Biochemistry Exam 3

Energy storage, membrane structural elements, hormones, cofactors in catalysis, detergents in digestion

What are some functions of biological lipids?

Plaque

Buildup of lipids in blood vessels, especially LDL, leads to __________.

Storage lipids and membrane lipids

What are the two types of lipids we went over?

triacylglycerol

What do lipids store energy as?

Saturated have not double bonds to kink the chains so they compact on one another. Ex. butter

Unsaturated have at least 1 double bond that kinks and causes them to not compact tightly. Ex. Oil

What is the difference between saturated fatty acids and unsaturated fatty acids?

Aliphatic

Lipids are considered _______ which means they have a polar part and non-polar part.

Trans-fats have a trans double bond so they can pack tight. Unsaturated fats have a cis double bond which kinks them.

Trans-fats have a double bond but are still able to pack tightly, making them harmful. Why are they able to still pack tightly?

A. Cis. The few natural trans fats are obtained from bacteria in the lumen and end up in dairy and meat products. We do not make any trans-fat.

Most natural fats are

A. Cis

B. Trans

Partial hydrogenation of unsaturated fatty acids

Dietary trans fats are formed by:

Trans fats can pack more regularly and show higher melting points than cis form. This means they will cook hotter when cooking such as in frying. These are have a longer shelf life.

Why are trans-fats created by industry?

Increased LDL and decreased HDL

Consuming trans-fats leads to increased _____________ and decreased ____________. (HDL or LDL)

C. Cardiovascular disease. Avoid fried foods, margarine, pie crusts

Trans-fats can lead to:

A. Weight loss

B. Edema

C. Cardiovascular disease

Triacylglycerols

___________ are the major animal fat components.

The triacylglycerol is a glycerol backbone connected to 2 saturated chains and 1 unsaturated chain.

Explain the structure of the triacylglycerol.

Using free fatty acids means we would need lots of free fatty acids. This would make our body much more acidic. Instead, we choose triacylglycerol because it will not make our body more acidic.

Why is triacylglycerol used for storage rather than free fatty acids?

B. Lipase. During long-term fasting, lipase degrades molecule and releases parts to be used for other purposes. In some, lipase does not work, triacylglycerol in blood will not break down and be increased in blood leading to high cholesterol.

Which enzyme cleaves the bonds of a triacylglycerol?

A. Ligase

B. Lipase

C. Glyase

D. Acylase

True

T/F Triacylglycerols are seen as droplets in adipocytes, serving as a source of metabolic energy.

Glycerol and fatty acids; lipases

What are Triacylglycerols broken down into and what breaks them down?

B and C

A should say they hold 2x as much energy per gram as glycogen

D should say they reduce acidity by using fatty acids and taking them out of the bloodstream

What are the advantages of using Triacylglycerols as storage? (Select all that apply)

A. Hold 4x as much energy per gram as glycogen

B. Does not require water to be carried since it is non-polar

C. Fat is a good insulator and keeps you warm.

D. They increase acidity allowing for better digestion.

B. Plasma membrane

Lipid is the structural component of which part of the cell

A. DNA

B. Plasma membrane

C. RNA

D. Both DNA and RNA

B. abnormally high levels of fats (lipids)

What is considered Hyperlipidemia?

A. abnormally high levels of proteins

B. abnormally high levels of fats (lipids)

C. abnormally high levels of carbohydrates

D. Both a glycerol backbone and 3 fatty acids

Triacylglycerols are composed of:

A. A glycerol backbone

B. A glycol backbone

C. Amide linkages b/w the fatty acids and the glycerol

D. Both a glycerol backbone and 3 fatty acids

E. A glycerol backbone, 3 fatty acids, and amide linkages b/w fatty acids and the glycerol

Phosphatidic acid

One type of membrane lipid we went over was glycerophospholipids. What are these derivatives of?

Glycerol backbone bound to a saturated fatty acid, unsaturated fatty acid, and a phosphate group that is usually bound to an -OH.

What does the structure of a glycerophospholipid have?

The backbone is a long-chain amino alcohol called a sphingosine. (it is not glycerol)

Another type of membrane lipid we went over was the sphingolipids. What is the backbone of this?

