Ch 2, Ch 3, & Ch 27: Metabolism

Define glycogenolysis

Breakdown of glycogen to glucose; occurs when the blood glucose levels are low & the liver hydrolyzes some of the glycogen back into glucose to release into the blood

Describe the structure of carbohydrates.

Carbohydrates are composed of simple sugars, monomers are called monosacchardies, dimers are disaccharides, & polymers are polysaccharides The general chemical formula is (CH2O)n where n indicates the number of carbon atoms in the molecule; each carbon is hydrated with a -H & -OH attached

What are the functions of proteins?

Catalyzes chemical reactions (enzymes), structural support, facilitation of body movement, transport in the blood, membrane transport, & body protection

What is the functional role of HDLs?

HDLs are the "good" cholesterol They transport excess cholesterol from peripheral tissues back to the liver for storage or excretion of bile

What are hydrolysis reactions & dehydration reactions?

Hydrolysis reaction is a type of decomposition reaction where organic compounds can be broken down into their building blocks, for example when sucrose is broken down into glucose & fructose molecules within the digestive system Dehydration reaction is a type of synthesis reaction where organic compounds are formed by joining their building blocks, for example when two amino acids are combined to form a dipeptide

What is the functional roles of LDLs?

LDLs are "bad" cholesterol They deliver cholesterol to the peripheral tissues for membranes, hormone production, & storage

Define lipogenesis

Lipid anabolism--formation of lipids, glycerol binds with fatty acids

Define lypolysis

Lipid catabolism--The breakdown of stored lipids

Define lipoproteins

Lipid-protein complexes, the form that most lipids circulate in the bloodstream; 3 main types: chylomicrons (largest), LDLs, & HDLs

Describe the structure of lipids.

Lipids are classified into 4 groups, all of which have different structures; these classes include triglycerides (the most abundant), phospholipids, steroids, & eicosanoids. Triglycerides are composed of a glycerol & 3 fatty acids (may be saturated or unsaturated) Phospholipids are composed of a glycerol molecule, 2 fatty acids, a phosphate, & various organic groups; the glycerol, phosphate, & organic group form the polar head while the two fatty acids form the nonpolar tails Steroids are composed of four rings made up of mostly hydrocarbons Eicosanoids are composed of modified 20-carbon fatty acids synthesized from arachidonic acid

Define gluconeogenesis

synthesis of new glucose from non-carbohydrate sources Liver forms glucose from non-carbohydrate sources such as amino acids

Briefly describe the general steps in the electron transport system.

*most important mechanism for generating ATP ETS occurs in the presence of oxygen within the mitochondria; the coenzymes NADH & FADH2 formed during citric acid cycle bring electrons (H+ atoms) to the ETS, these electrons are transferred through a series of electron carriers within the membrane of mitochondria cristae, the electrons are transferred to O2 (final electron acceptor) at the end of the ETS; energy from these electrons moving to O2 is used to move H+ up its concentration gradient from the matrix of the mitochondria to the outer compartment; ATP Synthase harnesses the kinetic energy of the H+ moving down its concentration gradient back into the matrix, this energy is used to bond ADP & Pi to form ATP

How much ATP is available from the complete oxidation of one glucose molecule?

36 ATP per one glucose

Summarize the main processes of protein metabolism.

Amino acid catabolism occurs when the body needs to utilize amino acids as a source for energy because other sources are unavailable, here amino acids undergo deamination; Deamination: process where the amino group (NH3) and a hydrogen atom are stripped from the amino acid which creates ammonium ion (transported to liver for synthesis into urea), once deamination has occurred the amino acid enters the TCA cycle for energy production Amino acid anabolism is the process of forming proteins, amino acids are bonded together to form dipeptides to build proteins through dehydration synthesis

**Describe the production of cholesterol. Compare and contrast between LDL's versus HDL's.

Cholesterol is a type of lipid; it's a component of animal plasma membranes as well as a precursor used to synthesize other steroids; cholesterol is synthesized in the liver from fatty acids and may be obtained from eating animal products such as meat, eggs, & milk LDL stands for low-density lipoprotein, these are considered "bad" cholesterol, they deliver cholesterol to the peripheral tissues for membranes, hormone production, & storage, excess cholesterol can cause formation of plaques and lead to atherosclerosis. HDL stands for high density lipoproteins, these are considered "good" cholesterol, they transport excess cholesterol from the peripheral tissues back to the liver for storage or excretion in bile, they don't cause circulatory problems.

