LS15 - Week 6 notes
LS15 - Week 6 notes Life Science 15
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This 8 page Class Notes was uploaded by AK315 on Thursday March 10, 2016. The Class Notes belongs to Life Science 15 at University of California - Los Angeles taught by Professor Phelan in Winter 2016. Since its upload, it has received 22 views. For similar materials see Life: Concepts and Issues in Biology at University of California - Los Angeles.
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Date Created: 03/10/16
Week 6 Fuel • What are some things that living systems need? ◦ Raw materials for growth ◦ Energy to do things that won’t happen spontaneously • How do we power machines? ◦ We use gasoline and many other fuels ◦ Their structures are Hydrocarbons (a mixture of hydrogen with 5-12 carbons) ◦ Automobile engines combust the hydrocarbons, forming new bonds, releasing energy that can be used ◦ biofuels: natural oils from plants, sugar, or starches modiﬁed into ethanol ◦ Essentially - you break bonds > reform them > and make use of the energy released in that process (Breaking the bonds and reforming new bonds releases energy that can be harnessed to do ‘work’ making things happen that would not happen spontaneously) • The origins of fuel ◦ Fuel comes from energy stored in chemical bonds ◦ Photosynthetic organisms create it initially Lipids • These are macromolecules • They have many features ◦ Not water soluble ◦ Major storehouses of energy ◦ good insulators • Lipids are used for storing and generating useful energy • We use them for creating cell membranes • Major types: ◦ Fats/triglycerides ◦ Phospholipids ◦ Sterols • Saturated fats vs Unsaturated fats ◦ Depends on whether there are double bonds in hydrocarbon tail ◦ If anywhere on the hydrocarbon tail there is a double bond, then it’s an unsaturated fat! (these are better than saturated fats) ◦ Hydrogen is the saturator so if you add the max number of hydrogens you can give then its a saturated fat, if not then its unsaturated ◦ Most plant fats are unsaturated and animal fats are saturated (they are mostly solid at room temperature e.g. bacon fat) ◦ Many snack foods contain ‘partially-hydrogenated’ vegetable oils. Why might it be desirable to add hydrogen atoms to a vegetable oil? Why might there also be some less desirable consequences? ◦ Saturated fats are very easy to store away (make links) but very diﬃcult for your body send an enzyme in there to break through so to access that energy it’s tough. ◦ They add the hydrogen to make it saturated to make it slightly solid but then the moment foods like chocolate etc. are put in your mouth, the heat melts them (they are solid but BARELY) and food chemists tweak it in such a way that they bring about this eﬀect ◦ In saturated fats - fatty acid molecules are tightly packed hence tend to be solid at room temp ◦ In unsaturated fats - kinks in the hydrocarbon tail means that molecules are not tightly packed and hence tend to be liquid at room temperature • Lipids are water-insoluble molecules important in energy storage, in membranes and as hormones Human taste preferences • We have a high preference for fatty foods (sugar is diﬀerent; not TOO sweet but not TOO unsweet either) • Ancestral humans vary in preferences • Questions we ask are; ◦ Who is less likely to starve - fatties ◦ Who leaves more oﬀspring - fatties (if alive) will pass on the genes ◦ Who are our ancestors? - fatties - they leave behind the kids • The same amount e.g. 1 gram of protein vs 1 gram of fat give diﬀerent caloric values; 1 g of fat = 9 cals and 1 gram of protein = 4 cals! • Evolution has shaped our food preferences, making us love energetically rich fats. Carbohydrates • Macromolecules # 2 is carbohydrates (it’s a carbon chain bonded to hydrogen H and OH groups) • Primary function is to serve as FUEL • Mono-saccharides are simple sugars (orange juice, white rice) - within minutes your blood sugar goes up and you get a lot of energy easily. • Our body has a very easy time in breaking down glucoses (carbohydrates) so we are able to QUICKLY get energy from carbs. • Starch and polysaccharides are complex sugars and take a lot more work from your body to break them down. There is a slow, long release (more energy). ◦ For