Cell Structure and Function Exam 1: Nucleic Acids, Polysaccharides, and Lipids

Nucleotides

linear polymers made up of repeating monomer units

The specific part of the nucleotide responsible for making DNA and RNA "acidic"

phosphate group

DNA contains the 5-carbon sugar D-deoxyribose, RNA contains

D-ribose

Purines

Bases with a double-ring structure.

Adenine and Guanine

Pyrimidines

Bases with a single-ring structure. cytosine, thymine, uracil

DNA nucleotide bases

Adenine, Thymine, Guanine, Cytosine

RNA nucleotide bases

adenine, guanine, cytosine, uracil

Components of nucleic acids

a nitrogenous base, a pentose sugar(5 carbon sugar), and a phosphate group

Phosphoanhydride bonds

links the individual phosphate groups to each other in nucleic acids

Nucleoside

A structural unit composed of a nitrogenous base attached only to a sugar ring

Phosphoester bond

The specific chemical bond that links the very first phosphate group to the sugar ring in a nucleotide.

Phosphodiester bridge

chemical link connecting the 3' carbon of one nucleotide sugar to the 5' carbon of the next via a phosphate group.

5' end of nucleic acid

starting tip of a nucleic acid strand, marked by a free phosphate group

3' end of nucleic acid

terminating tip of a nucleic acid strand, marked by a free hydroxyl (\(-\text{OH}\)) group.

nucleotide sequences are always written in which direction?

From the 5' end to the 3' end

According to the rules of complementary base pairing in DNA, which of the following base sets correctly pair with each other?

A pairs with T; G pairs with C

What types of incoming precursor nucleotides (template) are required for building a new DNA strand versus a new RNA strand along a template?

dNTPs for DNA; NTPs for RNA

Template

A pre-existing nucleic acid molecule used to guide the correct sequence order of a newly synthesized strand.

Antiparallel

The structural arrangement of DNA where the two strands run side-by-side but face in opposite directions. 5' to 3' vs. 3' to 5'

Hydroxyl group is at what end of polynucleotide

3'

Phosphate Group is at what end of polynucleotide

5'

Complementary Bases across from each other are held together by

hydrogen bonds

Because RNA is normally single-stranded, it folds up by forming pairs between bases located in different areas of the ____________ molecule.

same

When base pairing occurs in an RNA molecule, how does it typically happen compared to DNA?

usually happens locally between bases in different areas of the same molecule.

DNA is double stranded and RNA is ________

single-stranded

RNA is single stranded meaning

they consist of only one nucleotide chain rather than two.

primary biological functions that polysaccharides serve in cells

Structure and storage

What describes the typical monomer repeating unit arrangement found in most long-chain polysaccharides?

A single kind of repeating unit or an alternating pattern of two kinds.

Polysaccharides

long chain polymers made of sugars and sugar derivatives

Oligosaccharides

Short sugar polymers that are sometimes attached to cell surface protein

Primary Biological Functions of polysaccharides in cells

Structure and storage

repeating unit arrangement found in most long-chain polysaccharides

A single kind of repeating unit or an alternating pattern of two kinds.

Aldosugar

A sugar that contains a terminal carbonyl group (C=O) at the end of its carbon chain.

Ketosugar

contains an internal carbonyl group (C=O) within its carbon chain.

Pentose

5 carbon sugar, with biological examples being ribose and deoxyribose

Hexose

6 carbon sugar, with biological examples being glucose, galactose, and fructose

Fischer projection

A structural drawing style that represents a sugar molecule in its open, linear chain form

Haworth projection

A structural drawing style that represents a sugar molecule in its closed, cyclic ring form.

structural difference between an aldosugar and a ketosugar based on the functional group placement

Aldosugars have a terminal carbonyl group; ketosugars have an internal carbonyl group.

Sugars within functional categories are named generically based on how many ____________ atoms they contain.

carbon

How many carbons does a sugar have?

3-7

⍺-D-glucose

ring form of glucose where the Carbon-1 hydroxyl group points downward; repeating monomer unit for starch and glycogen.

β-D-glucose

ring form of glucose where the Carbon-1 hydroxyl group points upward repeating monomer unit for cellulose.

Glycosidic bond

chemical linkage formed between two sugar molecules by the elimination of a water molecule.

Maltose

composed of two glucose units connected by an ⍺ glycosidic bond.

Lactose

composed of one glucose unit and one galactose unit connected by a β glycosidic bond

Sucrose

composed of one glucose unit and one fructose unit connected by an ⍺ glycosidic bond.

Starch

primary storage polysaccharide found in plant cells

Glycogen

primary storage polysaccharide found in animal cells and bacteria

⍺(1→6)) bond

responsible for creating side chains and branching in polysaccharides like glycogen.

⍺(1→4) glycosidic bonds

Linkage holding ⍺-D-glucose units together to form linear backbones of both starch and glycogen

Amylose

unbranched form of plant starch

Amylopectin

A branched form of plant starch

⍺-glucose polysaccharides form

helices

Cellulose

structural polysaccharide made of β-D-glucose that forms plant cell walls.

