Lecture: Metabolism Flashcards
What is metabolism?
Metabolism refers to all chemical reactions that occur in the body.
What is catabolism?
Catabolism is a type of metabolism: the breaking down of complex molecules into simpler forms.
Why type of reaction is catabolism?
Catabolism is an exergonic reaction (energy, or ATP, is released).
What is anabolism?
Anabolism is a type of metabolism: the building of simple molecules into more complex molecules.
What type of reaction is anabolism?
Anabolism is an endergonic reaction (energy, or ATP, is used).
How is ATP used in catabolism?
Catabolic reactions transfer energy from complex molecules to ATP.
How is ATP used in anabolism?
Anabolic reactions transfer energy from ATP to complex molecules.
What is oxidation?
Oxidation is the removal of electrons. It results in a decrease in potential energy. There is also a loss of H+.
Oxidation Is
Loss of electrons
What is reduction?
Reduction is the addition of electrons. It results in an increase in potential energy. There is also a gain of H+.
Reduction Is
Gain of electrons
What are the two main mechanisms of ATP generation?
- substrate level phosphorylation 2. oxidative phosphorylation
What is substrate level phosphorylation?
the generation of ATP by transferring a high-energy phosphate group from a substrate to ADP.
What is oxidative phosphorylation?
the generation of ATP by removing electrons from organic compounds and passing them through the electron transport chain.
What are the breakdown products of carbohydrate metabolism used for?
- ATP production
- amino acid synthesis
- glycogen synthesis (process called glycogenesis)
- triglyceride synthesis (process called lipogenesis)
Before glucose can be used by the body, it must first enter the body cells by passing through the plasma membrane and entering the cytosol. What are the two methods this occurs?
- secondary active transport
2. facilitated diffusion
How does glucose enter the cell through secondary active transport?
glucose enters cells through Na+ glucose symporters.
How does glucose enter the cell through facilitated diffusion?
glucose enters cells by being transported on GluT molecules.
Where does secondary active transport of glucose mainly occur in the body?
mainly occurs in the GI tract.
Where does facilitated diffusion of glucose mainly occur in the body?
in most body cells besides the GI tract.
What is cellular respiration?
the oxidation of glucose to produce ATP.
What are the four steps in cellular respiration?
- glycolysis
- formation of acetyl coenzyme A
- the Krebs Cycle
- the electron transport chain reactions
Where does glycolysis occur?
In the cytosol of the cell.
What is the energy net gain in glycolysis?
2 ATP molecules, 2 NADH + H+
What are the end products in glycolysis?
2 pyruvic acids
Where does the formation of acetyl coenzyme A occur?
in the mitochondrial matrix.
What is the net energy gain in the formation of acetyl coenzyme A?
2 NADH + H+
What are other products released in the formation of acetyl coenzyme A?
2 CO2
Where does the Krebs Cycle occur?
mitochondrial matrix
What is the net energy gain in the Krebs Cycle?
6 NADH + H+, 2 FADH2, 2 ATP
What are other products released in the Krebs Cycle?
4 CO2 (or 6 total now)
Where do electron chain reactions occur?
within the inner membrane of the mitochondria.
What is the net energy gain in electron chain reactions?
book says 28, ppt says 32-34 ATP
What is the total amount of ATP produced at the end of cellular respiration?
30-32 ATP per glucose molecule
What is glycogenesis?
formation of glycogen for glucose storage
What hormone stimulate glycogenesis?
Insulin stimulate glycogenesis (glucose storage).
What is glycogenolysis?
glucose release.
What hormone stimulates glycogenolysis?
Glucagon and epinephrine stimulate glycogenolysis.
What is gluconeogenesis?
the process of glucose forming from fats and proteins.
What hormone stimulates gluconeogenesis?
Cortisol and glucagon stimulate gluconeogenesis.
What must occur to lipids before they can be transported in the blood? Why?
Lipids must be combined with proteins to form Lipoprotiens. This is because most lipids are insoluble in water/blood.
What are the four classes of lipoproteins?
- chylomicrons
- very-low-density lipoproteins (VLDL’s)
- low-density lipoproteins (LDL’s)
- high-density lipoproteins (HDL’s)
What are chylomicrons and what do they do?
a type of lipoprotein that transports dietary (ingested) lipids from small intestine to adipose tissue for storage.
