OnRamps Biology Unit 2

Flashcards covering all of unit 2-based off of the notes taken from Learning Modules and the additional readings

Monosaccharides

The simplest form of carbohydrates, consisting of a single sugar molecule such as glucose or fructose. They serve as the building blocks for more complex carbohydrates. Can exist as linear chain or ring-shaped molecules.

Disaccharides

Carbohydrates formed by the combination of two monosaccharides through a glycosidic bond, such as sucrose, lactose, and maltose. When the two monosaccharides combine, they release a molecule of water in a dehydration synthesis reaction and form a covalent bond.

Polysaccharides

Complex carbohydrates composed of long chains of monosaccharides. They serve various functions, including energy storage and structural support, and examples include starch, glycogen, cellulose, and chitin. They can be branched or unbranched structures, depending on the type.

Glycogen

A polysaccharide that serves as a form of energy storage in animals, primarily found in the liver and muscle tissues. It is made up of glucose units linked together in a branched structure, allowing for rapid release of glucose when energy is needed.

Glycogenolysis

The metabolic process of breaking down glycogen into glucose, primarily occurring in the liver and muscles to maintain blood sugar levels during fasting or intense exercise.

Cellulose

A complex polysaccharide composed of unbranched linear chains of glucose units connected by β(1→4) glycosidic bonds. It is the principal structural component of plant cell walls, providing high tensile strength and rigidity. Hydrogen bonding between parallel chains forms tough microfibrils, and because humans lack the cellulase enzyme required to break β-linkages, it passes through the human digestive tract undigested as dietary fiber.

Chitin

A structural polysaccharide found in the exoskeletons of arthropods and the cell walls of fungi, composed of N-acetylglucosamine units linked by β(1→4) glycosidic bonds. It provides strength and protection.

Examples of Monosaccharides

Glucose, galactose, fructose

Lipids

A diverse group of hydrophobic molecules, including fats, oils, and steroids, that are primarily composed of carbon and hydrogen. They serve as energy storage, provide insulation, and form the structural components of cell membranes.

Triacylglycerols/Triglycerides

A type of lipid formed from glycerol and three fatty acids. They are the main form of stored energy in animals and serve as an important energy source.

Saturated fat

Contain no double bonds between carbon atoms, making them solid at room temperature.

Unsaturated fat

Have one or more double bonds, resulting in a liquid state at room temperature.

Cis fat

A type of unsaturated fat where the hydrogen atoms are on the same side of the double bond, resulting in a kinked structure that prevents tight packing.

Trans fat

A type of unsaturated fat where the hydrogen atoms are on opposite sides of the double bond, leading to a straighter structure that allows for tighter packing.

Omega fatty acids

Essential fatty acids characterized by the position of the first double bond in their carbon chain, typically classified as omega-3 or omega-6. Must be supplemented through diet.

Waxes

A type of lipid that is nonpolar and typically solid at room temperature, composed of long-chain fatty acids esterified to long-chain alcohols. They have a hydrophobic nature and prevent water from sticking.

Phospholipids

A class of lipids consisting of two fatty acids and a phosphate group attached to a glycerol backbone, forming a hydrophilic head and hydrophobic tails. This structure is essential for cell membrane formation.

Amphipathic

Molecules that have both hydrophilic and hydrophobic regions, allowing them to interact with both water and lipid environments. One example would be phospholipids.

Steroids

A class of lipids characterized by a carbon skeleton with four fused rings. They play various roles in biological systems, including functioning as hormones and membrane stabilizers. An example is cholesterol.

Sucrose

A disaccharide composed of glucose and fructose, commonly found in plants and used as a primary form of sugar in many foods. It has a chemical formula of C₁₂H₂₂O_11.

Lactose

A disaccharide made up of one glucose and one galactose molecule, commonly found in milk and dairy products. It serves as a significant source of energy.

Maltose

A disaccharide consisting of two glucose molecules, it is formed during the digestion of starch and is commonly found in malted foods and beverages.

Structural difference between alpha and beta isomers of glucose

The difference is how they form a polymer. Alpha-glucose polymers are found in starch and glycogen and form the digestible or energy-rich carbohydrates.

What is made up of beta-glucose polymers?

Wood, cellulose, and insect exoskeletons

Starch and glycogen are both polysaccharides but differ in their structure and function. What are the functional differences between starch and glycogen?

Starch serves as an energy storage polysaccharide in plants, while glycogen serves a similar purpose in animals. Glycogen is more extensively branched than starch, allowing for quicker mobilization of glucose when energy is needed.

Which member of the lipid family comprises the majority of the structure of the plasma membrane?

Phospholipids, which form a bilayer, allow for selective permeability and fluidity of the membrane.