Define the nutrient pool

Contains all organic building blocks that a cell needs to provide energy & create new cellular components It's a source of substrates (nutrients) for various chemical reactions within the body

Define glycogenesis

Formation of glycogen from glucose, to store excess glucose for later use; liver & skeletal muscle tissue absorb the excess glucose and then bind the glucose monomers together to form the polysaccharide glycogen which can then be stored for later use

Describe the functions of the liver

Formation of plasma proteins; removal of bilirubin from blood following breakdown of hemoglobin as part of erythrocyte recycling; formation & release of bile into small intestine for emulsification of lipids; regulates blood glucose by serving as a "glucose bank"; synthesis of cholesterol; formation of lipoproteins; detoxification of drugs/toxins

What are the four stages of glucose oxidation, and where does each stage occur?

Glucose oxidation occurs within cells through cellular respiration; its the step-by-step enzymatic breakdown of glucose with accompanying release of energy to synthesize ATP Glycolysis (occurs within cytosol of cells), Intermediate stage (occurs within mitochondria of cells), Citric acid cycle (occurs within mitochondria of cells), & Electron transport system (occurs within mitochondria of cells)

** Define glycogenesis, glycogenolysis, and gluconeogenesis.

Glycogenesis is the process by which the liver and skeletal muscles store excess glucose as glycogen; they bind the glucose monomers together to form the polysaccharide glycogen; this process occurs when blood glucose levels are too high Glycogenolysis is the process by which the liver hydrolyzes some of the glycogen into glucose and releases it into the blood; this occurs when blood glucose levels are too low Gluconeogenesis is the process by which the liver forms glucose from noncarbohydrate sources, such as amino acids or fatty acids.

**Briefly describe the general steps in glycolysis. Include the products and energy yields that would result in aerobic and anaerobic conditions.

Glycolysis is the first stage of cellular respiration which occurs in the cytosol of cells which does not require oxygen; glycolysis is the metabolic pathway that breaks down glucose into two molecules of pyruvate with an accompanying energy transfer that forms a net production of 2 ATP & 2 NADH Glycolysis occurs through 10 enzymatically regulated chemical reactions; steps 1-5 occur once per glucose while steps 6-10 occur twice per glucose molecule because glucose splits into two 3-carbon molecules Steps 1-5 involve splitting a glucose molecule into two molecules of glyceraldehyde 3-phosphate (G3P), during this process ATP is invested twice; Steps 6 & 7 occur twice per glucose molecule, step 6 involves transferring an unattached Pi to the substrate & 2 H are released to NAD+ to form NADH, this transfer of hydrogen is catalyzed by dehydrogenase enzyme, step 7 involves the original Pi being transferred to ADP to form ATP through substrate-level phosphorylation; Steps 8-10 also occur twice, these steps involve converting the molecule produced in step 7 into an isomer and the loss of water, the remaining Pi is transferred to ADP to form ATP through substrate-level phosphorylation which leads to formation of the final pyruvate product Glycolysis results in the production of 2 pyruvate molecules along with 2 ATP and 2 NADH; if sufficient oxygen is available pyruvate will enter the intermediate stage to be turned into acetyl CoA, if insufficient oxygen is available pyruvate will convert to lactate

