Biology Assignment: Questions and Answers - Biology 101, Semester 1

This Biology assignment solution covers a range of topics, including cellular biology, human physiology, and immunology. It begins with multiple-choice questions testing knowledge of biological terms and processes, such as carbonic anhydrase, stem cells, and agglutinogens. The assignment then delves into more complex topics, such as Addison's disease and diabetes insipidus, explaining their causes and physiological impacts. The solution traces the path of red blood cells through the circulatory system and details the process of T cell and B cell activation within the immune system. Furthermore, it explores respiratory system components, metabolic processes, and the digestion and absorption of food, including the roles of various enzymes and hormones. Finally, it examines glomerular filtration and the factors influencing it. The assignment provides comprehensive answers and explanations to enhance understanding of key biological concepts.

Biology assignment

Table of Contents
Question 1...................................................................................................................................................3
Question 2:..................................................................................................................................................3
Question 3...................................................................................................................................................4
Question 4...................................................................................................................................................4
Question 5...................................................................................................................................................5
Question 6...................................................................................................................................................6
Question 7...................................................................................................................................................8
Question 8...................................................................................................................................................8
Question 9...................................................................................................................................................9
Question 10...............................................................................................................................................10

Question 1
a. carbonic anhydrase; carbonic acid
b. macrophages; spleen
c. stem cells; differentiate
d. endothelial wall; diapedesis
e. agglutinogens ; AB
f. contraction(contractile cells); conduction (auto-rhythmic cells)
g. atrio-ventricular (AV); ventricular
h. end-systolic; decreased
i. Ca2+ , K+
j. decreases ; decreases
Question 2:
Addison’s disease is caused by the insufficiency of steroidal hormones such as cortisol and
aldosterone which are produced by the adrenal cortex. Aldosterone regulates salt-water balance
and blood pressure. It promotes re-absorption of Na+ ions and secretion of K+ions in the kidneys.
The re-absorption of sodium is accompanied by the re-absorption of water as well. This leads to
an increase in blood volume and blood pressure. Thus, a person with Addison’s disease is likely
to have high potassium levels, low sodium levels and low blood pressure.
Diabetes insipidus is caused by the insufficiency of ADH ( antidiuretic hormone) produced by
the hypothalamus . It can also be caused by the inability of the kidneys to respond to ADH. ADH
is stored in the pituitary gland. Whenever the concentration of the extracellular fluid increases,
the hypothalamus sends a message to the pituitary gland to release ADH. The hormone helps to

conserve water in the body by stimulating the kidneys to reabsorb water. Hence, it contributes to
an increase in blood pressure. ADH also causes constriction of the peripheral blood vessels, due
to which the arterial blood pressure increases. It is now evident that a person with diabetes
insipidus is likely to experience low blood pressure too.
Hence, a patient with both Addison’s disease and diabetes insipidus is likely to exhibit extreme
hypotension and inability to retain water in the body. The chances of dehydration and sudden
loss of consciousness are extremely high. The body of the patient is likely to have great difficulty
in maintaining normal blood pressure and salt-water balance.
Question 3
The path followed by the RBC from the anterior of the right tibia to the heart is given below:
Capillaries in the anterior region of the right tibia ----- post-capillary venule ------muscular
venule -----right anterior tibial vein ------right polipteal vein -----right femoral vein ------right
external iliac vein ------ right common iliac vein------inferior vena cava------right atrium.
The blood from the right atrium reaches the right ventricle through the tricuspid valve. The
right ventricle sends the blood through the pulmonary valve to the pulmonary artery and the
lungs. The blood in the pulmonary capillaries undergoes oxygenation. From here, the course of
the RBC is described below:
Pulmonary vein -----left atrium----left ventricle ------aorta----left subclavian artery---left axillary
artery ----arterioles---capillaries that supply the muscles of the right shoulder ---venules -----left
axillary vein---- left subclavian vein-----brachiocephalic vein-----superior vena cava.
The RBC once again enters the heart through the superior vena cava.
Question 4
T cell activation is essential for proper immune response. The presence of an antigen presenting
cell (APC) along with MHC prepares the T cell for action. However, a T cell gets activated
only through the process of co-stimulation. The first signal is the antigen recognition signal
during which the antigen in the T cell receptor is matched with the peptide complex on the MHC

