Carbohydrates and Lipids Introduction PDF

Carbohydrates and Lipids Introduction BMS 531.03 SPRING 2025 Objectives Overall Goal: Evaluate the structure and function of carbon-based molecules and identify the features that enable unique chemical behaviors Carbohydrates 1. Summarize the common carbohydrates in the body and diet 2....

Carbohydrates and Lipids Introduction BMS 531.03 SPRING 2025 Objectives Overall Goal: Evaluate the structure and function of carbon-based molecules and identify the features that enable unique chemical behaviors Carbohydrates 1. Summarize the common carbohydrates in the body and diet 2. Explain carbohydrate structure by the following: ◦ Compare and contrast linear and cyclic forms ◦ Identify the anomeric carbon ◦ Differentiate between aldehydes and ketones ◦ Describe the type of bond formed between monosaccharides ◦ Explain the difference between alpha and beta conformations in monosaccharides and alpha and beta linkages in polysaccharides Lipids 3. Compare and contrast types of lipids and their uses in biological systems 4. Compare and contrast saturated and unsaturated forms of lipids 5. Compare and contrast types of adipose tissue and explain the role of adipose in energy storage 6. Explain how lipid structure contributes to lipid behavior and location/localization, storage, and usage in biological systems Overall Goal MACROMOLECULES Large carbon-containing molecules that are held together by covalent bonds ◦ Proteins, RNA, DNA, Etc… The bonds between the atoms of polymeric macromolecules are COVALENT bonds The bonds across polymeric macromolecules are frequently hydrogen bonds LO1, LO2 Carbohydrate Basics Polyhydroxy aldehyde vs Polyhydroxy ketone ◦ Both types contain a carbonyl group (C=O) ◦ In the carbon with the carbonyl group, if another bond is H instead of C, it is an aldehyde Nearly all sugars in the body have the D configuration LO1, LO2 Carbohydrates Basics Essential for key processes ◦ Play a key structural role ◦ Source of carbon skeletons for new molecules ◦ Useful to store energy (glycogen) ◦ Useful to transport energy (blood glucose) LO1, LO2 Stereochemistry and Sugars Sugars are optically active compounds due to asymmetric carbon centers Although there are a substantial number of possible configurations due to the multiple asymmetric centers, only a few configurations for sugars are actually present in the body and diet to substantial concentrations LO1, LO2 Natural Configuration Aldehyde residues are easily oxidizable and chemically reactive Glucose in aqueous environments predominantly exists in cyclical configuration making it inert and nonreactive ◦ Resistant to oxidation in this form ◦ Does not readily react with protein ◦ **Ideal for transport/blood sugar LO1, LO2 Simplification of Ring Structure (a) Linear and ring forms (b) Abbreviated ring structure © 2016 PEARSON EDUCATION, INC. LO1, LO2 Actual Ring Structures for Glucose and Fructose are More Complex Formation of rings can involve different conformations and carbon numbers in the ring Some of these forms can lead to the formation of new asymmetric carbons known as the anomeric carbon ◦ So called because the carbonyl group carbon is now involved in a new bond LO1, LO2 Polysaccharides Differences in sugar linkage contribute to differences in chemical behaviors Links between sugar molecules = glycosidic linkages/glycosidic bond ◦ Hemiacetal carbon of one sugar to hydroxyl of another sugar If the polysaccharide is entirely composed on only 1 type of monosaccharide = homoglycan If the polysaccharide is composed of different types of monosaccharides = heteroglycan LO1, LO2 A few quick reminders… Alpha = both carbons have the same stereochemistry (OH group on same side) Beta = both carbons have different stereochemistry (OH group on opposite sides) O-bond involves oxygen N-bond involves nitrogen There are alpha and beta forms of Glucose dependent on the location of the hydroxyl group on the anomeric carbon