Biochemistry Lecture Review - Flashcards

Flashcards covering key vocabulary terms from the biochemistry lecture notes on carbohydrates, lipids, proteins, nucleic acids, metabolism, and membrane transport to aid in exam preparation.

Carbohydrates

Polar and hydrophilic molecules containing many hydroxyl (-OH) groups, making them highly soluble.

Monosaccharides

The simplest form of sugar, consisting of a single sugar unit.

Glucose

The primary fuel source for your body's cells, a common monosaccharide.

Fructose

A sugar found in fruit that is converted into glucose in the liver.

Galactose

A monosaccharide usually found as part of lactose (milk sugar).

Disaccharides

Sugars composed of two monosaccharide units linked together.

Sucrose

A disaccharide made of glucose and fructose, commonly known as table sugar.

Lactose

A disaccharide made of glucose and galactose, found in milk.

Maltose

A disaccharide made of two glucose units, found when starch is broken down.

Polysaccharides

Long chains of sugar units, functioning in storage or structure.

Glycogen

The way your body stores carbohydrates; it is a long, branched chain of glucose found in muscles (for quick energy) and the liver (to stabilize blood glucose).

Starch

A polysaccharide that serves as the main energy storage for plants and animals, containing α-glucose.

Cellulose

The most abundant carbohydrate, providing structural support in plants (e.g., wood, cotton, plant cell walls), made of β-glucose and insoluble.

Trioses

Monosaccharides with a 3-carbon count, such as glyceraldehyde.

Pentoses

Monosaccharides with a 5-carbon count, such as ribose (in RNA) and deoxyribose (in DNA).

Hexoses

Monosaccharides with a 6-carbon count, such as glucose, fructose, and galactose.

Amino sugars

Normal sugars where one hydroxyl (-OH) group is replaced by an amino (-NH2) group, serving primarily in structure and signaling rather than energy.

Glucosamine

An amino sugar found in cartilage and chitin (in insects).

Galactosamine

An amino sugar present in glycoproteins.

Polymers

Big molecules made by linking many small units called monomers.

Dehydration synthesis (Condensation)

A chemical reaction where two monomers join, catalyzed by enzymes, with the removal of a water molecule to form a covalent bond.

Hydrolysis

A chemical reaction that breaks a polymer bond by adding a water molecule.

Glycosidic linkage

The specific covalent bond that links sugar units together in carbohydrates.

α-1,4/α-1,6 glycosidic linkage

Specific sugar linkages that are easy for humans to digest, found in starches and glycogen.

β-1,4 glycosidic linkage

Specific sugar linkages that are structural and hard for humans to digest, found in cellulose and chitin.

Proteins

Polymers of amino acids whose sequence (primary structure) dictates their folding and function.

Peptide bonds

Covalent (amide) bonds that link amino acids together in a protein chain.

Chitin

A polysaccharide that forms the exoskeletons of arthropods, made of β-1,4 N-acetylglucosamine.

Saturated fats

Fatty acids with no carbon-carbon double bonds, resulting in a straight, tightly packed structure that is solid at room temperature.

Unsaturated fats

Fatty acids with one or more carbon-carbon double bonds, causing kinks in the chain and a looser packing, making them liquid at room temperature.

Hydrophobic

A property meaning 'water-hating,' describing substances like lipids with long nonpolar hydrocarbon tails that cannot form hydrogen bonds with water and thus aggregate.

Triglycerides (Triacylglycerol, TAG)

Lipids used for energy storage, composed of glycerol linked to three fatty acids via three ester bonds formed by dehydration synthesis.

Phospholipids

Lipids similar to triglycerides but with one fatty acid replaced by a phosphate-containing head group, crucial components of cell membranes.

Amphipathic

A molecule possessing both hydrophilic (water-loving) and hydrophobic (water-fearing) properties, characteristic of phospholipids.

Lipid bilayers

Self-assembled structures formed by phospholipids, acting as fundamental barriers in cell membranes.

Ketones

Acetoacetate, β-hydroxybutyrate, and acetone are alternative fuels made in the liver from fatty acids when glucose is limited (e.g., low-carb diet), which can be toxic in excess.

Aquaporins

Protein channels that allow for fast water movement across cell membranes, which are otherwise low-permeable to water.

Nucleic acids

Macromolecules including DNA, RNA, and energy nucleotides like ATP, involved in genetic information storage and expression.

DNA

Deoxyribonucleic acid, responsible for long-term genetic information storage.

RNA

Ribonucleic acid, which uses genetic information to help make proteins and regulate genes.

ATP/ADP/AMP

Energy nucleotides, with ATP (adenosine triphosphate) being the main energy currency of the cell.

Nucleotide

The basic building block of nucleic acids, consisting of a sugar (ribose or deoxyribose), one or more phosphates, and a nitrogenous base.

Ribose

The 5-carbon sugar found in RNA and ATP.

Deoxyribose

The 5-carbon sugar found in DNA, which lacks one oxygen atom compared to ribose.

Purines

Nitrogenous bases characterized by a two-ring structure, including Adenine (A) and Guanine (G).

Pyrimidines

Nitrogenous bases characterized by a one-ring structure, including Cytosine (C), Thymine (T, in DNA), and Uracil (U, in RNA).

