Biochemistry Unit 2 Dr.Lee

Carbohydrates

provide the energy to power all biochemical processes that take place inside a cell or organism; break down glucose to provide energy

Aldose

aldehyde + sugar

Ketose

ketone + sugar

Complex monnosacharides

are basically polysaccharides-- polymers of covalently linked monosaccharides

Monnosaccharide

are aldehyes or ketones that have two or more hydroxl groups

Carbohydrates can differ in what way?

isomeric forms

Aldehyde + OH

hemiacetal

The open chain form of ribose, glucose, fructose and many other sugars cyclize into what?

Rings

Pre-dominant forms of sugars such as ribose, glucose and fructose in solution are not what?

open chains

Glucose

the form of sugar that circulates in the blood and provides the major source of energy for body tissues. When its level is low, we feel hunger.

Ribose

A five-carbon sugar present in RNA

Mannose

C2 epimer of glucose

Fructose

a hexose sugar found especially in honey and fruit.

Galactose

milk sugar

Lactose

glucose + galactose (beta 1,4)

Sucrose

(a)glucose + (b)fructose (alpha 1,2)

Starch

storage form of glucose in plants; aids the next generation of plants

Glyogen

the storage form of glucose in humans and animals, alpha 1,4 and alpha 1-6

Cellouse

Polysaccharides that provide structural support for plants

Carbohydrates enzyme

alpha-amylase

cellulose enzyme

Cellulate

lactose enzyme

lactase

ATP hydrolysis is

exergonic, spontaneous

Cow can survive by eating only hay, but human can't. Why?

Cows can digest cellulose because of the bacteria in their stomach produces cellulate; humans can't because we don't have that bacteria.

Describe the location and function of the enzyme lactase

Small intestine and its purpose is to breakdown glucose and galactose

How do the products generated by lactase enter intestinal epithelial cells and subsequently enter the blood stream?

Products generated by lactase enter the intestinal epithelial cells by the SGLT1 transporter and enter the bloodstream with the GLUT2 transporter

What happens in the intestines of individuals who are lactose intolerant?

They slowly metabolize galactose and glucose due to deficiency of the enzyme, lactase. If these individuals consume products that contain lactose (milk & cheese); it will cause gastrointestinal problems (major gas and diarrhea), which disturbs the absorption of fats and proteins.

Lactose intolerance can be diagnosed

Lactose Intolerance Test and Hydrogen breath test

Briefly explain catabolism

Catabolism: The breakdown of molecules in your body to obtain energy oxidation; and its products are CO2 and H2O (energetically favorable)

Explain anabolism

The synthesis of compounds in your body using the energy during catabolism reduction and its products are proteins, lips, & nucleic acids (energetically unfavorable)

Explain why The Oxidation of Carbon Fuels Is an Important Source of Cellular Energy

To aid in the formation of ATP

ATP

is the universal energy currency inside most cells

Why does the hydrolysis of ATP have a negative ∆G°’ value? Why doesn’t ATP spontaneously hydrolyze in the cell?

The hydrolysis of ATP has a negative (delta G not) because it gives up/releases the phosphate groups.

ATP doesn’t spontaneously hydrolyze in the cell because it has to overcome the activation energy (Ea) in the cell.

What properties of ATP make it an especially effective phosphoryl-transfer-potential compound?

The phosphate groups of ATP specifically the partial negative oxygens on the phosphate group, which are repelling each other, making the compound less stable

Which of these molecules is least stable because of electrostatic repulsion? How does this help to explain the high phosphoryl-transfer potential of ATP, i.e., the spontaneity of ATP hydrolysis?

The least stable molecule is ATP.

The more unstable they are, the more they want to give up that phosphate group, hence, the higher gibbs free energy & the high phosphoryl-transfer potential of ATP.

How are proteins digested?

enzymatic activity secreted by the pancreas; proteases

proteases convert proteins into amino acids and peptides

Pepsin optimal activity; 1 to 2 pH, very acidic

How are carbs digested?

the action of salivary amylases

how are lipids (fats) digested?

digestion in the stomach; with grinding and mixing in the stomach--converts lipids into emulsion, which is lipid droplets and water

Lactose tolerant blood glucose levels

should increase after drinking a lactose product

lactose intolerant blood glucose levels

should stay the same or decrease after consuming a lactose product, has trouble digesting and absorbing the product

Hydrogen breath tests for lactose tolerant

hydrogen levels should be less due to the enzyme lactase

Hydrogen breath tests for lactose intolerant

production of hydrogen gas increases due to the lack of the enzyme lactase

UDP-glucose

enhances the energy content of a molecule

activated energy rich molecule

glycotransferases

catalyze the formation of glycosidic bonds

glycosidic bond

A glycosidic bond is a covalent bond in which a carbohydrate to the side of Asparagine (N-Linked) or the side chain of serine or threonine ( O-Linked). THINK OF AST

erythroprotein

has oligosaccharides linked with 3 asparagine residues and one serine

AS

proteoglycans

function as structural components and lubricants

Carbohydrates make up a much larger percentage by weight of the proteoglycan compared with simple glycoproteins

mucoprotein or mucins

key component of mucus, serve as lubricants, reduce friction b/t surfaces and trap molecules

Lectins

carbohydrate binding proteins

lectins on one cell recognize and bind to carbohydrates on another cell with multiple weak interactions.

Emulsification

is enhanced with the aid of bile salts, amphipathic molecules, making the triacylglycerols more readily digested

emulsion

a mixture of lipid droplets and water.

