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DAT - Biology > Chapter 7 - Metabolism > Flashcards

Chapter 7 - Metabolism Flashcards

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1
Q

How do humans obtain energy?

A

Digestion of food to maintain their internal environment and power the basic activities of life

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2
Q

Define metabolism:

A

The sum of all chemical reactions that occur in the body - can be divided into:

  • Catabolic: Break dow large chemicals and release energy
  • Anabolic: Build up large chemicals and require energy
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3
Q

Define ingestion and digestion:

A

1) Ingestion: the acquisition and consumption of food into a usable soluble form so it can pass through membranes in the digestive tract and enter the body
2) Digestion: The process of converting good into a usable soluble form so it can pass through membranes in the digestive tract and enter the body

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4
Q

Define transport and absorption:

A

1) Transport: The circulation of essential compounds required o nourish tissues and the removal of waste products from the tissues
2) Absorption: The passage of nutrient molecules through the lining of the digestive tract into the body proper - absorbed molecules pass through cells lining the digestive tract by diffusion or active transport.

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5
Q

Define assimilation, respiration, and excretion::

A

1) Assimilation: The building up of new tissues from digested food materials
2) Respiration: The consumption of oxygen by the body - cells use oxygen to convert glucose into ATP, a ready source of energy for cellular activities
3) Excretion: Te removal of waste products produced during metabolic processes like respiration and assimilation

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6
Q

Define synthesis:

A

The creation of complex molecules from simple ones

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7
Q

Define regulation:

  • Steady state / Homeostasis

- Irritability

A

The control of physiological activities - the bodies metabolism functions to maintain its internal environment in a changing external environment

  • Steady state (homeostasis) includes regulation by hormones and the nervous system
  • Irritability is the ability to respond to a stimulus as a part of regulation
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8
Q

Define growth and reproduction:

A

1) Growth: The increase in size caused by cell division and synthesis of new materials
2) Reproduction: The generation of additional individuals of a species

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9
Q

What does respiration involve?

A

The conversion of chemical energy in molecular bonds into the usable energy needed to drive the process of life

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10
Q

What do all living cells need?

A

1) Energy for growth
2) Maintenance of homeostasis
3) Defense mechanisms
4) Repair
5) Reproduction

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11
Q

How do the cells of the human body obtain energy?

A

Aerobic respiration
- This process includes the intake of oxygen from the environment, transport of oxygen in the blood, and ultimate oxidation of fuel molecules in the cell

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12
Q

Whats external vs. internal respiration?

A

1) External: entrance air into the lungs and gas exchange between the alveoli and the blood
2) Internal: exchange of gas between the blood and the cells, and the intracellular processes of respiration

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13
Q

What are the favoured fuel molecules? Why?

A

Carbohydrate and fats

  • As H is removed, bond energy is made available
  • C-H bonds are rich in energy
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14
Q

What is the process of respiration? What type of reaction is it? Describe the process:

A

Dehydrogenation

  • Oxidation reaction
  • Acceptance of H by a hydrogen acceptor is the reduction component of the redox reaction - energy released by this reduction is used to form ATP
  • Note: These reductions occur in a series of small steps (electron transport chain)
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15
Q

What 2 stages does glucose catabolism (degradative oxidation of glucose) occur in?

A

1) Glycolysis

2) Cellular Respiration

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16
Q

What is the first stage of glucose catabolism? Describe this process:

  • What is it?
  • Where does it occur?
  • Steps?
A

1) Glycolysis: A series of reactions that leads to the oxidative breakdown of glucose into 2 molecules of pyruvate, production of ATP, and reduction of NAD+ to NADPH
- Occurs in the cytoplasm

Steps:

  • Glucose reacts with hexokinase to form G6P
  • G6P interacts with enzymes phosphoglucose isomerase and forms F6P
  • F6P interacts with enzyme phosphofructokinase to form F-1,6-BP
  • Enzyme aldolase converts F-1,6-BP into glyceraldehyde-3P
  • Series of enzymatic reactions… compounds phosphoenolpyruvate is formed
  • Enzyme pyruvate kinase converts phosphoenolpyruvate into pyruvate
  • Pathway complete
  • Notes
  • F-1,6-BP is split into 2 3-C molecules (dihydroxyacetone phosphate and PGAL)
  • I.e. 2 molecules of PGAL are formed per molecule of glucose and all the steps occur twice for each molecule of glucose
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17
Q

What is the net reaction of glycolysis?

A

One molecule of glucose:

  • 2 molecules of pyruvate
  • 2 ATP used (steps 1 and 3)
  • 4 ATP generated (steps 6 and 9)
  • Therefore… Net 2 ATP (Substrate-Level Phosphorylation)!

Net Reaction:
Glucose + 2ADP + 2Pi + 2NAD+ > 2Pyruvate + 2ATP + 2NADH + 2H + 2H2O

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18
Q

What occurs in the absence of oxygen in glycolysis?

A

Fermentation:

  • NAD must be regenerated for glycolysis to continue in the absence of O2
  • This is accomplished by reducing pyruvate to lactate acid or ethanol
  • Only produces 2 ATP
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19
Q

What is the difference between lactic acid fermentation and alcohol fermentation?

