen important?
Because they diffuse down their partial pressure gradients (like how solutes move down their concentration gradients)
What are two challenges that water breathers have to deal with?
- Water contains less oxygen relative to air
- Water is much denser (harder to move)
What are the three physical parameters that determine how quickly gases will diffuse?
- Gradient (difference in partial pressures)
- Diffusion distance
- Surface area
Fish gills are addressing the challenge of gas exchange. What are the two strategies that their gills use, to make gas exchange efficient?
- Large surface area
- Small diffusion distance (thin epithelium)
What kinds of pressure ventilation and feedback occur in human breathing?
Negative pressure ventilation (increase volume, decrease pressure, so air is pulled into lungs); used for negative feedback loop
Why do you have to breather harder at higher altitudes?
Because the partial pressure of oxygen is lower than at sea level
How is the function (gas exchange) of
fish gills supported by its structures?
Area - Maximized –> lots of surface area (capillaries and gills have high SA:V ratio)
Distance - Minimized –> capillaries right next to water (short diffusion distance)
Gradient - Maximized –> countercurrent exchange keeps a continual gradient
Why don’t humans have the structures for countercurrent exchange?
Ventilation & gas exchange is not as difficult (higher P(O2) than water; air is less dense)
What are the 4 components of blood?
Red blood cells, platelets, white blood cells, plasma
What are the two main components of blood?
Red blood cells and plasma
Diffusion is not the only method of moving gases. What is another method?
Bulk flow (convection) - movement of fluid molecules as a group; requires extra energy input into the system
Why do many animals (e.g. giraffes) need a circulatory system?
Rate of diffusion is inversely proportional to D; body is big, so D is huge, so rate of diffusion is too slow (bulk flow needed)
How are oxygen and carbon dioxide carried in the blood?
O2 - bound to hemoglobin
CO2 - dissolved in the plasma as HCO3-
Where is the highest % of hemoglobin saturation?
In the lungs (hemoglobin picks up oxygen when high amounts are present; drops off in tissues –> where low amounts of oxygen are present)
How can a slight change in pH affect the amount of oxygen carried in the blood?
Hemoglobin is a protein –> Change in pH=change in shape=change in affinity for oxygen (STRUCTURE-FUNCTION RELATIONSHIP)
Define pulmonary and systemic circulation.
Pulmonary - between lungs and heart
Systemic - between heart and body tissues
What are some roles of the nervous system?
Sensory processing & integration; communication & information storage; physiological response, regulation & homeostasis
What is the general path of a nervous impulse?
Sensor –> Afferent neuron –> integration (CNS) –> Efferent neuron –> Effector
What is the role of the afferent division of the nervous system?
Receives information from internal and external stimuli; transmits the information
What is the role of the central nervous system?
Processes the information received from sensory (afferent) neurons; sends a signal to other systems
What is the role of the somatic nervous system?
Controls the movement of skeletal muscles (via motor neurons); subdivision of the efferent division
What is the role of the autonomic nervous system?
Involuntary control of movement of smooth and cardiac muscles (e.g. increases heart rate and inhibits digestion); subdivision of efferent division
What are reflexes?
Reflexes are involuntary reactions that are not processed in the brain, but pass through the CNS in the spinal chord
What are the components of the central nervous system and peripheral nervous system?
CNS - brain and spinal cord
PNS - nerves leading to and from the CNS
What is the general flow of information in a neuron?
Dendrite - collects electrical signals
Cell body - integrates incoming signals and generates outgoing signal to axon
Axon - passes electrical signals to dendrites of another cell or to an effector cell
The resting potential of a neuron is -70mV. In a neuron at rest: (T/F)
There is an electrical (charge) gradient across the membrane
True
The resting potential of a neuron is -70mV. In a neuron at rest: (T/F)
The outside
of the cell is more negative than the inside
False; the inside is more negative
The resting potential of a neuron is -70mV. In a neuron at rest: (T/F)
There are more positively charged ions outside the cell than inside
True
The resting potential of a neuron is -70mV. In a neuron at rest: (T/F)
There are more Na+ ions outside the cell than inside
True
The resting potential of a neuron is -70mV. In a neuron at rest: (T/F)
There are more K+ ions outside the cell than inside
False; more K+ ions inside the cell than outside
The resting potential of a neuron is -70mV. In a neuron at rest: (T/F)
The system is at equilibrium
False, equilibrium is death!
What ions are moved using the sodium-potassium pump, and what are the resulting chemical and electrical gradients?
3 Na+ out, 2 K+ in; driven by ATP; increase [Na+] outside, [K+] inside; negatively charged inside
What ions are moved using the potassium leak channel, and what are the resulting chemical and electrical gradients?
K+ –> outside; increase [K+] inside; increase negative charge inside
What are the three stages of action potential?
Depolarization, repolarization and hyperpolarization
With respect to the pumps and channels, what will be functioning during each stage of action potential?
Depolarization - Na+/K+ pump is active; K+ leak channels and Na+ voltage gated channels are open; voltage gated K+ channel is closed
Repolarization - Na+/K+ pump is active; K+ leak channels and K+ voltage gated channels are open; voltage gated Na+ channel is closed
Hyperpolarization - Na+/K+ pump is active; K+ voltage gated channels and Na+ voltage gated channels are open; K+ leak channel is closed
What happens with respect to ion movement and cell charge during each stage of action potential?