**Describe the structure of lipids. Define lipogenesis, lipolysis, and beta-oxidation.

Lipids are the only biological macromolecule that is not a polymer, they are a very diverse group of fatty, water-insoluble molecules that function as stored energy, components of cellular membranes, & hormones; there are four primary classes-triglycerides, phospholipids, steroids, & eicosanoids Triglycerides are formed from a glycerol and 3 fatty acids; phospholipids are similar to triglycerides but on one end of the glycerol there is a polar phosphate group with various organic groups attached to it instead of a fatty acid, so its made up of a glycerol, phosphate, organic group, and two fatty acids; steroids have four attached carbon rings, three have 6 carbons and one has 5 carbons; eicosanoids are modified 20-carbon fatty acids Lipogenesis is the process that occurs when conditions of excess nutrients exist and adipose connective tissue binds fatty acids to glycerol to form triglycerides in a dehydration synthesis Lipolysis is the process that occurs when nutrients are needed in the blood, here adipose connective tissue breaks down triglycerides in a hydrolysis reaction and release its products into the blood Beta-oxidation is the process by which fatty acids are used to generate ATP, during this process fatty acids are enzymatically changed two carbon units at a time to form acetyl CoA

Briefly describe the general steps of glycolysis.

Metabolic pathway of glucose, glucose is broken down into two pyruvate molecules with the accompanying energy transfer to form a net production of 2 ATP molecules & 2 NADH molecules Steps 1-5 occur once per glucose molecule and involves glucose being split into 2 3 carbon molecules (G3P) Steps 6-10 occur twice (once per each G3P) and involve process of turning each G3P into a pyruvate molecule **ATP is invested in steps 1-5 while ATP is formed in step 7 & step 10

** Define metabolism, catabolism and anabolism. What are hydrolysis reactions and dehydration reactions?

Metabolism is the collective term for all biochemical reactions in living organisms. Catabolism refers to all of the decomposition reactions in the body; these reactions involve an initial large molecule being digested or broken down into smaller structures--hydrolysis is an example of decomposition Anabolism is the collective term for all synthesis reactions in the body; these synthesis reactions occur when two or more atoms, ions, or molecules are combined to form a larger chemical structure as existing bonds are broken and new bonds are formed--dehydration is an example of a synthesis reaction The hydrolysis reaction is the decomposition of sucrose into glucose & fructose molecules in the digestive tract The dehydration synthesis occurs during the formation of a dipeptide from two amino acids

Define metabolism, catabolism, & anabolism

Metabolism: the collective term for all biochemical reactions in living organisms Catabolism: collective term for all decomposition reactions in the body, reactions where the initial large molecule is digested or broken down into smaller structures EX: hydrolysis reaction Anabolism: collective term for all synthesis reactions in the body, reactions where two or more atoms, ions, molecules are combined to form a larger chemical structure as existing bonds are broken and new bonds are formed, EX: dehydration synthesis reaction

Define beta-oxidation

Process by which fatty acids are broken down into acetyl-CoA which then enters the TCA cycle

What are the products & energy yields of glycolysis when oxygen is sufficient?

Products of glycolysis: 2 pyruvate molecules, 2 ATP, & 2 NADH The energy yield for glycolysis is 2 ATP whether O2 is present or not When oxygen is sufficient pyruvate molecules are transported to the mitochondria for conversion into acetyl-CoA & CO2

What are the products & energy yields of glycolysis when oxygen is limited?

Products of glycolysis: 2 pyruvate molecules, 2 ATP, 2 NADH The energy yield for glycolysis is 2 ATP per one glucose When oxygen is limited the 2 pyruvate molecules are converted into lactate

What are the products & energy yields of the intermediate stage?

Products: 2 acetyl-CoA & 2 NADH Energy yield for intermediate stage is 2 NADH

What are the products & energy yields of the TCA cycle?

Products: 4 CO2 molecules, 2 CoA molecules, 2 ATP, 6 NADH, & 2 FADH2 Energy yield for the TCA cycle is 2 ATP, 6 NADH, & 2 FADH2 (the coenzymes will be used to create additional ATP in the next step)

