Bio 151 - Metabolism final exam

Define metabolism, catabolism, and anabolism.
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Define metabolism, catabolism, and anabolism.
Metabolism - all the chemical rxns that occur in an organism

Catabolism - Breaking down
▪ Breakdown of organic molecules
▪ Releases energy (exergonic)

Anabolism - Building up
▪ Synthesis of new organic molecules
▪ Requires energy (endergonic)
List some general reasons why cells need energy
• 1: metabolic turnover (cellular maintenance and repair)
• 2: growth and cell division
• 3: specialized processes (secretion, contraction, activetransport, etc.)
• 4: storage of nutrient reserves
Write the summary equations (in words or chemical notation) for photosynthesis and glucose metabolism.
Photosynthesis:
6H2O + 6CO2 + light energy → C6H12O6 + 6O2

Glucose metabolism:
C6H12O6 + 6O2 → 6H2O + 6CO2 + energy
Describe the systematic breakdown of glucose that allows us to produce large quantities of ATP. This includes:
o glycolysis
o acetyl-CoA formation
o citric acid cycle
o electron transport chain
Glycolysis: Glucose → (intermediates) → 2 pyruvate
•Use 2 ATP, make 4 ATP: net gain = 2 ATP
•Electron carriers are also produced (NADH)
•Glucose and many enzymes are required, but oxygen is not
•Occurs in the cytoplasm

acetyl-CoA formation: the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme.
• Electron carriers are also produced
• Basically, this converts the "food" molecule into something that can be used in the Citric Acid cycle

citric acid cycle:
•Acetyl CoA breaks back into → acetyl group +CoenzymeA
•Each acetyl group = broken into 2 CO2
•Net production per glucose:
• 2 ATP
• 4 CO2
• Some electron carriers (NADH, FADH2)
• Need acetyl CoA input, but other molecules can be reused

electron transport chain:
•Uses energy from the "charged" electron carriers (NADH, FADH2), produced by Citric Acid Cycle and glycolysis
•Creates a H+ gradient
• Requires energy (active transport!)
• Transport H+ out of the mitochondrial matrix...
• ...to cause a build up of H+ ions in intermembrane compartment
Here are a few more things you should be able to do related to the glucose metabolism described above:
o Name the locations in the cell where glycolysis, the citric acid cycle, and the electron transport chain occur.
o Trace the 6 carbon atoms from a single glucose molecule, and how they are broken down from glucose to pyruvate, then to CO2 and an acetyl group, then ultimately broken down to release more CO2.
o Describe the role of NADH and FADH2.
o Describe the formation and function of the H+ gradient (in the intermembrane space of mitochondria).
o Describe the role of oxygen in glucose metabolism.
Location:
- Glycolysis - cytoplasm
- The citric acid cycle - matrix of the mitochondria
-The electron transport chain - Intermembrane space


-The process begins with Glycolysis. In this first step, a molecule of glucose, which has six carbon atoms, is split into two three-carbon molecules (Pyruvate) using 2 ATP and produces two 4 ATP and 2 NADH.
-Next, If oxygen is available, aerobic respiration will go forward. In mitochondria, Pyruvate is oxidized and converted into Acetyl CoA that will be picked up by a carrier compound called coenzyme A (CoA).
-These two steps occur in the cytoplasm of the cell. Acetyl CoA enters into the matrix of mitochondria, where they start the Citric Acid Cycle (Krebs cycle). The third carbon from pyruvate combines with oxygen to form carbon dioxide, which is released as a waste product.
-Finally, During the process of oxidative phosphorylation, the electrons extracted from food move down the electron transport chain in the inner membrane of the mitochondrion. As the electrons move down the ETC and finally to oxygen, they lose energy. Energy from NADH and FADH2, which result from the previous stages of cellular respiration, is used to create ATP.

Role of NADH and FADH2: Carries electrons to the electron transport chain in mitochondria.

Formation and function of the H+ gradient: Created by the electron transport chain and transport H+ out of the mitochondria. The build up of H+ means that it can be released but only at certain point of the membrane (potential energy).
-enzyme: ATP synthase
- Use that potential energy to make the ATP

Role of oxygen in glucose metabolism: If enough O2 is present, Cellular Respiration will occur. It also is needed at the end stage of O2 and serves as the final electron acceptor. It will then combine with H+ to make water molecules.
If there is not enough oxygen present (anaerobic conditions) - why must lactate fermentation occur after glycolysis? (Why not just "stop" at the end of glycolysis?)
• An anaerobic process
• Pyruvate converted into lactate (aka lactic acid)
• To regenerate NAD+ (to allow for more glycolysis to occur)
• In your muscles -> creates an acidic environment there
Describe how cellular respiration can generate heat, and explain why this "heat" is important (...until it gets too high!).
• Cellular respiration is not 100% effecient
• Only 40% of the energy released by catabolism is used to make ATP
• ...the rest is "lost" as heat!
• This heat warms up surrounding tissues and maintains our body temperature
• Very active tissues produce lots of ATP, and therefore lots of heat
• We need to dissipate any excess heat, to prevent our body temp. from rising too high.
Describe how lipids can be used as an energy source (lipolysis) or for energy storage (lipogenesis).
Lipolysis: breakdown of lipids (triglycerides) and use for metabolism (making ATP). Beta oxidation of fatty acids can produce ketones which can be used as an energy source (fuel).