A

Lactic acid:

  • Occurs in certain fungi and bacteria, and in human muscle cells
  • NAD+ used in step 5 of glycolysis is regenerated when pyruvate is reduced

Alcohol:

  • Occurs in yeast and some bacteria
  • Pyruvate is converted to ethanol
  • NAD+ is regenerated
20
Q

What is the second stage of glucose catabolism?

A

2) Cellular Respiration
- Most efficient pathway = yields 36-38 ATP
- Aerobic process = oxygen acts as final acceptor of electrons
- Occurs in mitochondria

21
Q

What are the 3 stages of cellular respiration?

A

1) Pyruvate decarboxylation
2) Citric acid cycle
3) Electron transport chain

22
Q

Describe the process of pyruvate decarboxylation:

A

:Pyruvate formed during glycolysis is transported from cytoplasm to the mitochondria matrix where it is decarboxylated and the acetyl group that remains is transferred to coenzyme A to form acetyl-CoA
- In the process NAD+ is reduced to NADH

23
Q

Describe the process of the citric acid cycle:

A

Begins when two carbon acetyl group from acetyl-CoA combines with oxaloacetate (4C) to form 6C citrate then a series of reactions occur to release 2 CO2 and regenerate oxaloacetate is regenerated for further use in the cycle

24
Q

What is generated for each turn of the citric acid cycle?

A
  • 1 ATP
  • NADH and FADH2

Net Reaction:

2acetyl-CoA + 6NAD + 2FAD + 2GDP + 2Pi + 4H2O > 4CO2 + 6NADH + 2FADH2 + 2GTP + 4H + 2CoA

25
Q

Describe the process of the electron transport chain:

A

It is a complex carrier mechanism located on the inner side of the mitochondrial membrane

  • During oxidative phosphorylation, ATP is produced when high energy potential electrons are transferred from NADH and FADH2 to oxygen by a series of carrier molecules located in the inner mitochondrial membrane
  • As electrons are transferred from carrier to carrier, free energy is released, used in the form of ATP
  • Most molecules of ETC are cytochromes, containing a central iron atom that can undergo reversible redox reaction = sequential redox reactions continue to occur are the electrons are transferred form one carrier to the next, each carrier is reduced as it accepts an electron and is then oxidized when it passes it on to the next carrier
  • The last ETC carrier passes its electron to the final electron accepted (O2) which picks up a pair of H-ions from the surrounding medium forming H2O
26
Q

Calculate the total energy production of glucose catabolism:

A

1) Glycolysis
- 2 ATP invested
- 4 ATP generated (substrate)
- 4 ATP generated (oxidative)

2) Pyruvate Decarboxylation
- 6 ATP generated (oxidative)

3) Citric Acid Cycle
- 18 ATP generated (oxidative)
- 4 ATP generated (oxidative)
- 2 ATP generated (substrate)

TOTAl = 36 ATP

27
Q

What are other alternate sources of energy?

A

1) Carbohydrates, Fats, and Proteins

2) Photosynthesis
- Light and dark reactions

28
Q

Describe how carbohydrates, fats, and proteins contribute as an energy source:

A

1) Carbohydrates
- Disaccharide’s are hydrolyzed into monosaccharides which can be converted into glucose or glycolytic intermediates
- Glycogen stored in the liver can be converted when needed

2) Fats
- Fats are stored in adipose tissues in the form of triglycerides which when needed can be hydrolyzed by lipases to fatty acids and glycerols which are carried in the blood to tissues for oxidation
- Glycerol can be converted to PGAL
- Fatty acids must be activated by 2ATP then taken to the mitochondrion to be taken through a series of beta-oxidation that converts them into 2C fragments… these fragments can be converted into acetyl-CoA which can enter the citric acid cycle (generating 1 NADH and 1 FADH)

3) Proteins
- Amino acids can undergo transmutation reaction which is losing a amino group to form an a-keto acid
- Carbonatoms can be converted into acetyl-CoA, pyruvate, or intermediates of citric acid cycle which enter their respective metabolic pathways allowing the cell to produce fatty acids, glucose, or energy in the form of ATP

29
Q

Describe how photosynthesis contributes as an energy source:

A

Converts CO2 and H2O into glucose and oxygen

  • Glucose can be stored as starch or used for energy
  • Takes place in chloroplast
  • Photosynthesis involves reduction of CO2 to a carbohydrate by releasing oxygen from water

Net Reaction:
6CO2 + 12H2O + light energy > glucose + 6O2 + 6H2O

30
Q

What are the two distinct regions of photosynthesis?

