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CHM 201 > chapter 19 > Flashcards

chapter 19 Flashcards

1
Q

cholesterol

A
  • is a steroid
  • lipid whos structure is based on fused-ring
  • three 6-membered
    rings and one 5-membered ring
    -called steroid nucleus
  • no head or tail component
    -Cholesterol: C27 steroid molecule and precursor for other steroid-based lipids
    -Important in human cell membranes, nerve tissue, and brain tissue
    -Important in chemical synthesis of various hormones and vitamins essential for life
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2
Q

cell membrane (plasma membrane)

A
  • Lipid-based structure that separates aqueous interior of a cell from the aqueous environment surrounding the cell
    • 80% of plasma is lipid
  • the membranes are lipid bilayers made up of phospholipids
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3
Q

lipid bilayer

A
  • Nonpolar tails of phospholipids are in the middle and polar heads are on the surface
    • 6–9 nanometers thick
    • Contains at least one unsaturated fatty acid
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4
Q

Cholesterol in food

A
  • Liver synthesizes almost 1g of cholesterol everyday
    • Not necessary to consume in the form of diet
  • Cholesterol ingestion decreases biosynthetic cholesterol production
  • Cholesterol is distributed to cells via the bloodstream using a protein carrier system called lipoproteins.
  • Animal food contains lots of cholesterol
  • Plant food contains negligible amounts of cholesterol
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5
Q

cholesterol and cell membrane

A
  • Cholesterol molecules are also components of plasma membranes
    • Cholesterol helps regulate membrane fluidity–the fused-ring system does not allow rotation of fatty acid tails in the vicinity
    • Fits between fatty acid chains of the lipid bilayer
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6
Q

membrane proteins

A
  • Lipid bilayers also contain proteins
    • Responsible for moving substances such as nutrients and electrolytes across the membrane
    • Act as receptors that bind hormones and neurotransmitters
  • The membrane proteins and some lipids further react with carbohydrate molecules
    • Act as markers, substances that play roles in processes by which different cells recognize each other
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7
Q

transport across cell membranes

A

To maintain cellular processes, various types of molecules are transported across the cell membranes

Three types of transport:

  1. Passive transport
  2. Facilitated transport
  3. Active transport
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8
Q

Passive transport across cell membranes

A
  • Process in which a substance moves across a cell membrane by diffusion from a region of higher concentration to a region of lower concentration
    • No cellular energy expenditure
    • Only a few types of molecules, including O2, N2, urea, and ethanol, can cross membranes by this process
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9
Q

Facilitated transport across a cell membrane

A

Process in which a substance moves across a cell membrane, with the aid of a membrane protein, from a region of higher concentration to a region of lower concentration

- No cellular energy expenditure 
- Specific protein carriers or transporters are involved in the process
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10
Q

active transport across cell membranes

A

Process in which a substance moves across a cell membrane, with the aid of membrane proteins, against a concentration gradient

  • Involves expenditure of cellular energy
    • Supplied by ATP molecules
  • Proteins involved in active transport are called “pumps”
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11
Q

emulsification lipids

A

Substance that can disperse and stabilize water-insoluble substances as colloidal particles in an aqueous solution

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12
Q

bile acids

A

Cholesterol derivative that functions as an emulsifying agent that makes dietary lipids soluble in aqueous environment of the digestive tract

  - Approximately one third of cholesterol produced by liver is converted to bile acids
 - Similar to the action of soap in washing process   - Tri- or dihydroxy cholesterol derivatives
 - The carbon 17 side chain of cholesterol has been oxidized to a carboxylic acid
- The oxidized acid side chain is bonded to an amino acid (either glycine or taurine) through an amide linkage
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13
Q

Bile

A

A fluid containing emulsifying agents secreted by the liver, stored in the gallbladder, and released into the small intestine during digestion

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14
Q

Cholesterol derivatives

A

Cholic acid, 12-deoxycholic acid and 7-deoxycholic all function as a lipid-emulsifying agent in the aqueous environment of the digestive tract.