Microfibril

A bundle of long cellulose chains wrapped together to provide structural support in plant walls

N-acetylglucosamine (GlcNAc)

modified sugar monomer used to build both chitin and bacterial cell walls

N-acetylmuramic acid (MurNAc)

unique modified sugar monomer that pairs with GlcNAc to form bacterial cell walls.

Chitin

structural polysaccharide made entirely of GlcNAc units found in insect exoskeletons and crustacean shells

β-glucose structural polysaccharides like cellulose naturally form into

Extended strands

repeating building block for chitin

N-acetylglucosamine (GlcNAc)

In gram-negative bacterial cell walls, alternating units of GlcNAc and MurNAc make up the polysaccharide portion of which major membrane component?

Lipopolysaccharide (LPS)

β(1→4)

chemical linkage holding the repeating β-D-glucose monomers together in a cellulose chain

⍺ polysaccharides

Polymers like starch and glycogen that form loose, less-ordered helices due to their side chains

Microfibrils

Rigid aggregates of linear cellulose rods that measure about 5-20 nm in diameter.

Extensin

A specific protein found within the noncellulose matrix of plant and fungal cell walls.

Why are the loose helices formed by ⍺ polysaccharides (like starch and glycogen) not highly ordered?

Disruptive nature of side chains

In plant and fungal cell walls, rigid cellulose microfibrils are embedded in a noncellulose matrix. Which of the following sets of molecules makes up this matrix?

Hemicellulose, pectin, and extensin

Lipids

A class of macromolecules that are not formed by linear polymerization and are characterized by their hydrophobic nature.

Amphipathic

Having both distinct polar (water-loving) and nonpolar (water-fearing) regions within the same molecule

Biological Functions of Lipids

storage of energy, membrane structure, and signal transmission

How do lipids differ from other macromolecules?

not synthesized by linear polymerization of monomers.

fatty acid

long amphipathic, unbranched hydrocarbon chain with a carboxyl group at one end.

Saturated fatty acid

fatty acid with no carbon-carbon double bonds, forming a straight chain

Unsaturated fatty acid

fatty acid containing one or more carbon-carbon double bonds, which can alter the chain's shape

Cis double bond

double bond geometry that introduces a distinct bend or "kink" into a hydrocarbon chain

Trans double bond

double bond geometry that keeps the hydrocarbon chain relatively straight, resembling a saturated fat

Triacylglycerol

storage lipid formed by linking one glycerol molecule to three fatty acid chains.

Why are plant triacylglycerols (vegetable oils) liquid at room temperature, while animal triacylglycerols (fats) are solid or semisolid?

Plant fats are predominantly unsaturated, and their bent cis chains prevent tight packing.

During the synthesis of a single triacylglycerol molecule from glycerol and three fatty acids, how many water (\(\text{H}_2\text{O}\)) molecules are eliminated as byproducts?

3

A fatty acid molecule is considered ____________ because it features a polar carboxyl group at one end and a long, nonpolar hydrocarbon chain at the other.

amphipathic

Stearic acid, found in butter, is a classic example of a(n) ____________ fatty acid because it contains no double bonds.

saturated

While natural vegetable oils contain cis double bonds, some manufactured margarines contain ____________ double bonds, which keep the hydrocarbon chain straight.

trans

Triacylglycerols are primarily used by organisms for energy ____________.

storage

Phosphoglycerides

Phospholipids built on a glycerol backbone

Sphingolipids

Phospholipids built on a sphingosine backbone.

Glycolipids

Specialized membrane lipids containing a carbohydrate chain instead of a phosphate group.

Outer monolayer

The specific side of the plasma membrane where glycolipids are largely located.

What is the structural backbone difference between a phosphoglyceride and a sphingolipid?

Phosphoglycerides use a glycerol backbone; sphingolipids use a sphingosine backbone.

Common hydrophilic R groups attached to phosphoglycerides

Inositol, Choline, Ethanolamine, Serine

The carbohydrate groups attached to a specialized glycolipid typically consist of how many sugar units?

1 to 6 monosaccharide units

Phospholipids are highly critical to membrane structure because of their ____________ nature, meaning they have both hydrophilic and hydrophobic parts.

amphipathic

Glycolipids that are modified derivatives of sphingosine and glycerol are specifically called ____________.

glycosphingolipids

The carbohydrate chains attached to glycolipids are made up of sugars such as D-glucose, D-galactose, or ____________.

N-acetyl-D-galactosamine

Steroids

Lipids characterized by a distinctive four-ringed hydrocarbon skeleton.

Cholesterol

common molecular building block used to synthesize all other steroids.

Estradiol

An estrogen steroid hormone responsible for femininization.

Testosterone

An androgen steroid hormone responsible for masculinization.

Cortisol

A glucocorticoid steroid hormone that triggers gluconeogenesis

Aldosterone

A mineralocorticoid steroid hormone that regulates ion reabsorption