B. Amide linkage

Sphingosides are attached to the fatty acids by what type of bond?

A. Glycosidic

B. Amide linkage

C. Sphingosidic

D. Alcoholic

A ceramide

What is the structure containing the sphingosine and fatty acid chain called?

True. This is an important function of sphingolipids.

T/F Carbohydrate moieties of some sphingolipids define the human blood groups.

Oligosaccharide chain. Each blood type antigen has a different oligosaccharide sequence.

Glycosphingolipids determine blood groups because of the ____________ that are attached to the ceramide molecule.

Sphingosine

Glycerol is to triacylglycerol as _______________ is to sphingolipids.

False. They are continually degraded and replaced

T/F Most cells rarely degrade and replace membrane lipids.

Lysosomal

If complex membrane lipids are not degraded and replaced, they can lead to _________ diseases.

A. Beta galactosidase. This is an error in the 1st step of degradation.

Symptoms include: hepatospleenomegaly (enlarged spleen and liver)

Generalized gangliosidosis is caused by a deficiency in which enzyme.

A. Beta-galactosidase

B. Glucocerebrosidase

C. Sphingomyelinase

D. Hexosaminidase A and B

E. Hexosaminidase A

F. Alpha-galactosidase A

E. Hexoaminidase A.

This disease slow development; usually survive 1-4 years

Important: cherry-red spot on retina

Tay-Sachs disease is caused by a deficiency in which enzyme.

A. Beta-galactosidase

B. Glucocerebrosidase

C. Sphingomyelinase

D. Hexosaminidase A and B

E. Hexosaminidase A

F. Alpha-galactosidase A

F. Alpha-galactosidase A Cardiac, brain, and kidney damage by 30.

Death by 40; symptom= chronic burning and tingling of hands and feet.

Treatment costs $250000/year

Fabry's disease gangliosidosis is caused by a deficiency in which enzyme.

A. Beta-galactosidase

B. Glucocerebrosidase

C. Sphingomyelinase

D. Hexosaminidase A and B

E. Hexosaminidase A

F. Alpha-galactosidase A

Niemann-Pick disease is caused by a rare genetic defect in the enzyme sphingomyelinase, the enzyme that cleaves phosphocholine from sphingomyelin. Sphingomyelin accumulates in the brain, spleen, and liver. The disease becomes evident in infants and causes mental retardation and early death.

What happens in Niemann-Pick disease and what enzyme defect is responsible?

genetic counseling

What can predict and avert many inheritable disease?

Arachidonic acid. This is the result of the hydrolysis of the ester bonds.

Phospholipases degrade glycerophospholipids and the fatty acids released form an inflammatory mediator called

Phospholipase A2

Steroids prednisone and prednisolone inhibit what indirectly?

All.

Prostaglandins produce inflammation, pain, and fever.

Thromboxanes increase blood clotting ability of platelets.

Leukotrienes can cause asthma attacks. (Lung smooth muscle contracts)

NSAIDs block prostaglandin and thromboxane production.

Enzymatic oxidation of arachidonic acid yields (select which)

A. Prostaglandins

B. Thromboxanes

C. Leukotrienes

D. Phospholipases

What enzyme degrades glycerophospholipids?

A. Lysomerases

B. Polymerases

C. Glycerases

D. Phospholipases

It is the 3 products together that arachidonic acid breaks down to. These 3 together are called the eicosanoid.

What does eicosanoid mean?

Eicosanoids

lipid-based signaling molecules that play a unique role in innate immune responses

It means 20 as in they are a class of molecules derived from 20-carbon polyunsaturated fats. They are usually about 20 carbon long.

What is the origin of the portion of the word, "eicosa"?

True

T/F Some lipids act as signaling molecules. An example of these is hormones.

Sterol nucleus has 4 fused rings (almost planar)

Hydroxyl group (polar head)

Various non-polar side chains (non-polar part)

What are sterols composed of?

Sterols. Steroids have the sterol nucleus but do not have alkyl side chains.

Steroids are oxidized derivatives of _________.

False. Steroids are more polar cause they lack non-polar chains.

