Comprehensive AP® Biology: Carbohydrates, Lipids, Proteins, and Nucleic Acids

What are the primary functions of carbohydrates in organisms?

Carbohydrates are needed for cellular energy and provide structural support in plants, fungi, and arthropods.

What is the general composition of carbohydrates?

Carbohydrates are composed of carbon, hydrogen, and oxygen, typically following the CH2O ratio.

How are carbohydrates categorized based on monomer count?

Carbohydrates are categorized into monosaccharides, disaccharides, and polysaccharides.

What type of bond is formed between monosaccharides during dehydration synthesis?

Glycosidic bonds are formed between monosaccharides during dehydration synthesis.

Name examples of monosaccharides, disaccharides, and polysaccharides.

Monosaccharides: glucose, fructose; Disaccharides: sucrose; Polysaccharides: cellulose, starch, glycogen.

What is the role of starch and glycogen in glucose storage?

Storing glucose as starch and glycogen limits metabolic access, preventing cellular leakage and osmotic pressure issues.

What is chitin and its function?

Chitin is a nitrogen-containing polysaccharide that forms the hard exoskeleton of insects.

What is the stoichiometric formula for carbohydrates?

The stoichiometric formula for carbohydrates is (CH2O)n, indicating a 1:2:1 ratio of carbon to hydrogen to oxygen.

What are monosaccharides and how are they classified?

Monosaccharides are simple sugars with three to seven carbon atoms, classified as aldoses (with an aldehyde group) or ketoses (with a ketone group).

What are the classifications of monosaccharides based on carbon number?

Monosaccharides are classified as trioses (3 carbons), pentoses (5 carbons), and hexoses (6 carbons).

What is the significance of glucose in cellular respiration?

Glucose is a crucial energy source for humans, and its breakdown during cellular respiration yields adenosine triphosphate (ATP).

How do plants synthesize glucose?

Plants synthesize glucose from carbon dioxide and water for energy, storing excess as starch.

What are isomers of glucose and how do they differ?

Galactose and fructose are isomers of glucose, sharing the formula C6H12O6 but differing in the structural arrangement of functional groups.

What are the two forms of glucose in aqueous solutions?

Glucose can exist in linear forms or ring-shaped molecules, typically found in ring forms in aqueous solutions.

What are the two arrangements of the hydroxyl group in glucose's ring form?

In its ring form, glucose can have the hydroxyl group in an alpha (α) position if below the plane, or beta (β) if above the plane.

How are disaccharides formed?

Disaccharides are formed by the dehydration reaction of two monosaccharides, releasing a water molecule and creating a covalent glycosidic bond.

Name common disaccharides and their components.

Common disaccharides include lactose (glucose + galactose), maltose (two glucose molecules), and sucrose (glucose + fructose).

What are polysaccharides and how are they structured?

Polysaccharides are long chains of monosaccharides linked by glycosidic bonds, which can be branched or unbranched.

What are key examples of polysaccharides?

Key examples of polysaccharides include starch, glycogen, cellulose, and chitin.

What is the primary energy storage form in plants?

Starch, consisting of amylose and amylopectin, serves as the primary energy storage form in plants.

How does human digestion of starch occur?

Human digestion of starch involves enzymes like salivary amylases that break it down into smaller sugars like maltose and glucose for absorption.

What is glycogen and where is it primarily found?

Glycogen is the glucose storage form in animals, primarily found in liver and muscle cells.

What process mobilizes glycogen when blood glucose levels drop?

Glycogenolysis.

What is cellulose and what role does it play in plants?

Cellulose is the most abundant biopolymer that constitutes the plant cell wall, providing structural integrity.

Why can't humans digest cellulose?

Humans lack the necessary enzymes to break down cellulose.

How do herbivores digest cellulose?

Herbivores use specialized gut bacteria that produce cellulase to digest cellulose.

What is chitin and where is it found?

Chitin is a polysaccharide found in arthropod exoskeletons and fungal cell walls.

What are the energy contributions of carbohydrates compared to fats?

Carbohydrates provide 4.3 Kcal per gram, while fats provide 9 Kcal per gram.

What role does fiber play in digestive health?

Fiber aids in regular bowel movements, regulates blood glucose levels, and helps eliminate excess cholesterol.

What is the significance of including carbohydrates in a balanced diet?

