Study Guide – Exam I Spring 2015
1. Describe the structure and function of the cell membrane?
listen to cell video
∙ Membrane lipid bilayers consist primarily of phospholipids
∙ 3 carbon glycerol backbone
o Carbons 1 and 2 are esterified to fatty acids
o Carbon 3 bound to a phosphate group
∙ phosphate group bound to an amine
∙ fatty acids (inner part of bilayer) forms a nonpolar layer
∙ the polar/nonpolar contribute to the functions
o cell signaling
o bicosinoid biosynthesis
o maillard rxns
o glycosylation rxns
∙ arachidonic acid = synthesized in the cell membranes.. a part of lipid metabolism, part of the inflammatory response; polyunsaturated Don't forget about the age old question of How would researches conveniently organize large amounts of numerical data?
The cell membrane functions:
∙ to transmit signals between inside the cell and outside
∙ to allow transport of material through the cell
∙ supply compounds that play important roles in the inflammatory response
2. Briefly describe the functions of the following cellular organelles; nucleus, mitochondria, smooth and rough endoplasmic reticulum, Golgi apparatus, lysosomes.
∙ glycosylation reaction
∙ nucleus control center of the cell, has a nuclear envelope, has chromatin comprises → of DNA
∙ mitochondria energy powerhouse of cell, extracting energy stored in glucose, very important in metabolism and cell respiration (ATP production in the presence of oxygen), have their own DNA; fatty acid metabolism, electron transport
o The Krebs cycle and fatty oxidation occurs in the mitochondria.
∙ smooth er = lacks ribosomes, has enzymes embedded inside of it, major site for synthesis of lipids, also responsible for producing hormones (estrogen, steroid hormones) We also discuss several other topics like What are the components of aztec architecture?
We also discuss several other topics like How much calories can be found in lipids?
∙ rough er = has ribosomes, synthesizes proteins, (e.g. digestive enzymes and insulin) ∙ microsomes are artifacts of the endoplasmic reticulum
∙ Golgi apparatus shipping and transport, final packaging and processing site o 3 major fxns
o sorts proteins and lipids that are received from the endoplasmic reticulum o modify molecules that packages the materials in vesicles
∙ *lysosomes = in animal cells, formed by golgi bodies, contain enzymes that help w/breakdown of proteins, fats, carbs into their component parts;
o digestion of food particles
o digestion and destruction of defective organelles
∙ just watch the video; just review
3. What is clathrin?
*clathrin = the protein that provides the structure of secretory vesicles; a triskelion protein; endositized external signals and brings them into the cell to internalize it
*4. Describe how enzymes are regulated by “covalent modification.” SHORT ANSWER ∙ making an enzyme either inactive OR active
∙ go to the RCC complex; cAMP dependent protein kinase → phosphorylation or dephosphorylate We also discuss several other topics like Which shared derived traits unite the plant kingdom?
Don't forget about the age old question of What are the key features of classical criminology?
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∙ this kinase works when it’s activated by cAMP, has two subunits, cAMP will bind to regulatory subunits responsible for regulating the enzyme which will trigger catalytic subunits, these are what produce the phosphorylated substrate, can happen to an active or inactive enzyme
*5. Describe what is meant by “allosteric enzyme regulation.”
∙ Allosteric enzymes become more active when a substrate is bound to it. ∙ or cAMP is the allosteric stimulator, it activates the catalytic subunits o once the cAMP binds to the enzyme, the reaction takes off
∙ you can activate or inhibit it
∙ allosteric curves, show the different parts of the rxn
∙ connected to cAMP dependent protein kinase
∙ at low end of curve at 0, when the curve happens, this is when the cAMP activates the allosteric regulation
∙ there are also negative allosteric regulators
∙ know in basic terms what zero order, first order is…
∙ the substrate itself can turn on the enzyme
*6. How does “enzyme induction” differ from other mechanisms of enzyme regulation? ∙ enzyme induction refers to the stimulation of the production of the enzyme; inducing the actual synthesis of the enzyme. example PCBs = very stable in the environment, → potent inducers of cytochrome b
o conversion of pre carcinogens to carcinogens
o PCBs induce the production of enzymes that convert pre carcinogens to carcinogens.. good Phase 1 inducers
7. Describe the process of cell signaling via “stimulation of an internal signal.” ∙ look on the slide for this… think of conformational change
∙ second messenger inside the cell when a chemical binds to the cell, sends a chemical → change
∙ hormone binds to cell, causes conformational change of a G protein GDP and GTP → determines what can happen in the cell
