Important questions for homework

1. Assignment_38 9923183
Q: What are five types of taste receptors in human?
The sense of taste is equivalent to excitation of taste receptors, and receptors for
a large number of specific chemicals have been identified that contribute to the
reception of taste. Despite this complexity, five types of tastes are commonly
recognized by humans:
•Sweet - usually indicates energy rich nutrients
•Umami - the taste of amino acids (e.g. meat broth or aged cheese)
•Salty - allows modulating diet for electrolyte balance
•Sour - typically the taste of acids
•Bitter - allows sensing of diverse natural toxins
None of these tastes are elicited by a single chemical. Also, there are thresholds
for detection of taste that differ among chemicals that taste the same. For
example, sucrose, 1-propyl-2 amino-4-nitrobenzene and lactose all taste sweet to
humans, but the sweet taste is elicited by these chemicals at concentrations of
roughly 10 mm, 2 µm and 30 mm respectively - a range of potency of roughly
15,000-fold. Substances sensed as bitter typically have very low thresholds.

2. Examples of some human thresholds
Taste Substance Threshold for tasting
Salty NaCl 0.01 M
Sour HCl 0.0009 M
Sweet Sucrose 0.01 M
Bitter Quinine 0.000008 M
Umami Glutamate 0.0007 M
1. The sweet taste is created by carbohydrates such as sucrose and fructose, as
well as artificial sweeteners such as aspartame and saccharine.
2. The salty taste is generally created by salts containing sodium ions, such as
sodium chloride (table salt) and sodium bicarbonate (baking soda). Salts
containing potassium, lithium, and other alkali metal ions also produce a mildly
salty flavor.
3. Acidic compounds, such as citric acid and vinegar, produce sour flavors.
4. Bitter flavors are produced by a variety of organic compounds and are generally
considered an undesirable or unpalatable flavor. Many toxic chemicals produced
by poisonous plants have a bitter taste, thus leading to the negative reaction to
bitter foods.
5. Umami is the most recently discovered taste, found in foods that have a
“meaty” taste due to the presence of the chemical glutamate. Meat, cheese,
mushrooms, and the chemical monosodium glutamate (MSG) all contain
glutamate

4. 9923183
Homework 1
Q:Fungal skin diseases are persistent. Ointments and creams may not reach the deepest infected
skin layers. Oral antifungal drugs are far less common than antibacterials and often have bad side
effects. Reflect on the evolutionary relationships among bacteria, fungal and humans. Explain
why it is more difficult to create drugs against fungi than bacteria
Answer
Fungal infectons are difficult to treat because of the nature of fungi. They are phylogenetically
very closely related to animals and have a very similar biochemical makeup to animals. In
treating an internal fungal infection it is difficult to find a drug that kills the fungus and not the
animal. Most fungi are killed by the immune system, and if it is impossible for the immune
system to kill the fungus on its own, then the animal is likely to not survive.
Bacteria on the other hand are prokaryotic, making them very different from eukaryotic life
(plants, animals, fungi, and protists). It is easy to target the bacteria cells as they are so
biochemically different from our own. The only thing needed to do to kill a bacterium is to
destroy the cell wall, which can be done using a number of drugs. Although it may be true that
bacteria is easier to kill inside a human than fungus is, there are antibiotic resistant bacteria now.