A

1) Light reactions - Absorption of photon of light by chlorophyll molecules, when light strikes P700 in P1 it excites electrons to higher energy level which then flow along two pathways:
a) Cyclic - Excited electrons of P700 flow along chain of electron carriers, series of redox reactions return electrons to P700, reactions are harnessed to produce ATP from ADP and Pi, and the coenzyme carrier ferrodoxin is the early electron carrier in the ETC

b) Non-cyclic - Key pathway of light reactions and involves reactions of both photosystems
- Photons of light excite electrons in P700 in P1
- Electrons are transferred to electron acceptor NADP+ and forms NADPH
- P700 is left with hole and is now a powerful oxidizing agent
- Light strikes P680 in P2 and excites electrons which travel down same electron carries used by cyclic until they reach P700 and fill the holes
- Cascase produces ATP
- P680 now has how but is strong enough to oxidize water and fill holes
- Water is split into 2H-ions and oxygen atom and electrons produce release NADPH and ATP and the photolysis of water

2) Dark reactions - Use ATP and NADPH generated by light reactions to reduce CO2 to carbohydrates
- Do not directly require light, will only during day when the light reactions are replenishing the supply of ATP and NADPH

Also called carbon-fixation reactions

  • CO2 is the source of carbon for carbohydrate production in the Calvin Cycle
  • Product is 3PGAL
  • In order to produce 3 PGAL, the cycle must take place 3 times

Cycle:

  • Begins addition of CO2 to ribulose biphophate (5C sugar) to produce an unstable 6C intermediate that splits to give 3C molecules of 3-phosphoglyceric acid
  • The acid is phosphorylated by ATP and reduced by NADPH to give PGAL
  • Two molecules of PGAL can be converted to glucose which is oxidized to provide usable energy
31
Q

How is the Calvin cycle similar to the Krebs cycle in reverse?

A

1) CO2 is fed into cycle (Krebs it was produced)
2) Reducing power is utilized during cycle (NADPH) (Krebs cycle NADPH was removed)
3) Energy is used in the cycle (Krebs cycle is was produced)

32
Q

Summarize the Calvin Cycle:

A

CO2 is fixed to RBP resulting in an unstable 6C molecule that splits to form 2PGA which is them phosphorylated and reduced to form PGAL

  • PGAL is recycled to RBP
  • 6 turns of Calvin generates 12 PGAL, 6CO2, and 6RBP
33
Q

What are enzymes? What do they regulate?

A

Organic catalysts > A catalyst is a substance that effects the rate of chemical reactions without itself being changes

  • Crucial to living things because all living things have controlled chemical activity
  • Regulate metabolism by speeding up chemical reaction
34
Q

How do enzymes affect the reaction rate?

A

Decrease the activation energy

35
Q

What are enzymes composed of?

A

Proteins

  • Thousands of different kinds
  • Majority are conjugated
36
Q

Are enzymes selective?

A

Yes, very.

- May only catalyze one reaction or specific classes of reactions

37
Q

What does an enzyme act upon? Where do they bind?

A

Act upon substrates and bind to the active site

38
Q

What are some characteristics of enzymes?

A

1) They do not alter the equilibrium constant
2) They are not consumed (appear in both reactant/product)
3) Are pH and temperature sensitive (optimal activity)

39
Q

Are they reversible?

A

Most

- A product synthesized may be decomposed by same enzyme

40
Q

What is the lock and ket theory?

A

Holds that the spatial structure of an enzymes act site is exactly complementary to spatial structure of its substrate

  • Lock and key
  • Receptors are large proteins that contain a recognition site (lock) that is directly linked to transaction systems
  • When a drug or substance (key) bind to the receptor, a sequence of events occur
41
Q

What is the induced fit theory?

A

Describe the act sit as having flexibility of shape
- When appropriate substance comes in contact with the active site, the confirmation of the active site changes to fit the substrate

42
Q

What is enzyme specificity?

A

The enzyme action and reaction rate depend on factors that include:

1) pH
- Above or below the optimal will not function properly

2) Temperature
- Rate of enzyme action increases as temperature increases until optimal point has been reached, after this, decreased action rate

3) Concentration of enzyme and substrate
- Low = many active site unoccupied and therefore reaction rate is low
- Increasing substrate concentration will increase reaction rate
- Occupied = further increasing substrate concentration will have no affected (max. velocity reacher)

43
Q

What is competitive inhibition?

A

The active site of an enzyme is specific for a substrate but molecules similar to the substate may possibly be able to bind to the active site

  • They compete for the active site and interfere with enzyme activity
  • “The enzyme is inhibited by the inactive substrate or competitor”
  • Higher concentration of substrate needed to outcompete the competitor (reversible)
  • Can reach Vmax
44
Q

What is non-competitive inhibition?

A

A substance that forms strong covalent bonds with an enzyme, making it unable to bind with its substrate, and cannot be displaced by a higher concentration of the substrate
- Irreversible and therefore cannot reach Vmax

45
Q

What is an allosteric inhibitor?

A

Inhibition that takes places at a site other than the active site

46
Q

What are examples of enzyme activity?

A

1) Hydrolysis: Function to digest large molecules into smaller components
- Ex. Lactase hydrolyzes lactose
- Ex. Proteases degrade proteins to amino acids
- Ex. Lipases break own lipids to fatty acids and glycerol

2) Synthesis: Can be catalyzed by the same enzymes as hydrolysis reactions but the directions of the reactions are reversed
- Required for growth, repair, regulation, protection, and production of food reserves
- Vitamin synthesis

3) Cofactors: Many enzymes require incorporation of non-protein molecule to become active

DAT - Biology (16 decks)

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