∙ GDP inhibits it whatever the second messenger is, GTP activates it
∙ GTP interacts with adenyl cyclase cAMP, cascade of rxns →
∙ once it is done, will revert back to GDP, and reaction will cease
1. Describe the difference between an exothermic reaction and an endothermic reaction, in terms of free energy (ΔG).
free energy is the potential free energy in a chemical bond
deltaG, exothermic = results in release of energy
+deltaG, endothermic = energy must be added to produce the products
2. How does “Standard Free Energy” (ΔGo’) differ from ΔG?
free energy under very controlled conditions, vs. what happens in the cells ex: triosephosphate isomerase in the living cell, the → exothermic reaction was favored even though under controlled conditions, an endothermic reaction should be favored (look at video example)
standard free energy cannot be used to determine what’s going to happen INSIDE the cell
3. Describe (in terms of free energy) and cite an example of a “coupled reaction” in metabolism. ADP ATP → (7300 kcal)*
phosphocreatine dephosphorylation creatine (10,300 kcal/mole) → →
net standard free energy for this rxn is 3,000 kcal/more
ATP dephosphorylated to ADP →
glucose phosphorylated glucose6phosphate → →
4. What is “substratelevel phosphorylation” and describe how it occurs (in terms of free energy).
∙ substratelevel phosphorylation means any rxn where you produce a high energy phosphate group by transferring one compound to another, occurs outside the ETC and outside the Krebs cycle.
∙ one high energy compound to another
∙ glucose glucose6phosphate →
5. Understand the difference between “substratelevel phosphorylation” and “oxidative phosphorylation.”
∙ oxidative phosphorylation represents the production of ATP through the ETC in the mitochondria, starts in Krebs cycle,
∙ dehydrogenase enzymes that catalyze the removal of hydrogens and electrons from krebs cycle substrates
∙ produces the energy through the ETC and within the Krebs cycle to create ATP
6. What is “Standard Reduction Potential” and how is it related to oxidative phosphorylation? ∙ the more negative the Standard Reduction Potential, the more likely it is to pass its electrons
∙ measure of a substances tendency to lose electrons
∙ shows whether compounds will be oxidized or reduced
7. What is “brown adipose tissue” and how is it involved in “uncoupling” oxidative phosphorylation?
∙ brown adipose tissue more mitochondria, found more in infants →
∙ uncoupling proteins allow “proton leak” which allows protons to enter mitochondrial matrix without capturing any energy as ATP
∙ brown adipose tissue is less efficient at making ATP and more efficient at producing heat
8. What is “beige adipose tissue” and what factors may contribute to its formation?
∙ Beige Adipose Tissue: Develop in white fat tissue. Activities include reducing metabolic disease, including obesity, in mice and correlate with leanness in humans. Found in the neck and upper chest regions. When humans are exposed to cold, their beige cells are activated. Obese people have few or no beige cells.
1. What are the major organs of the GI tract and their functions?
∙ mouth: amylase enzymes break down carbs, produces saliva and mucous o lingual lipase: in infants, breaks down fats
esophagus: food takes 10 sec to pass thru
∙ *LES: opens as a reflex to swallowing, allows food to pass thru esophagus to stomach, closes to prevent chyme or acid to get into esophagus
∙ stomach: food enters, rugae allow stomach to expand to full carrying capacity o *pyloric sphincter: stronger than LES; allows small amounts of chyme to release into intestine
o gastric pits = important secretory cells for digestion G cells, secrete gastrin → o gastrin stimulates release of HCl, stimulates gastric motility
o parietal cell in gastric pits = responsible for produce HCl and intrinsic factor, responsible for absorbing vitamin B
o chief cells/pepsic cells = absorb pepsinogen → pepsinogen is activated by HCl or pepsin
o mucus cells = protect stomach lining
∙ small intestine =
o serosa layer
o muscularis layer = responsible for what moves the contents in small intestine o submucosa layer = largely comprised of nerves and glandular tissue
o mucosa layer = whiteish layer of small intestine
enterocytes are located = epithelial cells that have the microvilli which form the brush border in contact with the lumen
layer that lines the microvilli brush border called the glycocalyx = forms protective barrier for epithelial cells
epithelial cells: apical side, and the basolateral side
∙ large intestine = responsible for reabsorption of water and electrolytes from lumen, storing fecal matter
2. How is hydrochloric acid produced in the stomach?
∙ potassium chloride transport system… released from parietal cells, the Cl is released ∙ hydrogen potassium ATPase system … hydrogen are released out while Cl is pumped in
3. What are the functions of HCl in the stomach?
∙ activate pepsinogen to pepsin
∙ denatures proteins
∙ can release nutrients from organic substances… heme iron is better absorbed from organic sources, but hCl helps release the nonheme iron from organic sources ∙ killing bacteria in food (because of low pH)
4. Describe some of the causes and treatments for Gastroesophageal Reflux Disease (GERD).
obesity, pregnancy, smoking, alcohol, chocolate, peppermint, caffeine, spicy foods
calcium carbonate (TUMS, rolaids)
H2 blockers: pepsic AC and zantac
proton pump inhibitors = prevent the release of acid into the stomach; Nexium, Prilosec
5. What is “Barrett’s Esophagus”?
damage to the lining of the esophagus causes metaplasia which replaces the cells with normal cells, but abnormal for their location.
