Metabolism Introduction Carbohydrate Metabolism Lipid Metabolism Protein Metabolism
Metabolism Introduction Carbohydrate Metabolism Lipid Metabolism Protein Metabolism
Note: § I do not have time to cover these aspects of physiology in class. You are responsible for reading the Seeley text and knowing physiological aspects on the exam. § Integumentary System (Ch. 5). Know the functions of each layer and functions of accessory structures (hair, muscles, glands, and sensory organs-free nerve ending, Pacian corpuscle and Meissner’s disks) § Skeletal System (Ch. 6). Know how bone is built and degraded (cell types and hormones), the purpose of bone, how the two types of ossification occurs, and calcium homeostasis.
Metabolism § All the chemical reactions that take place in an organism § Cellular metabolism-cellular chemical reactions that produce ATP to maintain homeostasis + cellular functions such as: § Cell growth and division § Breakdown and replacement of components of a cell § Processes like secretion, contraction and propagation of action potentials § Also, body needs to build up energy reserves and store fuel
How does it work? § Cell absorb organic molcs (sugars + lipids + a. a. ) from interstitial fluid (ISF) cytoplasm and use those molcs for catabolism. § Catabolism is the breakdown of organic molcs in a series of steps to synthesize ATP or other high E compounds. § Catabolism starts in the cytoplasm and requires enzymes and cofactors (vit. and minerals) to break down molecules to ultimately make ATP.
Catabolism O 2
Metabolism § Once ATP is made it is used in the cell to: § Synthesize new organic molecules (anabolism) to replace components of the cell § Maintain cellular functions such as: § Cell growth and division, secretion, contraction and propagation of action potentials § Produce a nutrient pool cell can use in emergencies for fuel – 1 O fuel: Glc is stored as glycogen liver + skeletal muscle – 2 O fuel: Lipids are stored as triglycerides liver + adipocytes – 3 O fuel: Proteins-most abundant in cell but used last, why?
Metabolism § Metabolism= energy production by fuel degradation (catabolism) + using the energy produced to maintain cell functions/ homeostasis (anabolism) § In order for your body to carry out metabolism it requires: § Respiratory system § Cardiovascular system § Digestive system § A well balanced diet § Why are each of these required?
Metabolism Overview Figure 3. 26
Metabolism Overview
Carbohydrate Metabolism § Most cells generate ATP by breaking down carbohydratesspecifically glucose § C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + 38 ATP § 1 glucose molecule 38 ATP total § Some ATP are made from ADP (substrate-level phosphorylation) § Most ATP are made from using coenzymes NADH and FADH electron transport chain ATP (oxidative phosphorylation) § Consists of two parts: § Glycolysis (a part of anaerobic metabolism) + aerobic metabolism (Kreb’s citric acid cycle + electron transport chain)
I. Glycolysis § Glycolysis= 1 glucose (6 C) 2 pyruvate (3 C) § Occurs in cytosol, does not require oxygen, NETS 2 ATP § Requires enzymes, ATP, ADP, P, and coenzyme nicotinamide adenine dinucleotide (NAD) derived from a. a. , OR niacin, iron and B 6. § If any of these are missing glycolysis cannot occur.
NAD+ § NAD+ (ox) is a coenzyme that accepts electrons. It acts as a taxi cab for electrons-picking up electrons in glycolysis and Krebs and dropping them off at the electron transport chain (ETC).
Glycolysis Uses 2 ATP for the first part of glycolysis 2 Gly-3 -phos
Glycolysis We have 2 GAP’s so everything is doubled Produces 2 NADH Produces 4 ATP made -2 ATP used NET= 2 ATP
Carbohydrate Metabolism CYTO MITO
II. Krebs Citric Acid Cycle § If O 2 is present then pyruvate mitochondrion into Kreb’s Citric Acid Cycle to be further broken down to produce ATP § CAC is a series of reactions catalyzed by eight enzymes located in the mito. matrix § This produces 36 ATP: § 2 via substrate-level phos. § 34 via oxidative phos. § O 2 and NAD+/FAD+ are needed to do this 32 -34 ATP
Intermembrane space Matrix
Kreb’s Citric Acid Cycle IN MITO MATRIX Produces 8 NADH Produces 2 FADH Produces 2 ATP
III. Electron Transport Chain (requires O 2)
III. Electron Transport Chain § In order for the ETC to produce ATP there has to be: § Oxygen-it’s the final electron acceptor. § Without oxygen the electrons would get backed up and the NADH/FADH would not be able to regenerate NAD/FAD § Where does the O 2 come from and what if there isn’t enough O 2? § A proton gradient established by NADH/FADH donating electrons. § Where do the NADH and FADH come from?
