Cell Structure and Function: Harvesting Chemical Energy Flashcards
What is ATP?
ATP is the energy that powers cellular work
What releases energy?
The hydrolysis of ATP to ADP and inorganic phosphate releases energy
What is an anabolic pathway?
is the metabolic pathways that construct molecules, requiring energy. Complex molecules are formed from simple molecules
What is a catabolic pathway?
is the metabolic pathways that break down molecules, releasing energy. Complex molecules are broken down into simple molecule
What is an example of a catabolic pathway?
glycogen being broken down into glucose
Are catabolic and anabolic reaction spontaneous?
No
What are the main fuels needed to generate ATP?
Carbohydrates (which are broken down into simple sugars)
Proteins (which are broken down into amino acids)
Fats (which are broken down into simple fats)
What is cellular respiration?
Is the controlled release of energy from organic compounds to produce ATP
What are the four stages of cellular respiration?
Glycolysis, pyruvate oxidation, citric acid cycle, electron transport chain
Where does glycolysis occur?
In the cytosol of the cell
Where does pyruvate oxidation occur?
The mitochondrial matrix
Where does the citric acid cycle occur?
The mitochondrial matrix
Where does the electron transport chain occur?
The inner mitochondrial membrane
Is oxygen required for glycolysis?
No
What is an aerobic reaction?
A reaction requiring oxygen
What is an anaerobic reaction?
A reaction that doesn’t require oxygen
What is invested in glycolysis?
Two ATP molecules
What occurs in the energy investment phase of glycolysis?
Two ATP molecules are invested
6 carbon glucose is split into two 3 carbon molecules (Glyceraldehyde 3-phosphate)
2 ADP is formed
What occurs in the energy payoff phase of glycolysis?
Four ATP molecules are produced
The two 3 carbon molecules are converted into two molecules of Pyruvic acid (pyruvate)
2 NADH are formed
Net products of glycolysis
2 Pyruvic acid molecules and 2 H2O molecules
2 ATP (4 ATP formed - 2 ATP invested)
2 NADH + 2H+ (from 2 NAD+, 4e- and 4H+)
What is produced in the anaerobic reaction that occurs when there isn’t enough oxygen present?
Lactic acid
2 Pyruvic acid (is oxidised) + 2NADH → 2 Lactic acid + 2NAD+
Does pyruvate oxidation require oxygen?
Yes
What steps does pyruvate oxidation link?
Glycolysis and the citric acid cycle
What is pyruvate dehydrogenase?
An enzyme that converts pyruvic acid into an acetyl group (2 carbons)
What is lost when pyruvic acid is broken down into an acetyl group?
A CO2 molecule and a H+ and H-
What picks up the H- lost by pyruvic acid in pyruvate oxidation?
the NAD+ which is reduced to NADH
Where does the H+ go in pyruvate oxidation
It is released into the mitochondrial matrix
What is coenzyme A?
The enzyme that attaches itself to the acetyl group in pyruvate oxidation, producing acetyl coenzyme A (or Acetyl CoA)
Net products of pyruvate oxidation
2 NADH (1 NADH per pyruvate)
2 CO2 molecules (1 per pyruvate)
2 Acetyl CoA (1 per pyruvate)
Does pyruvate oxidation produce ATP?
No
Does the citric acid cycle require oxygen?
Yes
What happens to acetyl CoA as soon as it begins the citric acid cycle?
It loses the coenzyme A as it joins to a 4 carbon molecule (oxaloacetate), forming citrate
What is citrate converted into?
Its isomer, isocitrate
How is a-keto glutarate formed?
Isocitrate is oxidised and releases CO2 and NAD+ is reduced to NADH
Name of the enzyme that oxidises isocitrate
isocitrate dehydrogenase
How is succinyl CoA formed?
NAD+ is reduced to NADH releasing CO2 and A-ketoglutarate is oxidised, and creates a four carbon compound, succinyl CoA, which is unstable
How is succinate formed
The CoA of succinyl CoA is replaced by a phosphate group, which is then transferred to ADP to make ATP. The four carbon molecule produced by this step is called succinate
How is fumarate formed?