Carbohydrates should be included alongside proteins, vitamins, and fats for optimal health.

What are the main components of lipids?

Lipids are composed of carbon, hydrogen, and oxygen in distinct arrangements.

What are the key types of lipids?

Fats, oils, waxes, phospholipids, and steroids.

What is the structure of triglycerides?

Triglycerides consist of three fatty acids bonded to glycerol.

What distinguishes saturated fats from unsaturated fats?

Saturated fats have only single bonds in the fatty acid chain, while unsaturated fats contain one or more double bonds.

What is hydrogenation and its effect on fats?

Hydrogenation alters oils by converting some cis double bonds to trans configurations, which are linked to heart disease.

What is the structure of phospholipids?

Phospholipids consist of a glycerol backbone, two fatty acids, and a phosphate group, making them amphipathic.

What role does cholesterol play in the body?

Cholesterol serves as a precursor for important steroid hormones like testosterone.

What are the functions of lipids in organisms?

Lipids serve as long-term energy storage, insulation, and form protective layers for aquatic animals.

How are fatty acids named?

Fatty acids are named based on their origin, such as palmitic acid from palm trees and arachidic acid from peanuts.

What is the physical state of saturated fats at room temperature?

Saturated fats are typically solid at room temperature.

What is the physical state of unsaturated fats at room temperature?

Unsaturated fats are usually liquid at room temperature, often referred to as oils.

What is the role of lipids in cellular structure?

Lipids act as building blocks for hormones and components of cellular membranes.

What is the misconception about carbohydrates in modern diets?

Carbohydrates are often misunderstood as harmful, leading to diets that eliminate them.

What are the two configurations of double bonds in unsaturated fatty acids?

Cis (same plane) and trans (different planes)

How does a cis double bond affect the shape of fatty acids?

It causes a bend or a 'kink' that prevents tight packing, keeping them liquid at room temperature.

What process creates trans fats?

Hydrogenation, where hydrogen gas is added to oils, converting some cis double bonds to trans double bonds.

What are common sources of trans fats?

Margarine, certain peanut butters, and shortening.

How do trans fats affect cholesterol levels?

They elevate levels of low-density lipoproteins (LDL), known as 'bad' cholesterol.

What health risk is associated with elevated LDL levels due to trans fat consumption?

Increased risk of heart disease due to arterial plaque formation.

What actions have been taken in response to health concerns about trans fats?

Many fast food chains have eliminated trans fats, and regulations require clear labeling of trans fat content.

What are omega fatty acids and why are they essential?

Omega-3 and omega-6 fatty acids cannot be synthesized by the body and must be obtained through diet.

What are the main types of omega-3 fatty acids?

Alpha-linoleic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

What dietary sources are rich in omega-3 fatty acids?

Fatty fish such as salmon, trout, and tuna.

What health benefits are associated with omega-3 fatty acids?

Lowering risk of heart attacks, reducing triglycerides, lowering blood pressure, inhibiting blood clotting, and reducing inflammation.

What role do fats play in the body despite criticism?

They provide energy, aid in vitamin absorption, and provide body insulation.

What are waxes and their function in nature?

Waxes cover feathers of aquatic birds and leaf surfaces, preventing water from sticking due to their hydrophobic nature.

What are the structural components of phospholipids?

Two fatty acid chains linked to a glycerol or sphingosine backbone and a modified phosphate group.

What is the key characteristic of phospholipids?

Their amphipathic nature, having both hydrophobic tails and a hydrophilic head.

How do phospholipids arrange in aqueous environments?

They spontaneously form bilayers or micelles, maintaining membrane integrity.

What defines steroids in terms of structure?

They have a fused ring structure with four interconnected carbon rings.

What is a common characteristic of steroids, including cholesterol?

They are hydrophobic and insoluble in water.

What is the role of cholesterol in the body?

It serves as a precursor for steroid hormones, Vitamin D, and bile salts.

Where is cholesterol primarily synthesized?

In the liver.

Why is cholesterol essential for bodily functions?

Cholesterol contributes to the plasma membrane structure of animal cells and facilitates material transport, cellular recognition, and communication.

What are proteins composed of?

Proteins are composed of chains of amino acids linked by peptide bonds.

What are the four levels of protein structure?

The four levels are primary (amino acid sequence), secondary (local folding), tertiary (overall 3D shape), and quaternary (multi-polypeptide interactions).

