Practice Exam Questions DIAGRAMS
Write the appropriate term or process that is correct for the corresponding diagram.
1. Y pyrimidine
X purine
2. X follicle
3. X CORPUS CALLOSUM
4. V afferent arteriole
W glomerulus
X proximal tubule
Y distal tubule
Z collecting duct
5. View the image on the right. The arrow shows the direction of
movement. This process describes endocytosis
6. Z renal medulla
X renal artery
W renal cortex
7. A anticodon
8. The image to the left shows the process of transcription
9. Y cerebral cortex
W hypothalamus
Z cerebellum
10.
X nodes of Ranvier
Y myelin sheath
SHORT ANSWER
Please answer the following questions using COMPLETE SENTENCES and paragraphs where appropriate. You may use
diagrams to aid your answers where applicable.
1. Describe the differences between passive and active transport and use examples to support your answer. [6]
• Passive transport = movement of ions and other molecular substances across a cell membrane in the direction
of/along the concentration gradient
à Without the need of energy à concentration gradient as the “driving force”
à Simple diffusion = movement of hydrophobic/non-polar and small polar molecules from high to low
à facilitated diffusion = movement of larger polar/charged molecules and ions using a transport protein
(carrier/channel)à osmosis = movement of water using a specific channel protein
• Active transport = movement across a cell membrane from a region of low to high concentration à need energy
à use of transporter proteins
à primary transport = using ATP as the driving force to move molecules/ions against their concentration
gradient (i.e. Na+/K+ ion pump)
à secondary transport = using the electrochemical gradient created by the primary pump as the “driving force”
to move an ion down/along its gradient, coupled with the movement of another molecule/ion against its gradient
(i.e. Na+/glucose pump)
2. Describe the components that make up the fluid mosaic model. Why is this name appropriate and what purpose do
these different components serve in the overall function of the cell membrane? [6]
• fluid mosaic model is appropriate because it can explain observations of the structure/function of membranes
• fluid … the way lipids and proteins behave in a membrane à molecules are free to move/cell membrane must
be “fluid” to function properly (flexible)
à phospholipid bilayer = phospholipids are fluid that move laterally; hydrophobic/hydrophilic
components that allow the membrane to be selectively permeable (regulates what enters/exits cell)
à cholesterol = maintains fluidity; acts as a temperature buffer (keeps the membrane from
solidifying/keeps the membrane from being total “liquid”/falling apart)
• mosaic … of proteins/lipids/carbohydrates/etc.
à carbohydrates (glycoproteins/glycolipids) = involved in signaling, serve as attachment sites,
identification …
à proteins
- integral proteins = embedded in the bilayer/involved in transport ...
- peripheral proteins = bound to the inner or outer surface of the membrane/involved in cell
identification, enzymatic activity, cytoskeleton (structural) …
3. Describe how humans maintain a relatively stable body temperature using a negative feedback system. Be sure to
identify stimulus, set point, integrator, and effector in relation to body temperature. You may use a diagram if you wish
to aid your answer. [6]
• Negative feedback = response which acts to decrease or counteract change
• Stimulus = change in body temperature (increase or decrease)
• Sensor = detects the stimuli
• Set point = the optimal/ideal body temperature which is used to determine if a response is needed (37oC)
• Integrator = the control center which compares the change detected by the sensor to the set point to
determine if a response is required (hypothalamus)
• Effector = produces a response to counteract/decrease the change
• Heat response
o Sweating = sweat glands activated; secrete sweat (perspiration) which carries heat; release heat via
vaporization
o Vasodilation = skin blood vessels dilate; increase blood flow; heat radiates from skin surface
• Cold response
o Constriction = skin blood vessels constrict; blood is diverted from vessels and into the body;
minimize heat loss from skin
o Shivering = skeletal muscles activate when more heat must be generated
4. Describe the effect of ADH on the body. Name 2 things that inhibit the action of ADH. You may use a diagram if you
wish to aid your answer. [4]
• Antidiuretic hormone (ADH) = synthesized in the hypothalamus and stored in the posterior pituitary gland;
targets the nephron to increase water reabsorption (in the collecting duct)
• Alcohol and caffeine inhibit the action of ADH
o Decrease water reabsorption and increases urine output
5. Describe how blood sugar levels are regulated. [4]
• Level of blood sugar (glucose) is regulated by the pancreas (islets of Langerhans)
o Makes two hormones = insulin (beta-cells) and glucagon (alpha-cells)
• Insulin = released when blood glucose is high à to decrease blood glucose
o Stimulates glycogen formation (energy storage) in the liver
o Stimulates glucose uptake from blood into tissue cells
• Glucagon = released when blood glucose is low à to increase blood glucose
o Stimulates glycogen breakdown into glucose in the liver
6. What is the reflex arc? Briefly summarize the main events that occur in the reflex arc. You may use a diagram if you
wish to aid your answer. [4]
• Reflex arc = The nerve pathway that controls a reflex action; simplest type of neural circuit
o Most sensory neurons do not pass directly into the brain, but instead synapses in the spinal cord
o Allows for faster reflex actions to occur by using only the spinal cord of the CNS (no delay)
• Receptor = detects stimulus
• Sensory (afferent) neuron = nerve impulse is carried from the receptor to the CNS (spinal cord)
