Chapter 25. Metabolism And Nutrition Flashcards
Metabolism
Sum total of all chemical reactions occurring within the cells of an organism
- ATP is the primary energy-carrying molecule of the cell
How many stages occur in the processing of nutrients
3 stages, stage two has two different parts
Stage one of nutrient processing
Digestion occurs in the GIT and absorbed nutrients enter the blood to reach tissue cells
Stage Two of nutrient processing
- Occurs in the cytoplasm of tissue cells.
- Absorbed nutrients are:
I) used o build complex molecules (lipids, proteins, glycogen) by ANABOLIC pathways
Or
II) broken down by CATABOLIC pathways to harvest their bond energy to form pyruvic acid and acetyl CoA
Stage Three of Nutrient Porcessing
- Occurs in the mitochondria and is almost entirely catabolic (“breakdown”).
- Requires oxygen and completes the breakdown of food to CO2 and H2O, generating large amounts of ATP through oxidative phosphorylation
Anabolic Reactions
Takes the last phosphate and uses it to make new nutrients
40% is used
60% is released by heat
Carbohydrate metabolism
- Carbohydrates are broken down into monosaccharides: glucose (about 80%), fructose and galactose.
- can transfer energy from glucose to ATP
- other nutrients (fats, amino acids) can generate ATP and are linked to glucose breakdown pathways
- Glucose is the major fuel for cellular respiration to produce ATP (it is the most that gets broken down)
What does liver cells (hepatocytes) do to fructose and galactose
Converts fructose and galactose into glucose
Cellular respiration
- Is the process (series of catabolic reactions) that releases energy from glucose and makes it available for cellular use.
- in involves oxidation and reduction reactions (redox rxns)
- a substance is oxidized when it loses and electron
- a substance is reduced when it gains an electron
What happens when hydrogens are removed
They are attached to coenzymes
Coenzymes
Are assisting enzymes and they help grab on to hydrogen atoms and help lead them where they need to go.
Two coenzymes
- Nicotinamide adenine dinucleotide (NAD+)
- Flavin adenine dinucleotide (FAD)
Cellular respiration
Involves four sets of reactions:
1. Glycolyses
2. Formation of acetylene CoA
3. Krebs cycle (critic acid chain cycle)
4. Electron transport chain reaction (ETC)
Glycolysis
- Occurs in the cell cytoplasm
- is an anaerobic process (does not need oxygen)
- series of 10 reactions which convert 1 (6C) glucose into 2 molecules of pyruvic acid (3C)
- glucose loses 4 hydrogen atoms which are now bound to 2 molecules of NAD+
- Produces 2 NADH + 2H+
- this results in a net gain of 2 ATP
Formation of Acetyl CoA
- If oxygen is available ( aerobic conditions), them pyruvic acid is converted to acetyl coenzymes A (CoA)
- when Pyruvic acid enters the mitochondria, it loses a C atom and a pair of H atoms
- 2 C molecule formed (acetic acid) is attached to coenzymes A to produce acetyl CoA (form 2 for every molecule of glucose
- H’s are transferred to NAD+ TO PRODUCE NADH + H+
- Acetyl CoA Exeter’s the Krebs cycle
Krebs Cycle
- Occurs in matrix o if mitochondria
- an aerobic process (requires O2)
- series of 8 cyclical reactions
- beings with 1 acetyl CoA and results in
- formation of 2 CO2
- H’s are picked up by FAD to form 1 FADH2
-H’s are picked up by NAD+ to form 3 NADH - Formation of 1 ATP
Electron Transport Chain
- each par of electrons donated to ETC by NADH provides enough energy to pump enough protons to produce about 2.5 molecules of ATP ( 1.5 ATP for each FAH2)
- oxygen acts as the final electron acceptor at the end of the ETC
- electrons are recombined with protons (H+) to form hydrogen which is combined with oxygen to form water (6 H2O)
Cellular Respiration Numbers
ATP Produced by Glycolysis = 2 ATP
ATP produced by Krebs cycle = 2 ATP
NADH produced by glycolysis = 2 x 2.5 ATP = 5 ATP
NADH produced in formation of acetyl CoA from pyruvic acid = 2 x 2.5 ATP = 5 ATP
NADH produced in Krebs cycle = 6 x 2.5 ATP = 15 ATP
FADH2 produced in Krebs cycle = 2 x 1.5 ATP = 3 ATP
TOTAL = 32 ATP
NADH + H+ shuttles
Shuttle number 1
- found in liver, kidney, and heart muscle
- NADH passes e-‘s to a shuttle molecule that delivers e-‘s to beginning of ETC
- Anything that starts at the beginning generates 2.5 ATP
Shuttle Number 2
- Found in skeletal muscle and brain cells
- NADH passes e-‘s to a different shuttle that deliver e-‘s farther down ETC
- only generates 1.5 ATP, just like FADH2.