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15
Q

hormones

A
  • Biochemical substances produced by a ductless gland that has a messenger function
  • Serve as a means of communication between various tissues
    • Some hormones are lipids
  • The lipids that play the role of “chemical messengers” include:
    • Steroid hormone - Derivative of cholesterol
    • Eicosanoid - Derivative of fatty acids
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16
Q

Sex hormones

A

control reproduction and secondary sex characteristics

  • 3 major subclasses
    1. Estrogens—the female sex hormones
    2. Androgens—the male sex hormones
    3. Progestins—the pregnancy hormones
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17
Q

adrenocorticoid hormones

A
  • regulate numerous biochemical processes in the body
  • Produced by the adrenal glands
  • 28 Different hormones have been isolated from the adrenal cortex
  • Types of adrenocorticoid hormones:
    • Mineralocorticoids - Control the balance of Na+ and K+ ions in cells
    • Glucocorticoids - Control glucose metabolism and counteract inflammation
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18
Q

eicosanoids

A
  • Arachidonic acid (20:4) derivatives
  • Have profound physiological effects at extremely low concentrations
  • Are hormone-like molecules
  • Exert their effects in the tissues where they are synthesized
  • Usually have a very short “life”
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19
Q

physiological effects of eicosanoids

A

Include mediation of:

  1. Inflammatory response
  2. Production of pain and fever
  3. Regulation of blood pressure
  4. Induction of blood clotting
  5. Control of reproductive functions, such as induction of labor
  6. Regulation of the sleep/wake cycle
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20
Q

Principle type of eicosanoids: 1. prostaglandin

A
  • C20-fatty-acid derivative containing cyclopentane ring and oxygen-containing functional groups
    • Involved in:
      • Raising body temperature
      • Inhibiting the secretion of gastric juices
      • Increasing the secretion of a protective mucus layer into the stomach
      • Relaxing and contracting smooth muscle
      • Directing water and electrolyte balance
      • Intensifying pain and enhancing inflammation responses
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21
Q

Principle type of eicosanoids: 2. thromboxane

A
  • C20-fatty-acid derivative containing a cyclic ether ring and oxygen-containing functional groups
    • Promote platelet aggregation
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22
Q

Principle types of eicosanoids: 3. Leukotriene

A

C20-fatty-acid derivative containing three conjugated double bonds and hydroxy groups
-Promote inflammatory and hypersensitivity (allergy) responses

23
Q

biological wax

A
  • Monoester of a long-chain fatty acid and a long-chain alcohol
  • The fatty acids found in biological waxes:
    • Generally saturated fatty acids
    • Contain 14 to 36 carbon atoms
  • The alcohols found in biological waxes:
    • May be saturated or unsaturated
    • May contain 16 to 30 carbon atoms
24
Q

saponifiable lipids

A

Lipids that undergo hydrolysis in a basic solution to yield 2 or more small molecules

Linkage makeup:
Triacylglycerols—3 ester bonds
Glycerophospholipids—4 ester bonds
Sphingophospholipids—1 amide and 2 ester bonds
Sphingoglycolipids—1 amide, 1 ester, and 1 glycosidic bond
Biological waxes—1 ester bond

25
Q

Nonsaponifiable lipids

A
  • Cholesterol
  • bile acids
  • steriod hormones
  • eicosanoids
26
Q

lipid

A

An organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in non-polar organic solvents
-Unlike other biomolecules, lipids do not have a common structural feature that serves as the basis for defining such compounds
Classification is based in two different ways:
1. Biochemical function
2. Saponification

27
Q

biochemical function

A

For purposes of simplicity of study, lipids are divided into five categories based on their biochemical function:

- Energy-storage lipids (triacylglycerols)
- Membrane lipids (phospholipids,       sphingoglycolipids, and cholesterol)
- Emulsification lipids (bile acids)    - Messenger lipids (steroid hormones and eicosanoids)    - Protective-coating lipids (biological waxes)
28
Q

Saponification

A

Reaction: Hydrolysis reaction that occurs in a basic solution (NaOH)

