Ch. 27, 2, 3 - Metabolism Flashcards
metabolism
all biochemical reactions in living organisms.
Chemical reactions
occur when chemical bonds in existing molecular structures are broken and new bonds are formed. This is expressed as a chemical equation.
Reactants
Substances present prior to start of a chemical reaction and written on left side of equation
Products
substances formed by the reaction; written on right side of the equation.
balanced equation
an equation where the number of elements are equal on both sides.
Classification criteria for chemical reactions
- changes in chemical structure
- changes in chemical energy
- whether the reaction is reversible or not
These determine what kind of chemical reaction occurred (decomp, synthesis, exchange)
Decomposition reaction- catabolism
initial large molecule broken down into smaller structures. AB –> A + B
Synthesis reaction- anabolism
two or more structures combined to form larger structure A + B –> AB
Exchange reactions
Where two structures switch parts AB + CD –> AD + BC
Carbs
structurally classified as mono, di, or polysaccharides. when describing dietary sources they are classified as sugars, starch, and fiber.
Sugars
include the monosaccharides glucose, fructose, and galactose, and the disaccharides sucrose, lactose, maltose and dextrose.
Sucrose dietary sources
table sugar, syrup, fruit
Lactose dietary sources
milk sugar
Maltose dietary sources
cereals
Starch
polysaccharide polymer of glucose found in foods like tubers, grains, beans, and peas. Refined starches are sometimes used as thickeners like cornstarch.
Fiber
Carb that includes fibrous molecules of both plants and animals and cannot be digested. Comes from lentils, peas, beans, whole grain, oatmeal, berries, nuts. Simulates peristalsis and lowers cholesterol.
Glucose
6 carbon carb, most common monosaccharide and primary nutrient so level must be carefully maintained.
Glycogen
liver and skeletal muscle store excess glucose and bind glucose monomers together (glycogenesis) and can also form glucose from noncarb sources (gluconeogenesis). Glycogen can be broken down via glycogenolysis.
Hexose monosaccharides
glucose isomers (galactose, fructose)
five carbon monosaccharides
pentose sugars; ribose and deoxyribose
Lipids
fatty, water-insoluble molecules that function as stored energy, cellular membrane components and hormones. 4 main classes are triglycerides, phospholipids, steroids, and eicosanoids
Triglycerides
used for long-term energy storage. Formed from glycerol and three fatty acids. Fatty acids vary in length and number of double bonds. Adipose tissue stores triglycerides
Saturated fat
fatty acid that lacks double bonds
Unsaturated fat
fatty acid that has one double bond. liquid at room temp. generally healthier.
Polyunsaturated fat
fatty acid that has two or more double bonds. liquid at room temp and are found in certain oils such as soybean oil, corn oil, and safflower oil.
Lipogenesis
formation of triglycerides when conditions of excess nutrients exist
Lypolysis
breakdown of triglycerides when nutrients are needed.
Phospholipids
amphipathic molecules that form chemical barriers of cell membranes. Has one end with a polar phosphate group such as glycerol, phosphate, or organic groups and form hydrophilic head and fatty acid group is nonpolar and forms hydrophobic tails.
Steroids
Composed of hydrocarbons arranged in multi-ringed structure. There are 4 carbon rings, three have 6 carbon atoms and one has 5 carbon atoms. They differ in side chains extending from their rings. Includes Cholesterol, steroid hormones, and bile salts.
Cholesterol
a steroid. component of animal plasma membranes and precursor to other steroid synthesis (steroid hormones, bile salts, vitamin d). Comes from diet or metabolic pathway in liver.
Steroid hormones
testosterone and estrogen
Eicosanoids
modified 20-carbon fatty acids synthesized from arachidonic acid (a membrane component). Primary functions include inflammation response and nervous system communication. Have four classes: prostaglandins, prostacyclins, thromboxanes, and leukotrienes.
Most animal fats are…
saturated and solid at room temp.
Most vegetable fats are…
liquid at room temp. and unsaturated. They tend to be healthier and can be converted to saturated fats through hydrogenation.
Trans fats
partial hydrogenation of unsaturated fats. Increases the risk of heart attack and stroke.