that has attached itself to the APC. The second signal is generated by the interaction between co-
stimulatory molecules on the T cell and the APC.
After the process of maturation, T cells circulate throughout the body until they encounter an
APC with which its receptor matches. After maturation, T cells are identified as helper,
regulatory or cyto-toxic cells. However, after activation, T cells form a blast cell which
proliferates through the process of clonal expansion. The cells then differentiate to yield memory
T cells or effector T cells. The effector T cells expel the foreign substance while the memory
T cells help to protect against future attacks by the same antigen. In the event of a future
attack by the same antigen, the memory T cells proliferate and differentiate to release more
active T cells and memory T cells.
B lymphocyte cells are the part of adaptive immunity system because it is responsible for
antibody secretion process within whhite blood cells. B cells represents antigens through B cell
receptors and secrete cytokines. B cells are developed in hematopoietic stem cells and activated
in the secondary lymphoid organs. The B cell activation can be T cell dependent or independent.
In the T cell independent activation process of B cell, CD 21, 19 and 81 play vital role. This co
receptor complex enhances the activation efficiency of B cell. B cells are activated when a
specific antigen binds itself to the receptors on the surface of the B cell. Cytokines such as
interleukin-2 provide the second signal in the co-stimulation of the B cells. Following activation,
the B cells go through a process called clonal selection during which they proliferate and
differentiate to form plasma cells and memory cells. While the plasma cells produce antibodies,
the memory cells protect against future invasions by the same antigen. The differentiation of B
cells is placed in two separate processes. The first step is extrafollicular response which induces
class switching of immunoglobulins or antibodies. The second step consists of extensive B cell
proliferation and affinity maturation.
Question 5
Pharynx – (1) serves as a sound resonating chamber; contains tonsils; directs air inferiorly.
Larynx – (2) passes air from pharynx into windpipe; site of sound production.

Paranasal sinuses – (3) resonate sound; not part of pharynx.
Fauces – (4) opening from oral cavity into pharynx.
Tertiary bronchus – (5) carries air to a segment of a lung.
Terminal bronchiole – (6) carries air directly into a respiratory bronchiole.
Pleural membranes – (7) surround the lungs.
Surfactant – (8) reduces surface tension at sites of gas exchange.
Alveoli – (9) actual sites of gas exchange.
Eupnea – (10) normal, quiet breathing.
Costal breathing – (11) shallow breathing using just the external intercostal muscles
Compliance – (12) amount of effort required to expand the lungs and chest wall.
Inspiratory capacity – (13) tidal volume + inspiratory reserve volume, usually about 3600 mL in
males.
Vital capacity – (14) tidal volume + inspiratory reserve volume + expiratory reserve volume;
usually about 4800 mL in males.
Functional residual capacity – (15) residual volume + expiratory reserve volume, usually about
2400 mL in males.
Henry’s law – (16) states that the amount of gas that will disso.lve in a liquid is proportional to
the
partial pressure of that gas and its solubility.
Bohr effect – (17) when pH decreases, O2 saturation of hemoglobin decreases.
Dalton’s law – (18) each gas in a mixture of gases exerts its own partial pressure.
Medulla oblongata – (19) sets basic rhythm of breathing.

