Bio 240W Final Exam

Describe the different steps of the signal transduction pathway

\-Environmental or developmental signal (can be internal or external)

\-Receptor (or sensor)

\-Signal transmission/transduction

\-Response (by an effector)

Distinguish between negative and positive feedback mechanisms

Positive feedback

\-Keeps a process going that has a cutoff point

\-does NOT maintain homeostasis

\-An effector (provides response or effect) continues to stimulate a sensor/receptor so that a greater change occurs in the internal environment

\
Negative feedback

\-Primary homeostatic mechanism

\-Keeps variable close to set point

Demonstrate how the hydrogen ion gradient across the thylakoid membrane is produced

As electrons move through the proteins that reside between PSII and PSI, they lose energy. This energy is used to move hydrogen atoms from the stromal side of the membrane to the thylakoid lumen.

\-will be used to synthesize ATP in a later step.

Explain how ATP is produced through photophosphorylation

light energy is used to pump protons across the thylakoid (mediated by flow of electrons through an electron transport chain) This stores energy in a proton gradient. As the protons flow back through an enzyme called ATP synthase, ATP is generated from ADP and inorganic phosphate.

Explain the importance of Rubisco in the carbon reactions/Calvin cycle

\-Carbon fixation is catalyzed by Rubisco

\-accounts for 50% of soluble protein in leaves

\-also catalyzes RuBP + O2 reaction

\-nitrogen source?

Describe the relationship between the light reactions and the carbon reactions/Calvin cycle

Outputs of one are used as the Inputs of the other

Describe the inputs and outputs for the carbon reactions/Calvin cycle

Inputs

\-ATP

\-NADPH

\-CO2

\
Outputs

\-ADP + P

\-NADP+

\-sugar (G3P for C3 plants)

If your **blood glucose levels drop**, the **negative feedback** response to maintain homeostasis would be...

convert glycogen into glucose

TRUE or FALSE

**Positive** feedback mechanisms help to **maintain homeostasis.**

FALSE

Use the following figure to answer this question. 

Which **wavelength of light** in the figure is most effective in **driving photosynthesis**?

420 nm

Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated.  He noted that the largest groups were found in the areas **illuminated by the red and blue light**.

**Which of the following statements describes a relationship that Engelmann's experiment helped to determine?**

\
A) the relationship between wavelength of light and the rate of aerobic respiration

B) the relationship between wavelength of light and the amount of heat released

C) the relationship between wavelength of light and the rate of photosynthesis

D) the relationship between carbon dioxide concentration and the rate of photosynthesis

 

C) the relationship between wavelength of light and the rate of photosynthesis

Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added **aerobic bacteria** and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas **illuminated by the red and blue light**.

**What did Engelmann conclude about the congregation of bacteria in the red and blue areas?**

  

A) Bacteria congregated in these areas due to an increase in the temperature of the red and blue light.

B) Bacteria congregated in these areas because these areas had the most oxygen being released.

C) Bacteria are attracted to red and blue light and thus these wavelengths are more reactive than other wavelengths.

D) Bacteria congregated in these areas due to an increase in the temperature caused by an increase in photosynthesis.

B) Bacteria congregated in these areas because these areas had the most oxygen being released.

A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be needed. **Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow.**

**What wavelengths of visible light are** ***absorbed*** **by this pigment?**

blue and violet

(anything but red and yellow)

What is the function of the **pigment molecules** in a **light-harvesting complex** in the thylakoid membranes?

They absorb and transfer light energy to the reaction-center chlorophyll.

What are the products of **cyclic electron flow** during the light reactions of photosynthesis?

ATP

Which of the following statements summarizes the **metabolic results of photorespiration**?

It produces carbon dioxide and consumes ATP and oxygen.

Discuss the role of ATP in energy transfer in the cell

\-allows the cell to store energy briefly and transport it within the cell to support endergonic chemical reactions.

\-Energy derived from glucose catabolism is used to convert ADP into ATP.

\-Two processes of ATP regeneration are substrate-level phosphorylation and oxidative phosphorylation through the process of chemiosmosis.

