Chemistry - Unit 12 :lipids
Carbohydrates are present only on the exterior surface of the plasma membrane and are attached to proteins, forming __________.
glycoproteins
A phospholipid molecule has a polar "head" and a nonpolar "tail." Much of the structure of the plasma membrane consists of a double layer of these molecules. Going from the outside of the cell membrane to the inside of the cell membrane, which of the following gives the correct orientation of the two layers of phospholipid molecules?
head-tail, tail-head
A single substance tends to move from an area of _____concentration to an area of _____concentration until the concentration is equal across a space.
higher to lower
Lipid molecules are predominately
hydrocarbon
Cholesterol is mainly synthesized in the liver. Identify the precursor of cholesterol.
non-cyclic, 30-carbon squalene
Covalent compound
nonmetal + nonmetal
Covalent bonds typically form between two
nonmetal atoms
The hydrophobic tails of one layer line up with the hydrophobic tails of the second layer so that the inner portion of the bilayer is ______.
nonpolar
Lipids are soluble in
nonpolar solvent
Which of the following is not component of a plasma membrane?
nucleic acid
Each ester bond formed from a carboxylic acid and an alcohol leads to the loss of
one water molecule, for a total of three.
After which chemical procedure can the presence of trans carbon-carbon double bonds be observed in a triglyceride?
partial hydrogenation
Transport by diffusion expends no energy but requires that the substance be able to
pass through the membrane without assistance.
The hydrophilic head group of a phospholipid consists of a __________ group attached to a glycerol molecule.
phosphate
Which of the following is component of a plasma membrane?
phospholipids glycolipids cholesterol
Ions that consist of two or more atoms are known as __________.
polyatomic ions
Multiple double bonds are
polyunsaturated
Fatty acids with more than one double bond are called
polyunsaturated Linoleic acid is an example of a polyunsaturated fatty acid that has two double bonds between carbon atoms.
Which of the following types of lipids have a glycerol group?
glycerophospholipids oils
What are the two major kinds of phospholipids?
glycerophospholipids and sphingomyelin
When a protein is attached to a carbohydrate, it is called a __________.
glycoprotein
The group that is least likely to ionize is the __________.
noble gases
Two atoms of the same element are most likely to form __________.
non polar covalent bond
The __________ describes the structure of the plasma membrane as a fluid combination of phospholipids, cholesterol, and proteins.
fluid mosaic model
Steroids are composed of
four connected rings of carbon atoms.
Transmembrane proteins facilitate diffusion through the
cell membrane by forming pores or channels, or by binding to the substance and moving it through the membrane
Which of the lipids do not generally have a fatty acid component?
Steroids
A ___________ region of the phospholipid bilayer faces the outside of the cell; a ___________ region faces the inside of the cell. In the center of the bilayer is a ___________ region.
A polar region of the phospholipid bilayer faces the outside of the cell; a polar region faces the inside of the cell. In the center of the bilayer is a nonpolar region.
All steroids have
four linked carbon rings, and several of them (like cholesterol) have a short tail.
Steroid component
four ring carbon nucleus
Structure of cholesterol
fused ring structure
Partially hydrogenated glycerides that contain trans double bonds are called
"trans fats."
Fatty acids contain the _____ group and _____ chain
-COOH (carboxyl group) and hydrocarbon chain
sphingomyelin contains _____ fatty acids
1
Carbohydrates account for about __________ of the composition by mass in a typical human cell.
10%
Fatty acid chain consist of how many carbons
12-18
Myelin, an outgrowth of the membrane of specialized cells that insulates the axons of the peripheral nerves, contains about ___ percent protein and ____ percent lipid.
18 protein 76 lipid
Instead of 3 fatty acids, phospholipids have _fatty acids.
2
glycerophospholipid contains _____ fatty acid components
2
Elements in group 2 will tend to form ions with a charge of __________.