What do very-low-density lipoproteins (VLDL’s) do?
carry triglycerides from the liver to muscle and adipose tissue.
What do low-density lipoproteins (LDL’s) do?
deliver cholesterol to body cells. They provide up to 75% of the body’s cholesterol. This is “bad” because it can block arterial walls.
What do high-density lipoproteins (HDL’s) do?
remove excess cholesterol from body cells and transport it to the liver to make bile.
What are the two sources of cholesterol for the body?
- food
2. hepatocytes
What is “good” cholesterol?
high-density lipoproteins (HDL’s)
What is “bad” cholesterol?
low-density lipoproteins (LDL’s)
In an adult, what should the total cholesterol (TC) be?
less than 200 mg/dL.
In an adult, what should the total low-density lipoprotein (LDL) count be?
less than 130 mg/dL.
In an adult, what should the total high-density lipoprotein count be?
greater than 40 mg/dL.
In an adult, what should the total triglyceride count be?
between 10 and 190 mg/dL.
What is lipolysis?
lipid catabolism; triglycerides are split into fatty acids and glycerol. They are then released from adipose tissue.
What hormones stimulate lipolysis?
Epinephrine and norepinephrine stimulate lipolysis.
Cortisol, thyroid hormones, and insulin-like growth factors also play a part.
What is beta oxidation?
fatty acid catabolism, turned into acetyl coA for the krebs cycle
What is lipogenesis?
lipid anabolism; the formation of lipids by the liver and adipose cells rom glucose and amino acids.
What hormones stimulate lipogenesis?
Insulin
When does lipogenesis occur?
when individuals consume more calories than are needed to satisfy their ATP needs.
Unlike carbs/ triglycerides, proteins are not stored for future use. What happens to proteins instead?
- oxidized to produce ATP
2. synthesized to new proteins
What are proteins often times used for?
- enzymes
- transportation
- antibodies
- hormones
- collagen, elastin, keratin (structurally)
What is protein catabolism?
the conversion of amino acids into fatty acids, ketone bodies, and glucose by hapatocytes.
What hormone stimulates protein catabolism?
Cortisol
Before amino acids can enter the Krebs Cycle, what must occur?
deamination (removal of their amino group).
What is protein anabolism?
the formation of peptide bonds between amino acids to produce new proteins.
Where is protein anabolism carried out?
on the ribosomes (directed by DNA and RNA) of almost every cell.
What hormones stimulate protein anabolism?
Insulin-like growth factors, thyroid hormones (T3 and T4), insulin, estrogen, and testosterone
How many amino acids are in the body?
20
What are essential amino acids, and how many are there?
10
What are nonessential amino acids, and how many are there?
Nonessential amino acids are synthesized (formed) in the body. There are 10.
What are the three key molecules in metabolism?
- glucose 6-phosphate
- pyruvic acid
- acetyl coenzyme A
What are the four roles of glucose 6-phosphate?
- synthesis of glycogen
- release of glucose into the bloodstream
- synthesis of nucleic acids
- glycolysis
Explain synthesis of nucleic acids:
Glucose 6-phosphate is used by cells to make substances needed for the formation of DNA and RNA.
Explain glycolysis:
Most body cells carry out glycolysis- producing ATP anaerobically. Glucose 6-phosphate is converted to pyruvic acid.
What are the three roles of pyruvic acid?
- production of lactic acid
- production of alanine
- gluconeogenesis
Explain production of lactic acid
When oxygen is in short supply in a tissue, pyruvic acid is changed to lactic acid.
Explain production of alanine
Amino groups are sometimes added to pyruvic acid to produce alanine.
Explain gluconeogenesis
Pyruvic acid can be converted to oxaloacetic acid and can be used to form glucose 6-phosphate.
What are the three roles of acetyl coenzyme A?
- begins the Krebs Cycle and electron transport chain: by conversion from pyruvic acid.
- entry into the Krebs Cycle
- synthesis of lipids
Explain the synthesis of lipids:
Because pyruvic acid can be converted to acetyl coenzyme A, carbohydrates can be turned into triglycerides.
What does regulation of metabolic reactions depend on? Regulation of metabolic reactions depends both
- chemical environment within body cells (such as levels of ATP and oxygen)
- signals from the nervous and endocrine systems.
What occurs during the absorptive state?
ingested nutrients enter the blood and lymph from the GI tract.