LO1, Storage structures (plastids) LO2 containing starch granules in a potato Amylose (unbranched) tuber cell Amylopectin Glucose (somewhat monomer branched) 50 µm (a) Starch Muscle tissue Glycogen granules Glycogen in muscle (extensively tissue branched) Cell wall 1 µm (b) Glycogen Cellulose microfibrils in a plant cell wall Cellulose molecule (unbranched) Plant cell, surrounded 10 µm by cell wall Microfibril Hydrogen bonds 0.5 µm (c) Cellulose © 2016 PEARSON EDUCATION, INC. LO3, LO4, LO6 Lipids Non-polar, hydrophobic HYDROCARBONS ◦ Composed of carbons and hydrogens Multiple Functions ◦ Store Energy (fats, oils) ◦ Cell Membranes (phospholipids) ◦ Regulatory Roles (steroids) ◦ Photosynthesis (chlorophylls) ◦ Thermal Insulation (fat) ◦ Electrical Insulation (myelin) ◦ Repel Water (oil, wax) LO4 Saturated vs. Unsaturated Defined by hydrocarbon structure and presence of double bonds (a) Saturated fat (b) Unsaturated fat Saturated ◦ fully bound with hydrogen; no double bonds ◦ Linear structure allows for tight associations ◦ Solid at typical temps Unsaturated ◦ contains double bonds that alter the linear structure ◦ Bends produced by double bonds prevents tight associations between molecules Cis double bond causes bending. ◦ Liquid forms at typical temps LO3, LO4, LO6 Lipids Found Primarily in adipose, plasma, and membranes Fatty Acids (simplest form; found in plasma) Triglycerides (storage form; primarily in adipose) Phospholipids (amphipathic; in membranes) LO3, LO6 A Little About Fatty Acids… Immediate source of energy (except in Brain and RBCs) Do NOT exist in free from in the body at significant concentrations Fatty acids released from adipose stores are transported in the plasma Fatty acids in plasma are bound with albumin ◦ Each albumin can hold 6 to 8 fatty acid molecules Fatty acids in the cytosol are bound with a series of fatty acid binding proteins ◦ Regulation of trafficking in the cytosol and between subcellular compartments LO3, LO6 Triacylglycerols (Triglycerides) Storage form of lipids in adipose Esterification of fatty acids to glycerol Natural triglycerides are mixtures with different fatty acid compositions Thus, fats in the body are a mixture of fatty acids LO5 Regarding Adipose Tissue The number and fat content of adipocytes increases with imbalanced in energy input (diet) and energy expenditure (exercise) HOWEVER, is ALSO an active endocrine organ with implications on energy balance ◦ Adipocytes produce Adipokines ◦ Hormones: Leptin (secretion linked to tissue mass and size of cells), Adiponectin (increases insulin sensitivity; absence leads to insulin resistance; physical training increases its production and upregulates its receptors on muscle), and Resistin ◦ Growth factors: Endothelial growth factor ◦ Proinflammatory Cytokines: In obesity: secrete monocyte attractant protein-1 (MCP-1) enabling monocyte recruitment to the tissue resulting in tissue macrophages that secrete cytokines TNF-α and IL-6 Complex tissue stored in 3 distinct depots ◦ Subcutaneous fat under skin = benign energy store ◦ Visceral fat within abdominal cavity = active endocrine organ ◦ Ectopic Fat (i.e. cardiac fat pad, liver, myocytes) = less well understood During weight loss, visceral and ectopic fat is preferentially utilized and depleted LO3, LO4, LO6 Phospholipids Complex lipids combining hydrophobic hydrocarbons with glycerol and a polar head group ◦ Phosphate attaches the glycerol to the polar head groups Variations in the hydrocarbons and the polar head group generate variation in behavior ◦ Contribute to membrane charge ◦ Contribute to membrane fluidity Overall Goal Proteins verses Carbohydrates: The Most Simplified Comparison SIMILARITIES DIFFERENCES Polymers constructed from basic components STRUCTURE and FUNCTION (monomers) Proteins are composed of Amino Acids while Contain Carbon, Hydrogen, and Oxygen Carbohydrates are composed of Sugar Molecules Proteins can contain additional elements including nitrogen and sulfur