BIOCHEM REVIEWER.docx

**THE STRUCTURE AND FUNCTION OF LARGE BIOLOGICAL MOLECULES** - All living things are made up of four classes of large biological molecules: **carbohydrates, lipids, proteins, and nucleic acids.** - Within cells, small organic molecules are joined together to form larger molecules....

**THE STRUCTURE AND FUNCTION OF LARGE BIOLOGICAL MOLECULES** - All living things are made up of four classes of large biological molecules: **carbohydrates, lipids, proteins, and nucleic acids.** - Within cells, small organic molecules are joined together to form larger molecules. - **Macromolecules** are large molecules composed of thousands of covalently connected atoms. - Molecular structure and function are **inseparable** **MACROMOLECULES ARE POLYMERS, BUILT FROM MONOMERS** - A **polymer** is a *long chain-like* molecule consisting of many similar building blocks. - These small building-block molecules are called **monomers.** - Three of the four classes of life's organic molecules are **polymers**: -- Carbohydrates -- Proteins -- Nucleic acid **THE SYNTHESIS AND BREAKDOWN OF POLYMERS** A **condensation reaction** or more specifically a **dehydration reaction** occurs when two monomers bond together through the loss of a water molecule: *dehydration synthesis = build by removing HOH.* - **Enzymes** are ***organic catalyst*s** = macromolecules that ***speed up*** chemical reactions. - **Polymers** are disassembled to monomers by ***hydrolysis: breaking down by adding HOH*** **THE DIVERSITY OF POLYMERS** - Each cell has thousands of different kinds of macromolecules. - Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species. - *An immense variety of polymers can be built from a small set of monomers.* **CARBOHYDRATES SERVE AS FUEL AND BUILDING MATERIAL** - Carbohydrates include sugars and the polymers of sugars. - The simplest carbohydrates are monosaccharides, or single sugars. - Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks. - **Monosaccharides** have molecular formulas that are usually multiples of ***CH2O*** - **Glucose** *(C6H12O6)* is the ***most common monosaccharide.*** - Monosaccharides are classified by - Though often drawn as linear skeletons, in aqueous solutions many sugars form rings. - **Monosaccharides** serve as a major ***fuel*** for cells and as raw material for building molecules. A **disaccharide** is formed when a dehydration reaction joins **two monosaccharides** by *removing* HOH to form a **covalent bond**. This covalent bond is called a **glycosidic linkage.** The condensation or dehydration synthesis reaction**: C6H12O6 + C6H12O6** = **C12H22O11** *(figure3)* **POLYSACCHARIDES** - **Polysaccharides**, the **polymers of sugars**, have *storage* and structural roles. - The structure and function of polysaccharides are **determined by their sugar monomers** and **the positions of the glycosidic linkages.** **STORAGE POLYSACCHARIDES** - **Starch** is a **plant storage** polysaccharide. - Starch is made of **glucose monomers**. - Plants store surplus starch as granules within **chloroplasts** and other **plastids**. - **Glycogen** is an **animal storage** polysaccharide. - Glycogen is found in the **liver and muscles**. *(figure4)* **STRUCTURAL POLYSACCHARIDES** - The **polysaccharide cellulose** is a major component of **plant cell walls.** - Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ. - The difference is based on two ring forms for glucose: **alpha ( )** and **beta ( )** - Polymers **with alpha glucose** are ***helical.*** - Polymers **with beta glucose** are ***straight.*** - In straight structures, H atoms on one strand can bond with OH groups on other strands. - Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants. - Enzymes that digest starch by hydrolyzing alpha linkages can't hydrolyze beta linkages in cellulose. - **Cellulose** in human food passes through the digestive tract as **insoluble fiber.** - Some microbes use enzymes to digest cellulose. - Many **herbivores,** from cows to termites, have **symbiotic relationships** with these **microbes**. - **Chitin**, another **structural polysaccharide**, is found in the *exoskeleton of arthropods.* - Chitin also provides structural support for the **cell walls of *fungi.*** - Unlike starch and glycogen, chitin is a polysaccharide **with nitrogen ( N ) in each sugar monomer.** **LIPIDS ARE A DIVERSE GROUP OF HYDROPHOBIC MOLECULES** - **Lipids** are the one class of **large biological molecules that do *not* form polymers.** - The unifying feature of lipids is having little or no affinity for water. - Lipids are **hydrophobic** because they consist mostly of hydrocarbons, which form nonpolar covalent bonds. - The most biologically important lipids are **fats, phospholipids, and steroids.** **FATS** - **Fats** are constructed from two types of smaller molecules: **glycerol** and **fatty acids.** - Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon. - A **fatty acid** consists of a **carboxyl group** attached to a **long hydrocarbon chain.** - This **fatty acid hydrocarbon** can be either ***saturated*** or ***unsaturated.*** *(figure8)* - Fats **separate from water** because water molecules form hydrogen bonds with each other and exclude the fats. - In a fat**, three fatty acids** are joined to **glycerol** by an **ester linkage** (covalent bond), creating a **triacylglycerol**, or **triglyceride.