\-Energy must be infused into the system to regenerate ATP.

Describe how a proton (H+) gradient is established and maintained by the electron transport chain and used in the process of chemiosmosis

\-a series of redox reactions is used to pump hydrogen ions across the mitochondrial membrane.

\-The uneven distribution of H+ ions establishes both concentration and electrical gradients

\-hydrogen ions pass through the inner mitochondrial membrane by an integral membrane protein called ATP synthase.

\-the proton gradient is used for the addition of a phosphate to ADP, forming ATP

The mechanism of **photophosphorylation** is most similar to which of the following processes?

  

A) substrate-level phosphorylation in glycolysis  

B) oxidative phosphorylation in cellular respiration

C) the Calvin cycle

D) reduction of NADP+

B) oxidative phosphorylation in cellular respiration

In **photosynthetic cells**, synthesis of **ATP by chemiosmosis** occurs during ________. 

photosynthesis and respiration

Which of the following statements best **describes the relationship between photosynthesis and cellular respiration?**

  

A) Cellular respiration runs the biochemical pathways of photosynthesis in reverse.  

B) Photosynthesis stores energy in complex organic molecules; cellular respiration releases energy from complex organic molecules.

 C) Photosynthesis occurs only in plants; cellular respiration occurs only in animals.

D) Photosynthesis is catabolic; cellular respiration is anabolic.

B) Photosynthesis stores energy in complex organic molecules; cellular respiration releases energy from complex organic molecules.

In **mitochondria**, an **electron transport chain** pumps protons from the **matrix into the intermembrane space**, whereas in **chloroplasts**, an **electron transport chain** pumps protons from the ________. 

stroma to the thylakoid space

The **oxygen consumed during cellular respiration** is directly involved in which of the following processes or events?

  

A) glycolysis

B) accepting electrons at the end of the electron transport chain

C) the citric acid cycle

 D) the oxidation of pyruvate to acetyl CoA

B) accepting electrons at the end of the electron transport chain

In **glycolysis**, for **each molecule** of glucose oxidized to pyruvate, ________. 

two molecules of ATP are used and four molecules of ATP are produced

Which one of the following is formed by **the removal of a carbon (as CO2) from a molecule of pyruvate and sent to the mitochondria to start the Krebs/citric acid cycle**?

  

A) acetyl CoA

B) ATP

C) citrate

D) water

A) acetyl CoA

Where does **glycolysis** occur in plant and animals cells?

cytoplasm

Even though plants cells carry out photosynthesis, they still use their **mitochondria** for oxidation of pyruvate. **Under what conditions will plant cell mitochondria be active in this process?**

 

in all cells, with or without light

Approximately how many molecules of ATP are produced from the **complete oxidation of one molecule of glucose** (C6H12O6) in aerobic cellular respiration?

30-32

Discuss the ways in which carbohydrate metabolic pathways, glycolysis, and the citric acid cycle interrelate with protein and lipid metabolic pathways

Describe the absorptive state and the major events associated with this state

* called the fed state and lasts about 4 hours after eating
* anabolism exceeds catabolism
* excess nutrients stored as fats and sometimes carbs
* glucose → glycogen for storage
* triglycerides are used for energy by adipose tissue, the liver, and skeletal and cardiac muscles
* triglycerides → glycerol and fatty acids → triglycerides for storage
* removal of the amino group produces keto acids- energy in the citric acid cycle
* amino acids → fat in the liver
* amino acids are used for protein synthesis
* absorptive state controlled by insulin

Describe the post-absorptive state, and the major events associated with this state

* fasting state
* gi tract is empty, energy sources are supplied by the breakdown of body reserves
* catabolism exceeds anabolism
* maintains blood glucose
* glucose sparing
* proteins → amino acids
* glycogen → glucose
* triglycerides → glycerol and fatty acids
* sympathetic nervous system- controlled by several hormones (more complex)

Discuss homeostatic imbalances (diabetes mellitus is an example)

Type 1

* inadequate insulin production

Type 2

* abnormal insulin receptors

\
both result in

* proteins and fats are used for energy
* unavailability of glucose to most body cells
* excessively high blood glucose levels (hyperglycemia)
* glucose loss in urine
* can lead to metabolic acidosis, protein wasting, weight loss
* may lead to coma and death

Why isn’t it sufficient to reduce only dietary fat intake to prevent new fatty deposits from forming in the body?