Pons – (20) includes the pontine respiratory group.
Question 6
Marinara sauce is a rich source of Vitamin A(13%), Vitamin C(3%) , Vitamin B6 (10%), and
minerals such as iron, calcium and magnesium. Carbohydrates and water are present in
significant amounts. Spaghetti is made out of wheat and is rich in complex carbohydrates. It
contains about 10% dietary fiber. Meatballs are a good source of protein , fats and VitaminB12.
Finally, oranges are citrus fruits with high Vitamin C content. Hence, orange juice contains
plenty of Vitamin C in addition to significant amounts of folate, potassium, water and citric acid.
In the mouth, the spaghetti is broken down into small pieces by the act of chewing. The saliva
provides a suitable liquid medium for the enzymes to act upon the food. The salivary amylase
that is secreted by the parotid glands breaks down starch in the spaghetti into the disaccharide
maltose, the trisaccharide maltotriose, and dextrins. The saliva also contains an enzyme called
lingual lipase that converts the triglycerides in the meatballs into partial triglycerides and free
fatty acids. The saliva functions as a lubricant to convert the food material into a soft mass
(bolus) that makes swallowing easier.
The food from the mouth enters the fundus of the stomach through the esophagus with the aid of
peristaltic contractions. The primary function of the fundus is to store food in the stomach. The
food remains in the fundus up to about one hour after its ingestion.
 The salivary amylase present in the food continues to break down the existing
polysaccharides.
 The parietal cells of the stomach secrete hydrochloric acid. The resulting low pH level
also activates the enzyme, pepsin that helps break down proteins.
 The parietal cells also secrete a glycoprotein called the intrinsic factor (IF) that plays a
crucial role in the absorption of the Vitamin B12 in the small intestine.
 The stomach digests the proteins in the meatballs but not the fats and carbohydrates in
the food. The acidic medium prevents the action of amylase.
 The hydrochloric acid starts the digestion of proteins by denaturing them.
 The action of pepsin then disintegrates the proteins into small peptide chains.

 The gastric lipase hydrolyses the remaining triglycerides into diglycerides,
monoglycerides and fatty acids.
The small intestine can absorb a huge amount of water. Stomach absorb very little amount of
water. The ileocecal valve and jejunum absorb most of the water and the residual water is
absorbed by the large intestine to make solid tools. Hydrostatic pressure and endocytosis play the
main role in water absorption through the small intestine. Absorption of water increases if the
water contains salts and minerals. Body absorbs only 59% of distil water but it absorbs 95% of
mineral water according to the articles. Electrolytes or salts mainly absorbs through small
intestine. Electrolyte absorption depends upon physical needs. In the small intestine, vitamins
and minerals are not digested but are absorbed by the finger-like projections called villi through
a variety of mechanisms – passive diffusion, facilitated diffusion and active diffusion. Water
soluble vitamins can directly enters into the cells through villi but fat soluble vitamins cannot
enter directly. Fat soluble vitamins get entry inside the bloodstream through lymph channels.
Sodium is absorbed through the process of co transport with amino acids and glucose. As a result
of the osmotic gradient produced by sodium, water enters the blood as well. After absorption
sodium salt creates electric gradient which encourage the absorption of chloride ions through
epithelial cells.
Question 7
a. Metabolism; catabolism
b . Reduction; oxidation
c. Nicotinamide adenine dinucleatide(NAD); redox
d. Adenosine triphosphate (ATP); oxidative phosphorylation
e. Glycolysis; gluconeogenesis
f. Lipoproteins; lipid triglycerides
g. Acetyl coenzyme A; cholesterol
h. Insulin; postabsorptive

i. Basal metabolic rate (BMR); vasodilation
j. Sodium; fluid
Question 8
Glomerular filtration is the ultrafiltration of the plasma of the blood. Components of the plasma
such as the water and the nitrogeneous wastes pass through the glomerular membrane into the
Bowman’s capsule. The serum proteins and cells that cannot pass through the membrane exit
throught the efferent arteriole.. The pressures that affect glomerular filtration are:
 The glomerular blood hydrostatic pressure (GBHP) is the pressure exerted by the
blood on the capillaries of the glomerulus. This is the pressure that aids the production of
glomerular filtrate by driving the plasma through the glomerular membrane. The value of
GBHP is usually 55mm of Hg.
 The capsular hydrostatic pressure (CHP) is the hydrostatic pressure exerted on the
glomerular filtrate in the opposite direction. This recoil of the Bowman’s capsule tends to
send the filtrate back into the glomerular capillaries. This pressure that opposes filtration
has an average value of 15 mm of Hg.
 The blood colloid osmotic pressure (BCOP) is the pressure that arises due to the
concentration gradient between the blood plasma and the glomerular filtrate. The proteins
such as albumin, fibrinogen and globulins that fail to pass through the barrier exert an
osmotic force that attempts to pull the water from the filtrate. Hence, BCOP opposes
filtration. The value of BCOP is generally 30 mm of Hg.
The net filtration pressure is hence GBHP-(CHP+BCOP) = 55 –(30+15) = 10 mm of Hg
An excess of any alcoholic drink such as beer can have a serious negative impact on the urinary
system.
 An excess of beer can lead to an abnormal thickening of the basement membrane of the
glomerulus. It can also lead to altered cell structure in the uriniferous tubules. Significant
nephromegaly ( kidney enlargement) is often observed in chronic alcoholics.

