Biochem exam 3 Compilation

1. hemiacetal is formed from... 2. hemiketal is formed from...

1. an aldehyde and a alcohol 2. a ketone with an alcohol

Monosaccharides are modified by

Amines, alcohols, phosphates

Discuss prostaglandin and its precursor. How can we reduce the production of prostaglandin? Its precursor is __________ acid; To reduce the production, inhibit the enzyme _________________)

Arachidonic; cyclooxygenase

What is the linkage of cellulose? And why cannot mammals digest cellulose?

Beta-1,4 linkages. They give rise to long straight chains that form fibrils with high tensile strength. Mammals cannot digest cellulose because they lack cellulases and therefore cannot digest wood and vegetable fibers.

common monosaccharides

D-Ribose, D-Deoxyribose, D-Glucose, D-Mannose, D-Galactose, D-Fructose

6 carbon aldoses

D-glucose, D-mannose, D-galactose

5 carbon aldoses (have aldehydes)

D-ribose, D-deoxyribose

Discuss the integral and peripheral membrane proteins.

Integral- interact extensively with the hydrocarbon region of the bilayer most transverse the lipid bilayer Peripheral- interact with the polar head groups of the lipids or bind to surfaces of integral proteins.

Which carbon is w-carbon atom of a fatty acid?

Methyl carbon atom at the distal end of the chain.

Many pathogens gain entry into cells by

•first binding to carbohydrates on the cell surface

Discuss melting points of different length fatty acids (and the number of double bonds).

The longer the fatty acids and less double bonds equals a higher melting point

What are the simplest carbohydrates (the 3-carbon molecules)?

The simplest carbohydrates are monosaccharides. These types of carbohydrates are aldehydes or ketones that have two or more hydroxyl groups. They are composed of 3 carbon atoms.

Monosaccharides are

aldehydes or ketones that contain two or more hydroxyl groups

b-d-fructofuranose

alpha moves the OH down

Formation of cyclic hemiacetal creates

another diastereoisomeric form called an anomer (a & b)

a-d-fructopyranose

beta moves OH up

6 carbon ketone

d-fructose

The b form means

that the hydroxyl at c-1 is above the plane of the ring

The a forms means

that the hydroxyl at c-1 is below the plane of the ring

In the case of ketose fructose the hemiketal

(a five carbon ring) is called a furanose

In the case of glucose the hemiacetal...

(a six carbon ring) called a pyranose

•There are three main classes of glycoproteins:

1.Glycoproteins: mainly protein by weight. Play a variety of roles, including as membrane proteins. 2.Proteoglycans: attached to a particular polysaccharide called a glycosaminoglycan. Mainly carbohydrate by weight. Play structural roles or act as lubricants. 3.Mucins or mucoproteins: protein is characteristically attached to the carbohydrate by N-acetylgalactosamine. Mainly carbohydrate by weight. Often act as lubricants.

Many Common Features Underlie the Diversity of Biological Membranes

1.Membranes are sheetlike structures, two molecules thick, that form closed boundaries. 2.Membranes are composed of lipids and proteins, either of which can be decorated with carbohydrates. 3.Membrane lipids are small amphipathic molecules that form closed bimolecular sheets that prevent the movement of polar or charged molecules. 4.Proteins serve to mitigate the impermeability of membranes and allow movement of molecules and information across the cell membrane. 5.Membranes are noncovalent assemblies. 6.Membranes are asymmetric in that the outer surface is always different from the inner surface. 7.Membranes are fluid structures. 8.Most cell membranes are electrically polarized.

What is the example of glycoproteins?

3 classes are glycoproteins, proteoglycans, and mucins. An example would be glucosaminoglycan.

•catalyze the formation of glycosidic bonds

A large class of enzymes, glycosyltransferases

Discuss the structure of cholesterol.

A steroid built from 4 linked hydrocarbon rings, hydrocarbon tails is linked to the steroid at one end, and a hydroxyl group is attached at the other end.

What is the micelle?

Amphipathicc globular structure. Polar head groups form the outside surface, that is surrounded by water, and hydrocarbon tails are sequestered inside, interacting with each other.

What is the function of alpha-amylase?

Amylopectin, amylose, and glycogen are rapidly hydrolyzed by this enzyme that is secreted by the salivary glands and the pancreas

What is the linkage of the polysaccharides of amylose, amylopectin, and glycogen?