2+
Arachidonic acid is a polyunsaturated fatty acid with 20 carbons and 4 double bonds, so its structure is summarized as
20:4.
How many fatty acids are found on a fat molecule?
3
steroids always have _ rings
4
Steroids examples
Cholesterol Cortisol
Unsaturated meaning
Containing double bonds
How are the two fatty acids and the phosphate amino alcohol in a glycerophospholipid connected to the glycerol?
Each fatty acid and the alcohol are attached by ester bonds.
Why are fats also called triacylglycerols?
Fats are composed of three fatty acids attached to a glycerol backbone by a dehydration reaction. Fat molecules contain three ester groups.
Triacylglycerols are composed of two components
Glycerol Fatty acids
Why are HDLs viewed as a good form of cholesterol compared to LDLs?
HDLs transport cholesterol back to the liver without depositing it in the arteries.
Oil and water =
Heterogeneous mixture Do not mix
Saturated fatty acids melt at _______ temp
Higher
Steroids 3 types
Hormones Vitamins Cholesterol
__________ consist of electrostatic forces of attraction between oppositely charged ions (cations and anions).
Ionic bonds
How does a glycerophospholipid differ from a triacylglycerol?
It contains a phosphate group, and a triacylglycerol does not. It contains an amino alcohol, and a triacylglycerol does not. It contains two fatty acid chains, while a triacylglycerol contains three.
How does a glycerophospholipid differ from a triacylglycerol?
It contains a phosphate group, and a triacylglycerol does not. It contains an amino alcohol, and a triacylglycerol does not. It contains two fatty acid chains, while a triacylglycerol contains three.
Which of the following is a characteristic of an HDL, a high-density lipoprotein?
It is a lipoprotein that removes excess cholesterol from the tissues and carries it to the liver.
Most of the cholesterol in the body is produced in the liver and must be transported by the bloodstream to the rest of the body. How is it transported?
It is packed into a lipoprotein structure.
R′ group is the rest of the
glycerol (a three-carbon chain).
It is spherical in shape, with an inner core of nonpolar lipids and a polar surface made up of the head of phospholipid molecules.
LDL
Why is LDL thought of as bad cholesterol?
LDL transports cholesterol from the liver to the rest of the body; if there is extra, it gets deposited in the arteries.
Unsaturated fatty acids melt at _____ temp
Lower kink in the chain interferes with crystal packing
Structure of cortisol
Nonpolar hydrocarbons
Why are saturated acids harder to melt?
Packed together
Head of the phospholipid is made up of
Phosphate Glycerol
Waxes are found on
Plant leaves Bird feathers
Cellulose and starch are both examples of
Polysaccharides
The proportions of proteins, lipids, and carbohydrates in the plasma membrane vary with cell type, but for a typical human cell, protein accounts for about __% of the composition by mass and lipids (of all types) account for about __% of the composition by mass
Protein 50% Mass and lipids 40%
The tail of a phospholipid is made up of
Saturated and unsaturated fatty acid
Saturated meaning
Single bonds
How does a sphingomyelin differ from a glycerophospholipid?
The glycerol and one fatty acid is replaced by a sphingosine group.
n a phospholipid bilayer, what is the nature of the inner portion of the bilayer?
The inner portion is nonpolar; the hydrophobic tails of the phospholipid molecule, which are nonpolar, make up the inner core of the membrane phospholipid bilayer. In an aqueous solution, phospholipids tend to arrange themselves with their polar heads facing outward and their hydrophobic tails facing inward.
How are phospholipid molecules arranged in the structure of the lipid bilayer?
They are arranged with their hydrophobic tails facing each other and hydrophilic heads facing out.
Although steroids do not resemble other lipids, they are grouped with them. Why?
They are hydrophobic and insoluble in water.
Phospholipids are major constituents of the plasma membrane and are composed of fatty acid chains attached to a glycerol or sphingosine backbone, resulting in glycerophospholipids and sphingolipids. What is the nature of the fatty acids in phospholipids?