5. 9923183
Homework Chapter 37
Q: What are four major lobes of the human brain?
The cerebral cortex can be divided into four sections, which are known as lobes (see image below). The
frontal lobe, parietal lobe, occipital lobe, and temporal lobe have been associated with different
functions ranging from reasoning to auditory perception.
 The frontal lobe is located at the front of the brain and is associated with reasoning, motor
skills, higher level cognition, and expressive language. At the back of the frontal lobe, near the
central sulcus, lies the motor cortex. This area of the brain receives information from various
lobes of the brain and utilizes this information to carry out body movements. Damage to the
frontal lobe can lead to changes in sexual habits, socialization, and attention as well as increased
risk-taking.
 The parietal lobe is located in the middle section of the brain and is associated with processing
tactile sensory information such as pressure, touch, and pain. A portion of the brain known as
the somatosensory cortex is located in this lobe and is essential to the processing of the body's
senses. Damage to the parietal lobe can result in problems with verbal memory, an impaired
ability to control eye gaze and problems with language.
 The temporal lobe is located on the bottom section of the brain. This lobe is also the location of
the primary auditory cortex, which is important for interpreting sounds and the language we
hear. The hippocampus is also located in the temporal lobe, which is why this portion of the
brain is also heavily associated with the formation of memories. Damage to the temporal lobe
can lead to problems with memory, speech perception, and language skills.
• The occipital lobe is located at the back portion of the brain and is associated with interpreting visual
stimuli and information. The primary visual cortex, which receives and interprets information from the
retinas of the eyes, is located in the occipital lobe. Damage to this lobe can cause visual problems such
as difficulty recognizing objects, an inability to identify colors, and trouble recognizing words.

8. Homework Ch. 36 9923183
Q1. What are four major functions of human kidneys in maintaining homeostasis?
The four major functions of human kidneys in maintaining homeostasis are:
1. Excretion of metabolic wastes
The Kidney excretes metabolic wastes such as urea, which is the primary nitrogenous waste of
humans.
2. Maintain the Salt Water Balance
Water and salt reabsorption occurs through the wall of the proximal convoluted tubule.
This is important for excreting hypertonic urine
 Loop of nephron
 Collecting Duct
 Water => Aquaporin

9.  Loop of the nephron
Renal medulla
 The loop of the nephron is composed of a descending limb and an ascending limb.
 The bottom of the ascending limb is thin, and salt passively diffuses out.
 The upper part of the ascending limb is thicker and the salt is actively
transported out.
 No water can leave the ascending limb because it is
impermeable to water.
 Osmotic gradient in the tissues of the renal medulla;
Salt > concentration in direction of the inner medulla.
 This is because the further up the thick part of the ascending
limb the fluid goes; less salt is available for transport.
 The innermost medulla itself has the highest concentration of solutes;
◦ Because urea leaks out of the collecting duct.
 Water diffuses out the entire length of the descending limb due to this osmotic
gradient.
 Countercurrent mechanism
◦ Water leaves the descending limb, and as it diffuses out, the remaining
fluid contains a greater osmotic concentration of solutes, and therefore
can diffuse through the limb from top to bottom.
 The collecting duct also has the osmotic gradient
Water defuses out into the renal medulla, and thus urine is hypertonic to blood plasma.

10.  ADH + Reabsorption
 Antidiuretic hormone regulates urine formation and excretion.
 This is released by the posterior lobe of the pituitary gland.
 More ADH = More water reabsorption, less urine, raise in blood volume + pressure
 Less ADH = Less water reabsorption, more urine
◦ Ideally, dependent on how much water you drink
Diuretics (ex. caffeine and alcohol) interfere with ADH and cause increased urine
 Hormones + Salt Reabsorption
99% of Na+ filtered at the glomerulus returns to blood; 67% reabsorbed at the proximal
convoluted tubule; 25% extruded by the ascending limb.
Blood volume + pressure is partially regulated by salt reabsorptions.
When glomerular filtration cannot be supported, renin is secreted.
 Renin (enzyme)