** - Fatty acids vary in length (number of carbons) and in the number and locations of double bonds. - **Saturated fatty acids** have the maximum number of hydrogen atoms possible and no double bonds**. All C - C bonds are single.** - **Unsaturated fatty acids** have one or more **double bonds C = C** *(figure9)* - Fats made from **saturated** fatty acids are called saturated fats, and are **solid at room temperature.** - **Most animal fats** are **saturated.** - Fats made from **unsaturated** fatty acids are called unsaturated fats or oils, and are **liquid at room temperature.** - **Plant fats** and **fish fats** are usually **unsaturated.** - A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits. - **Hydrogenation** is the process of converting **unsaturated fats** to **saturated fats** by *adding hydrogen*. - **Hydrogenating** *vegetable oils* also creates **unsaturated fats** with **trans double bonds** = **trans fats.** - **These trans fats may contribute more than saturated fats to cardiovascular disease.** - The major function of **fats** is **energy storage.** - Humans and other mammals store their fat in **adipose** cells. - Adipose tissue also **cushions** vital organs and **insulates** the body. **PHOSPHOLIPIDS \-- MEMBRANES** - In a **phospholipid**, two fatty acids and a phosphate group are attached to glycerol. - The two fatty acid tails are **hydrophobic**, but the phosphate group and its attachments form a **hydrophilic** head. - A phospholipid is an **amphipathic** molecule: hydrophillic head and hydrophobic tails. *(figure10)* - When **phospholipids** are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior. - The **amphipathic** structure of phospholipids results in a **bilayer arrangement** found in cell **membranes.** - **Phospholipids** are the major component of **all cell membranes.** *(figure11)* **STEROIDS = LIPIDS WITH 4 FUSED RINGS...** - **Steroids** are **lipids** characterized by a carbon skeleton consisting of **four fused rings.** - **Cholesterol**, an important steroid, is a component in animal cell membranes. - Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease. *(figure12)* **PROTEINS HAVE MANY STRUCTURES, RESULTING IN A WIDE RANGE OF FUNCTIONS** - **Proteins** account for **more than 50% of the dry mass of most cells.** - Protein **functions** include structural **support, storage, transport, cellular communications, movement, defense** against foreign substances, and organic catalysts (enzymes). - Proteins are **polymers** called **polypeptides.** - **Amino acids** are the **monomers** used to build proteins. Type of Proteins 1. **Enzymatic proteins** **Function:** Selective acceleration of chemical reaction **Examples:** Digestive Enzymes 2. **Structural proteins** **Function:** Support **Examples:** Silk fibers; collagen and elastin in animal connective tissues; keratin in hair, horns, feathers, and other skin appendages 3. **Storage proteins** **Function:** storage of amino acid **Examples:** ovalbumin in white egg; casein, the protein milk; storage proteins in plant seed 4. **Transport proteins** **Function:** Transport of other substances **Examples:** Hemoglobin, transport proteins 5. **Hormonal proteins** **Function:** coordination of an organism\'s activities **Examples:** Insulin, a hormone secreted by the pancreas 6. **Receptor proteins** **Function:** response of cell to chemical stimuli **Examples:** receptors in nerve cell membranes 7. **Contractile and motor proteins** **Function:** Movement **Examples:** actin and myocin in muscles, proteins in cilia and flagella 8. **Defensive proteins** **Function:** protection against disease **Examples:** antibodies combat bacteria and viruses - **Enzymes** are LARGE proteins that act as **catalysts** to **speed up** the rate of chemical reactions in cells. - Enzymes are **specific**. They must have a **shape-match** with molecules in the chemical reaction. - Enzymes can perform their functions repeatedly, working constantly to carry out the processes of life. *(figure13)* **PROTEINS = POLYPEPTIDES** - **Polypeptides** are **polymers** built from a set of **20** **amino acids (monomers).** - The **sequence of amino acids determines** a protein's **3D** three-dimensional **structure.** - A protein's structure determines its function. - A wide **variety** of proteins can be made from a few monomers by varying the **amino acid sequence.** **PROTEINS - AMINO ACID MONOMERS** - **Amino acids** are organic molecules with **carboxyl** and **amino groups** *attached* to a **central carbon.** - Amino acids differ in their properties due to **variable side chains**, called **R groups**. The R group is also ***attached to the central carbon.*** - There are **20 different amino acids** because there are **20 different side chains.** *(figure14&15)* **AMINO ACID POLYMERS** - **Amino acids are linked** by covalent bonds called **peptide bonds C - N** - A **polypeptide** is **a polymer of amino acids.** - Polypeptides range in length from a few to more than a thousand monomers. - Each polypeptide has a unique linear sequence of amino acids. *(figuure16)* - The **sequence of amino acids** determines a protein's three-dimensional structure. - **A protein's structure determines its function.** - A **functional protein** consists of one or more polypeptides twisted, folded, and coiled into a **unique shape.