Nucleotide

The monomer of nucleic acids, consisting of a nitrogenous base, a pentose (five-carbon) sugar, and one or more phosphate groups.

Deoxyribonucleic acid (DNA)

The genetic material in all living organisms that carries genetic information, remains in the nucleus of eukaryotic cells, and forms an antiparallel double helix.

Ribonucleic acid (RNA)

A usually single-stranded nucleic acid comprised of ribonucleotides linked by phosphodiester bonds, involved in protein synthesis under the direction of DNA.

Genome

The entire genetic content of a cell.

Genomics

The study of genomes.

Chromatin

The substance of eukaryotic chromosomes, formed by a complex of DNA and histone proteins.

Purines

Nitrogenous bases containing a double carbon-nitrogen ring primary structure, which includes adenine ($A$) and guanine ($G$).

Pyrimidines

Nitrogenous bases containing a single carbon-nitrogen ring primary structure, which includes cytosine ($C$), thymine ($T$), and uracil ($U$).

Nitrogenous base

An organic carbon- and nitrogen-containing molecule that acts as a base because its amino group can bind an extra hydrogen, decreasing hydrogen ion concentration in its environment.

Deoxyribose

The five-carbon pentose sugar found in DNA nucleotides that has an $-H$ atom instead of an $-OH$ group at the $2'$ carbon position.

Ribose

The five-carbon pentose sugar found in RNA nucleotides that contains a hydroxyl group ($-OH$) at the $2'$ carbon position.

Phosphodiester linkage

The $5'$–$3'$ covalent bond formed when a phosphate attached to the $5'$ carbon of one sugar connects to the hydroxyl group at the $3'$ carbon of the next sugar, releasing two phosphate groups.

Antiparallel orientation

The structural arrangement of double-stranded DNA where one strand runs in the $5'$ to $3'$ direction while the matching strand runs $3'$ to $5'$.

Base complementary rule

The rule stating that in DNA, adenine ($A$) pairs specifically with thymine ($T$) via $2$ hydrogen bonds, and guanine ($G$) pairs with cytosine ($C$) via $3$ hydrogen bonds.

Chargaff's rule

The principle stating that within the DNA of an organism, the amount of adenine ($A$) equals thymine ($T$) ($A = T$) and the amount of guanine ($G$) equals cytosine ($C$) ($C = G$).

Watson-Crick base pairing rules

The rules describing specific hydrogen-bonding relationships between base pairs ($A$ with $T$, $C$ with $G$), named after the scientists who discovered their structural basis.

Messenger RNA (mRNA)

The intermediary RNA synthesized in the nucleus that carries the complementary message from DNA to the cytoplasm to direct cellular protein synthesis.

Codon

A set of three consecutive nitrogenous bases on an mRNA strand that codes for a single amino acid during protein synthesis.

Ribosomal RNA (rRNA)

A major constituent of ribosomes that aligns mRNA properly and catalyzes peptide bond formation using its peptidyl transferase activity.

Transfer RNA (tRNA)

A small RNA molecule ($70$–$90$ nucleotides long) that carries the correct amino acid to the protein synthesis site by base pairing with complementary mRNA codons.

MicroRNA (miRNA)

The smallest type of RNA molecule, which regulates gene expression by interfering with the expression of specific mRNA messages.

Central Dogma of Life

The fundamental principle of cellular information flow stating that genetic information flows from DNA to RNA via transcription, and from RNA to protein via translation.

Transcription

The cellular process by which DNA dictates the synthesis and structural sequence of an mRNA molecule.

Translation

The cellular process by which mRNA sequence dictates the amino acid sequence of a protein product.

Base pairing spatial restriction

The structural limitation in the DNA double helix where a $20\,\text{Å}$ width prevents two purines from fitting and keeps two pyrimidines too far apart to form hydrogen bonds.

DNA base pair distance

The exact physical separation distance of $0.34\,nm$ between consecutive base pairs in the DNA double helix.

Template Strand for RNA

The DNA strand that serves as the guide for synthesizing complementary RNA during transcription. The resulting mRNA strand will be a mirror of this strand.

Coding Strand for RNA

The natural partner to the DNA strand, this strand sits to the side and does not actually transcribe to anything. Because it is the natural DNA partner to the template strand, it ends up looking almost identical to the new mRNA transcript. They share the exact same 5'-to-3' direction and the exact same order of letters—the only catch is that the coding strand uses Thymine (T) while the mRNA uses Uracil (U).

Why do adenine and thymine form only two hydrogen bonds?

The C-H bond in adenine is non-polar.

The backbone of DNA is formed by ___ between the 3’____ of a nucleotide to the 5’ ______ of the next nucleotide

Hydrogen bonds, hydroxyl, phosphate