11. ◦ Angiotensinogen angiotensin I angiotensin II
 This vasoconstrictor stimulates adrenal glands on the
kidneys to release aldosterone.
 Aldosterone is a hormone that promotes excreting K+ and absorbing Na+ at the
distal convoluted tubule.
 Water reabsorption follows and blood volume + pressure increase (and therefore
glomerular filtration can now occur).
 Atrial Natriuretic Hormone does the exact opposite.
 Secreted by the atria of the heart when cardiac cells get too stretched from higher
blood volume and pressure.
 Inhibits the secretion of renin (from the juxtaglomerular apparatus) and aldosterone
(from the adrenal cortex)
◦ As a result, natriuretic occurs (increased secretion of Na+ and water,
lowering blood volume + pressure.
Other hormones secreted to regulate other ions as well ( ex. K+, HCO3-, Mg2+)
3. Maintaining Acid- Base Balance
 Bicarbonate Buffer System
◦ Respiratory, powerful, does most of the work regulating blood pH
 Essentially, kidneys reabsorb bicarbonate ions and excrete hydrogen ions as
needed.
◦ pH high (acidic) = Hydrogen excreted and bicarbonate reabsorbed.
◦ pH Low (basic) = Hydrogen excreted, but bicarbonate NOT reabsorbed.
 Urine is usually acidic, showing excess hydrogen is usually excreted.
◦ Ammonia = NH3 + H+ = NH4+
4. Secretion of Hormones
One of the hormones secreted by the kidneys boosts the number of red blood cells when
insufficient oxygen is being delivered to the cells. This hormone, called erythropoietin,
stimulates the stem cells in the bone marrow to produce more red blood cells. Another hormone
called renin is produced.

12. Assignment 40 9923183
Q 1. What are two types of hormones released by posterior pituitary gland?
The two types of hormones released by the Posterior pituitary gland are
1. Oxytocin
2. Vasopressin.
These hormones are created in the hypothalamus and released in the posterior pituitary. After
creation, they are stored in neurosecretory vesicles regrouped into Herring bodies before being
secreted in the posterior pituitary into the bloodstream.
Hormone
Other
names
Symbol
(s)
Main
targets
Effect Source
Oxytocin OT
Uterus,
mammary
glands
Uterine contractions;
lactation
supraoptic and
paraventricular nuclei
Vasopressin
Antidiuretic
hormone
VP,
AVP,
ADH
Kidneys an
d arterioles
Stimulates water
retention; raises
blood pressure by
contracting arterioles
supraoptic and
paraventricular nuclei
 Oxytocin
 Oxytocin is a hormone, neuropeptide, and medication. It is normally
produced by the paraventricular nucleus of the hypothalamus and released
by the posterior pituitary.
It plays a role in social bonding, sexual reproduction in both sexes, and
during and after childbirth. Oxytocin is released into the bloodstream as a
hormone in response to stretching of the cervix and uterus during labor and
with stimulation of the nipples from breastfeeding. This helps with birth,
bonding with the baby, and milk production.

13. Chemical structure of Oxytocin
 Vasopressin
 Vasopressin, also known as antidiuretic hormone (ADH), is a
neurohypophysial hormone found in most mammals. In most species it
contains arginine and is thus also called arginine vasopressin (AVP) or
argipressin. Its two primary functions are to retain water in the body and to
constrict blood vessels.
 Vasopressin regulates the body's retention of water by acting to increase
water reabsorption in the kidney's collecting ducts, the tubules which
receive the very dilute urine produced by the functional unit of the kidney,
the nephrons.
 Vasopressin is a peptide hormone that increases water permeability of the
kidney's collecting duct and distal convoluted tubule by inducing
translocation of aquaporin-CD water channels in the plasma membrane of
collecting duct cells.
 Vasopressin also increases peripheral vascular resistance, which in turn
increases arterial blood pressure.
 Vasopressin plays a key role in homeostasis, by the regulation of water,
glucose, and salts in the blood.