T/F Cholesterol is more polar than steroids.

Gonads and adrenal glands

Steroids are synthesized from cholesterol in the __________ and __________.

Through the bloodstream

How are steroids carried in the body?

Hydrocortisone

What medication containing a hormone suppresses localized inflammation such as after a bee sting?

To calm down your body's immune response to reduce pain, itching, and swelling (inflammation).

What is hydrocortisone typically used for?

They inhibit the release of arachidonic acid by phospholipase A2 which does not allow the synthesis of eicosanoids.

How do prednisone and prednisolone work?

Cortisol

Chronic stress leads to high amounts of _______ which is bad for our health because it destroys the epithelial lining. A symptom can be heart burn.

Vit D and A

Ex. Vitamin D3 (cholecalciferol) creates calcitrol, a hormone that helps in calcium absorption.

Ex. Vitamin A1 (retinol) is oxidized to cis-retinal; visible light turns cis to trans and we can see; retinal also becomes retinoic acids which is a hormone that helps with dry eyes

What 2 vitamins act as a hormone precursor?

In a derivative of cholesterol, 7-dehydrocholesterol, a bond is broken to make it into cholecalciferol (Vit D3), which is then activated in the liver to calcitriol.

How is Vit D produced in our bodies?

Cleaving of beta-carotene

Where does Vit A come from?

A. Cardiolipin

Sphingosine is NOT a component of:

A. cardiolipin

B. ceramide

C. cerebrosides

D. gangliosides

E. sphingomyelin

C. Vitamin D

Which vitamin is derived from cholesterol?

A. A

B. B12

C. D

D. E

Define cell boundaries, divide cells into compartments, organize complex reaction sequences, act in signal reception and transmission, platform to move solute in and out of cell

What are some functions of biological membranes?

Amphotericin B

Which drugs target ergosterol in fungal and yeast infections?

Proteins = 52%

Phospholipids = 7%

Sterol = 4% (ergosterol)

What percentage by weight are proteins, phospholipids and sterols in yeast?

D. None of the above

Peripheral membrane proteins

A. Are generally non-covalently bound to membrane lipids

B. Penetrate deeply into the lipid bilayer

C. Are usually denatured when released from membranes

D. None of the above

True

T/F Glycoproteins, Cholesterol, or Channel proteins can be drug targets in the plasma membrane.

High protein; no sterol type

E. coli has __________ protein content because they have lots of enzymes in their membrane. They also contain ____________ sterol type.

Integral goes fully through membrane and can be glycoconjugate.

Peripheral is covalently linked to lipid bilayer on either side.

What is the difference between integral proteins and peripheral membrane proteins?

Important for membrane fluidity. They can actually move around the membrane laterally (not static)

What is the purpose of cholesterol in the plasma membrane?

Peripheral- use change in pH, clearing agent, urea, carbonate

Integral- use detergent

How can you isolate peripheral and integral proteins from the plasma membrane?

A and B

What are the type of passive transport?

A. Facilitated diffusion

B. Simple diffusion

C. Secondary active transport

The sodium-dependent glucose transporter in human intestine.

Secondary cause Na is following gradient, but glucose is going against. Glucose is hitching a ride with Na.

Also called co-transport. ATP is used to bring Na back against gradient.

What is an example of secondary active transport?

High Kt means a lower affinity of the substrate because more is needed to reach 1/2 of Vmax.

Low Kt means a ligh affinity because less substrate is needed to reach 1/2 of Vmax.

What does a high or low Kt mean?

Ionophore transports works by a protein binding to the solute then transporting it inside the cell. Ion channels just let ions flow through when opened. Both ionophore and ion channels are not stereospecific. Ionophores and ion channels transport down concentration gradient.

How do ionophore-mediated transporters work and how are they similar and different from ion channels?

GLUT 1 = RBCs

GLUT 2 = liver hepatocytes

GLUT 4 = myocytes and adipocytes

There are 12 different glucose transporters. Where are GLUT 1, GLUT 2, and GLUT 4 located?

This implies that 4.5-6% of RBCs are saturated with glucose.

The Kt value for GLUT 1 is 3 mM. The blood glucose is 4.5 mM to 6mM. What does this imply?

