Class Notes (839,189)
Canada (511,223)
LIFESCI 2N03 (107)

Oct 24 - Updated Carbohydrates Lecture Notes - LIFESCI 2N03

13 Pages

Life Sciences
Course Code
Danny M.Pincivero

This preview shows pages 1,2,3. Sign up to view the full 13 pages of the document.
LECTURE 5 LIFESCI 2N03 Lecture 5: Carbohydrates October 21, 23, 24, 2013  Carbohydrate – “hydrate of carbon”; manufactured by plants o Making a glucose molecule o Eg/ making a glucose molecule  6 CO2+ 6 H 2 + Energy  C H6O12 66O 2  Storage form of glucose o Animals – glycogen  Glycogen – branches at points; compact manner; liver higher in glucose; 8-10 glucose units then branch o Plants – starch (amylopectin and amylose) and fiber  Amylopectin – more bioavailable; ¾ starch; branched linear chains 25-30 glucose units, then branch  Amylose – ¼ of all starch available in plant based sources; less bioavailable than amylopectin (more compact)  Fiber – non-digestible carbohydrates (in plants); our bodies do not have the enzymes to breakdown certain fibers o Soluble Fibre  Dissolves in hot water  Forms a gel in GI system – does not move fast  Slows gastric/intestinal motility – advantage; absorbs fatty acids consumed with this fiber  “Fuller” feeling, absorbs FA’s  Decreases cardiovascular disease, because less cholesterol is absorbed into body  Eg/ Oat, bran, dried beans, nuts o Insoluble Fibre  Does not dissolve in hot water  Absorbs water into GI system  Speeds intestinal motility  Decreases Type II DM – because increased motility decreases glucose absorption time  Can lead to nutrient deficiencies  Eg/ Vegetable, fruit skins, whole grains  Function of Carbohydrates 1. Burned for energy 2. Ribose and deoxyribose sugars – serve as part of DNA and RNA 3. Structure and strength of plants 4. Linked to proteins and lipids  Glycoprotein – covalent link between protein and a carbohydrate monomer; found on cell surfaces – help to strengthen outer membrane of cells and for cell-cell adhesion  Glycolipid – forms myelin around neuron axons (insulation barrier for increase in speed of transmission along neuron)  Forms of Carbohydrates o Monosaccharide’s – simple form of CHO  Contains 3-9 carbon atoms  Eg/ Glucose, fructose, galactose,6C12 O6  Sugar alcohols  Derived from monosaccharide  Used as a sweetener (sorbitol made from glucose); sweetness in sugarless gum  Chemical modification of glucose molecule – changes the way our body perceives and senses monosaccharide o Glucose does not provide sweet flavor; fructose provides sweetness o Sorbitol can add the sweet flavor (carries calories, and larger sweet effect – negligible amount needed to be included, negligible about of calories)  Figure:  Monosaccharides enter into cardiovascular system from intestinal villi  Note: lipids and cholesterol do not go directly into cardiovascular system 1 LECTURE 5 LIFESCI 2N03 o Disaccharides – sucrose, lactose, maltose o Oligosaccharides – 3-9 CHO monomers  Considered to be a complex carbohydrate o Polysaccharides (≥ 10 monosaccharides)  Dietary from – starch  Vegetables and fruits  Grains – wheat, corn, oats, barley, rice  Legumes – peas, beans, lentils, soy  Tubers – potatoes, yams, cassava (toxic in raw form) Fiber  Soluble fiber – fermentable (bacteria can break it down anaerobically) becomes short chain fatty acids and can be absorbed to the body (very small amount) Starch  Begins in mouth, salivary glands begins to break down larger chain glucose molecules  Small intestine, pancreatic amylases accelerates breakdown of polysaccharides  Maltase, sucrose, lactase – intestinal cells use these enzymes to breakdown disaccharide in small intestines 2 LECTURE 5 LIFESCI 2N03  Purpose of consuming carbohydrates 1. Energy needs  Fuel source for neurons (only uses glucose except during starvation; can uptake protein); most amino acids are considered to be glucogenic  RBCs only use glucose; anaerobic, lacking mitochondria and nuclei; no ability to regenerate  Need CHO to metabolize other fuels; “fat burns in a flame of carbohydrates”  Ketone Bodies  Major source of production is the liver (in mitochondria)  Accumulation from protein and fat metabolism  Heart and renal cortex cells; ketone bodies are used as fuel  Starvation and Other Diseases o Brain neurons use ketone bodies (water soluble) – converted to Acetyl CoA o High levels of ketone bodies in blood reduces adipocyte lipolysis (regulates fat breakdown; feedback mechanism); increases reliance on CHO for energy  Type I Diabetes Mellitus – characterized by high level of ketones produced, and high lipolysis; no insulin (insulin has the effect of reducing lipolysis; no regulatory mechanism for fat breakdown) 2. Pregnancy  Fetus and placenta “feed” on glucose  Gestational diabetes – elevated blood glucose (inability to regulate glucose) during pregnancy; greater risk of developing Type I diabetes; usually ceases after birth but can persist 3. Spares muscle protein degradation for energy  Glucose must be synthesized from muscle protein when insufficient carbs from diet  proper diet will prevent muscle protein degradation  Amino acids converted to 1) ketone bodies 2) fatty acids 3) glucose o Ketone bodies – when harnessed from muscle tissues; recycle and use tissue o Fatty