14.  Vasopressin is derived from a preprohormone precursor that is synthesized
in the hypothalamus and stored in vesicles at the posterior pituitary. Most
of it is stored in the posterior pituitary to be released into the bloodstream.
However, some AVP may also be released directly into the brain, and
accumulating evidence suggests it plays an important role in social
behavior, sexual motivation and pair bonding, and maternal responses to
stress. It has a very short half-life between 16–24 minutes.
Chemical structure of Vasopressin

15. Homework Chapter 28 9923183
Q.1
What are hermaphrodites? The invertebrates that are hermaphrodites cannot fertilize their own
eggs, but tapeworms can. Explain the advantages and disadvantages of self-fertilization.
Ans: Advantages of Self Fertilization
1. Self-fertilization is more common in animals that have limited mobility or are not motile,
2. It can reproduce when alone.
3. It does not need to expend energy in seeking a mating partner, nor in conducting courtship of
any kind.
4. Its offspring has a genome that's proven to be working in this environment.
Disadvantages of Self Fertilization
1. Its offspring have limited genetic variation. If the environment changes so that one dies,
then it's likely to kill all of them.
2. It is disadvantageous because of inbreeding depression—the reduced fitness of offspring
because of the unmasking of deleterious recessive alleles due to the breeding of closely
related individuals.
3. Another disadvantage of self-fertilization is not having the ability to exchange genes with
other cestodes which leads to increased genetic variation.
Q2. How is the behavior of animals with cephalization different from that without cephalization?
Ans.
Cephalization is the development of a functional “head” end of an organism. Several things
results from this developmental step. First, is the concept of polarity. The organism now
demonstrates significant differences along the length of its body, so that a head end can now be

16. distinguished from a tail end. These differences represent enhanced areas of specialization – a
mouth in front, a stomach in the middle, an anus at the end. Regional specialization allows for
more efficient concentration of effort in one region rather than having the entire body fulfill that
function. Yes, there are some regional specializations in non-cephalad creatures – but the design
concept does not really take-off until polarity becomes an important part of the body plan.
One example of polarity in the body plan is cephalization – the formation of a head and a brain.
In this early stage, the brain is still relatively simple, but through polarity it shows differences
from the rest of the nervous system. Now there are many advantages of having a brain. It allows
for the development of sense organs (sight, hearing and smell) that can be used to identify
threats, or opportunities, before the creature comes into contact with them. Notice that these
major sense organs (eyes, ears, nose) are located near the brain since they are effectively
elaborations of the brain. The sense of touch (pain and temperatures) occurs all over the body
and does not even require a brain for interpretation (a reflex is a response to a touch sensation
that has not been interpreted by the brain).
With the ability to sense the environment at a distance, the organism also makes use of the brain
to develop a more intricate behavioral script. At the simplest level the “behaviors” may not seem
like much. But, this simple brain allows for a variety of responses to environmental
circumstances. An organism with a brain with not always respond to a stimulus in exactly the
same way – an organism without a brain will. The simplest little behavioral complexity would
give the organism a survival advantage over creatures that always respond in exactly the same
fashion (plants, or plant-like animals).

17. Assignment 29 9923183
Q1.Does Alaska, USA have more native birds or reptiles?
Alaska, USA has more birds than reptiles.
Nearly 450 species of birds have been spotted in Alaska; of those, more than half
are native to the state. Some of Alaska’s more notable bird species, according to
the website of Alaska Trekker, include the bald eagle, owls (10 species), the
puffin, the red-faced cormorant, the sandpiper, the common loon, the ptarmigan
and lesser yellowlegs. Other birds commonly seen are the raven, the
oystercatcher, the trumpeter swan, Bonaparte’s gull, the Sandhill crane and the
Arctic tern. Alaskan duck species include both freshwater and sea ducks, including
mallard, pintail, teal, goldeneye, bufflehead, merganser, harlequin, oldsquaw,
king eider and Pacific eider. Goose species include Canada, Aleutian, black Brant
and speckle belly.
In case of Reptiles, Alaska’s only reptiles are four species of sea turtle, including
green, leatherback, loggerhead, and olive Ridley.

18. Q2:
Amphibians have rudimentary lungs; skin is also a respiratory
organ. Why would skin be more sensitive to pollution than
lungs?
When air passes through nostrils or the mouth to get to lungs, large particles are
removed by adhering to moist membranes. In contrast, amphibians have no way
to protect the skin from being clogged by particulate pollution in the air. Skin
clogged by pollution can no longer be efficient in gas exchange and the animal
dies.