Amylose- alpha 1,4 linkage Amylopectin- 1 alpha-1,6 linkages per 30 alpha-1,4 linkages Glycogen- alpha-1,4 units and alpha-1,6 glycosidic bonds

What are proteoglycans and the unique feature?

Carbs make up a much larger percentage by weight of them. Proteins attached to glycosaminoglycans takes up to 95% of the biomolecule by weight. 2nd class of glycoproteins function as structural components and lubricants.

Do naturally occurring fatty acids have cis or trans double bonds?

Configuration of double bonds in most unsaturated fatty acids is cis.

What is peptidoglycan?

Consists of polysaccharide chains that are crossed linked by short peptides

What is the definition of epimers? Are D-glucose and L-glucose epimers? Are D-glucose and D-galactose epimers?

Epimers are sugars that are diastereoisomers differing in configuration at only a single asymmetric center. D-glucose and L-glucose are NOT epimers. D-glucose and D-galactose are epimers. D-glucose and D-mannose are epimers.

There are the fatty acids containing an even number of carbon atoms or an odd number of carbon atoms. Which fatty acids are dominating?

Even usually between 14 and 24. 16 and 18 are the most common. Reflects the manner in which they are biosynthesized.

What are the storage forms (polysaccharides) of the energy source glucose?

Glycogen and starch

If there are K+, H2O, and Benzene, which one has better permeability through a planar bilayer membrane (composed of only phospholipids)?

H2O, Na+, K+ transverse these membranes 10^9 times as slowly as H2O does. H2O is better because of low molecular weight high concentration and lack of a complete charge.

What is the definition of anomers?

Isomers that differ at a new asymmetric carbon atom formed on ring closure.

What is the role of cholesterol?

Key regulator of membrane fluidity in animals

What is glucoaminoglycans?

Large polymers made up of many repeats of dimers.

Discuss lateral diffusion and transverse diffusion.

Lateral: much more rapid than transverse Transverse- (flip-flop) transition of a molecule from one membrane surface to the other. Very slow

What is the structure of fatty acid? Is this amphipathic?

Long hydrocarbon chains of various lengths and degrees of unsaturation that terminate with carboxylic acid. Yes, the fatty acid components provide a hydrophobic barrier where the remainder of the molecule has hydrophilic properties that enable interaction with aqueous environment.

used to identify the released sugars

MALDI-TOF

In connecting between carbohydrates and proteins, which amino acids are involved in N-linkage and O-linkage, respectively?

N-linkage uses asparagine O-linkage uses theronine or serine

Is chitin a hetero-polysaccharide? (what is the function of chitin?)

No. The function of the processed version, chitosan, is used as a carrier to assist in drug delivery, as surgical stitches, as a component of skin, hair, and oral care products. Recent research shows it can be used as an component of an adhesive that strongly adheres to wet tissues, allowing the adhesive to be used as a surgical dressing.

What is the difference between O-glycosidic bond and N-glycosidic bond?

O-glycosidic is an anomeric carbon of carbohydrate and the oxygen atom of an alcohol. N-glycosidic is anomeric carbon atom of a sugar can be linked to the nitrogen atom of an amine

What are the three examples of the lipid-linkage for lipid-linked proteins?

Palmitoyl group- specific cysteine residue by thioester bond. Farnesyl group- cysteine residue at the carboxyl terminus Glycolipid structure- termed GPI anchor attached to the carboxyl terminus

Protein Glycosylation Takes Place

Place in the Lumen of the Endoplasmic Reticulum and in the Golgi Complex

Proteins interact with membranes in a variety of ways. Discuss the interaction between the phospholipid membrane and the protein.

Proteins mitigate the unpermeability of membranes and allow movement of molecules and information across the cell membrane

Why is glucose a reducing sugar?

Reducing sugar because the alpha and beta isomers of glucose are in an equilibrium that passes through the open-chain form. This has the ability to react with oxidizing reagents.

Discuss melting points of cis-unsaturated, trans-unsaturated, and saturated fatty acids.

Saturated fatty acids- highest melting point Cis-unsaturated- lowest melting point Trans-unsaturated- middle melting point

What is the difference between saturated and unsaturated fatty acid?

Saturated-no double bonds mainly saturated with hydrogen. Unsaturated-yes double bonds. Lower melting points saturated fats.

What is the example of glycolipids?

Simplest - cerebroside More complex - gangliosides

What is the function of the polysaccharide cellulose?