* *34 -36 ATP
Carbohydrate Metabolism CYTO
Anaerobic Metabolism (no O 2 present) Glucose pyruvate yields 2 ATP but you need to regenerate NAD+ in order to keep making ATP (when not enough oxygen is present) Lactate dehydrogenase enzyme How do you regenerate NAD+? http: //intranet. canacad. ac. jp: 3445/bioibsl 1/4453
Anaerobic metabolism Generates ATP when not enough oxygen is present in the skeletal muscle to go thru aerobic metabolism Aerobic metabolism Generates ATP when enough oxygen is present in the muscle
Cori Cycle § Glucose lactate in skeletal muscle § Lactate glucose in the liver themedicalbiochemistrypage. com
Carbohydrate Metabolism § What if you want to store glucose? § Glycogenesis-synthesis of glycogen from glucose § Where would you store the glycogen? § Glycogen accounts for 1% of body’s storage fuel § Once you have glycogen stores filled what is excess glucose stored as?
Carbohydrate Metabolism § What if you don’t have enough glucose to make ATP? § Gluconeogenesis-synthesis of glucose from noncarbohydrate precursors: § Lactic acid § Glycerol § Amino acids
Lipid Metabolism § Triglycerides are the most common energy storage molecule (99%) and the second most commonly used fuel for cells § After a meal triglycerides are stored in adipocytes § When you need them for fuel triglycerides glycerol + free fatty acids (b-oxidation) § Skeletal muscle and liver use the free fatty acids as fuel when glucose supply is limited § Triglycerides yield~ twice as much ATP than carbs. or prot.
§ Adipose triglycerides are broken down and released as free fatty acids § Free fatty acids are taken up by cells and broken down by beta-oxidation into acetyl-Co. A which: § Enter citric acid cycle OR § Are converted to ketone bodies (ketogenesis) in liver. § Ketones travel to skeletal muscle and are used in citric acid cycle to produce ATP 25 -32
Protein Metabolism § After a meal proteins amino acids taken up by body cells and liver § Amino acids are used to synthesize needed proteins in the body and used last as a fuel source § Amino acids are NOT stored in the body as a. a. ’s, they are converted to glycogen OR triglycerides for storage.
Protein Metabolism § The body can use amino acids to ultimately produce ATP via two different methods: § They can be converted into intermediates of Kreb’s cycle and enter Kreb’s that way § They can go through oxidative deamination to produce NADH
Protein Metabolism
Protein Metabolism § Oxidative deamination § Amine group is removed from glutamic acid (a. a. was converted to glutamic acid) ammonia + keto acid § This reaction produces NADH and NADH produces ATP (how? )
Amino Acid Reactions Occurs in the liver
Starvation § Consists of three phases § 1 st phase: blood glc is maintained by breaking down glycogen. § Liver glycogen stores can only maintain the body for a few hrs. § After that, lipids and proteins are broken down as fuel for body cells. § The brain doesn’t store glucose and can’t use fatty acids to make glucose, so most glc comes from proteins
Starvation § 2 st phase: fats are primary energy source § Liver converts fatty acids ketone bodies for fuel (ketosis) § Ketone bodies produce sweet smelling breath § The brain will use ketone bodies + glucose as fuel § This can last for several weeks
Starvation § 3 rd phase: proteins are primary energy source § Fat reserves are depleted and the body switches over to protein degradation as a fuel source § Body will degrade cellular proteins and skeletal muscles for fuel § People usu. die from a secondary infection as a result of long-term starvation
Diabetic Ketoacidosis § Diabetic ketoacidosis occurs in insulin dependent patients only: § Glucose cannot get into the cell because of lack of insulin § 1 st Body uses lipids and proteins as fuel source ketone bodies (ketosis) § 2 nd Body uses muscle, fat, and liver cells as fuel excessive ketone bodies in blood acidifies blood and damages organs
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