Acetyl CoA is a starting point for fatty acid synthesis.

TRUE OR FALSE.  The preferred energy fuel for the brain is fat.

FALSE

TRUE OR FALSE.  Carbohydrate and fat pools are oxidized directly to produce cellular energy, but amino acid pools must first be converted to a carbohydrate intermediate before being sent through cellular respiration pathways.

TRUE

When proteins undergo deamination (removal of amino group), the waste substance found in the urine is mostly ________.

urea

Glycogen is formed in the liver during the ________

absorptive state

Lipogenesis occurs when ________.

cellular ATP and glucose levels are high

Which of the following statements is FALSE?

A) The amino acid pool is the body's total supply of amino acids in the body's proteins.

B) Fats and carbohydrates are oxidized directly to produce cellular energy.

C) Amino acids can be used to supply energy only after being converted to a citric acid cycle intermediate.

D) Excess carbohydrate and fat can be stored as such, whereas excess amino acids are oxidized for energy or converted to fat or glycogen for storage.

A) The amino acid pool is the body's total supply of amino acids in the body's proteins.

If you were to jog one kilometer a few hours after lunch, which stored fuel would you probably tap?

liver glycogen and muscle glycogen

A fasting animal whose energy needs exceed those provided in its diet will draw on its stored resources in which order?

liver glycogen, then muscle glycogen, then fat

Humans store glucose in the form of ________________; plants store glucose in the form of ________________.

glycogen; starch

Which of the following glucose storage forms is the most difficult for human digestive systems to break down?

A) glycogen

B) cellulose

C) starch

D) triglycerides

 

B) cellulose

Explain how contraction and relaxation of the chambers of the heart create pressure gradients and how these gradients cause the flow of blood in relation to anatomy

1. All chambers in diastole

– Blood flows passively through atria and into ventricles

– Both AV valves open

– Note both atria and ventricles fill with blood

– But not all blood leaves atria


2. Atrial systole

– Ventricles (still in diastole) swell with extra blood that has been pumped in by atria


3. Ventricular systole (atrial diastole)

– Right and left AV valves pushed shut

– Blood forced into arteries through pulmonary and aortic semilunar valves

– ventricles contract from the bottom up


4. Now back to all chambers in diastole

– as ventricles enter diastole, a little blood sucked back in

– however right and left semilunar valves snap shut

Analyze how the major regions of an EKG correlate with the conduction system function and contraction (i.e., P wave = SA node excitement and atrial depolarization)

P wave- SA node excitement and atrial depolarization

PR segment- atrial depolarization is complete, the impulse is delayed at the AV node

QRS complex- ventricular depolarization, atrial repolarization

ST segment- ventricular depolarization is complete

T wave- ventricular repolarization begins at the apex

after the T wave- ventricular repolarization is complete

Describe the afferent signals to the brain, including three types of receptors, and how they affect heart rate

Propriocenters- sensory input from muscles and tendons

* informs the brain on changes in physical activity

Baroreceptors- sensory input from blood vessels

* informs the brain on changes to pressure in vessels

Chemoreceptors- sensory input from blood vessels

* informs the brain on changes in carbon dioxide or oxygen levels in the blood
* important in respiratory system but has some affect on heart rate

Compare and contrast the efferent responses that affect heart rate and how they alter the SA node activity including the neurotransmitters associated with these responses

Sympathetic system

* cardioacceleratory system- increased heart rate
* Postganglionic neuron secretes norepinephrine (NE)
* Adrenergic receptors on cells of the SA node bind to NE
* Cause an increased rate of action potentials of SA node
* Maximum heart rate is 230 beats/minute
* Limit of SA node excitation