  • Based on saponification reactions, lipids are divided into two categories:
    - Saponifiable lipids (triacylglycerols, phospholipids, sphingoglycolipids, cholesterol, and biological waxes)
    • Nonsaponifiable lipids (bile acids, steroid hormones, and eicosanoids)
29
Q

fatty acids

A

Naturally occurring monocarboxylic acids with linear (unbranched) carbon chain
-Have even number of carbon atoms
-Long-chain fatty acids (C12 to C26)
-Medium-chain fatty acids (C8 to C10)
-Short-chain fatty acids (C4 to C6)
Two types:
-Saturated - All C–C bonds are single bonds
-Unsaturated
-Monounsaturated (MUFA)
-Polyunsaturated (PUFA)

30
Q

saturated fatty acids

A
  • Fatty acids with a carbon chain in which all C–C bonds are single bonds
  • Numbering starts from the end of –COOH group
  • Structural notations for palmitic acid
31
Q

monounsaturated fatty acids (MUFAs)

A
  • Monounsaturated fatty acid: Fatty acid with a carbon chain in which one carbon–carbon double bond is present.
  • There are different ways of depicting the structure:
32
Q

polyunsaturated fatty acids

A
  • Fatty acids with a carbon chain in which two or more carbon–carbon double bonds are present
  • Up to six double bonds are found in biochemically important PUFAs
33
Q

20:5

A

20 carbons 5 double bonds

34
Q

water solubility

A
  • Short-chain fatty acids have some solubility, whereas long-chain fatty acids are insoluble
  • Short-chain fatty acids are sparingly soluble because of the presence of carboxylic group
35
Q

melting point

A

Melting points of fatty acids are influenced by the carbon chain length.
Melting points of fatty acids are influenced by their degree of unsaturation.

36
Q

bends

A
  • Number of “bends” in a fatty acid chain increases as the number of double bonds increases
    • Less packing occurs
    • Melting point is lower
    • Tend to be liquid at room temperature
37
Q

energy storage materials

A
  • With the notable exception of nerve cells, human cells store small amounts of energy-providing materials
    - Carbohydrate glycogen - Most widespread energy storage material present in small amounts
  • Major energy-storage material is triacylglycerol
    • Concentrated primarily in special cells (adipocytes) which are nearly filled with triacylglycerols
38
Q

2 types of triacylglycerols

A
  • Simple triacylglycerol: Triester formed from the esterification if glycerol with three identical fatty acid molecules
    - Naturally occurring simple triacylglycerols are rare
  • Mixed triacylglycerol: Triester formed from the esterification of glycerol with more than one kind of fatty acid molecule
39
Q

formation of a triacylglycerol- esterification

A

Triacylglycerols are more efficient in their ability to store energy when compared to glycogen, the energy storing form of glucose in the human body.

40
Q

fats and oils

A
  • Naturally occurring mixtures of triacylglycerols molecules.
  • Fats and oils have different types of triacylglycerol molecules present (mixed triacylglycerol or triglyceride).
  • The distinction between fats and oils lie in their physical state.

-pure fats and oils are colorless, ordorless and tasteless

41
Q

fats

A
  • Predominantly Saturated
  • Solids or semisolids at room temperature
  • Source: Animals
42
Q

oils

A
  • Predominantly unsaturated
  • Liquids at room temperature
  • Source: Plants and fish oil
43
Q

good fats vs. bad fats

A

-Studies indicate that type of dietary fat and amount of dietary fat are important to determine body responses to dietary fat
-Current recommended amount for total fat intake in calories:
-15% - Monounsaturated fat
-10% - Polyunsaturated
-

44
Q

essential fatty acids

A
  • Fatty acids that must be obtained from dietary sources because they cannot be synthesized within the body
  • Two most important essential fatty acids are:
    • Linoleic acid (18:2) - Omega 6
    • Linolenic acid (18:3) - Omega 3
      • Needed for proper membrane structure
      • Serve as starting materials for the production of several nutritionally important longer-chain omega-6 and omega-3 fatty acids
45
Q