acids – can only occur when there is a high energy diet – there is a metabolic pathway to convert amino acids to fatty acids if energy needs are met o Glucose – amino acids are glucogenic  Gatorade will spare muscle breakdown o Exercise  glycolysis is elevated; storage of carbs in liver cells are begin metabolized and have to be restocked o Illness  infection  increased WBC (glucose); continues intake of carbohydrates to feed elevated metabolic state Carbohydrates and Energy  Glucose carried in the body o Always supply of glycogen in cardiovascular system o Liver stores glycogen more densely than muscle o Plasma glucose fluctuates with amount eaten, what was eaten, type of carbohydrate o Muscle tissue contains more energy than liver tissue – more muscle cells in the body than liver cells; muscle distributed throughout body  Overall glucose content o Blood glucose – 30 g o Liver glycogen – 90 g o Muscle glycogen – 350 g  ATP yield for CHO and fats 3 LECTURE 5 LIFESCI 2N03 o 5.1 kcal/L of2O (carbohydrates) – better fuel source when metabolized aerobically than fat o 4.8 kcal/L of2O (fats) o Due to substrate level phosphorylation – refers only to glucose; direct making of ATP from transformation of macronutrient; 4 extra ATP from glycolysis in cytoplasm  Minimum intake of CHO: 130 g/day for nervous system function  Figure: Body reactions to ingesting carbohydrates o 2. Glucose in blood binds to B-cells in pancreas which stimulates insulin production  Type I DM – B-cells are destroyed by body; insulin is not produced (#2 inhibition; pancreas)  high blood glucose o 3. Insulin binds muscle and liver cells to promote glucose uptake in cells – remove glucose from blood as glycogen  Type II DM – 9/10 of Canadians with DM; muscle cells not responding to insulin (insulin resistant) (#3 inhibition; muscle tissue)  high blood glucose o 4. Homeostatic level; blood glucose declines but does not deplete (not too high, not too low) o 5. Glucagon from a-cells in pancreas to maintain homeostasis of blood glucose – promotes glycogen breakdown (glycogenolysis) from liver and blood glucose increases  External cellular signal, stimulant of glycogenolysis  Glycemic Index (GI) – a measure (no units) of the potential food to raise blood glucose levels o High GI – blood glucose response is quicker in cardiovascular system  Increase [glucose] fast  increase blood [insulin] fast  7TM (7 transmembrane) receptor binds insulin – deactivates lipase  Diet chronically high in high GI foods – insulin continues to be secreted, muscle cells begin to be resistant to insulin  Exercise causes muscle cell contraction – same effect as insulin, stimulates proteins that pull glucose into cell o Fructose content; have to convert to glucose  lower GI o 2 different standards – one slide of white bread or pure glucose (both taken as 100%) o High GI ≥80 o Mid GI 56-59 o Low GI <56 4 LECTURE 5 LIFESCI 2N03 o Factors affecting the GI of foods 1. Proportion of CHO content of the ingested food  Increased % CHO, increase GI  Examples (compare to pure glucose ingestion) o Ice Cream 61  Fat molecules slow rate of glucose absorption o Baked Potato 85 o Instant Rice 91 o CHO easily broken down and absorbed o If GI is the factor – french fries are healthier than baked potatoes because lower GI 2. Type of carbohydrates  Simple vs. Complex  Role in Fat Storage – insulin action 3. Cooking  Heat helps to disrupt chemical bonds – faster digestion  Eg/ o Pasta GI (5 min boiled) 34 o Pasta GI (10 min boiled) 40  Blood glucose response to feeding o Glycemic Load – amount of carbs, blood glucose will increase (as opposed to rate of blood glucose increase)  GI multiplied by the amount of available carbohydrates in a food source/100  Predictor of developing Type II diabetes mellitus and cardiovascular disease  Eg/  Corn Muffin GI = 102 (compared to glucose), 29 g carbs/serving, GL = 20  Bran Muffin GI = 60 (compared to glucose), 24 g carbs/serving, GL = 15 o High fibre – indigestible  Fruits – high GI, low glycemic load  Watermelon – blood glucose increases quickly, but not by a lot  Blood Glucose Response to Feeding  Eat  blood glucose begins to rise  eventually goes down, undershoots then stabilizes  Baked potatoes  magnitude of increase in blood glucose is much larger and enters system more quickly (dotted line)  Ice cream (red line) o Fat molecules compete with intestinal absorption of glucose  Glycemic Index – slope of curve; how fast blood glucose concentration increases  Glycemic Load – magnitude of blood glucose concentration 5 LECTURE 5 LIFESCI 2N03 Pancreatic Hormones  Insulin o Produced by beta cells of the pancreas o Helps cells take in glucose from the blood o Stimulates the liver to take up glucose and convert it to glycogen o Overall effect of lowering blood glucose o 51 amino acid sequence, with 2 chains (A and B) o Disulfide bridges between cysteine residues  Glucagon o Produced by alpha cells of the pancreas o 29 amino acid polypeptide o Signals a physiologically starved state o Stimulates the breakdown of glycogen to glucose o More glucose is available to cells of the body o Stimulates gluconeogen
More Less
Unlock Document

Only pages 1,2,3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.