What happens to the catalytic activity of pepsin as chyme moves from stomach into small intestine? Why?
It decreases in response to change in pH.
Which of the following is the best explanation for why pancreatic enzymes are secreted in zymogen form?
D. Pancreatic cells are not as easily replaced as intestinal epithelium
What activates pepsinogen to pepsin?
Low pH
In humans, where does most chemical digestion of food occur?
In the duodenum
Is DNA a protein?
NO. It's a nucleic acid.
What is the impact of heat-killing bacteria on the coat?
The degradation of the polysaccharide coat
A colony of smooth strain bacteria is grown on a culture containing an experimental drug that cleaves nucleic acid base sequences whenever adenine is paired with uracil. Which of the following processes will be directly affected?
Transcription, Translation, or Transformation?
Transcription & Translation.
Both require mRNA, which require uracil. However, during transformation, DNA is transferred from one bacteria to another. Since DNA contains no uracil, the drug would have no effect on this process.
What was the key to transformation in Griffin's experiment?
That the rough strain could reproduce, because it WASN'T heat-killed.
How does one get "acquired immunity"?
Via a vaccine
What types of cells can bacterial cells transform?
Only bacterial! Not plant or animal cells.
Which of the following conditions increases the affinity of hemoglobin for oxygen?
I. Increased H+ concentration in blood
II. Increased CO2 concentration in blood
III. Increased O2 concentration in alveolar capillaries.
only III.
I & II would decrease hemoglobin's affinity for oxygen.
What decreases affinity of hemoglobin for oxygen? (3)
1) Low pH
2) High CO2
3) Releasing oxygen from one of the heme subunits
What is the Bohr effect?
Affinity of hemoglobin for oxygen decreases under acidic conditions.
Glucagon release is stimulated by excess amino acids in the blood. This leads to:
C. increased gluconeogenesis.
What would cause glycogenesis? (Formation of glycogen)
Insulin
The role played by tropomyosin in skeletal muscle contraction is most similar to what?
A repressor.
Background: skeletal muscle fibers are comprised of smaller units of contraction known as sarcomeres..
Each sarcomere has thick & thin filaments. Thick filaments - myosin protein molecules wrapped around each other w/ head of each indiv myosin molecule turning outward from filament. Thin filament - made of actin filaments, which are associated with 2 other proteins: tropomyosin & troponin. The actin filaments have myosin binding sites.
What is tropomyosin's role in muscle contraction and relaxation?
Tropomyosin physically inhibits muscle contraction until Ca2+ binds to troponin.
Tropomyosin molecules cover myosin-binding sites on actin, until Ca2+ binds to troponin molecules on thin filaments, causing tropomyosin to shift, exposing myosin-binding sites on the actin.
What protein causes skeletal muscle contraction? Where?
Myosin's binding to myosin-binding sites on the actin filament.
What is the catalyst in sarcomere contraction?
ATPase
What is the inducer in sarcomere contraction?
Ca2+.
Which would have a higher boiling point: a carboxylic acid or an alcohol? Why?
A carboxylic acid, because it can h-bond at 2 different sites.
Cerebellum:
- receives signals from? (2)
- function?
Receives signals from motor cortex & peripheral position sensors.
Function: to allow unconscious coordinated motion of skeletal muscles.
Assuming a patient has MS plaques limited to the brain, which of the following functions would not be affected? Why?
A. Eye muscle control
B. Reasoning ability
C. Sense of touch in arms
D. Knee jerk reflex
Only D.
Because knee jerk reflex is a very simple nervous loop that goes from the patellar tendon to the spinal cord and back with only one synapse in the spinal cord!
Why is it possible for fetus to obtain enough oxygen when blood entering fetus has a partial pressure of only 20 mmHg?
Fetal lungs are not functional prior to birth.
Until born, obtains oxygen from mother across placenta (which serves as fetus' lungs & only link to external world)
Why does oxygen enter fetal blood?
Because oxygen concentration in mother's blood is higher than that of the fetus.
What are three explanations for how a fetus can get enough oxygen when blood entering fetus has low partial pressure of oxygen?
1) Fetal hemoglobin has a greater affinity for oxygen than does maternal hemoglobin
2) At low PO2, fetal hemoglobin can carry 20-30% more oxygen than can maternal hemoglobin.
3) Concentration of hemoglobin in fetal blood is 50% higher than that of maternal blood.
How will an increasingly rigid ring system affect the ability of the compound to undergo SN1? Why?
It will decrease reactivity of the compound by decreasing planar carbocation formation.
What inhibits GnRH (gonadotropin-releasing hormone)
High levels of estrogen & progesterone
How does sickle cell anemia affect white blood cells?
It doesn't, unlike aplastic anemia.
Why would you see decreased oxygen carrying capacity in anemia?
Because anemia is defined as deficiency in RBCs, which means less oxygen carrying in body, because RBCs are oxygen carrying components of the body.
Which of these are true about RBCs?
A. They cannot synthesize ATP
B. They are incapable of cell division
C. They don't have mitochondria
D. They are derived from the same original type of cells as white blood cells.
B, C, and D.
RBCs are produced from differentiation of stem cells that undergo mitotic division - not other RBCs.
RBCs are just cellular bags of hemoglobin - not many organelles.
How does somebody store a ton of energy without adding a lot of extra weight?
Via TAGs instead of glycogen
Why, after several weeks of starvation, is acetyl CoA is used almost exclusively to produce ketone bodies?
Because gluconeogenesis depletes supply of oxaloacetate, which is essential for the entry of acetyl CoA into Krebs Cycle, so acetyl CoA can only be used for ketone bodies.
Why does brain use glucose rather than FAs as its major metabolic fuel during the early stages of starvation?
Because glucose can cross the blood-brain barrier via specific varrier molecules, while fatty acids can't.
What are the only types of substances that can enter the brain?
(1) hydrophobic substances that dissolve through plasma membrane
(2) have a specific carrier molecule on epithelial cell surface that will transport hydrophilic substsance across plasma membrane.
In terms of sterics, which is larger: CH3 or X?
X - halogen
X
What happens when alkenes are mixed with hydrogen halides in the presence of UV light?
Anti-mark addition occurs
What are 3 functions of bile?
1. Emulsification of fat particles (into minute particles that are susceptible to the action of lipases)
2. Transport of end products of fat digestion through intestinal mucosal membrane
3. Excretion of bilirubin (end product of hemoglobin destruction).
What happens when RBCs die? (3)
1. Bilrubin formed from hemoglobin degradation
2. Bilirubin enters circulation
3. Bilirubin binds to blood protein albumin until it reaches liver & disssociates
What is the antagonist of PTH? What is PTH's goal?
1. Calcitonin
2. To raise blood levels of Ca2+
What are the functions of aldosterone?
Where does aldosterone come from?
Aldosterone is responsible for reabsorption of Na+ from distal tubule & collecting duct, as well as secretion of K+ into them.
Basically, increases blood pressure, increases Na+ in extracellular fluid, and decreases K+ in extracellular fluid.