Parasympathetic system

* cardioinhibitory system- decreased heart rate
* Postganglionic neuron secretes acetylcholine (ACh)
* Cholinergic receptors on cells of the SA node bind ACh
* Allow potassium to leave the cell → hyperpolarizing reaction
* The rate of action potentials decrease
* Normal heart rate is about 75 beats/minute
* Without nervous control, the heart rate would be about 100 beats/minute

Describe the roles of the sympathetic and parasympathetic nervous systems in controlling heart rate

Sympathetic

* blood pressure is too low
* visceral motor neurons cause
* increase heart rate by activating cardioacceleratory neurons
* vasoconstriction which is the constriction of blood vessels regulated by the sympathetic release of norepinephrine or epinephrine

Parasympathetic

* blood pressure is too high
* visceral motor neurons cause
* decrease heart rate by activation of cardioinhibitory neurons
* vasodilation which is the dilation of blood vessels due to a decrease in norepinephrine

If the **right AV valve does not close completely** and **allows blood to pass through when it should be shut**, then you could expect:

the output of the right ventricle to be decreased.

The **semilunar valves** prevent blood from **flowing backwards into** the...

ventricles

Normal heart sounds are caused by which of the following events?

closing of the heart valves

Without SA node activity, what type of heart surgery would be indicated?

inserting an artificial pacemaker

Which of the following develops the greatest pressure on the blood in the aorta?

\
A) systole of the left atrium

B) diastole of the right ventricle

C) systole of the left ventricle

D) diastole of the right atrium

C) systole of the left ventricle

Among the following choices, which organism likely has the highest systolic pressure?

\
A) mouse

B) human

C) hippopotamus

D) giraffe

D) giraffe

TRUE or FALSE

The heart muscle (myocardium) receives its nutrients from the blood moving through the left atrium and ventricle.

FALSE

TRUE or FALSE

The left side of the heart pumps the same volume of blood as the right.

TRUE

The atrioventricular (AV) valves are closed ________.

when the ventricles are in systole

During exercise, which of the following would occur on an electrocardiogram (ECG/EKG) compared to an individual at rest?

\
A) the T wave would decrease

B) the P-R interval would decrease

C) the time from one R to the R of the next heartbeat would decrease

D) the S-T segment would decrease

C) the time from one R to the R of the next heartbeat would decrease

Explain how oxygen and carbon dioxide are transported in the blood

Oxygen transport

\-98% bound to hemoglobin in red blood cells

\-2% dissolved in blood plasma

\-high pressure in alveoli, low in body cells, so oxygen goes into body cells

\
CO2 transport

\-10% dissolved in blood plasma

\-20% bound to hemoglobin

\-70% in the form of Plasma bicarbonate

* More important in determining the respiratory rate

\-high pressure in body cells, lower in alveoli, so co2 goes into alveoli

Describe the factors that affect oxygen loading and unloading from hemoglobin

O2 pressure

\-O2 saturation increases as the partial pressure of O2 increases

\-starts to level off and plateau as partial pressure of O2 increases

\
pH differences

\-hemoglobin retains less O2 at lower pH

\-lower pH has a higher CO2 concentration

Analyze how changes in carbon dioxide levels alter pH (based on protons and the carbonic acid equation)

\-CO2 increase, decreases pH by increasing H+ ions

\-CO2 decrease, increases pH by decreasing H+ ions

Explain how the respiratory system works with the cardiovascular system to help regulate pH

\-When the pH is too low, the chemoreceptors signal the respiratory system to increase ventilation and remove carbon dioxide.

\-The chemoreceptors initiate the contraction of the diaphragm and intercostal muscles.

\-High pH leads to a decrease in breathing rate

Contraction of the **intercostal muscles** causes which of the following to occur?

 

A) The diaphragm moves downward.

B) The rib cage is compressed.

C) The thoracic cavity volume decreases.

D) The ribs and sternum move upward.

D) The ribs and sternum move upward.

If the **pH of the blood has decreased**, this means that the ________.

amount of carbon dioxide has increased

During most daily activities, the human **respiration rate** is most closely **linked to the blood levels** of ________.

carbon dioxide

Which of the following events would you predict as **carbon dioxide** is released **from your muscles into the surrounding capillary bed?**

Oxygen delivery to muscle is increased when more carbon dioxide is produced by the muscle.

