(02) Harvesting Chemical Energy Flashcards
how is ATP used to produce energy
the HYDROLYSIS of ATP to ADP + inorganic phosphate releases energy
describe the ATP cycle
transformation of ATP to ADP then back to ATP
energy transfer between complex and simple molecules in the body
define anabolic reactions
simple –> complex molecules
transfer energy from ATP to complex molecules
define catabolic reactions
complex –> simple molecules
transfer energy from complex molecules to ATP
name some simple molecules (involved in ATP cycle)
glucose
amino acids
glycerol
fatty acids
what is glycerol
a type of carbohydrate called a sugar alcohol (it’s a triol)
forms backbone of glycerides
name some complex molecules involved in the ATP cycle
glycogen (a stored form of glucose made up of many connected glucose molecules)
proteins
triglycerides
three major categories of “fuel” to generate ATP
Carbohydrates (–> simple sugars)
Protein (–> amino acids)
Fats (–> simple fats)
pathway that glucose takes into a cell
glucose in food / intestines –> bloodstream –> into a cell via insulin
then either:
storage
cellular respiration –> cellular work
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)
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)
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)
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
in what part of the cell does glycolysis take place?
cytosol
net product of glycolysis
2 ATP and 2 NADH produced
inputs and outputs of glycolysis
input: glucose molecule
output: 2 pyruvic acid molecules (3C each)
where does pyruvate oxidation take place
the mitochondrial matrix
what is required for pyruvate oxidation
oxygen, duh
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
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
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