Lipogenesis: Is building fats (triglycerides) from protein and carbohydrates and putting them into storage. Triglycerides are the main storage form of energy in body.
Describe how lipolysis can result in ketosis, and possible ketoacidosis (and how this pH shift might affect your respiratory or renal systems)
• Liver cells can break down lipids (and amino acids), producing acetyl-CoA and some ketone bodies
• These ketones travel in the blood to skeletal muscle
• Can be converted back to acetyl-CoA and used in the citric acid cycle
• However... excessive production of ketones = ketosis
• Can result in ketoacidosis (ketones leading to a decrease in blood pH)if the blood's buffering systems can't cope with this much acid
• Excess ketone bodies end up in the urine (result in diabetes)
Describe the role of lipoprotein lipase. (hint: see Fig. 25-8)
Released in the capillary endothelium
-Breaks down the chylomicrons and releases fatty acids and monoglycerides into the intestinal fluid.
-breaks down triglycerides into fatty acids and glycerol for the cell to use.
Briefly describe the roles of VLDL, LDL, and HDL in the bodyVLDL (Very Low Density Lipoproteins): -Primary function is to transport triglycerides to skeletal muscles and adipose tissues. LDL (Low Density Lipoproteins) -Deliver cholesterol to peripheral tissues. HDL (High Density Lipoproteins) -Transport excess cholesterol from peripheral tissues back to the liver for storage or excretion in the bile.Define/describe the following terms related to protein metabolism: transamination, deamination, and "essential amino acid".Transamination: The process by which an amino group from one amino acid is transferred to a carbon compound to form a new amino acid. -"Remodeling" to form other amino acids Deamination: The amino group is removed and an ammonium ion is released. -produces a different amino acid -this new acid molecule can be converted into pyruvic acid or acetyl-CoA Essential amino acid - Amino acids that are needed, but cannot be made by the body; they must be eaten in foodsDescribe the roles of insulin and glucagon in regulating blood glucose levels•Insulin: lowers blood glucose levels • Secreted by β cells of the pancreas • Increases glucose uptake by cells • Increases conversion of glucose → glycogen •Glucagon: raises blood glucose levels • Secreted by α cells of the pancreas • Increases rate of breakdown of glycogen → glucoseDefine/describe the following terms relating to the conversion of glucose: glucogenesis, glycogenolysis, gluconeogenesis, glycogenesis, plus how glucose conversion relates to lipogenesis and lipolysis.glucogenesis: If a cell needs glucose, it can get it -The formation of glucose through the breakdown of glycogen. glycogenolysis: Breaking down glycogen gluconeogenesis: Converting non-carbohydrate molecules into glucose molecules glycogenesis: production of glycogen from glucose If a cell needs to store glucose If a cell needs to be stored -it can Convert it to lipid (by a process called lipogenesis)Compare and contrast the absorptive and post-absorptive states. Include a general description of each, the timing (relative to the time since your last meal), and the key hormone(s) of eachAbsorptive State: -Follows a meal (4 hours) -Nutrient absorption occurs -Insulin is main hormone -Others include: gastrin, secretin, and CCK... Plus GH, androgens, and estrogens Post-absorptive State: -No nutrient absorption; body must rely on stored energy reserves (carbs, then lipids + proteins...) -Glucagon is main hormone -Others include: epinephrine, growth hormone, and glucocorticoids (Ex: Cortisol)Describe the role of TH in regulation of metabolic rate and heat production.• Activates the gene to produce the Na+-K+ pump • More Na+-K+ pumps, more ATP used, more heat given off • Within mitochondria, TH causes the inner membrane to become "leaky" to H+ ions • Less of a H+ gradient in the intermembrane space • Less efficient production of ATP • More glucose needs to be broken down to produce the ATP that the cell needs • More heat given offDescribe the role of leptin in appetite regulation-Inhibits NPY and stimulates melanocortin secretion, therefore inhibits appetite overall -Released by fat cells (adipose tissue) to let body know how much fat stores it has -However, some obese people have lots of leptinIdentify the following chemicals as either stimulating appetite or signaling satiety: ghrelin, CCK, leptin, insulin, melanocortin, NPY (no additional details needed).-Ghrelin (short term) → Stimulates hunger Stimulate satiety -Peptide YY (short term) -cholecystokinin (CCK) (short term) -Obestatin? (short term) -Leptin (longer term) -Insulin (longer term) -Stimulate brain to release or inhibit either neuropeptide Y (NPY - an appetite stimulant) or melanocortin (inhibits eating)