Depolarization - Na+ in (following electrical and chemical gradients); cell becomes positive
Repolarization - K+ moves out (following its gradients); cell becomes positive
Hyperpolarization - Na+ out, K+ in (Na/K pump), K+ out (leak channels); cell is negative
What kind of feedback occurs during action potential, to open voltage-gated sodium channels and potassium channels?
Sodium - Positive feedback
Potassium - negative feedback
What effect does myelination have on action potential propagation?
Increases the speed by reducing the leaking of ions across the membrane
Where does the signal end up?
At a synapse
What are the two types of synapses?
Chemical; indirect signalling via release of neurotransmitter
Electrical; direct signalling via flow of ions through specialized channel
What are the four steps that occur at a chemical synapse?
1) Action potential arrives at synapse, depolarizes presynaptic membrane
2) Voltage-gated calcium channels open up and there is an influx of calcium into the cell
3) Synaptic vesicles move to/fuse with the presynaptic membrane & release neurotransmitters into the synaptic cleft
4) Neurotransmitters diffuse across the synaptic cleft and bind to proteins on the post synaptic membrane
What kind of channel is the protein on the post-synaptic membrane?
Ligand-gated ion channel (ligand=small molecule that binds to a macromolecule)
What is an advantage and disadvantage of chemical synapses?
Advantage - allows for integration of many signals (unlike “all or none” action potentials in electrical synapses)
Disadvantage - takes longer than an electrical synapse
What are the two types of post-synaptic potentials (PSP’s) and what is the difference between them?
Exitatory - increases the likelihood of an action potential being initiated
Inhibitory - decreases the likelihood of an action potential being initiated
Where are PSP’s summed up? What must occur in order to generate an action potential?
Summed up at axon hillock; must reach threshold fro action potential to occur
What are 5 types of sensory receptors, and what stimuli do they respond to?
Mechanoreceptors - touch, sound Thermoreceptors - heat Chemoreceptors - chemicals Nocireceptors - pain Photoreceptors - light
What does a stimulus cause in the sensory neuron?
Signal transduction - receptors convert the stimuli into an electrical signal (change in membrane potential)
How many muscle cells are in each muscle fiber? What is each muscle cell made up of?
One muscle fiber=one muscle cell; contains many myofibrils, which contain many sarcomeres
What chemical is released by the neuron at a neuromuscular junction? Where does it go?
Acetylcholine; binds to receptor on the muscle membrane
What does the release of acetylcholine trigger in the post-synaptic (muscle) membrane? What gets released as a result?
Depolarization and opening of the voltage-gated calcium channels; results in calcium being released from sarcoplasmic reticulum
What occurs after calcium is released from the sarcoplasmic reticulum in a neuromuscular junction?
Binds troponin; troponin/tropomyosin leave the myosin-binding site
Allows actin and myosin to bind each other & slide along, bringing the Z-disks closer together
What’s the difference between actin and myosin? Tropomyosin and troponin?
Actin is thicker (myosin=multiple, thinner fibres combined);
tropomyosin=thinner
What two conditions must be met for myosin molecules to continue to move along actin molecules?
ATP present and intracellular Ca2+ is high
How are hormones like wifi?
Signal is broadcast widely; specificity of the response is determined by the ability to receive the signal
How is it possible for there to be multiple different responses to a single hormone? Why does this occur?
Different receptors (same hormone) --> different responses OR Different intracellular proteins (same hormone, receptor) --> different responses
Regulation of gene expression (different expression of same gene=different structure=different function)
What would occur in a cell that expresses the epinephrine receptor, but had a defect in its ability to get the receptor out to the membrane?
It would no longer be able to respond.
How can you determine whether or not a hormone is a peptide or amino acid derivative?
If it cannot cross the membrane (received on the outside of the call), then it is a peptide or amino acid derivative
What kind of hormone (steroid or non-steroid) requires a receptor protein on the membrane?
Nonsteroid hormone
What is the pathway of the HPA axis (endocrine example)
Stimulus (stress) –> Sensory (afferent) neuron –> hypothalamus/anterior pituitary –> secretes CRH –> triggers release of ACTH –> Adrenal gland (target cells) –> Secretes cortisol –> Maintains blood glucose
What are three methods that cortisol uses to maintain blood glucose levels?
1) Activate liver to synthesize enzymes that make glucose
2) Prevent fat cells (adipose tissue) from taking up glucose
3) Cause fat cells to release fatty acids into the blood, so that muscles and heart use fatty acids instead of glucose
What are some advantages of bother the nervous and endocrine systems?
Nervous - faster; targets directly to specific cells
Endocrine - Longer-lasting, whole-body effects
What is the general pathway to receive environmental signals?
Stimuli –> Sensory receptors activated (conformational change) –> sensory (afferent) neuron activated (action potential) –> Signal sent to CNS
What is the immediate reaction to a stimulus (e.g. oncoming car while walking) once the action potential reaches the hypothalamus?
Efferent neuron activated –> neuromuscular junction –> contract muscles –> move out of the way
Sympathetic nervous system –> increase heart rate, blood flow to muscles; decreases blood flow to digestive system –> person moves away
What is the reaction within a couple of seconds to a stimulus (e.g. oncoming car while walking)?
Secretion of CRH –> received by pituitary gland –> secretes ACTH –> received by adrenal gland –> secretes cortisol, adrenaline
adrenaline –> person moves away
What is the reaction within minutes and continuing if stress (e.g. oncoming car while walking) is prolonged?
Continual cortisol secretion –> increased blood glucose levels