6. Describe examples of restrictive and malabsorptive weight loss surgery procedures. restrictive and malabsorptive
restrictive is reversible, cheaper, less sideeffects
lap band = creates feeling of fullness, can be adjusted
restrictive AND malabsorptive = rouxenY gastric bypass surgery
7. What is “dumping syndrome?”
Dumping Syndrome = common early side effects of gastric bypass surgery Early (acute) dumping
∙ 1030 min after a meal
∙ severe GI distress
∙ nausea, bloating, abdominal cramps, explosive diarrhea
∙ due to accelerated gastric emptying and hyperosmolar (draw a lot of water in to dilute it) content of small intestine
Late (delayed) dumping
∙ 13 hours after a meal
∙ flushing, dizziness, palpitations, intense desire to lie down
∙ due to exaggerated release of insulin and reactive hypoglycemia
8. What are the roles of gastrin, GIP, secretin, and CCK in the regulation of gastrointestinal activity?
∙ gastrin = released by the G cells from the presence of food in stomach o (USE THE DIAGRAM in the video)
o HCl, gastrin, gastric motility
∙ GIP = role in insulin (circulation)
∙ secretin = inhibitory role, released bicarbonate, neutralize the stomach acid pH, inhibit pepsinogen release and gastric emptying
∙ Cholecystokinin (CCK) = released by mucosal cells, stops gastric emptying
9. What is “enterohepatic circulation” and why is it important in bile acid metabolism? enterohepatic circulation = the movement of bile between the intestine and the liver bile acids = when they’re secreted into the intestine, 90% are recovered by the small intestine and circulated back to the liver… important to cholesterol
10.How does enterohepatic circulation contribute to how 1,2dimethylhydrazine causes colon cancer in rats? SHORT ANSWERS
∙ can cause colon cancer in rats … DMH (precarcinogen) stable in the environment; ∙ when given to animal orally, is oxidized in intestine to azomethane..
∙ Azomethane is taken to liver → in liver converted azoxymethane
∙ Azoxymethane oxidized to Methylozoxymethanol ( the proximate carcinogen )(very unstable) … can cause destruction to DNA
∙ conjugated to methylozyxy… protects the rats liver from getting liver cancer ∙ glucaronide portion is very polar… can be excreted in urine
∙ some of this ends up in the bile, so it ends up in the large intestine and eventually the colon
∙ it converts to the cancer causing form when the bacteria in the colon cleave the glucaronide conjugate… carcinogen in the colon, non carcinogenic in the liver ∙ Phase 1 is when it can get converted to the carcinogenic form
11.How do “resintype” cholesterollowering drugs work?
the importance of these drugs is that they bind the cholesterol and aid in its excretion.. the property that is important to enterohepatic circulation is that it binds to bile acids prevent the cholesterol from being reabsorbed
cholesterol has to be upregulated from the body’s stores bc the body needs to use it to excrete the bile acids
12.What is gluten?
a general term for the proteins that are found in wheat, rye, barley
prolimens are the plant storage protein, only soluble in strong alcohol solution, culprits for gluten sensitivity and CD
13.What are the differences between celiac disease and gluten sensitivity? *DIAGNOSIS differences
CD diagnosis = presence of the genetic factors.. not the most reliable bc some ppl have them but don’t have CD; autoantibodies = specific antibodies that can be identified in a blood tests, antigliadin and anitransglutamase; enteropathy = change of the villi in the intestine… inflammatory response cause the villi to flatten out
Gluten Sensitivity =
a. GI symptoms rechallenged by reintroducing GF products
b. CD test is negative
1. What are the “essential” or “indispensable” amino acids?
2. Compare and contrast the various methods of estimating protein quality.
3. Describe the role of the enzymes Alanine Aminotranferase and Aspartate Aminotransferase in metabolism.
4. Describe the diagnostic importance of serum levels of Alanine Aminotranferase and Aspartate Aminotransferase.
5. Briefly describe the metabolic functions of glutathione.
6. Be able to describe the major reactions and products of phenylalanine, tryptophan, and methionine metabolism.
7. What is homocysteine, how is it formed, what are the health concerns related to elevated serum homocysteine, and what vitamins play a role in homocysteine metabolism?
8. What is Hemoglobin A1c and why is it a good marker of glucose control in individuals with diabetes?
Terms to Know: great for MC questions.. highlight when they show up in your answers. these could also show up in short answer questions… brief explanations of them Microsome
Mitochondrial DNA = mitochondria have their own DNA & function in their own respect, means they can replicate themselves
Potential Free Energy (ΔG)
Standard Free Energy (ΔGo’)
Standard Reduction Potential
Proton Pump Inhibitor
Lower Esophageal Sphincter
Gastric Inhibitory Peptide (GlucoseDependent Insulinotropic Peptide) The Delaney Clause