False. GLUT are stereospecific and only transport D-glucose.

T/F The GLUT transporters can transport D or L glucose.

Transports glucose out of liver cells and into the liver when blood glucose levels are high for storage as glycogen

What does GLUT 2 do?

3mM for GLUT 1 and 17mM for GLUT 2. The high Kt value is important in liver cells so the glycogen can be quickly converted to glucose when the body needs to use it. A higher Kt means less affinity of glucose to the transporter.

What are the Kt values of GLUT 1 and GLUT 2? Why is this important?

Insulin

What is GLUT 4 waiting on a signal from to be activated?

Between meals, some GLUT4 is present in the plasma membrane, but most (90%) is sequestered in the membranes of small intracellular vesicles. Insulin released from the pancreas in response to high blood glucose triggers, within minutes, the movement of these vesicles to the plasma membrane, with which they fuse, bringing most of the GLUT4 molecules to the membrane. With more GLUT4 molecules in action, the rate of glucose uptake increases 15-fold or more. When blood glucose levels return to normal, insulin release slows and most GLUT4 molecules are removed from the plasma membrane and stored in vesicles.

How does GLUT 4 work?

Symport and antiport

Which classes of transport are considered cotransport?

A. They transport 2 molecules at a time.

How are symport and antiport different from uniport?

A. They transport 2 molecules at a time

B. The transport molecules in the same direction

C. They are always larger than uniport

C.

Which statement is TRUE concerning the chloride-bicarbonate exchanger?

A. This transporter is an active transporter

B. The exchanger is a passive symporter

C. The exchanger is a passive antiporter, and this protein is involved in carbon dioxide transport in the blood stream.

On RBCs to exchange HCO3- for Cl- and vice versa.

Where is the chloride-bicarbonate exchanger located?

False. It dissolves in the blood plasma. CO2 cannot be dissolved in the plasma.

T/F Bicarbonate (HCO3-) cannot dissolve in the blood plasma.

0 1 negative in and 1 negative out

What is the net charge of the RBC after the Chloride bicarbonate exchanger has done its thing?

Reversible and active transporters of protons

Are F-type ATPases reversible or irreversible and active or passive?

F-type ATPases

These are reversible ATP-driven proton pumps.

Break down; synthesize

F-type ATPases can serve as ATPases which _________ ATP or ATP synthases which ___________ ATP.

F-type ATPases

What serve as ATP synthases in mitochondria and bacteria?

ATP (adenosine triphosphate)

ABC (ATP binding cassette) transporters use ______ to drive active transport of a wide variety of substrates. This is an transmembrane transporter.

P-glycoprotein

BCRP (breast cancer resistant protein)

MRP (multi drug resistant protein)

What are 3 types of ABC transporters?

P-glycoprotein. MDR1 is also a P-glycoprotein

Vinblastine, adriamycin, and doxorubicin are substrates of what?

Phe 508

Change form -> change function. If Cl- can no longer get out, water cannot follow it; Outside will get dry; infections can happen easier

CFTR is a transmembrane conductance regulator for cystic fibrosis. It normally transports Cl- out of the cell. A mutation in what part of this causes improper folding of this protein that does not allow Cl- to be transported out.

ATP dependent

CFTR is an _________ dependent transporter.

C. A solution containing detergent

Peripheral membrane protein can be removed with A and B.

An integral membrane protein can be extracted with:

A. a buffer of alkaline or acid pH

B. a chelating agent that removes divalent cations

C. a solution containing detergent

Cancer cell signals require a lot of intermediate steps and signaling proteins, more than regular cells do. This means we can target these other proteins to kill the cancer.

It was discovered that cancer cell signaling pathways are different from regular cell signaling pathways. How are they different?

50%

What percentage of drugs today target GPCR?

They must be received by receptors since hydrophilic molecules cannot cross the membrane.

Many signal molecules are hydrophilic. What does this mean in regards to how they have to be received?

Steroid hormones, nitric oxide (from nitroglycerin (prodrug))

What signals are hydrophobic in nature?

Signal, receptor, cellular response

What are the 3 main components of the signal transduction pathway?