Lecture -1/31Function of carbohydrates1. As glycogen – storage form of glucose in animal cells. The human body can store up to 600 g of glycogen mostly and skeletal muscle cells (fibers) and the hepatocytes (cells)2. 2. Glucose is the most preferred fuel in the body – cells prefer to catabolize (breakdwn) glucose for energy production3. 3. In the form of glycoproteins, glycolipids, and glycocalyx – carbohydrates act as signal molecules on the surface of cells 2nd tiem of organic compound – lipids - Hydrophobic – insoluble in water4 types of lipids1. Neutral fats2. Triglycerides3. triacylglycerolsNeutral fats – most common type of lipid in the human diet2 forms of neutral fats in the diet 1. Saturated fats2. Unsaturated fatsSaturated fatsSaturated fats – single covalent bonds between adjacent carbon atoms is the neutral fatSolid at room temperatureUsually obtained from animals fats (butter)Increase LDL (bad cholesterol)Because LDL in excess deposits cholesterol in the walls of blood vessels – causing a atherosclerosis – atherosclerotic plaque - decrease the lumen in the blood vessels impeding blood flow resulting in high blood pressure. When these atherosclerosis plaques black blood vessels then blood flow in vital organs is blocked leading to death of tissue: if the blocking is in acoronary artery – myocardial infarction (“heart attack”) blockage is in cerebral artery = ischemic stroke Lumen = space within blood vesselLDL = low density lipoproteinLipids are hydrophobic and are transported in the blood (=aqueous) by being coated by proteins Lipid + protein – lipoprotein Lipid transportation in blood as lipoprotein – 3 types of lipoprotein1. VLDL a very low density lipoprotein a. Will contain mostly triglycerides (major lipid)2. LDL – low density lipoprotein – major lipid is cholesterola. You need LDL but not in excess b. Transports cholesterol to cells for the synthesis of steroid hormones (testosterone, progesterone, cortisol) c. LDL will transport cholesterol to plasma membranes where cholesterol is require for the maintenance of the structure of the plasma membrane (fluid mosaic model of the plasma membranes)d. Too much LDL is bad for youe. LDL – atherosclerosis hence LDL = bad cholesterol 3. HDL – high density lipoprotein – transports excess cholesterol from the blood to the liverwhere the cholesterol is metabolized and eliminated from the body hence HDL is referredto as the good cholesterol Fats 1. Contain at least one double covalent bond between carbon atoms 2. 2. Liquid at room temperature they are referred to as oilsOils better option in the diet then saturated fats with the exception of coconut oil. Which is full of saturated fats Trans fat – unsaturated fats + hydrogen. Very bad. LDL goes up more so than naturally Structure-2nd type of lipids – phospholipids structures – glycerol backbone -2 free fatty acid chains attached one side – non polar and hydrophobicSummaryPhospholipids – 1 polar head (phosphorous containing group) and 2 non-polar tails (2 free fatty acid chainsLecture 2/2Lipids1. Triacyl2. Phospholipids – polar heads and nonpolar tails3. Steroids – hormones, which are derived from cholesterolThe steroid hormones control all physiological processes occurring in the body4. Eicoscinoids – derived from an organic acida. Arachidonic acid i. Cyclooxygenase (used for conversion) to prostaglaninsii. Lipoxygenase (used for conversion to) leakotrienesEicoscinoids – mediate most physiological processes such as hemostasis (cessation of bleeding from an injured blood vessel), smooth muscle contraction3rd organic compound – proteins – made up of amino acids – building blocks of proteins In the human body – 20 naturally occurring amino acids2 main types of amino acids – essential and nonessential amino acidsEssential amino acids must be taken into the body through the dietNonessential amino acids can be made by the body using the essential amino acids 20 naturally occurring amino acids are required for the synthesis of proteins – different types of amino acids with different combinations will result in the different types of proteins in the bodyThe type and postion of amino acids in a protein determine the overall structure of protein and hence the function of the protein – “structure defines function”Amino acids – has both an acidic end (carbonyl) and a basic end (amino) hence, amino acids are referred to as amphoteric substance -4 structures levels of protein1. Primary sequence (structure) – type/position of the amino acids, which form the polypeptide chain - 2. Secondary structures – in human cells there are 2 types of secondary structure of proteins – thealpha helix and the beta helix sheetAlpha helical structure – the primary structure coils to form an alpha helix “slinky”Beta pleated sheets – appear like ribbons – the primary structures are arranged end to end to formpleats. The primary structures are folded/arranged end to end are held by hydrogen bonds. 3. Tertiary structure of proteins – some proteins attains the tertiary structure by folding the secondary structures into compact, globular, ball-like structure with depth – gives the 3 dimensional (3-D) shape. 4. Quaternary structure of proteins – few proteins in the human cell achieve the quaternary structure – this involves at least 2 primary sequences held together by ExampleHemoglobin = 4 chains – 2 alpha and 2 beta chains - 2 main classes of proteins - 1. Fibrouso Insoluble in watero Extendedo High tensile strength and provide mechanical support for cellso Since fibrous proteins form the structural framework of cells, they are also referred to as “structural proteins”o Ex: collagen - 2. Globularo Soluble in water o Structure – compact, “globular” in shape with active sites exposed. o Globular proteins involved n all physiological processes hence, they are referred to as functional proteinso Ex: enzymeso Globular proteins are denatured (irreversibly destroyed) in the presence of low pHand high temperature - 4th organic compound – nuclear acids – the largest macromolecules in the human cellso Nucleic acids are composed of structural units called nucleotideso Each nucleotide is composed of Nitrogen containing base – 5 types of such bases - Thymine (T)- Uracil (U)- Cytosine (C)- Guanine (G)- Adenine (A) Pentose sugar- Deoxyribose and ribose Phosphorouso 2 types of nucleic acids
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