Biology 1521 - Unit 3 Q&A

Chordates, namely vertebrates, are the only animals possessing an endoskeleton, and all vertebrate species possess endoskeletons. This statement is:

False because other animal lineages possess endoskeletons

The reason a particular hormone only affects specific target cells in the body is that:

Only target cells express the hormone receptors

Which of the following signals indicates shade to a plant?

far-red light

Analysis of a blood sample from a fasting individual who had not eaten for twenty-four hours would be expected to reveal high levels of _____.

glucagon

Which of the following is a mechanism underlying learning/memory?

growth of new synapses between existing neurons

When a signalling molecule binds to a receptor at the cell membrane, it gets transduced. What is meant by the term "signal transduction"?

The signal is transmitted inside the cell in another form.

How is the signal from a steroid hormone amplified?

The steroid hormone repeatedly activates transcription of target genes. Each mRNA copy of a steroid-hormone target gene can be translated into protein multiple times

A nerve is:

one bundle of many axons from either afferent or efferent neurons

Cilia, flagella, and muscle activity are all dependent upon

ATP Motor proteins; motor proteins all require protein 'tracks' to move along; the track in muscle is composed of actin, and the track in cilia and flagella is composed of microtubules.

Blue light induces the phototropic response. It does so through which hormone?

Auxins

Match the function/activity to the appropriate brain region.

Cerebrum - Working a crossword puzzle Diencephalon - Sending signals from the senses to the appropriate brain region Corpus Callosum - Communicating between the left and right cerebral hemispheres Brainstem - Regulating your resting heart rate Cerebellum - Maintaining your balance while you walk

Which of the following is not a role of the autonomic nervous system?

Controls voluntary skeletal muscle activity

Red light induces germination. Which hormone also contributes to germination (through a different mechanism)?

Gibberellins

Saltatory conduction occurs only

In myelinated nerve fibers. by definition, saltatory conduction is propagation of action potentials along a myelinated axon. because of the insulation from the myelin, saltatory conduction is much more rapid than propagation of action potentials along unmyelinated axons.

Which of the following statements correctly describe(s) the relationship between Ca2+ in the cytosol and the behavior of the sarcomere?

Increasing Ca2+ concentration causes movement of tropomyosin, exposing myosin-binding sites on actin. tropomyosin lies along the actin filament and physically blocks the sites that myosin binds to (the myosin-binding sites) along the actin filament. when calcium binds to troponin, a protein associated with tropomyosin, there is a conformational change that moves the troponin-tropomyosin complex away from the myosin-binding sites on the actin, allowing myosin to bind and "walk along" the actin to contract the sarcomere.

What causes membrane depolarization in a neuron?

Influx of sodium ions. sodium is concentrated outside the cell and potassium is concentrated inside the cell due to the energy-driven activity of the sodium-potassium pump. the inside of the cell is more negative than the outside of the cell. "depolarization" means becoming more positive ("hyperpolarization" means becoming more negative). the membrane depolarizes because of voltage-gated sodium channels open, allowing a rapid influx of sodium into the cell along its electrochemical gradient; sodium moves into the cell both because of its chemical gradient (more concentrated outside the cell), and because of its electrical gradient (more positive outside the cell).

Which of the following ions is most likely to passively cross the plasma membrane of a resting neuron?

K+

Muscle contraction is accomplished by

Movement of myosin motor proteins along actin filaments

Why are muscles paired in skeletal systems?

Muscles can only contract; movement is controlled by one muscle contracting while the other relaxes

Gravitropism in roots is mediated by:

Redistribution of auxin to the bottom side of a growing root in response to gravity The movement of statoliths altering the distribution of auxin the roots

Which of the following is a reason that muscle contraction is graded (varies in strength)?

Some motor units may not be activated during a given muscle contracition.

Why are the structural differences among amino-acid-derivative (structurally derived from amino acids), polypeptide (small proteins), and steroid hormones significant?

Steroids are lipid soluble and readily cross plasma membranes, while polypeptide and most amino acid-derived hormones cannot.

Which of the following statements correctly describe(s) T tubules and their role in conducting action potentials in muscle cells?

