Biochemistry Exam 3

Locking in!!

What are lipids?

A highly reduced carbon-rich substance, nonpolar organic solvents.

Lipids can be both

hydrophobic (nonpolar) and amphiphatic (nonpolar & polar regions)

Three common fatty acid lipids are

1. Triaglycerols (triglycerides)

2. Glycerophospholipids

3. Sphingolipids

A common non-fatty acid containing lipid is

Sterols

The active functions of lipids are

Energy storage

Membrane structure

Electron carriers

Emulsifying agents

Horomones

What is a fatty acid?

A caboxcylic acid with a hydrocarbon chain

Which FA has no C-C double bonds?

Saturated

Which FA has at least one C-C double bond?

Unsaturated

Which FA has ONLY one C-C double bond?

Monounsaturated

Which FA has two or more C-C double bonds?

Polyunsaturated

In standard nomenclature, what carbon is named 1? What are the names of carbon 2 and 3?

1 - Goes to the carboxyl carbon

2. alpha

3. beta

What does the nomenclature 18:1^{^}Δ9

It is an 18-carbon fatty acid with one double bond between c-9 and c-10

FA nomenclature specifies what?

The chain length (starting @ carboxyl carbon) and # of double bonds (n)

Polyunsaturated fatty acids start their numbering at

the methyl carbon (carbon most distant from carboxyl group) aka the omega (Ω) carbon.
Because of this, double bonds are numbered relative to the Ω carbon

Polyunsaturated fatty acids with a double bond between C3 and C4 and called

omega-3 fatty acids

What essential nutrients do omega-3 fatty acids have?

a-linolenic acid (ALA), docosahecaneoic acid (DHA), and eicosapentaenoic acid (EPA)

What are essential fatty acids?

fatty acids that cannot be synthesized by the body but must be obtained from the diet

Melting points of FA are determined by

length and degree of unsaturation of the hydrocarbon chain

The longer the FA chain (at same degree of unsat.), the _____ the melting point

higher

The ____ the double bonds in a FA (assuming length is same) the higher the melting point

fewer

For saturated FA, their most stable arrangement is what?

Very closely packed - almost crystalline array

The kink found in unsaturated fatty acids is a result of

cis double bonds

Tight packing between these FA have less extensive interactions, taking less energy to disrupt them→ lower melting point

unsaturated fatty acids

Triacyglycerols (trigylcerides) contain what?

Three FA molecules esterified to three hydroxyl groups of glycerol

The primary storage form of body fat is

triacyglycerols

The abbreviation and melting point for Stearic Acid is

18:0 , 70 C

The abbreviation and melting point of Oleic acid is

18:1 , 16 C

The abbreviation and melting point of linoleic acid is

18:2 , -5 C

The abbreviation and melting point for Linolenic acid is

18:3 , -11 C

Triaglycerols are very

nonpolar

What specialized enzymes catalyze the hydrolysis of the ester in triaglycerols in order for the FA to be used as fuel?

lipases

Triacylglycerols wich in unsat. FA and are generally liquid at room temperature are called

oils

Triacylglycerols rich in saturated fatty acids and are generally semisolids or solids at room temperature are called

fats

What are the two major classifications for lipids?

Storage lipids (triacylglycerols) and Structural lipids

What do storage lipids do?

They are used primarily to store energy, they are neutral and nonpolar

What do structural lipids do?

they provide structure for membranes, they contain polar and nonpolar groups

What are the two main types of structural lipids?

Glycerophospholipids and sphingolipids

What are the primary constituents of cell membranes?

Glycerophopholipids

Glycerophospholipids differ from triacylglycerols in that

only two of the hydroxyl groups of glycerol are esterified to FA

The third hydroxyl group in glycerophospholipids contains a _____ group that is connected to a given “head group” via a phosphodiester bond

phosphate

The difference between sphingosine and glycerophospholipids is

the backbone of sphingosine is NOT glycerol

Sterols contain

four fused rings (steroid nucleus) and a hydroxyl group

What is the structural basis for all biological membranes?

Lipid bilayers

What makes lipid molecules self-sealing and flexible?

Their noncovalent interactions

The direction lipids face in bilayers are

polar head groups contact aqueous medium
nonpolar tails point toward interior

What defines the external boundaries of cells and separates cellular compartments?