instance, when you want to study for hours in a row - getting such type of carbs means that your body releases the energy slowly rather in short busts which sustains you for a longer duration of time. • Disaccharides = 2 molecules and polysaccharide = 2 or more molecules • Carbohydrates give us easily accessible energy Proteins • Proteins = construction (fats = energy storage and carbs = fuel) • We can’t get the simple sugars from cellulose molecules because we can’t break through them easily and thus they just pass through our digestive system. • Notice that the basic amino acid structure contains an ’N’ which is Nitrogen! We need nitrogen for protein. This is why for plants to grow - all fertilizers used are made of Nitrogen! • Valine and phenylanine • Certain amino acids code for certain types of hair; curly or straight. • These can be altered semi-permanently • Cells and tissues are primarily built from proteins, sequences of amino acids Diet variation amongst animals • Herbivores (Zebras) - only eats plants • Plants can’t run away so they evolve to have defenses against Herbivores (poisonous chemicals etc.) • Carnivores (Tiger) - only eats animals • Omnivores (Crows/Humans) - eats plants and animals But processing and deriving energy from the food is exactly the same Metabolism • The kilocalories = 1000 calories (a calorie is energy required to raise 1 gram of water by 1 degree celsius (C)) • How many are needed? ◦ Human female = 1800-2400 Kcal ◦ Human male = 2400-3200 Kcal ◦ Guys need more because they are bigger ◦ When you think harder, you also burn more calories! • BMR (Basal metabolic rate) = energy needed to maintain life without activity. Generally we need twice as much. ◦ For females = 1400 kcal/d ◦ For males = 1700 kcal/d ◦ 1700 kcal = a 75 watt light bulb for 24 hours ◦ In humans: 1 calorie/g/hr ◦ In shrews: 35x as high. Heart rate ~ 500 beat/min ◦ Why is it higher for shrews? One theory is they are warm blooded, if they are losing heat quickly then they need to compensate by having a high metabolism rate to retain heat (Surface area of body) ◦ 5g shrew * 35 cal/g/hr * 24 hrs * 2 = ___ kcal/g ◦ Carbo = 4 kcal/g, protein = 4kcal/g, Fat = 9 kcal/g ◦ Shrews prefer fatty foods as it can eat less (But fatty food) and gain same calories leaving more time for them to mate etc. • Basal Metabolic rate is the energy expenditure necessary to keep a resting animal alive. It depends on size and species. Digestion and Absorption • Digestion is breaking down the food into it’s component parts (the taking apart of food molecules) ◦ Mouth = 2 functions ▪ Mash up food (mechanical breakdown) ▪ Partially digest starch (amylase - enzyme that breaks down carbs found in saliva) ◦ Stomach = 3 functions ▪ More food mashing (HCL, pepsin) ▪ Start protein digestion ▪ Secretes acid: denature protein, kill bacteria ▪ Acid denatures proteins and causes it unfold ◦ Small intestine = 4 functions ▪ Neutralize chyme pH (with bicarbonates) ▪ Finish protein/starch digestion (Breaking starches into simple sugars AND proteins into individual amino acids) ▪ emulsify & digest lipids (bile) ▪ absorb nutrients & H2O (these are absorbed into our bloodstream and transported around our body) ▪ Animals can increase the surface area of small intestine to absorb and extract more from their foods, if they are on low-calorie diet. ◦ Large intestine = 3 functions ▪ Absorb H2O (water) & Salts ▪ Push chyme into rectum for excretion ▪ Absorb nutrients produced by bacteria ◦ Harsh conditions help break down foods. This frees the food to interact w/ enzymes. Humans aid this process by: ▪ Cooking food at high temps ▪ Marinating in harsh acids (Lime juice/vinegar) ◦ What is indigestion? How do antacids cure it? ◦ Why does diet coke lose its sweetness if it gets too hot? Diet coke is sweetened from nutrisweet (made of 2 amino acids stuck together) • Harsh mechanical (Chewing/churning) and chemical (HCL and amylase) processes aid in the ﬁrst steps of digestion. • Most nutrients are absorbed in the small intestines. H2O is absorbed in the large intestines. Fiber • What is ﬁber? - Cellulose, lignin, pectins, gums (plant structures that CANT be digested by humans) • But it is helpful (despite being a mass of material that’s not going to be digested): ◦ Helps move