Pyranose formation

The open-chain form of glucose cyclizes when the C-5 hydroxyl group attacks carbon atom C-1 of the aldehyde group to form an intramolecular hemiacetal. Two anomeric forms, designated α and β,can result

D-glucose and L-glucose are enantiomers, meaning that their molecular structures are mirror images of each other.

TRUE

Anomeric Carbon

Before becoming cyclic, it is the carbonyl carbon

After becoming cyclic, it is bonded to the OH that determines anomeric form (alpha or beta)

The cyclic forms of carbohydrates

can exist in two forms, α- and β-based on the position of the substituent at the anomeric center.

Carbohydrates Are Attached to Proteins to Form Glycoproteins

True! as 50% of the proteome consists of glycoproteins

Homeostasis.

Maintaining a constant cellular environment requires complex metabolic regulation that coordinates the use of nutrient pools

OIL RIG stands for

oxidation is loss, reduction is gain (of electrons)

Four factors differentiate the stability of the reactants and products:

1. electrostatic repulsion,
2. resonance stabilization,
3. an increase in entropy,
4. stabilization due to hydration.

Energy charge ranges from 0 (all AMP) to 1(all ATP)

TRUE

ATP, ADP and AMP are

Recycled

ATP + ADP + AMP =

Constant

Chylomicron formation

Free fatty acids and monoacylglycerols are absorbed by intestinal epithelial cells.

Triacylglycerols are resynthesized and packaged with other lipids and proteins to form chylomicrons, which are then released into the lymph system

Lack of Glycosylation Can Result in Pathological Conditions

TRUE because of Hurler's disease

Many of the proteins secreted from cells are glycosylated, or modified by the attachment of carbohydrates, including most proteins present in the serum component of blood

True because of ABO blood type

Blood Groups

Are Based on Protein Glycosylation Patterns on the surfaces of red blood cells

The results of carbohydrate digestion, primarily glucose, galactose, and fructose, are transported into the intestinal cells by specific transport proteins

The carbohydrates also exit the cell with the assistance of transport proteins

SGLT1 and GLUT2 transporters

as carbon becomes oxidized throughout glycolysis or b-oxidation (basically carbon loses electrons by associating with oxygen –energy is released)

The energy is captured to make ATP

An oxidation-reduction reaction

is a reaction in which electrons are transferred.

Why does glucose need a transporter to cross the cell membrane?

It is a large, hydrophilic, polar molecule

GLUT1 location and function

location: all mammalian tissues
function: basal glucose uptake

GLUT2 location and function

location: liver & pancreatic B cells
function: in pancreas, plays role in insulin regulation. in liver, removes excess glucose from blood.

GLUT3 location and function

location: all mammalian tissues
function: basal glucose uptake

GLUT4 location and function

location: muscle and fat cells
function: transport of glucose into muscle + fat, regulated by insulin

GLUT5 location and function

location: small intestine
function: primarily a fructose transporter

Which glucose transporter (GLUT) is responsible for transport of glucose into muscle and fat cells?

GLUT4

What molecule regulates transport of GLUT protein to the cell surface in muscle and fat cells?

insulin

What is the main role of glycolysis?

to generate ATP

WHY are steps 1, 3, and 10 energetically favorable?

irreversible reactions
steps 1 +3 : ATP hydrolysis
step 10: phosphoenolpyruvate has a higher phosphoryl transfer potential than ATP

Regulated enzymes often catalyze __ reactions.

irreversible

function of allosteric enzymes

regulate the flux of biochemicals through metabolic pathways

allosteric enzymes depend on alterations in ___ structure

quarternary

Which form is active form?

R form

Which form is less active form?

T form

When [ATP] is low, describe kM.

How does this effect glycolysis?

low Km.

activates glycolysis

When [ATP] is high, describe kM.

How does this effect glycolysis?

high Km

inhibits glycolysis

What is the glycolysis pathway regulated by?

energy charge

High energy charge ____ glycolysis

inhibits

bc ATP generating pathway is high

Low energy charge ___ glycolysis

stimulates

bc ATP generating pathway is low

How many moles of ATP, NADH, and pyruvate are formed from 1 mole of glucose in glycolysis?

ATP: 2
NADH: 2
pyruvate: 2

When ATP is needed, glycolysis is __.

activated

When ATP levels are sufficient, glycolysis is __.

inhibited

Hexokinase is inhibited by

glucose-6-phosphate

PFK-1 is inhibited by

ATP and citrate

Pyruvate kinase is inhibited by

ATP

Why is oxidation of the aldehyde carbon energetically favorable?

Oxygen is very electronegative. Energy is released when it goes into oxidized form

Referring to Figure 16.3, explain in your own words how glyceraldehyde 3-phosphate dehydrogenase overcomes the energetically unfavorable process of phosphorylation after oxidation.

study

The enzyme aldolase catalyzes the following reaction in the glycolytic pathway:


The ΔG°′ for the reaction is +23.8 kJ mol−1, whereas the ΔG in the cell is −1.3 kJ mol−1. Explain how the reaction can be endergonic under standard conditions and exergonic under intracellular conditions.

Under the standard conditions the reaction is endergonic because it doesn't account for the concentrations of reactants and products. With concentrations accounted for in intracellular conditions, the reaction can be exergonic if the concentration of reactants is greater than concentration of products

Substrate-Level Phosphorylation

The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.

What is the phosphate donor in substrate level phosphorylation?

a kinase substrate with high phosphoryl transfer potential