** *(figure17 & 18)* **FOUR LEVELS OF PROTEIN STRUCTURE \-- BECOMING** *(figure19)* Functional Proteins: - The **primary** structure of a protein is its **unique** sequence of amino acids in a **polypeptide chain.** - **Primary structure** is the **sequence of amino acids** in **a polypeptide chain** (protein). This is like the order of letters in a long word. - Primary structure is determined by **inherited genetic information** **(DNA).** *(figure20)* - **Secondary** structure consists of **regular *coils*** and ***folds*** in the polypeptide **backbone** made by **hydrogen bonds**. - The coils and folds of **secondary structure** result from **hydrogen bonds** between repeating constituents of the **polypeptide backbone.** - These regular bonds often make **fibrous proteins.** - Typical secondary structures are a **coil called an alpha helix** and **a folded structure called a beta pleated sheet.** ***(**figure21 & 22)* - **Tertiary** structure is determined by interactions among various side chains **R groups.** - **Tertiary structure** is determined by interactions between **R groups**, rather than interactions between backbone constituents. - These **R group interactions** fold the polypeptide into a **globular shape.** - These **interactions** between R groups include **hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions.** Strong covalent bonds called **disulfide bridges** may reinforce the protein's structure. - **Quaternary** structure results when a protein consists of **multiple** polypeptide **chains.** - **Quaternary structur**e results **when two or more polypeptide chains** form one macromolecule. - **Collagen** is a **fibrous protein** consisting of three **polypeptides coiled like a rope.** - **Hemoglobin** is a **globular protein** consisting of four polypeptides: two alpha and two beta chains each with an iron **heme** group. *(figure24)* **SICKLE-CELL DISEASE: A CHANGE IN DNA AND PRIMARY STRUCTURE** - A slight change in a proteins DNA can change its primary structure (amino acid sequence). This can affect a protein's structure and ability to function. - Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin. *(figure25 &26)* I. CARBOHYDRATE DEFICIT DISORDERS Disorders **resulting from insufficient carbohydrate intake or metabolism**, leading to energy deficiencies and metabolic complications. **DISORDERS** 1. **Hypoglycemia** **Symptoms:** Weakness, sweating, confusion, irritability. **Causes:** Excessive insulin, prolonged fasting, inadequate carbohydrate intake. 2. **Ketoacidosis** **Symptoms:** Nausea, vomiting, abdominal pain, fruity breath. **Causes:** Lack of carbohydrates in diabetics, leading to fat breakdown and ketone production. 3. **Glycogen Storage Disease (GSD)** **Types:** Several types based on enzyme deficiencies (e.g., GSD type I). **Symptoms:** Hypoglycemia, enlarged liver, growth delay. 4. **Starvation** **Symptoms:** Extreme weight loss, muscle wasting, fatigue. **Causes:** Prolonged lack of food intake. 5. **Muscle Wasting** **Symptoms:** Decreased muscle mass and strength. **Causes:** Inadequate carbohydrate intake leading to protein breakdown for energy. 6. **Ketosis** **Symptoms:** Fatigue, bad breath (fruity odor), nausea. **Causes:** Low carbohydrate availability, leading to fat utilization for energy. 7. **Marasmus** **Symptoms:** Severe weight loss, stunted growth. **Causes**: Deficiency in carbohydrates and proteins. 8. **Lactic Acidosis** **Symptoms:** Muscle pain, fatigue, rapid breathing. **Causes:** Accumulation of lactic acid due to impaired glucose metabolism. 9. **Hypoglycemic Shock** **Symptoms:** Confusion, seizures, loss of consciousness. **Causes:** Severe drop in blood sugar levels. 10. **Fatigue and Weakness** **Symptoms:** Persistent tiredness, low energy. **Causes:** Inadequate glucose supply for energy. **DIAGNOSIS AND TREATMENT** **Diagnosis:** Blood tests for glucose levels, metabolic panels, genetic testing for GSD. **Treatment:** Dietary management (increased carbohydrates), glucose supplementation, enzyme replacement therapy (for GSD). II\. LIPID DISORDERS Disorders characterized **by abnormal lipid levels in the blood**, leading to **cardiovascular** and **metabolic complications**. **DISORDERS** 1. **Hyperlipidemia** **Symptoms**: Often asymptomatic but may lead to cardiovascular disease. **Causes:** Diet high in saturated fats, genetic factors, sedentary lifestyle. 2. **Atherosclerosis** **Symptoms:** Chest pain (angina), shortness of breath, fatigue. **Causes:** Buildup of lipids and plaque in arterial walls. 3. **Familial Hypercholesterolemia** **Symptoms:** Early onset heart disease, xanthomas (cholesterol deposits in skin). **Causes:** Genetic mutation affecting LDL receptor function. 4. **Obesity** **Symptoms:** Excess body fat, increased body mass index (BMI). **Causes:** Excessive caloric intake, particularly from lipids, combined with low physical activity. 5. **Lipid Storage Disease** **Types:** Includes disorders like Gaucher and Tay-Sachs disease. **Symptoms:** Vary widely depending on the specific disorder; often involves organ dysfunction. **Causes**: Genetic mutations leading to defective lipid metabolism. **DIAGNOSIS AND TREATMENT** **Diagnosis:** Lipid panels to measure cholesterol and triglyceride levels, imaging tests for atherosclerosis. **Treatment:** Dietary modifications (lowering saturated fats), medications (statins, fibrates), lifestyle changes (exercise).       \