Structural role for the cell wall

Which of the three common disaccharides is not a reducing sugar (explain the reason)?

Sucrose is not a reducing sugar. The anomeric carbon acts as the reducing agent in glucose and fructose. In sucrose, the anomeric carbon atoms of glucose and fructose are joined by a covalent bond and are not available to react.

Common Disaccharides

Sucrose, Lactose, and Maltose

Describe the three common disaccharides.

Sucrose- common table sugar. Made up of anomeric carbon atoms of a glucose unit and a fructose unit are joined. The configuration of this glycosidic linkage is alpha for glucose and beta for fructose. Lactose-disaccharide of milk, consists of galatose joined to glucose by a beta-1,4-glycosidic linkage. Maltose-comes from the hydrolysis of large polymeric oligosaccharides such as starch and glycogen and is in turn hydrolyzed to glucose by maltase. Maltase will also degrade oligosaccharides linked by alpha-1,4-glycosidic linkages.

Discuss the structural components of sphingomyelin.

The backbone is sphingosine (an amino alcohol that contains a long unsaturated hydrocarbon chain. The amino group of the sphingosine backbone is linked to a fatty acid by an amide bond

How does the fluorescence recovery after photobleaching (FRAP) technique support the fluid mosaic model?

They allow measurement of the rate of movement of membrane components They demonstrate 2-dimensional movement of membrane phospholipids They demonstrate flipping of phospholipids between the two biomembrane leaflets.

•Cholesterol is

a steroid that is modified on one end by the attachment of a fatty acid chain and at the other end by a hydroxyl group

Two competitive inhibitors of α-glucosidase

acarbose and miglitol; either can be administered at the start of a meal to reduce post-meal glucose absorption in type 2 diabetes

Milk oligosaccharides

appear to prevent the growth of certain Streptococcusbacteria, which may otherwise be transferred from the mother's vaginal epithelium and cause pneumonia, blood poisoning, or meningitis in the infant

•Sphingomyelin is a

common membrane lipid in which the primary hydroxyl group of sphingosine is esterified to phosphorylcholine

Phosphoglycerides are derived from

from phosphatidate by the formation of an ester bond between the phosphate and an alcohol

Discuss the structural components of phosphoglycerides.

glycerol backbone which are attached 2 fatty acids chains and a phosphorylated alcohol.

The polysaccharide________ is the glucose storage form in animals

glycogen

Proteoglycans are proteins attached to

glycosaminoglycans, which make up as much as 95% of the proteoglycan by weight

What is a liposome?

lipid vesicles. Aqueous compartments enclosed by a lipid bilayer. Used to study membrane permeability or deliver chemicals to cells

What are three common types of membrane lipids?

phospholipids, glycolipids, cholesterol

Glucose is a

reducing sugar

Mucopolysaccharidoses

such as Hurler disease, are pathological conditions that result from the inability to degrade proteoglycans

The smallest monosaccharides are composed of

three carbons

Blood Groups Are Based on Protein Glycosylation Patterns

•All of the blood groups share the oligosaccharide foundation called O •The A form is then created if N-acetylgalactosamine is added to the O by a specific glycosyltransferase, while the B form is created if galactose is added by another transferase •Individuals with the O blood type lack both enzymes, while individuals with the AB blood type express both enzymes. • Individuals with either the A or B blood type express only one enzyme (the one capable of creating that oligosaccharide)

•In plants, glucose is stored as starch, of which there are two forms:

•Amylose is a linear polymer of glucose units linked by α-1,4-glycosidic bonds. •Amylopectin is a branched polymer, with an α-1,6-glycosidic bond for every 30 α-1,4-glycosidic bonds.

Glucose is a Reducing Sugar

•As a reducing sugar, glucose can react with amino groups, often Lys or Arg residues in proteins •Reactions between carbohydrates and proteins often impair protein function •Such modifications, called advanced glycation end products (AGEs), have been implicated in a number of pathological conditions

•In the ribose component of most biomolecules, two conformations are observed:

•C-2 is out of the plane on the same side as C-5 (C-2-endo) or •C-3 is out of the plane on the same side as C-5 (C-3-endo)

Membrane Lipids Can Include Carbohydrate Moieties

•Glycolipids are carbohydrate-containing lipids derived from sphingosine. The carbohydrate is linked to the primary alcohol of sphingosine •Cerebrosides are the simplest glycolipids, containing only a single sugar (glucose or galactose) •Gangliosides contain a branched chain of as many as seven sugar molecules •The carbohydrate components of glycolipids are on the extracellular surface of the cell membrane, where they play a role in cell-cell recognition