Without T tubules, the muscle cell would not be able to contract. T tubules carry action potentials throughout the muscle cell

A drug that that disrupts (prevents) bacterial quorum sensing (select all that apply):

Would be useful as an antibiotic Would prevent biofilm formation Would prevent bacterial virulence

A muscle fiber that has few mitochondria, has low myoglobin content, generates a large amount force but fatigues quickly would be classified as:

a fast twitch fiber

A motor unit is best described as:

a single motor neuron and all the muscle fibers it enervates

Fight-or-flight reactions include activation of the _____.

adrenal medulla, leading to increased secretion of epinephrine

Rods are sensitive to [blank], and cones are sensitive to [blank].

any light including dim light, different wavelengths of light

Plant Hormones

auxin - leaf abscission; apical dominance; phototropic response; gravitropic response cytokinins - cell division gibberellins - stem elongation; seed germination; fruit growth jasmonic acid - defense against herbivory abscissic acid - seed dormancy; bud dormancy inhibits cell division ethylene - fruit ripening; leaf abscission methyl salicylate - defense againts pathogens

If a plant failed to grow taller, which of the following hormones might you artificially add to stimulate growth?

auxins gibberellins cytokinins

A neuron sends a signal toward another neuron along its _____.

axon

What is the largest (most prominent) structure of the human brain?

cerebrum

peripheral nervous system

divided into the sensory/afferent (incoming sensory information) and the motor/efferent (outgoing responses) divisions.

motor/efferent division

divided into the somatic (voluntary) and autonomic (involuntary) divisions.

autonomic division

divided into the sympathetic ("fight or flight") and the parasympathetic ("rest and digest") divisions.

parasympathetic nervous system

does the opposite of the sympathetic, diverting blood flow to the intestines for digestion, decreasing heart rate and breathing rate, etc.

Degree of stimulus (how loud, strong, etc) can be communicated to the CNS via:

how many sensory neurons are activated how frequently the action potentials occur in the sensory neuron

What is the role of the actin (thin) filament in muscle contraction?

it is the filament that is pulled towards the center of the sarcomere it provides binding sites for motor protein head

What is the role of tropomyosin in muscle contraction?

it is the protein that controls access to myosin-binding sites. tropomyosin lies along the actin filament and physically blocks the sites that myosin binds to (the myosin-binding sites) along the actin filament. when calcium binds to troponin, a protein associated with tropomyosin, there is a conformational change that moves the troponin-tropomyosin complex away from the myosin-binding sites on the actin, allowing myosin to bind and "walk along" the actin to contract the sarcomere.

Which of the following is/are TRUE of mechanoreceptors?

mechanoreceptors respond to physical deformation of the cell plasma membrane mechanoreceptors are involved in the sensation of hearing mechanoreceptors are involved in the sensation of touch

A tastant is a

molecule that binds a specific taste cell receptor. each taste bud is composed of multiple receptor cell types, each capable of detecting a different type of tastant (sweet, salty, sour, bitter, umami). each type of taste receptor cell detects only ONE of these five types of tastants. each taste bud is capable of detecting all types of tastants, because it contains all types of taste receptor cells.

Which of these glands is located within the abdominal cavity?

pancreas Tip: the parathyroid and thyroid are located in the throat; the pituitary is located in the brain; the pancreas and adrenal glands are located in the abdomen.

sympathetic nervous system

prepares and supports the body in intense physical activity by diverting blood flow from intestines to skeletal/heart muscles, increasing blood glucose levels, increasing breathing rate, and other changes.

Increased activity of the parasympathetic division of the autonomic nervous system is likely when

resting on the sofa after dinner.

What is the key piece of cellular machinery maintaining the resting potential of a neuron?

sodium-potassium pump

Reflexes such as the knee-jerk reflex result in a very rapid involuntary response to a stimulus without altering activity in

the brain.

Myosin Filament

the myosin filament has ATP-drivin motor protein heads that pull the actin filament toward the center of the sarcomere to cause contraction.

Negative feedback is defined as ________.

the product of a process inhibits its production

Action Potential Speed and Strength

the speed and strength of an action potential never change for a given neuron. it is 'digital' in that what varies is WHETHER the action potential occurs and how FREQUENTLY it occurs; not how fast or how large it is.

Increased activity of the parasympathetic division of the autonomic nervous system is likely not when

there is an emergency, for example, a car accident. vigorous exercise has just been initiated. blood pressure decreases to dangerously low levels.

Nociceptors are sensory receptors sensitive to:

tissue damage