Succinate is oxidised to form another 4 carbon molecules, called fumarate
How is FADH2 formed?
After succinate has been oxidised into fumarate, Two hydrogen atoms (and their electrons) are transferred to FAD which produces FADH2
How is malate formed?
Water is added to fumarate to form another four carbon molecule called malate
What occurs to malate after it has been formed?
Malate is oxidised into oxaloacetate (starting four carbon compound) and NAD+ is reduced to NADH
Net products of citric acid cycle
2 ATP (1 per acetyl CoA) 6 NADH (3 per acetyl CoA) 2 FADH2 (1 per acetyl CoA) 4 CO2 (2 per acetyl CoA)
What is substrate phosphorylation?
is where ATP is generated by the direct transfer of a phosphate group to ADP
Glycolysis and Citric acid cycle make ATP via substrate phosphorylation
What is Oxidative phosphorylation
is when ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons (doesn’t rely on substrates)
Does the electron transport chain require oxygen?
Yes
What are the electron donors in the electron transport chain?
NADH and FADH2 (from Glycolysis and the citric acid cycle) are oxidized to donate 1 or 2 electrons
(FADH2 comes in at protein 2)
What do electrons move between in the ETC?
they move from protein to protein
What happens to the electrons every time they are transferred between proteins?
each electron gives up a small number of energy which enables H+ to be pumped into the intermembrane space
What is the function of oxygen in the electron transport chain?
Oxygen “pulls” the electrons down the chain and is then the final electron acceptor where it is reduced to water (H2O)
What is chemiosmosis?
Hydrogen ions in the intermembrane space rush down their concentration gradient through enzyme ATP synthase
How much ATP is produced by chemiosmosis?
26 or 28
What can block electrons reaching oxygen and the death of the cell?
Cyanide
What is Oxidative phosphorylation?
is the electron transport chain and chemiosmosis. It is much more efficient than substrate phosphorylation and is where the bulk of ATP production occurs
What can be used to derive energy from apart from glucose?
Fats
Proteins
Complex carbohydrates
(Monomers enter glycolysis and the citric acid cycle at different points)
What is Phosphofructokinase?
is a rate limiting enzyme that can be rate limiting for glycolysis
What inhibits phosphofructokinase?
It is inhibited by citrate and ATP (ie. products of cellular respiration)
What stimulates phosphofructokinase?
AMP ( which accumulates when ADP not phosphate binds to to ATP)
What is negative feedback?
is where a reaction causes a decrease in a function. It occurs in response to some kind of stimulus to try and bring homeostasis back to equilibrium
An example of negative feedback
blood glucose levels
What is positive feedback?
is is a cyclic process that can continue to amplify your body’s response to a stimulus until a negative feedback response takes over
An example of positive feedback
Blood clotting
What is homeostasis?
Homeostasis is the body’s ability to maintain a stable internal environment/equilibrium (within physiologically tolerable levels), despite fluctuations in external/internal conditions.
What is insulin?
is the hormone that is produced by the beta cells in endocrine glands in the pancreas to allow glucose to enter cells
What can glucose be used for in a cell?
Once glucose has entered the cell it is either used for cellular respiration and cellular work or is stored as glycogen in the liver and skeletal muscle
What is glucagon?
is the hormone that is produced by alpha cells in the pancreas. It causes the body to break down stored glucose (glycogen) when needed by the body so that blood glucose levels increase.
What type of glands are in the Islets of Langerhan?
Endocrine (excrete straight into blood)
What is diabetes mellitus?
is a condition where the body’s ability to produce or respond to the hormone insulin is impaired. This results in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood
What is type 1 diabetes?
Diabetes where the body does not produce insulin, as beta cells of pancreas are destroyed, often this is autoimmune, or genetic or through environmental factors
Limit for blood glucose level
7 mmol/L
How many diabetics have type 1
5 – 10 % of diabetics, and onset usually occurs in children or adolescents.
What is type 2 diabetes
Diabetes where the body produces insulin, but receptors are non functional (insulin resistance)
How many people have type 2 diabetes
Most (>90%) diabetics are Type II, usually adults over the age of 40
Symptoms of diabetes
significantly increased hunger
significant weight loss