Proteins Associate With the Lipid Bilayer in a Variety of Ways

•Integral membrane proteins are embedded in the hydrocarbon core of the membrane •Peripheral membrane proteins are bound to the polar head groups of membrane lipids or to the exposed surfaces of integral membrane proteins •Some proteins are associated with membranes by attachment to a hydrophobic moiety that is inserted into the membrane

Lipid Vesicles Can Be Formed From Phospholipids

•Liposomes, or lipid vesicles, are aqueous compartments enclosed by a lipid membrane •Protein-liposome complexes can be used to investigate membrane protein functions •Liposomes, formed by sonicating a mixture of phospholipids in aqueous solution, can be useful as drug delivery systems •Planar bilayer membranes are also useful for examining membrane properties such as ion permeability in the presence of a voltage difference across the membrane

Glycosylation Functions in Nutrient Sensing

•Many proteins are modified by the attachment of N-acetylglucosamine (GlcNAc) to serine or threonine residues by GlcNAc transferase. GlcNAc is attached to protein when nutrients are abundant •The attachment is reversible, with GlcNAcase removing the carbohydrate •Improper regulation of the transferase has been linked to a number of pathological conditions

Protein Glycosylation

•N-linked glycosylation begins in the endoplasmic reticulum and continues in the Golgi complex •O-linked glycosylation occurs only in the Golgi complex •The Golgi complex is a sorting center for proteins of various fates •Dolichol phosphate, an isoprene derivative, carries large oligosaccharides destined for attachment to asparagine

•When the body cannot achieve glucose homeostasis on its own, pharmacologic intervention is possible. What are some reasonable targets?

•One of several possibilities is α-glucosidase (maltase); medications currently exist to inhibit this enzyme.

How are the common disaccharides obtained?

•Sucrose is obtained from sugar cane and sugar beets and is composed of a glucose linked to a fructose. The linkage is α for glucose and β for fructose. Sucrose is cleaved by sucrase (also called invertase). •Lactose is the disaccharide of milk that consists of a galactose linked to a glucose by a β-1,4 linkage. Lactase cleaves lactose. •Maltose, a degradation product of large oligosaccharides, is composed of two glucose molecules linked by an α-1,4 linkage. Maltose is hydrolyzed by maltase.

Myelination of a Neuron

•The Schwann cell is an example of a cell type with relatively low membrane protein content •Instead, its plasma membrane is lipid-rich; the lipid serves as an insulator, allowing rapid transmission of nerve impulses •The wrapping of this type of cell around an axon is referred to as myelination •Multiple sclerosis is an example of a demyelination disease, impairing myelin assembly or damaging existing myelin

Erythropoietin

•a glycoprotein 40% carbohydrate by weight, is secreted into the blood by the kidneys to stimulate the production of red blood cells •Glycosylation of erythropoietin enhances the stability of the protein in the blood

Chitin

•a glycosaminoglycan, is found in the exoskeleton of insects, crustaceans, and arachnids •It is one of the most abundant carbohydrates in the world

Membrane lipids are

•amphipathic molecules, containing hydrophobic and hydrophilic properties • •The fatty acid tail components provide the hydrophobic properties • •The alcohol and phosphate components, called the polar head group, provide the hydrophilic properties

Monosaccharides

•are aldehydes or ketones that contain two or more hydroxyl groups •The smallest monosaccharides are composed of three carbons Monosaccharides exist in many isomeric forms

Fatty acids are

•chains of hydrogen-bearing carbon atoms that have a carboxylic acid at one end and a methyl group at the other end and may be saturated or unsaturated

Phospholipids are composed of

•four components: one or two fatty acid tails, a platform, a phosphate, and an alcohol •Two common platforms are glycerol and sphingosine •Phospholipids with a glycerol platform are called phosphoglycerides or phosphoglycerols

The ability of small molecules to cross a lipid bilayer is a function of their

•hydrophobicity (lack of polarity)

Cartilage is composed of

•in part, of the proteoglycan aggrecan as well as the protein collagen

Proteoglycans

•key components of the extracellular matrix and serve as lubricants

•The common types of membrane lipids

•phospholipids •glycolipids •cholesterol