• Interneuron (integration center)
• Motor (efferent) neuron = carries the impulse from the interneuron to the effector
• Effector = muscle/organ that produces a response
7. Describe the 3 phases of the action potential. Be sure to identify the membrane potential during each phase and indicate
what is happening with the voltage gated ion channels. [6]
• Initially, at resting potential = positive Na+ ions outside the membrane; K+ ions inside (-70 mV)
1) Depolarization = if threshold is reached (-55 mV), voltage-gated Na+ channels open and allow Na+ to
enter the cell à membrane potential becomes more positive (increases)
2) Repolarization = at +30 mV, Na+ channels are closed; K+ channels are open and allow K+ to exit the
cell
3) Hyperpolarization = whereas Na+ channels open and close very quickly; K+ channels close very slowly
à go below the threshold level à K+ channels are closed at -80 mV
• Na+/K+ pump brings the membrane back to resting membrane potential (RMP) = 3 Na+ out/2 K+ in
8. Which part of the nervous system is most active during a stressful situation? Describe 3 changes that occur in the body
as a result [4]
• Peripheral nervous system à The autonomic system à sympathetic system is most active
• “fight or flight”; sympathetic is involved in stress response (positive feedback)
• The body may respond …
o Pupils dilate
o Increases heart rate
o Increase blood pressure
o Breathing accelerates
o Blood sugar is released from the liver (breakdown of glycogen)
9. Describe the story of a menstrual flow from day 1 to day 28. You may use diagrams to aid your answer. Use key
hormones and concepts involved with the process. [5]
• Flow phase (day 1-5)
o Cycle restarts; endometrium lining in the uterus is shed (menstruation)
o FSH begins to be released à follicle growth
• Follicular phase (day 6-13)
o Follicle-stimulating hormone (FSH) increases à developing egg releases estrogen
o Endometrium lining grows and thickens in the uterus
• Ovulation (day 14)
o Estrogen reaches optimal level à positive feedback à spike in luteinizing hormone (LH) =
ovulation à egg is released from the ovaries into the fallopian tubes
o Remaining follicle forms corpus luteum
o Endometrium lining continues to thicken
• Luteal phase (day 15-28)
o Corpus luteum grows and releases progesterone and estrogen à inhibits FSH and LH
o Prevents ovulation and contraction of uterus
o Endometrium lining is maintained; near the end of the cycle, if implantation does not occur, the
corpus luteum degenerates and the endometrium lining begins to break down
10. Describe the process of DNA replication from start to finish. Make sure to include all enzymes and proteins involved
[6]
• Helicase = unwinds the parental double helix (DNA)
• Topoisomerase = located in front of helicase à relieves tension on the double stranded DNA
• SINGLE-STRAND binding proteins (SSBP) = stabilize the unwound parental DNA; prevent annealing
• Leading strand = synthesized continuously in the 5’ à 3’ direction towards the replication fork
o RNA primase creates an RNA primer
o DNA polymerase III begins at the RNA primer and begins to read the template strand 3’ à 5’ o DNA polymerase I = replaces the RNA primer with DNA
o Ligase = seals the strand (phosphodiester bond)
• Lagging strand
o Synthesized discontinuously because DNA is anti-parallel à away from the replication fork
o Slower because requires multiple steps compared to the leading strand
o RNA primase must continue to lay down RNA primers
o DNA polymerase III will create short strands of DNA (Okazaki fragments) from the RNA primers
o DNA polymerase I must replace many RNA primers with DNA
o Ligase must seal the complementary strand in multiple locations
• Repair
o DNA polymerase III will check as it replicates the strand à if it makes a mistake; go back, replace,
continue
o DNA polymerase II = will scan the strand for base-pair errors; if it finds a mistake, will cleave out a
section of the strand, replace it with the correct bases à ligase will seal the strand
11. Describe the process of protein synthesis from start to finish. You may use diagrams to aid your answer if needed.
Make sure to include the important key terms and components involved [8]
• Transcription (nucleus) o Initiation = RNA polymerase will bind to the promoter region by recognizing a TATA sequence
(TATA box) o Elongation = RNA polymerase will begin to unwind the double-stranded DNA and transcribe an
mRNA transcript from the template DNA o Termination = RNA polymerase will detach once it reaches a termination sequence and mRNA will
be released à precursor mRNA (pre-mRNA) • Post-transcriptional modifications = Pre-mRNA must be modified before leaving the nucleus (increase
mRNA stability; protect from enzymes outside the nucleus) = pre-mRNA à mature mRNA o Splicing = introns (non-coding regions) are spliced out by spliceosomes o Capping = capping enzymes will add a 5’ cap o Tailing = poly-A polymerase will add a tail of adenosine nucleotides (Poly-A tail)
• Translation (cytoplasm) o Initiation = small ribosomal subunit binds to the 5’ cap region of the mRNA transcript and begins to
scan the mRNA à once it recognizes a start codon (AUG); the appropriate tRNA (Met) will bind and the large ribosomal subunit will bind to create the ribosome complex
o Elongation = amino acids are brought to the mRNA A-site by tRNAs and are added one by one to the growing polypeptide chain
§ The growing polypeptide chain is attached to the A-site and cleaved from the P-site § The ribosome moves over (tRNA in A site is now in P site) § tRNA in P site is now in E site with no amino acid à released (exits ribosome)
o Termination = a stop codon in the mRNA is reached à protein release factor (prf) enters the A site and the translational complex comes apart to release a completed polypeptide chain