How can a single amino acid change affect protein function?

A single amino acid change can significantly affect protein function, as exemplified by sickle cell anemia caused by one substitution in hemoglobin.

What environmental factors can denature proteins?

Temperature and pH can denature proteins, disrupting their three-dimensional structure and rendering them nonfunctional.

What are the main functions of proteins?

Proteins serve various functions including structural support, regulatory roles, transport, and enzymatic activity.

What role do enzymes play in biological processes?

Enzymes act as biological catalysts, accelerating biochemical reactions specific to their substrates.

How are enzymes categorized?

Enzymes are categorized as catabolic, anabolic, or catalytic.

What is the role of hormones in the body?

Hormones regulate essential physiological processes like metabolism and growth, exemplified by insulin's role in glucose regulation.

What determines the properties of amino acids?

The properties of amino acids are determined by the nature of their R groups.

How many common amino acids are there, and how many are essential for humans?

There are 20 common amino acids, with nine deemed essential for humans.

What is the difference between a polypeptide and a protein?

A polypeptide is a chain of amino acids, while a protein consists of one or more polypeptides that have undergone modifications.

What is the significance of post-translational modifications?

Post-translational modifications are essential for proteins to achieve their functional state, including alterations like cleavage and the addition of chemical groups.

What is the primary structure of a protein?

The primary structure is determined by its unique amino acid sequence.

What is an active site in the context of enzymes?

The active site is the specific region where an enzyme binds to its substrate.

What happens if the active site of an enzyme is altered?

If the active site is altered, the enzyme may be unable to bind to the substrate.

What are the distinct ends of a polypeptide chain?

The distinct ends are the N terminal (amino end) and C terminal (carboxyl end).

What is the role of disulfide bonds in protein structure?

Disulfide bonds connect chains of proteins, such as the two chains of insulin, contributing to the protein's stability.

What can cause denaturation of proteins?

Denaturation can be caused by environmental factors like temperature and pH changes.

What is the significance of protein shape?

The shape of a protein is critical to its function, as it determines how it interacts with other molecules.

What is the difference between globular and fibrous proteins?

Globular proteins are typically soluble and functional, while fibrous proteins provide structural support.

How do amino acids link to form proteins?

Amino acids link to form proteins via peptide bonds created through dehydration reactions between the carboxyl and amino groups of adjacent amino acids.

How is the amino acid sequence of proteins determined?

It is dictated by the corresponding gene, and changes in the gene's nucleotide sequence can alter the protein's structure and function.

What condition illustrates the impact of a single amino acid substitution in hemoglobin?

Sickle cell anemia, where glutamic acid is replaced by valine in the beta chain.

What is the composition of hemoglobin?

Hemoglobin consists of two alpha and two beta chains, totaling approximately 600 amino acids.

What type of mutation causes sickle cell anemia?

A point mutation, affecting just one base out of 1800 in the DNA sequence.

What are the consequences of the mutation responsible for sickle cell anemia?

It leads to the formation of fibrous hemoglobin, resulting in deformed red blood cells that cause blockages in blood vessels.

What health complications can individuals with sickle cell anemia experience?

Severe health complications including breathlessness, dizziness, headaches, and abdominal pain.

What are the two main types of secondary protein structures?

α-helices and β-pleated sheets.

What stabilizes the α-helix structure in proteins?

Hydrogen bonds between carbonyl groups of one amino acid and the amino group of another four residues down the chain.

How many amino acid residues are typically in each turn of an α-helix?

3.6 amino acid residues.

What characterizes the β-pleated sheet structure?

Hydrogen bonds between the backbone atoms of the polypeptide, creating pleated segments.

How do R groups behave in β-pleated sheets?

R groups are attached to carbon atoms and alternate above and below the folds of the sheet.

What are the two configurations that segments in β-pleated sheets can align in?

Parallel or antiparallel configurations.

What defines the tertiary structure of a polypeptide?

Its unique three-dimensional shape formed by various chemical interactions.

What types of interactions among R groups contribute to the stability of proteins?

Like-charged R groups repel each other, while unlike-charged R groups attract, contributing to ionic bonds.

What is the role of hydrophobic interactions in protein folding?

Nonpolar amino acids' hydrophobic R groups tend to cluster in the interior, influencing overall protein conformation.