food through your gut (stimulates the intestine muscles that tries to push the ﬁber and subsequently the food out) ◦ It also bonds with bile which eliminates bile and this reduces our ability to absorb cholesterol. ◦ May lower cholesterol (see point above) ◦ May reduce colon cancer risk ◦ Too much ﬁber = a lot of undigested food is moved out but too little water is extracted so the resulting fecal matter has a lot of water (Diarrhea) ◦ Too little ﬁber = too much water extracted as food not pushed out properly and this means fecal matter moves more slowly and is tougher to push out (constipation) Why vegetarians are at a higher risk for protein deﬁciency • Are all proteins created equal? NO. • There are 20 diﬀerent amino acids needed by Animals. We can produce 11 of them. You need to eat the 9 others because our bodies cannot produce them. • Milks, egg, meat have ALL 9 of the ‘essential amino acids’ - as these are essential to your diet. • Corn has only 6 amino acids (it has protein but this is made of LESS of the essential amino acids) • Beans also have 6 amino acids (but this is NOT the same as the ones that corn has) • It’s not suﬃcient just to get certain amount (Grams) of protein; you ALSO need to get all the diﬀerent amino acids. That’s why you can be protein deﬁcient even though you eat a lot of protein but lack all 9 amino acids. Soy, quinoa etc. are all complete proteins (they have all the 9 amino acids). • Nearly all plants have incomplete proteins. Essential nutrients • vitamins are necessary organic molecules ◦ They assist in chemical reactions ◦ Fat soluble ▪ A - precursor to eye pigment ▪ D - calcium absorption ▪ E - antioxidant function ▪ K - blood clotting ◦ Water soluble ▪ B - coenzymes in metabolism ▪ C - collagen formation protection from oxidative damage ◦ You either have the suﬃcient amount of vitamins or you DON’t. Buying and eating additional supplements, doesn’t help you! ◦ In fact, in the US - almost no adults suﬀer from any vitamin and mineral deﬁciency diseases. ◦ Excess consumption of ▪ Vitamin A: Can lead to hair loss in men ▪ Vitamin D: can lead to growth retardation • Minerals are necessary inorganic elements ◦ Ca - nerve propagation ◦ P - ATP ◦ K, Na, Cl - action potentials, etc. • Our metabolism is basically involved in modiﬁcation; breaking down or building up molecules ◦ For example to build eye colors in fruit ﬂies takes 20 steps! • Who might need vitamin supplements? ◦ Pregnant or breast-feeding women ◦ People on extreme caloric restriction ◦ People with low milk consumption and extremely low sun exposure may need extra Vitamin D. ◦ Women who lose unusually large amounts of blood during menstruation may need extra iron! More about mutations • Central dogma - the ﬂow of information from the DNA moving to messenger mRNA >>> protein. The DNA is nucleus and mRNA is leave nucleus. • DNA in 23 pairs of chromosomes. • 2 chromosome lines - but both are double stranded and they may be slightly diﬀerent from one and another. • If they have 2 diﬀerent bases (like G and T) on the strands then that individual is heterozygous for that trait. • Mutation - random alteration to DNA. If it happens at intergenic regions (Where no trait is really there) then mutation eﬀects are minimal. ◦ Silent mutation example = No amino acid change (ATCCGG = ATGCGG) where ATC = Lysine and CGG = Tryptophan ◦ Point mutation example - a change in a single nucleotide ◦ Mis-sense mutation = change amino acid (so Lysine may become Arginine) ◦ Non-sense mutation - premature stop (truncated protein). The shape of a protein is generated by how it folds and how it folds is determined by the properties of amino acids. So if you change an amino acid (like one that likes to be around water) to an amino acid that doesn’t - it could aﬀect the folds and hence the shape of the protein. ◦ Insertion and deletions can ensure that the reading frame does not change. Lest, any insertion would shift all the triplets by one place which would change. • What can mutations do to our phenotypes? ◦ loss of functions = recessive phenotypes ◦ Gain a function ◦ Neutral and Lethal mutations • Remember: Red foxes always jump over logs add XX to it: frame shift: XXR edfox esalwa ysju mpov eslogs
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