The partial pressure of carbon dioxide is 45 mm Hg in the **blood** and 40 mm Hg in the **alveoli**.

* **What happens to the carbon dioxide?**

It diffuses into the alveoli.

**Oxygen** saturation (loading/unloading) of **hemoglobin** depends on...

Oxygen pressure differences in the tissues and pH differences in the blood

Define water potential and explain how it is influenced by solutes

* Water potential is the water’s capacity to perform work.
* Water flows from regions of higher water potential to regions of lower water potential
* Adding solute causes water to diffuse to the place with the solute
* Adding positive pressure causes the water to move away from the pressure
* Adding negative pressure causes the water to move toward the pressure
* Overall, water moves from an area of high water potential to low water potential

Describe how water potential, evapotranspiration, and stomatal regulation influence how water is transported in plants

* Evapotranspiration- the loss of water from the plant through evaporation at the leaf surface
* Creates a negative pressure at the leaf surface (water potential)
* Pulls water from the roots up towards the leaf
* Happens during the day when the stomata are open, at night the stomata close and transpiration stops.
* Stomata are open when there is a K+ influx, closed when the K+ is moving out

Plants do not have a circulatory system like that of some animals. If a water molecule in a plant did "circulate" **it would require…**

both the xylem and the phloem

Plants need to **control stomatal opening** primarily so they can…

prevent water from leaving the plant cell.

**Most of the water** taken up by a plant is...

lost through transpiration.

The **opening** of stomata is thought to involve...

movement of K+ into the guard cells.

For sucrose to be moved from a leaf (source) cell to a root (sink) cell, **sucrose is first actively transported into the phloem** from the source cell. **What happens next?**

Water diffuses from the xylem to the phloem.

Discuss the role of the autonomic nervous system in regulation of body systems

regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal.

The **sensory (afferent) and motor (efferent)** divisions are part of the...

peripheral nervous system

The region of the neuron that carries **the nerve impulse away from the cell body** is called the...

axon

For a neuron at **resting membrane potential**…

\
A) a higher concentration of potassium ions is found outside the membrane

B) a higher concentration of potassium ions is found inside the membrane

C) a higher concentration of sodium ions is found inside the membrane

D) the inside of the membrane is positive relative to the outside of the membrane

B) a higher concentration of potassium ions is found inside the membrane

The **"threshold" potential** of a membrane is the…

minimum depolarization needed to operate the voltage-gated sodium and potassium channels.

Why does **hyperpolarization of the neuron membrane** occur?

The potassium channels close more slowly, allowing more potassium to flow from inside to outside the membrane.

If you wanted to **inhibit a signal from propagating along the axon**, which of the following **ion channels would you want to ONLY open**?

potassium

The following steps refer to various stages in **transmission of the signal at a chemical synapse.**


1. Neurotransmitter binds with receptors associated with the postsynaptic membrane.
2. Calcium ions rush into neuron's cytoplasm.
3. An action potential depolarizes the membrane of the presynaptic axon terminal.
4. The ligand-gated ion channels open.
5. The synaptic vesicles release neurotransmitter into the synaptic cleft.

3 → 2 → 5 → 1 → 4

Which **cardio center in the brain** is paired with the correct division of the **autonomic nervous system transmitting that signal to the heart**?

\
A) cardioacceleratory center : parasympathetic system

B) cardioacceleratory center : sympathetic system

C) cardioinhibitory center : sympathetic system

B) cardioacceleratory center : sympathetic system

Describe the importance of aquaporins in the plasma membrane

* Integral membrane proteins that form water-selective channels across membrane
* Accounts for observed higher rates of water movement than diffusion alone

Describe how osmosis is used in regulating stomatal opening

* Changes in turgor pressure inflate or deflate guard cells, changing the stoma size
* Guard cell turgor pressure is controlled by the regulation of K+ movement
* Stomata Open
* K+ influx
* Water follows
* Increase Turgor pressure
* Stomata Close
* K+ efflux
* Water follows
* Decrease Turgor pressure

