UNIT 7 - CELLULAR RESPIRATION & ENERGY METABOLISM Flashcards
Cellular respiration
Catabolic process by which cells produce energy from glucose molecules (respiration using oxygen at a cellular level); electrons and H+ released from organic molecules
Catabolic
Reaction of breaking up molecules and are exergonic (release energy); Breaking up ATP to ADP + phosphate to release energy to be used for anabolic reactions to cell
Anabolic
Reaction of combining molecules and are endergonic (absorb energy); Regenerating ADP + phosphate to ATP which use energy provided by cellular respiration
Use of energy in cells (5)
- Metabolism
- Movement
- Growth
- Cell division
- Action potentials
ATP
Chemical energy released when glucose is broken down and captured in adenosine triphosphate and directly powers chemical reactions in cells via immediate useable energy
How many ATP molecules per cell and how much does our body use
Billion ATP molecules per cell, each of which lasts 1 minute before being used. We use one half of our body weight in ATP everyday
ATP structure
Adenine base attached to ribose sugar with 3 phosphate groups
Phosphoanhydride bonds
High energy bonds that link the phosphate groups in ATP
Nutrients used to generate ATP (4)
- Glucose (primary)
- Carbohydrates
- Lipids
- Proteins
Formula for cellular respiration
C6H12O6 + 6O2 + 36 ADP + 36 P = 6CO2 + 6H2O + 36 ATP + heat
Locations of cellular respiration
Cytoplasm & mitochondria
Electron levels/shells
Fixed distances from the nucleus of an atom where electrons may be found. Higher electron shells = higher energy; so if electron moves from high electron shell to lower, they release energy
Oxidation-reduction (redox) reaction
Chemical reaction involving transfer of electrons between two species
Oxidation
Loss of electrons eg. NADH –> NAD+ (OIL = oxidation is loss)
Reduction
Gain of electrons eg. NAD+ –> NADH (RIG = reduction is gain)
Nicotinamide adenine dinucleotide (NAD)
Accepts high energy electrons and carry them to electron transport chain to make ATP and central to metabolism found in all living cells
Niacin (vitamin B3)
Precursor to NAD and can be converted into NAD in the body
Flavin adenine dinucleotide (FAD)
Coenzyme that act as hydrogen and accompanying electron acceptors central to metabolism found in all living cells
Riboflavin (vitamin B2)
Precursor to FAD and can be converted into FAD in the body
NAD & FAD function
Act as electron carriers to transport electrons that are released during cellular respiration via redox reactions to a small “machine” to produce ATP from the energy of these electrons
Substrate level phosphorylation
Metabolic reaction that results in the formation of ATP by the direct transfer of a phosphoryl group to ADP from another phosphorylated compound
Oxidative phosphorylation:
Process by which the energy stored in NADH and FADH2 is used to produce ATP
Stages of cellular respiration (4)
- Glycolysis (cytosol)
- Pyruvic acid oxidation (mitochondria)
- Krebs cycle (mitochondria)
- Electron transport chain (mitochondrial inner membrane since mitochondria has two membranes )
Energy investment phase
Ivolves the use of two ATP molecules to phosphorylate glucose, resulting in the formation of two molecules of glyceraldehyde-3-phosphate (intermediate in glycolytic pathway)
Glycolysis
Operates without oxygen, using 2 ATP molecules in the energy investment phase to activate glucose to transform glucose into two pyretic acid
Results of glycolysis (remaining products)
2 pyruvic acid molecules, 2 ATP molecules, 2 NADH
Anaerobic respiration
Respiratory process where cells break down sugar molecules to produce energy WITHOUT oxygen; organisms can convert pyruvic acid to lactic acid (or ethanol in microorganisms/plants), and when oxygen is available again, lactic acid is converted back to pyruvic acid
Aerobic respiration
Uses oxygen to create energy from food
Pyruvic acid oxidation
Pyruvic acid enters the mitochondria, loses a carboxyl group (producing CO2), and undergoes electron removal by NAD+, along with hydrogen. The resulting pyruvate transforms into an Acetyl group, joining with acetyl coenzyme A to form acetyl-CoA
Results of pyruvic acid oxidation (remaining products
2 CO2, 2 NADH, 2 Acetyl-CoA
Krebs cycle (citric acid cycle/tricarboxylic acid cycle)
Acetyl group combines with oxaloacetic acid to form citric acid, releasing carbon as CO2. This cycle then transforms oxoloacetic acid back into oxaloacetate, producing NADH, FADH2, and one ATP through substrate-level phosphorylation
Results of Krebs cycle (remaining products)
4 CO2, 6NADH, 2FADH2, 2 ATP; 1 glucose molecule yields 2 acetyl CoA so two cycles through Krebs cycle will occur for each glucose molecule
Oxidative phosphorylation
Cellular process that harness the reduction of oxygen to generate high energy phosphate bonds in the form of ATP; consisting of 2 parts
2 parts of oxidative phosphorylation:
- Electron transport chain: produce electrochemical gradient by pumping hydrogen ions into intermembrane
- Chemiosmosis: uses energy stored in hydrogen ion gradient across membrane to produce ATP
Electron transport chain
Consists of a series of protein complexes linked together and embedded on inner mitochondrial membrane of cristae (folds) which electrons pass through via redox reactions
Protein complex of electron transport chain
Each protein complex in the chain has a higher attraction for electrons than the one before it
Flavin mononucleotides (FMN)