Pre-mRNA

The freshly transcribed RNA molecule that undergoes splicing and processing to become mature mRNA.

mRNA

Messenger RNA, which carries the coding 'recipe' for proteins from DNA to the ribosome.

tRNA

Transfer RNA, which brings the correct amino acids to the ribosome during translation by matching its anticodon to the mRNA codon.

rRNA

Ribosomal RNA, which forms the core of the ribosome and catalyzes the formation of peptide bonds.

Amino acids (AA)

The monomers of proteins, each containing an amino group (-NH2), a carboxyl group (-COOH), and a variable R-group (side chain).

N-terminus

The beginning of a polypeptide chain, characterized by a free amino group (-NH2).

C-terminus

The end of a polypeptide chain, characterized by a free carboxyl group (-COOH).

Essential amino acids

Amino acids that cannot be synthesized by the body and must be obtained from the diet.

Nonessential amino acids

Amino acids that the body can synthesize on its own.

Glycine (Gly)

The smallest amino acid (with a hydrogen as its side chain), providing flexibility often seen in tight turns of protein structure.

Cysteine (Cys)

An amino acid with a sulfhydryl (-SH) group, allowing two cysteines to form a disulfide bond that stabilizes protein structure.

Disulfide bond

A covalent -S-S- bond formed between two cysteine residues, crucial for stabilizing the tertiary and sometimes quaternary structure of proteins.

Primary structure (protein)

The unique linear sequence of amino acids in a polypeptide chain, held together by covalent peptide bonds.

Secondary structure (protein)

Regular, repeating local structures within a polypeptide chain, such as α-helices and β-sheets, stabilized by hydrogen bonds between backbone atoms.

Tertiary structure (protein)

The full, three-dimensional folded shape of a single polypeptide chain, stabilized by various interactions including hydrophobic interactions, hydrogen bonds, ionic bonds (salt bridges), and disulfide bonds.

Quaternary structure (protein)

The arrangement of multiple polypeptide subunits (if present) to form a functional protein complex, held together by noncovalent forces and sometimes disulfide bonds.

Transcription

The process by which DNA is used as a template to synthesize pre-mRNA, which is then processed into mRNA.

Translation

The process where ribosomes read mRNA codons, tRNA molecules bring corresponding amino acids, and a polypeptide chain is synthesized (N-terminus to C-terminus).

Start Codon (AUG)

The specific mRNA codon that signals the beginning of protein synthesis and codes for the amino acid methionine.

Stop Codons (UAA, UAG, UGA)

mRNA codons that signal the termination of translation, leading to the release of the polypeptide chain.

Cytosol

The site in eukaryotic cells where glycolysis occurs, producing pyruvate.

Glycolysis

The metabolic pathway in the cytosol that breaks down glucose into pyruvate, yielding a net of 2 ATP and 2 NADH per glucose molecule.

Mitochondria

The powerhouse of the cell where pyruvate is converted to acetyl-CoA, which then enters the Citric Acid Cycle, followed by the Electron Transport Chain and ATP synthesis.

Aerobic respiration

Metabolic process that occurs in the presence of oxygen, where pyruvate is completely oxidized through the Citric Acid Cycle and Electron Transport Chain (with O2 as the final electron acceptor), yielding approximately 30-32 ATP per glucose.

Anaerobic respiration

Metabolic process that occurs without oxygen, where pyruvate is reduced (e.g., to lactate or ethanol) to regenerate NAD+ and keep glycolysis running, yielding only 2 ATP per glucose.

Lactic acid fermentation

An anaerobic process in humans where pyruvate is converted to lactate (via LDH), regenerating NAD+ to sustain glycolysis.

Electron carriers

Molecules like NAD/NADH and FAD/FADH2 that shuttle high-energy electrons from glycolysis and the Citric Acid Cycle to the Electron Transport Chain for ATP production.

Cori Cycle

A metabolic pathway for lactate recycling where lactate produced in muscles (under low O2) is transported to the liver, converted back to pyruvate then glucose (gluconeogenesis), and returned to the muscle.

Beta-oxidation

The process of breaking down fatty acids into acetyl-CoA, leading to a high ATP yield for energy.

Deamination

The removal of an amino group from amino acids, allowing their carbon skeletons to enter various metabolic pathways (pyruvate, acetyl-CoA, or Krebs cycle steps).

Simple (passive) diffusion

A type of membrane transport where small, nonpolar molecules (e.g., O2, CO2) and some small uncharged polar molecules cross the membrane down their concentration gradient without energy or protein assistance.

Facilitated diffusion

A type of passive membrane transport where ions and polar molecules (e.g., glucose via GLUT) move down their concentration gradient through specific protein channels or carriers (uniporters) without direct energy input, and is saturable.

Primary active transport

A type of membrane transport where ions are moved against their concentration gradient directly using energy from ATP hydrolysis, carried out by protein pumps/ATPases (e.g., Na+/K+-ATPase).

Secondary active transport (Cotransport)

A type of membrane transport where the movement of one solute down its established electrochemical gradient (usually Na+) provides the energy to drive another solute against its gradient, relying on an indirect energy source (a gradient set up by a primary pump).