4 types of reactions triacylglycerols undergo

A
  1. Hydrolysis – reverse of esterification. Different products depending on acidic versus basic conditions.
  2. Saponification – a specific type of hydrolysis. Always under basic conditions (NaOH).
  3. Hydrogenation – adding H2 across a double bond.
  4. Oxidation – C=C bonds break. Aldehydes (and COOH) and ketones are produced.
46
Q

Hydrolysis

A
  • Chemical properties of triacylglycerols are typical of the functional groups esters and alkenes
  • Carried out by enzymes produced by the pancreas in a stepwise manner
    • Breaking of outer fatty acids produces diacylglycerol and monoacylglycerol
  • Complete hydrolysis - When all three fatty acids are removed
  • Partial hydrolysis - When one or more fatty acid residue remains
47
Q

saponification

A
  • Hydrolysis in basic solution (NaOH)

- Products: Fatty acid and glycerol salts

48
Q

hydrogenation

A
  • Addition of hydrogen across C–C multiple bonds, which increases degree of saturation
  • Many food products are produced by partial hydrogenation of oils and fats
    • Peanut oil  Peanut butter
    • Liquid plant oil  Margarine
49
Q

oxidation

A
  • Double bonds in triacylglycerols are subject to oxidation with oxygen (an oxidizing agent)
  • Leads to C=C breakage that produces both aldehyde and carboxylic acid products
    • Products often have objectionable odors, and fats and oils are said to be rancid
  • To avoid this unwanted oxidation process, antioxidants are added as preservatives
    • Example: Vitamin C and vitamin E are naturally occurring antioxidant
50
Q

phospholipids

A

All cells are surrounded by a membrane that confines their contents
Up to 80% of the mass of a cell membrane can be lipid materials dominated by phospholipids
Phospholipid –
Lipid that contains one or more fatty acids, a phosphate group, a platform molecule to which the fatty acid(s) and the phosphate group are attached, and an alcohol that is attached to the phosphate group

51
Q

Glycerophospholipids

A
  • Lipids that contain two fatty acids and a phosphate group esterified to a glycerol molecule and an alcohol esterified to the phosphate group
  • All attachments (bonds) between groups are ester linkages
    • Contain four ester linkages when contrasted to three ester linkages in triacylglycerols
  • Undergo hydrolysis and saponification reactions in a manner similar to that for triacylglycerols
  • The alcohol attached to the phosphate group in a glycophospholipid is usually one of three amino alcohols:

Choline - Phosphatidylcholines
Ethanolamine - Phosphatidylethanolamines
Serine - Phosphatidylserines
Structurally glycerophospholipids are similar to triacylglycerols, but they have different biochemical functions
Triacylglycerols serve as energy-storage molecules
Glycerophospholipids function as components of cell membranes
A major structural difference between the two types of lipids is that of their “polarity”, which is responsible for their differing biochemical functions
Triacylglycerols are a nonpolar
Glycerophospholipids are polar

52
Q

sphingophospholipids

A
  • Structures based on the 18-carbon monounsaturated aminodialcohol sphingosine
  • Contains one fatty acid and one phosphate group attached to a sphingosine molecule, and an alcohol attached to the phosphate group
  • Participate in hydrolysis and saponification reaction
  • Sphingophospholipids in which the alcohol esterified to the phosphate group is choline are called sphingomyelins
    • Found in all cell membranes and are important structural components of the myelin sheath of neurons
53
Q

sphingoglycolipid

A
  • Contains both a fatty acid and a carbohydrate component attached to a sphingosine molecule.
  • Contains amide linkage and glycosidic linkage.
54
Q

cerebrosides

A
  • Simplest sphingoglycolipids
  • Contain a single monosaccharide unit – either glucose or galactose
  • Occur primarily in brain (7% of dry mass)
  • More complex sphingoglycolipids are called gangliosides and contain a branched chain of up to 7 monosaccharide residues.

CHM 201 (4 decks)

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