**Describe the structure and functions of proteins. Summarize the main processes of protein metabolism.

Proteins are polymers composed of one or more linear strands of amino acid monomers held together by peptide bonds, the ends of proteins include an N-terminal & C-terminal; each amino acid has an amine functional group & carboxyl functional group, both covalently linked to the same carbon atom; proteins have a primary, secondary, tertiary, & occasionally a quaternary structure; amino acids go through a dehydration synthesis to form dipeptides and connect together to form proteins Proteins have many possible functions, including catalyzing chemical reactions (act as enzymes), structural support, initiated body movements, transportation in blood, membrane transport, & aide in protection as antibodies Cellular proteins are continuously recycled in the cytosol of cells, their peptide bonds are broken & protein is broken down into amino acids which are then used to make new proteins; Amino acid catabolism: if our energy sources are unavailable and amino acids are needed then the amino acids undergo deamination, a process where the amino group and a hydrogen atom are stripped from amino acids to create an ammonium ion, once stripped of the ammonium ion the amino acid enters the TCA cycle to be used as energy source; Amino acid anabolism is the process of building proteins with the amino acid monomers

Describe the structure of proteins.

Proteins are polymers of amino acids (monomers) which are connected via peptide bonds; proteins have primary, secondary, tertiary, & quaternary structures. Primary structure: linear sequence of amino acids joined by peptide bonds Secondary structure: structural patterns within a protein--alpha helix & beta sheets Tertiary structure: Final 3D shape of protein which contains repeating secondary structures Quaternary structure: molecules composed of more than one separate protein--not always present

Briefly describe the general steps in the TCA cycle.

TCA cycle, citric acid cycle, occurs in the presence of oxygen within the mitochondria which involves the conversion of each acetyl-CoA molecule into 2 CO2 molecules & CoA

**Briefly describe the general steps in the electron transport system. What are the products of the electron transport system?

The electron transport system is the final step of cellular respiration which occurs in the mitochondria and requires oxygen; this stage involves the transfer of electrons from the coenzymes NADH & FADH2 which releases energy that is then used to form ATP The electron transport system occurs in 3 steps: in the first step electrons are transferred from coenzymes to O2; either the coenzyme NADH or FADH2 is oxidized, releasing hydrogen (electrons), these electrons are passed through the electron transport chain to O2 (the final electron acceptor); in the second step an H+ gradient is established, as the electrons are passing down the electron transport chain their kinetic energy is harnessed by H+ pumps to move H+ from the matrix into the outer compartment; the last step involves the H+ gradient being harnessed to form ATP, H+ moves down its concentration gradient as its transported across the membrane by ATP synthase, it moves from the outer compartment back into the matrix, the kinetic energy of the falling H+ is harnessed by ATP synthase to form a new bond between ADP and Pi to produce ATP The products of the electron transport system are formed via oxidative phosphorylation--each NADH molecule generates 3 ATP and each FADH2 molecule generates 2 ATP so consequently a net total of 30 ATP is made

**What are the four stages of cellular respiration, and where does each stage occur?

The four stages of cellular respiration include glycolysis, the intermediate stage, citric acid cycle, and the electron transport system. Glycolysis occurs within the cytosol of the cells while the other three stages (intermediate stage, citric acid cycle, & electron transport system) occur within the mitochondria of the cell.

**Briefly describe the general steps in the intermediate stage. What are the products of the intermediate stage?

The intermediate stage is the second stage of cellular respiration which occurs in the mitochondria and requires oxygen; this stage is catalyzed by pyruvate dehydrogenase; the first step of the intermediate stage involves pyruvate dehydrogenase binding together a pyruvate molecule and. molecule of coenzyme A (CoA) to form acetyl CoA, while this is occurring a carboxyl group is also released from pyruvate as CO2 (decarboxylation), energy is released during decarboxylation as 2 H atoms are transferred to coenzymes NAD+ to form NADH--this process occurs twice since there are two pyruvate molecules created from glucose The intermediate stage produces 2 acetyl CoA molecules & 2 NADH molecules

Briefly describe the general steps in the intermediate stage.

The intermediate stage occurs in the presence of oxygen within the mitochondria; this stage results in the conversion of pyruvate into acetyl CoA and is catalyzed by pyruvate dehydrogenase Pyruvate dehydrogenase combines pyruvate & a molecule of coenzyme A (CoA), during this process pyruvate goes through decarboxylation process and releases a CO2 causing the release of energy forming NADH This process occurs twice, once per pyruvate molecule