Cofactors that carry and transfer electrons in the electron transport chain (protein complex I)
NADH in electron transport chain
Passes a hydrogen to FMN (complex I) and yields 3 ATP
FADH2 in electron transport chain
Passes hydrogen to a protein complex further down the chain (complex II) and yields 2 ATP
Cytochromes
Makes up most of the protein complexes on the electron transport chain that contain an iron atom at core
Chemiosmosis:
Movement of ions across semipermeable membrane down electrochemical gradient (eg. Generation of ATP by movement of hydrogen ions across membrane during cellular respiration)
How much ATP is produced in cellular respiration total
- However, sometimes it can be 36 due to transport of NADH from cytosol to mitochondrial matrix can lose 2 ATP
How much ATP produced in glycolysis
2 ATP
How much ATP produced in krebs cycle
2 ATP
How much ATP produced in electron transport
34 ATP
Oxygen significance
Has the strongest attraction for electrons in the electron transport chain and is the final electron acceptor so it combines the electrons with hydrogen ions from matrix and forms water
What would happen if oxygen was not present to finally accept the electrons
Without oxygen, the electron transport chain becomes overwhelmed leading to buildup of electrons. This means NADH and FADH2 cannot release their electrons and NAD+ and FAD won’t be generated; only applies for reactions in mitochondria
Why is aerobic respiration more efficient than anaerobic respiration
Because aerobic respiration uses oxygen to create energy from food, whereas anaerobic respiration works without oxygen
Aerobic respiration formula
C6H12O6 + 6O2 = 6CO2 + 6H2O + 2830kJ
Anaerobic respiration formula
C6H12O6 = 2C2H5OH + 2CO2 + 210kJ
Energy metabolism
Combined process of energy storage and energy production from various nutrient sources (carbohydrates, lipids, proteins)
Energy storage in the human body (3)
- Glycogen: 4.2 calories/g, makes up 1% stored energy, can sustain energy needs for 1 day
- Lipids: 9.5 calories/g, makes up 77% stored energy, can sustain energy needs for 2 months
- Proteins: 4.3 calories/g, makes up 22% of stored energy, extensive breakdown (catabolism) of proteins are fatal
Glucose
Primary energy source for most tissues and yields ATP through cellular respiration
Metabolism
Refers to all the chemical processes that occur in the cell/organism and consists of 2 basic types; anabolic, catabolic
Anabolic reaction
Reactions involved in building more complex molecules and structures (generally requiring energy)
Catabolic reactions
Reactions involved in breaking down structures into simpler/smaller bits (generally release energy)
Distinct mechanisms to meet body’s demands for energy (3)
- Absorptive state
- Postabsorptive state
- Starvation
Absorptive state
Between 0-3 hours, body is going through the process of ingesting and storing the last thing you ate. Body is breaking down carbohydrates, proteins and fat into glucose, amino acids, and fatty acids and metabolizes them for energy/stores for later
Postabsorptive state
Between 4-24 hours, Body switches to catabolic state where stored nutrients are put to use
Starvation
Between 24-72 hours, body is deprived of nourishment for an extended period of time and goes into survival mode
Carbohydrates
Organic molecules composed of carbon, hydrogen and oxygen atoms, including sugars (monosaccharides, disaccharides) and polysaccharides. Carbohydrates broken down into glucose which is oxidized to release energy stored in its bonds to produce ATP
When glucose is in excess (2)
- Glycogenolysis: Converts glucose to pyruvic acid
- Glycogenesis: Converts polymerizes glucose to form glycogen
When glucose is at low levels (3)
- Glycogenolysis: Hydrolyzes glycogen to glucose monomers
- Gluconeogenesis: Forms glucose from noncarbohydrate precursors (eg. glycerol)
- Triglycerides broken down to glycerol and individual fatty acids via lipolysis
Triglycerides
Primary long term energy storage molecules
Fatty acids
Becomes a major source of ATP production in tissues when glucose levels are low and are broken down to acetyl-CoA via beta oxidation
Beta oxidation
Catabolic process by which fatty acids are broken down in cytosol to generate acetyl-CoA and enter Krebs cycle where ATP, NADH, FADH2 is produced
Tissues that prefer fatty acids for ATP synthesis (3)
- Liver
- Cardiac muscle
- Resting skeletal muscle
What happens when nutrients are in excess
Then the excess of glucose, amino acids or lipids can be stored as triglycerides
Can the liver perform gluconeogenesis
Yes
Ketone bodies
Produced by the liver for energy when glucose is not available
3 types of ketone bodies (3)
- Acetoacetate
- 3-hydroxybutyrate
- Acetone
Significance of ketone body production
Important to minimize gluconeogenesis and save protein catabolism, they leave the liver and get transported to other tissues, then they get converted back to acetyl-CoA and used for energy
What happens to excess amino acids
They are deaminated (amino group removed) and converted to urea in liver
Urea
Waste product made when liver breaks down protein
Uses of carbon skeleton (3)
- Cellular respiration
- Lipid production
- Gluconeogenesis
Amino acid catabolism significance during fasting
Provides oxaloacetate for gluconeogenesis
Uses of fatty acids (by muscle) and ketone body (by brain) resul
Minimize amino acid catabolism which is important for maintaining overall health and tissue integrity