(02) Harvesting Chemical Energy Flashcards by Joanna Li

how is ATP used to produce energy

the HYDROLYSIS of ATP to ADP + inorganic phosphate releases energy

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describe the ATP cycle

transformation of ATP to ADP then back to ATP
energy transfer between complex and simple molecules in the body

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define anabolic reactions

simple –> complex molecules
transfer energy from ATP to complex molecules

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define catabolic reactions

complex –> simple molecules
transfer energy from complex molecules to ATP

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name some simple molecules (involved in ATP cycle)

glucose
amino acids
glycerol
fatty acids

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what is glycerol

a type of carbohydrate called a sugar alcohol (it’s a triol)
forms backbone of glycerides

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name some complex molecules involved in the ATP cycle

glycogen (a stored form of glucose made up of many connected glucose molecules)
proteins
triglycerides

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three major categories of “fuel” to generate ATP

Carbohydrates (–> simple sugars)
Protein (–> amino acids)
Fats (–> simple fats)

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pathway that glucose takes into a cell

glucose in food / intestines –> bloodstream –> into a cell via insulin

then either:
storage
cellular respiration –> cellular work

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how is glucose stored and released from storage

glucose in a cell can cross-link –> glycogen in liver and skeletal muscle

returns to the bloodstream via glucagon (then back to cell via insulin… etc)

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how is homeostasis restored after in increase in blood glucose level

beta cells in pancreatic islets (receptors) respond by SECRETING INSULIN
which affects all body cells
–> increase rate of glucose transport, increased rate of glucose use and ATP generation, increased conversion of glucose to glycogen (to store)

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how is homeostasis restored after a decrease in blood glucose level

alpha cells in pancreatic islets respond by secreting GLUCAGON
affects liver, skeletal muscle, adipose cells
–> increased breakdown of glycogen to glucose (liver, skeletal muscle)
–> increased breakdown of fat to fatty acids (adipose)

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name the four main steps in the conversion of glucose to ATP

Glycolysis
Pyruvate oxidation
Citric acid cycle (Krebs cycle)
Electron transport chain

summarised in the eqn
glucose + 6O2 –> 6 CO2 + 6H2O + energy

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in what part of the cell does glycolysis take place?

cytosol

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net product of glycolysis

2 ATP and 2 NADH produced

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inputs and outputs of glycolysis

input: glucose molecule
output: 2 pyruvic acid molecules (3C each)

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where does pyruvate oxidation take place

the mitochondrial matrix

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what is required for pyruvate oxidation

oxygen, duh

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inputs and outputs of pyruvate oxidation

input: pyruvate molecule
output: Acetyl CoA + 1 CO2, 1 NADH
(so x2 per glucose molecule)

Acetyl CoA has 2C chain

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what is the function of the acetyl CoA?

enables the 2-carbon acetyl group to enter the citric acid cycle

links the glycolysis and citric acid cycle

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where does the citric acid cycle take place?

in the mitochondrial matrix

Products of the citric acid cycle

2 ATP
6 NADH
2 FADH2
4 CO2
(per glucose molecule)

what does the citric acid cycle require

oxygen - it is an aerobic process

what are the electron donors in the electron transport chain?

NADH and FADH2

define intermediates (in a cycle)

in a series of reaction, the product of one reaction is the substrate for the next

how many ATP are produced per glucose in each of the first three stages of cellular respiration?

glycolysis: 2 ATP Pyruvate oxidation: 0 ATP Citric acid cycle: 2 ATP

name the two types of phosphorylation

substrate phosphorylation oxidative phosphorylation

define substrate phosphorylation

ATP generated by direct transfer of phosphate group from a substrate to ADP

which two steps in cellular respiration involve substrate phosphorylation?

Glycolysis and Citric acid cycle both make ATP via substrate phosphorylation

define oxidative phosphorylation

ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons

what are the two processes involved in oxidative phosphorylation?

the Electron Transport Chain Chemiosmosis

in what specific part of the cell does the Electron Transport Chain take place?

in protein complexes in/on the inner membrane

what type of reaction occurs in the electron transport chain?

it is oxidative phosphorylation, therefore OXIDATION occurs

what happens at each transfer in the electron transport chain

at each transfer, each e- gives up a small amount of energy enables H+ ions to be pumped into the Intermembrane space

describe chemiosmosis in oxidative phosphorylation

after electrons are transported down the chain and H+ is released into the IMS, H+ rush down their concentration gradient causes "turbine" within ATP synthase to turn enables phosphorylation of ADP --> ATP

products of chemiosmosis

26 or 28 ATP produced per glucose

summarise the steps of oxidative phosphorylation

the bulk of ATP production occurs here fall of e- down chain --> movement of H+ into IMS --> proton gradient --> ATP synthase turbine O2 is the final e- acceptor, turns into water

what molecule pulls electrons from the electron transport chain

oxygen, forming H2O

in what form do fats, proteins and complex carbohydrates enter the cell to generate ATP?

as monomers: fatty acids, glucose, amino acids 3C chains (all) or 2C chains (fatty acids and amino acids)

what is the role of phosphofructokinase

an enzyme that catalyses a phosphorylation step in glycolysis therefore controls the rate of glycolysis - positive / negative feedback mechanisms

what is phosphofructokinase inhibited and stimulated by?

inhibited by citrate and ATP (the products of cellular respiration) stimulated by AMP (which accumulates when ATP is being used rapidly)

normal blood glucose level

4-6 mmol/L

define hyperglycemia and steps to maintain homeostasis

hypER = exaggerated (as in hyperbole) beta cells in pancreatic islets secrete insulin to increase rate of glucose --> ATP / glycogen

define hypoglycemia and steps to maintain homeostasis

low blood glucose level alpha cells in pancreatic islets secrete glucagon --> increased breakdown of glycogen in liver / skeletal muscle and fat in adipose tissue

where are beta and alpha cells produced?

the Islets of Langerhans in the pancreas

what is diabetes mellitus

impaired ability to produce or respond to insulin results in abnormal metabolism of carbs and elevated levels of blood glucose (>7 mmol/L)

describe the mechanism of diabetes mellitus

insulin hormone normally binds to receptor so the glucose receptor opens either insulin not present or receptors not functional no glucose in cells --> no ATP from glucose --> no stored glycogen

describe type 1 diabetes

insulin-dependent diabetes the body does NOT produce insulin as beta cells of pancreas are destroyed less common requires insulin replacement

describe type 2 diabetes

non-insulin-dependent body produces insulin but receptors are non-functional (insulin resistance) more common, usually adults over age of 40

what are the two main symptoms of diabetes mellitus and why?

significantly increased hunger significant weight loss because of a lack of functional insulin, glucose cannot get into cells to make ATP body asks for more glucose from food and stores