Cholesterol synthesis
synthesized by hepatocytes. Fatty acids are transported to liver and enter hepatocytes where they are broken down into two-carbon molecule called acetyl CoA through beta oxidation. Acetyl CoA turns into cholesterol using HMG-Coa reductase. Cholesterol is produced at basal level which varies among individuals and synthesis decreases with higher cholesterol intake.
Cholesterol following synthesis
released into blood in very-low-density lipoproteins or synthesized into bile salts as part of bile.
Bile salt reabsorption rate
90%. Other 10% is lost in feces.
Transport of Lipids
VLDLs and LDLs are involved to transport lipids from liver to peripheral tissue.
Very-low-density lipoproteins VLDLs
various types of lipids with protein. They are assembled within liver and released in blood. They circulate in blood and release triglycerides to peripheral tissues. They are primarily adipose tissue. After release of triglycerides, they become LDLs.
Low-density lipoproteins LDLs
contain high amounts of cholesterol and deliver it to cells. Bind to LDL receptors in plasma membranes and are engulfed via endocytosis and the cholesterol is incorporated into the plasma membrane.
High-density lipoproteins HDLs
Proteins formed in liver and released into blood without addition of lipid. They circulate the blood and fill with lipids from peripheral tissues. Like LDLs, HDLs also make cholesterol but it is not engulfed by cells. The lipids are then transported to the liver and excess cholesterol is converted to bile salts within liver.
Blood Cholesterol Levels
High levels of LDLs or total cholesterol and low levels of HDL are a risk factor for cardiovascular disease. above 200 mm/dl is considered high. LDLs considered bad cholesterol because excess is deposited on inner arterial walls
Liver Metabolic functions
carb, protein, and lipid metabolism, transport of lipids, storage, and drug detox.
Proteins
most structurally and functionally diverse molecules needed to replace worn out protein structures in body. Amount needed depends on age (children need more) and sex, as well as injury, stress, and pregnancy. 8 amino acids are essential and the other 12 can be synthesized by body.
How many amino acids are there
- 8 cannot by synthesized.
Protein functions
catalysts, defense, transport, support, movement, regulation, storage
General Protein structure
one or more strands of amino acid monomers; each amino acid has an amine and carboxyl functional group both linked to the same carbon atom. That carbon is also covalently bonded to a hydrogen and different side chain structures called R groups. R groups distinguish aa’s from one another. AA’s are linked by peptide bonds.
Peptide bond formation
formed during dehydration synthesis reaction between amine group of one amino acid and the carboxylic group of another. The H is lost from the amine group and the OH is lost from carboxylic acid.
N- terminal end
end of polypeptide with free amine group
C-terminal end
end of polypeptide with free carboxyl group.
Oligopeptide
b/w 3 - 20 amino acids
polypeptide
b/w 21 - 199 amino acids
protein
more than 200 amino acids
glycoproteins
proteins with carb attached. glycoproteins on erythrocytes determine ABO blood group.
4 stages of cellular respiration
glycolysis, intermediate stage, citric acid cycle, electron transport system.
glycolysis
anaerobic pathway occurring in cytoplasm. glucose is oxidized to 2 pyruvate molecules. 2 ATP and 2 NADH are formed. The pyruvate is converted to lactate if insufficient O2 is available.
Intermediate phase
aerobic, in mitochondria. Pyruvate is converted to acetyl CoA and CO2 and NADH are formed.
Citric acid cycle
acetyl CoA forms citric acid. CO2, ATP, FADH, and NADH are produced in each cycle.
Electron transport chain
transfer of hydrogen and electron from NADH and FADH2. ATP formed through oxidative phosphorylation.
Glycerol and Fatty acids in ATP production
glycerol enters pathway of glycolysis and is converted to glucose in liver. Carbons of fatty acids are removed to form acetyl CoA by beta oxidation and those molecules enter the citric acid cycle.
amino acids and ATP production
may be used to generate ATP by removing the amine group by deamination. This occurs in liver hepatocytes and amine group is converted to urea and eliminated by kidneys. The remainder enters the metabolic pathway at different areas depending on the aa. It can enter glycolysis, intermediate, or citric acid cycle.