Analyze how changes to the function of the nephron loop may disrupt water conservation

Descending limb is only permeable to water

* Osmolarity of medulla increases moving away from cortex
* Water moves via osmosis through aquaporins and is reabsorbed into the blood concentrating the filtrate in nephron

\
Ascending limb is only permeable to ions (primarily Na+ and Cl-)

* In thin segment, NaCl, which had become concentrated in descending limb, diffuses out of nephron (helps maintain high osmotic concentration)
* In thick segment, NaCl is actively transported out and filtrate becomes more dilute

Explain how the nephron and respiratory system works together to help balance blood pH

The Distal convoluted tubule (DCT)

* Important site of proton (H+) reabsorption or secretion

\
* Lungs can rid the body of excess acid very rapidly (seconds to minutes) through the conversion of HCO3– into CO2, which is then exhaled
* Rapid but has limited capacity in a significant acid challenge
* Kidneys can rid the body of both acid and base.
* Renal capacity is large but slow (minutes to hours). The cells of the DCT actively secrete H+ into the forming urine as Na+ is reabsorbed.
* The body rids itself of excess H+ and raises blood pH.

List the four hormones that affect renal function

– directly effected by ADH and aldosterone

– indirectly effected by renin and angiotensin

Describe where each hormone is produced, its target tissue and ultimate physiological effect

Renin

* Macula densa cells detect the dilute filtrate
* trigger JG cells to release renin from the kidneys

Angiotensin

* Renin activates a protein called angiotensinogen in blood which is a precursor to angiotensin I.
* Angiotensin I is activated to angiotensin II by ACE, primarily in the lungs
* Angiotensin II results in increased blood pressure via vasoconstriction and thirst
* released by liver

Aldosterone

* angiotensin II triggers the release of aldosterone
* stimulates reabsorption of sodium ions in the DCT and collecting duct
* water follows because of osmosis, more water in blood increases pressure
* released by adrenal glands

ADH

* is triggered by water moving into the blood and increasing pressure.
* ADH leads to more water reabsorption in the kidneys
* released by pituitary gland

Plants may move Na+ into their cells to reduce the water potential and allow water to move from the soil into the cells.  But too much Na+ can be toxic.  **Which of the following is NOT a process for plants to deal with high levels of Na+?**

\
A) compartmentalization of Na+ in vacuoles

B) excretion of Na+ though salt glands

C) disrupting cell membranes

D) reduction of Na+ influx into the cell

 

C) disrupting cell membranes

There is a **build-up of carbon dioxide** in the blood (respiratory acidosis).  **What will occur in the distal convoluted tubule (DCT) of the nephron to negate the acidosis?**

Secretion of more protons

If the **DCT is unable to secrete protons** in the situation described in Q1, **what will happen to the respiratory rate?**

The respiratory rate will increase.

Alcohol **blocks the production of antidiuretic hormone (ADH)** from the hypothalamus.  **When you drink alcohol, what happens?**

More water is eliminated in the urine and you become dehydrated.

 

Why is **water reabsorption** in the **descending limb of the nephron** and the **collecting duct passive**?

There is more NaCl in the surrounding tissue compared to the nephron.

In this example in this figure, Net Filtration Pressure (NFP) is 10mm Hg **toward** the nephron (out of the blood).

**What would happen if Blood Hydrostatic Pressure (BHP) changed to 45mm Hg and the other pressures remained constant?**

 

Filtration would stop

What effect would you expect the drug furosemide, which **blocks transport of Na+ and Cl– in the ascending limb of the loop of Henle, to have on urine volume?**

 

increase urine volume

Which part of the nephron helps to **regulate the pH of the blood?**

Distal Convoluted Tubule (DCT)

Which of the following actions **requires energy**?

  

A) Transport of the filtrate through the nephron.

B) Transport of water into the medulla.

C) Transport of sodium chloride into the nephron loop.

D) Transport of sodium chloride into the medulla.

 

D) Transport of sodium chloride into the medulla.

What is the main result of the **"salty medulla"** created by the nephron loop?

Reabsorption of water in the descending limb of the nephron