 Excessive beer leads to urinary flow within twenty minutes of its consumption. This
happens due to a reduction in the levels of ADH (anti-diuretic hormone). ADH increases
the concentration of urine and reduces the loss of water. A fall in ADH levels is
accompanied by an increase in the concentration of electrolytes in the blood. Hence,
people who consume a lot of beer tend to get dehydrated soon.
 Renal impairment due to excessive beer consumption can also lead to acid-base
imbalance in the body. This can have an adverse impact on metabolism.
Question 9
Acid-base homeostasis refers to the mechanisms which ensure that there is a balance
between the intake/production of H+ ions and their removal from the body. The acid-base
balance mechanisms maintain the pH level of the extracellular fluid in the limited range
between 7.32 and 7.42. The three mechanisms of acid-base balance are given below:
 Buffer mechanism : The chemical acid-base buffers prevent an abrupt change in the
concentration of hydrogen ions in the blood. The buffers do not actively provide H+ ions
or remove them from the body. The keep the hydrogen ions in reserve until the balance
is established. This mechanism operates in the body fluids. The most important
buffer mechanisms in the body are the protein, bicarbonate and phosphate buffer
systems.
 Respiratory mechanism: The respiratory system helps maintain a balance between acids
and bases in the body. An excess of CO2 in the blood leads to carbonic acid formation
and high H+ concentration. The depth and rate of respiration increases to expel more
CO2 and prevent a significant lowering of pH. Conversely, if the pH increases, the rate
and depth of breathing is reduced to retain more CO2 and increase H+ ion concentration.
This phenomenon takes place in the lungs.
 Renal mechanism : This process takes places in the kidneys and is the slowest
mechanism for the maintenance of acid-base balance. There are certain cells in the

kidney tubules that secrete H+ ions into the urine and reduce acidity in the blood. Re-
absorption and formation of bicarbonate ions by the tubular cells also prevent acidosis.
Question 10
 The site of maturation of the sperm is the epididymis.
 From the epididymis, sperms travel through the ductus deferens to the ampulla. Here,
the seminal vesicles add the bulk of the ejaculate matter in the form of a viscous
secretion that provides fructose to the sperm. This secretion also improves the motility
of the sperm.
 During ejaculation, the seminal fluid flows from the ampulla toward the urethra. It
receives a mildly acidic fluid from the prostrate that is rich in citric acid, Ca2+, Zn2+,
fibrinolysin and alkaline phosphatase. This secretion further improves the motility of the
sperm and prolongs its life.
 The bulbourethral glands (Cowper’s glands) secrete an alkaline lubricant that partially
neutralizes the acidic secretions from the vagina.
 The sperm are expelled from the body through the penis during sexual stimulation.
 Upon entering the female genital tract, the semen that is deposited first coagulates but
liquefies within about half an hour due to the action of the proteolytic enzymes secreted
by the prostrate. This coagulation prevents the sperm from being expelled from the
vagina.
 The cervical mucus contains mucin molecules that align themselves in parallel in
estrogen dominant conditions to facilitate the passage of the sperm.
 Organized movement of sperm is aided by chemo-attractants in the follicular liquid. The
sperm also attracted to certain chemical released by the ovum.
 Substances secreted by the female genital tract stimulate the removal of the plasma
membrane over the acrosome of the sperm.
 The capacitation of the sperm occurs during its journey through the Fallopian tube.
During the capacitation, the sperm morphology is altered and the zone pellucida

surrounding the secondary oocyte contains glycoproteins that activate the enzymes in the
acrosome. The site of the acrosomal reaction is the ampulla of the fallopian tube.