They are saturated fatty acids. They are unsaturated fatty acids. They have hydrophobic tails.
Some steroids are referred to as sterols. What specifically characterizes a sterol as distinct from other steroids?
They have an (OH) functional group.
Which of the following is true of covalent bonds?
They have lower melting points than ionic bonds. They have lower boiling points than ionic bonds. They do not conduct electricity or heat well.
Wax covering the feathers of some aquatic birds and the leaf surfaces of some plants provides a barrier to water because of the hydrophobic nature of waxes. What contributes to the hydrophobic nature of waxes?
Waxes are esters that are mostly made up of nonpolar carbon-carbon or carbon-hydrogen bonds.
Ionic compounds always consist of __________.
cations and anions whose summed charges yield a neutral compound
Cholesterol is a precursor of many compounds. For which of the following compounds is it a precursor? Select all that apply. a. steroid hormones b. bile salts c. vitamin D d. phospholipids
a b c
Which of the following statements correctly describe an aspect of cholesterol structure? a. It contains four fused rings. b. It contains a double bond in ring B. c. There is a hydrocarbon chain on C-17. d. Ring D contains six carbons.
a b c
What are the primary components of a fatty acid?
a carboxyl group a long aliphatic chain
Which of the following is NOT a component of a steroid?
a fatty acid a phosphate group a glycerol backbone
Which of the following is NOT a component of a steroid?
a fatty acid a phosphate group a glycerol backbone
Phospholipids
a lipid containing a phosphate group in its molecule
The components of fatty acids led to their name. What are those components?
a long chain of hydrocarbons to which a carboxyl group is attached
Which transport process involves the movement of substances from an area of low concentration to an area of high concentration?
active transport
Which transport processes involve substances being transported across the plasma membrane through transmembrane proteins?
active transport facilitated transport
Complete hydrogenation fully removes
all carbon-carbon double bonds, and no trans double bonds can be present.
A molecule with a positively or negatively charged area and an uncharged, or non-polar, area is referred to as __________.
amphiphilic
Structural isomers
are molecules that have the same molecular formula, but differ in the way the atoms are connected. In other words, they have different structural formulas.
Fatty acid has a ________ group
carboxylic acid group −(C=O)−OH.
A phospholipid is a molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone. What chemical group or groups modify the phosphate group?
choline and serine
Natural occuring double bond fatty acids
cis
Valence electrons are shared in
covalent bonds ionic bonds
Compounds consisting of atoms that share electrons with one another instead of gaining or losing electrons are called
covalent compounds molecular compounds
Potential energy ______________ as orbitals begin to overlap and ________________ as protons are pushed too close together.
decrease increase
Which transport processes are passive, in the sense that they do not require metabolic energy from the cell in order to work?
diffusion facilitated transport
Which transport processes involve the movement of substances from an area of high concentration to an area of low concentration?
diffusion facilitated transport
Three main types of transport through cell membranes are
diffusion (or passive) transport facilitated transport active transport
Covalent compounds are typically:
electrically neutral poor conductors of electricity water insoluble
An ion results from an atom that gains or loses __________.
electrons
Different ions of a given element will have differing numbers of __________.
electrons
nonpolar covalent bonds: _____distribution of electrons
equal
fatty acids are connected to glycerol by
ester groups
Hydroxides can hydrolyze the
esters
Peripheral proteins are found on the
exterior and interior surfaces of membranes, attached either to integral proteins or to phospholipids.
Lipids include a wide range of compounds. Which of the following are lipids?
fats oils waxes phospholipids steroids
R group is the rest of the
fatty acid (the hydrocarbon chain),
Waxes contain what kind of chains
fatty acid chains
Waxes are made up of long
fatty acid chains esterified to long-chain alcohols.
An ester bond forms when a
fatty acid is incorporated into a phospholipid.