Biological membranes

A biological membrane consists of

proteins embedded in/or associated with a lipid bilayer

Which membrane proteins contain hydrophobic regions embedded in the hydrophobic lipid bilayer as well as penetrate or span the bilayer

Integral membrane proteins (trans membrane proteins)

Which membrane proteins are associated with the membrane through change-change or hydrogen bonding interactions to integral proteins/membrane lipids as well as readily dissociate from membranes

Peripheral membrane proteins

What are functions of membrane proteins?

mediate movement of ions and polar molecules across a membrane

generate proton gradients for ATP production

respond to extracellular signals and communicate them to cell interior

Hydrophobic (fat soluble) molecules can pass through the membrane’s hydrophobic interior by

simple diffusion

Cell membranes are essential impermeable to

ions and large polar molecules

Ions / large polar molecules require this to form passages through hydrophobic barrier

membrane transporter proteins

Three types of integral membrane transporter proteins are

1. Channels

2. Passive transporters

3. active transporters

What are the transmembrane proteins with aqueous pores that extend across the membrane called?

Channels

In channels, the ion movement is

down the concentration gradient

How much energy do channels require?

None

Which is faster? Channels or membrane transporters?

Channels

Passive transporters are

transmembrane proteins

Passive transporters move the solute

down its concentration gradient

How much energy do passive transporters require?

None

Channels are usually

not saturable

Carrier proteins are

saturable

Active transport requires energy to move a solute

up the concentration gradient

Active transport can be powered by

a direct source of energy (e.g. ATP, electron transport, light)

What are the characteristics of simple diffusion?

No protein carrier

Unable to saturate with solute

DOWN the conc. gradient

No energy required

What are the characteristics of Channel facilitated diffusion?

Unable to saturate with solute

DOWN conc. gradient

No energy input required

What are the characteristics of Passive transporter facilitated diffusion?

Able to saturate with solution

DOWN the conc. gradient

No energy input required

What are the characteristics of Active transport?

Able to saturate with solute

UP the conc. gradient
Energy input required

The membrane consists of

Lipids

Proteins

Carbohydrates

Fats are digested by enzymes called

lipases

Lipases degrade what?

fats to free fatty acids and a glycerol

Where does glycerol from degraded fats travel to?

The liver

Fatty acids become bound to what? (a protein)

serum albumin

Fats → Glycerol → ( in liver cell) (Glycolysis) →

pyruvate

Fat → glycerol → (in liver cell) (gluconeogenesis )→

glucose

Fat → Fatty Acids → (Fat synthesis) →

Fats

Fat → fatty acids → (FA oxidation) → acetyl coA → (citric acid cycle) →

CO2 + H2O

Fat → Fatty acids → (membrane lipid synthesis) →

glycerophospholipids , sphingolipids

What are the three steps FA needs to complete to be degraded?

1. Activation of FA to a fatty acyl-CoA

2. Uptake into mitochondria

   1. Degradation (beta-oxidation) in the mitochondrial matrix

Prior to oxidation, what must FA do?

must be activated and transported to the mitochondria where the necessary enzymes are located

Before free FA can pass across the barrier, the must first be converted into

fatty acyl-CoA derivativesW

When free fatty acids are converted to acyl-CoA derivatives, what is consumed?

The equivalent of 2 ATP in the conversion of ATP to AMP

True/False: Fatty acyl-CoA esters cannot cross over the inner mitochondrial membrane. (why?)

True. They must be attached to a molecule of carnitine first (to form acyl-carntine)

What are the four pathways in beta-oxidation?

1. Oxidation

2. Hydration

3. Oxidation

4. Thiolysis

For each pathway in the beta-oxidation pathway, what is released and produced?

Each pathway releases two carbon fragments (acetyl coA) and return the FA that has 2 fewer carbons than the starting one

1 FADH2 and 1 NADH are produced

What happens during oxidation?

Generation of a double bond between alpha and beta bonds

What happens during Hydration?

Addition of water to the double bond

What happens during Oxidation (2)?

Oxidation of the beta-hydroxylacyl-CoA to a ketone

What happens during Thiolysis

Thiolytic cleavage by CoA

Each turn of the beta oxidation pathway forms what?

an Acetyl-CoA

The number of acetyl-CoA units formed is equal to

the number of carbons in the fatty acid, divided by 2

The last acetyl-CoA is formed without what?

formation of NADH and FADH2. This is because the last step forms two acetyl-CoA if the fatty acid has an even number of carbons

The number of ___ and ___ units formed is less than the number of acetyl-coA formed.

NADH , FADH2

Palmitic acid:

CH3-(CH2)₁₄-COOH —— 16C

When palmitic acid is beta-oxidized, what is produced?

8 acetyl-CoA, +AMP + 2P_ⁱ + 7 FADH2 + 7 NADH

Oxidation of 1 glucose (6 C) to CO2 and water yields how many ATP’s?

32

Oxidation of palmitate ( 16 C) yields how many ATP’s?

106 ATP → 106 ATP /16 carbons → 6.6 ATP per carbon

True/False: Oxidation of fatty acids yields more energy than Carbohydrates?

True

Free fatty acids are transported in the blood bound to

serum albumin protein