In the structure of a glycerophospholipid, which among the following is hydrophobic in nature?
fatty acids
A steroid does not contain
fatty acids phosphate groups glycerol.
Fats are formed from
fatty acids and glycerol with the loss of the three water molecules (one for each ester bond formed).
Triacylglycerols have three
fatty acids per molecule
Glycerophospholipids have two
fatty acids per molecule.
Which of the following are structural components of fats?
glycerols fatty acids
An important distinction in types of fatty acids is whether they are saturated or unsaturated. These terms are a reference to whether the molecule is saturated with __________.
hydrogen
Revert fats to fatty acids and glycerol reaction
hydrolysis, and it requires three water molecules (H2O) to break the ester bonds
Head of phospholipid is
hydrophilic (water loving) polar
The tail of a phospholipid is?
hydrophobic nonpolar
Steroid is groups with lipids because it is
hydrophobic and made up primarily of carbon and hydrogen.
What are the primary interactions between the fatty acid chains in a phospholipid bilayer?
hydrophobic interactions
Glycerol has a ____ group
hydroxyl (−OH)
Peripheral proteins attached either to
inegral protein or to phosopholipids
Metals and nonmetals are joined by __________.
ionic bonds
choline
is an amino alcohol
Partial hydrogenation of unsaturated triglycerides tends to result in
isomerization of cis carbon-carbon double bonds to trans double bonds.
Oils are fats that are _____ at room temperature.
liquid
LDL is a low-density lipoprotein involved in transporting cholesterol from the
liver to the tissues.
Trans double bond fatty acids are found
man-made
In facilitated transport (facilitated diffusion), what helps move particles across the plasma membrane?
membrane proteins
One of the carbons in a phospholipid is occupied by a
modified phosphate group.
The phosphate-containing group on a phospholipid generally has a __________ charge at biological pH levels.
negative
Active transport mechanisms are also called __________.
pumps
The noble gases are also called the inert gases because they are very unlikely to
react. This is because they have a full valence shell of electrons, which means they do not want to gain or lose any electrons. The other groups listed all readily ionize.
A steroid does not
resemble other lipids
Single bonds are
saturated
Molecular compounds differ from ionic compounds because atoms will __________ electrons in molecular compounds instead of gaining or losing them.
share
Covalent bonds form when two atoms
share electrons between them.
What about the phospholipid bilayer prevents fluid from outside the cell from mixing with fluid inside the cell?
the fatty acid section of the phospholipids in the center of the membrane
One of the unique aspects of a phospholipid structure is that it is amphiphilic. Which of the following is the portion of a phospholipid that is connected to both the hydrophobic part and the hydrophilic part?
the glycerol backbone
A triacylglycerol, or fat, contains _____ fatty acid components
three
Glycerol has three
three carbons three hydroxyl gorups three fatty acids
Triacylglycerides, or fats, are formed by combining
three fatty acids with glycerol (a triol) to form three ester bonds.
Glycerol is an organic compound (alcohol) with __________ carbons, __________ hydrogens, and __________ hydroxyl (OH) groups.
three, five, three
Partially hydrogenated glycerides can therefore contain .
trans carbon-carbon double bonds
Carrier proteins that bind to substances to move them through the membrane and proteins that form pores or channels to allow passage of substances through the membrane are collectively called __________.
transmembrane proteins
Diffusion is a passive process of
transport
Identify the lipid(s) present in the body.
triacylglycerols steroids glycerophospholipids
Fats are also called
triglycerides
In general, covalent bonding can occur between which of the following?
two neutral atoms
Fatty acids tails are _____ and with an ______ of carbons
unbranched and with an even number of c
polar covalent bonds: ______ distribution of electrons
unequal
Double bonds are
unsaturated
Phytosterols are present in
vegetable oils.
Lipids are insoluble in
water
Which of the following types of lipids have a fatty acid component?
waxes phospholipids oils
