Metabolism (cellular respiration) Flashcards
Metabolism
the sum of all chemical reactions in a cell or organism e.g. digestion, production of molecules, etc.
Energy
Ability to do work, e.g. performed when energy is used to move an object against an opposing force (such as friction or gravity)
Anabolic reactions
building new chemicals
Catabolic reactions
break substances down
combination of these reactions in our cells is called?
metabolism
breaking a bond…?
requires and absorbs energy
forming a bond….?
releases energy
what do catalysts do
reduce the amount of activation energy to start a reaction ex. lower temp, and reaction and faster
What do chemical bonds do?
power work
What must occur for a reaction to occur or progress?
chemical bonds must be broken
All reactions require energy to begin (activation energy)
Kinetic energy
energy possessed by moving objects. e.g. thermal energy or heat, mechanical energy, electromagnetic energy, and electrical energy
Potential energy
Stored energy that an object possess as a result of its position relative to other objects or its internal structure. e.g. gravitational potential energy, chemical potential energy
1st law of thermo dynamics
law of conservation energy
energy cannot be created nor destroyed but converted from one form to another
- in most cases organisms obtain energy in one form and convert it t another form before it can be used. e.g. photosynthesis and food chains
Bond energy
a measure of the stability of a covalent bond
What happens when reactant products break
energy is absorbed
what happens when product bonds form
energy is released
What kind of systems are organisms (endergonic vs exergonic)
Endergonic- we need energy for various processes…
muscle contraction
active transport
synthesis- making polymers like protein or glycogen
movement
chemical reactions
temperature regulation
Endergonic reactions
if reaction absorbs more energy than it releases
- requires an input of energy
- all condensation reactions
Exergonic reactions
if reaction produces more energy than it absorbs
-overall release of energy
Energy coupling
we use exergonic (catabolic ) reactions to fuel endergonic (anabolic reactions)
Heat or enthalpy
overall change in energy
Which kind of reaction proceed spontaneously
Exothermic- products are more stable , less potential energy than reactants
What kind of reactions are non-spontaneous
Endothermic
Reaction is cooler than its surroundings
Endothermic
Reaction is hotter than its surroundings
Exothermic
2nd Law of thermodynamics
Only some energy ends up in a new form the rest is lost
State of disorder
Systems tend toward a state of disorder, systems, such as living things, run down if not continually supplied with energy
How does cell ¨clean up¨
using lysosomes
-restores order
-requires energy
highly ordered system
low entropy
Very disorder system
high entropy
Does a spontaneous change require a continuous supply of energy?
false- once started it does not
A non-spontaneous change
cannot occur without a continual supply of energy
Gibbs free energy
-Useful energy not lost in transformation which can be used to do work in a system is called free energy
-free energy value indicates which type of reactions provide fuel for our energy
0free energy is represented by the symbol G
What is free energy responsible for
Chemical and physical work in activities such as synthesis of molecules reproduction and movement
What is the energy currency of our cells?
ATP
adenosine triphosphate a derivative of nucleotides
What kind of reaction is the conversion of ATP to ADP?
Exothermic, increase of entropy in the system
What is the hydrolysis of ATP
Exergonic- provides free energy for many processes needed to sustain
What happens when the bond between 2nd and 3rd Piś break?
energy that is stored in the bond is released and made available to the reaction requiring it. ADP and one phosphate are formed
Hydrolysis of ATP
- breaking of the last phosphate group from the addition of water
- ADP and inorganic phosphate
- Water (hydrolysis) is added so bonds form
- H+ released in solution
- free energy released as new bonds form (30.5 kj/mol (will see as +ve since it releases energy
Release of Energy
Energy from food is useless until it is transferred from the chemical bonds in food to the phosphate bonds of ATP
How ATP works?
- third phosphate is hardest to keep attached
-repulsion in the O groups - breaking of o and p bond requires a little energy
phosphate forms bonds with water, releases a lot of energy, creates very stable structures
-entropy increases
1 molecule broken into 2
exergonic rxn- energy released
ADP and ATP
Can be recycled into ATP when energy is available - called phosphorylation
- same quantity of energy is required to make ATP as is released in reaction ADP + Pi
energy for the reformation is created by oxidation of sugars
What is the point of digestion? What does the products help in?
Energy is used to add inorganic phosphates to ADP to form ATP
How many molecules of ATP can be made from 1 cell from from 1 glucose molecule
37.6 ATP
38 rounded- optimal production
Redox reactions
When electrons are lost another must gain. Oxidation is always coupled with reduction, Picked up by compounds called e- acceptors
Biological oxidation
oxidation of organic compounds
cellular respiration -oxidation of glucose is exergonic (releases energy)
Can an exergonic reaction be exothermic
yes, energy released in form of heat
- others release in form of light
Oxidation occurs when..?
Hydrogen is removed and oxygen is added
happens during cellular respiration and involves energy release
Reduction involves..
addition of hydrogen and the removal of oxygen
happens during photosynthesis involves energy consumption
Lose e-
oxidation
gain e-
reduction
Decarboxylation
removal of a carbon
Coenzymes
help reactions involving enzymes
NAD, FAD
NADH FADH
Cellular respiration purpose
to convert energy trapped within glucose to energy available to do work in a cell in the form of ATP
What are the four stages of Cellular Respiration
- many small steps, controlled by enzymes
1. glycolysis
2. pyruvate oxidation
3. Krebś cycle
4. ETC/ chemiosmosis
Where does glycolysis occur
in the cytosol
Where does pyruvate oxidation occur?
mitochondrion
Where does Krebs cycle occur?
Mitohondrion
Where does ETC occur
mitochondrion
Cristae- inner membrane
folded into many plant like extensions
-inc surface area which respiratory processes can take place (oxidative phosphorylation)
-covered in stalked particles, particles are the site of ETC and ATP production
Outer membrane mitochondrion
separates mitochondrial contents from the rest of the cell
-ideal conditions for aerobic respiration
Matrix
space inside inner membrane
fluid filled with enzymes
known as the central matrix
Is Krebs cycle aerobic or anaerobic
aerobic (with oxygen)
Is glycolysis anaerobic or aerobic
anaerobic no oxygen
Most organisms rely on aerobic respiration for survival, can they survive anaerobically?
May be able to survive for short periods of time.
What two methods are used to catch energy (cellular respiration)
- Substrate level phosphorylation
- oxidative phosphorylation
Substrate Level phosphorylation
ATP formed directly from enzyme controlled reactions (glycolysis and krebs)
occurs when a phosphate from one molecule is transferred to ADP
Oxidative Phosphorylation
ATP formed indirectly from a series of redox reactions
oxygen acts as final receptor
carried out by NADH and FADH2 (two cofactors- assist enzymes in their actions)
2 forms… Oxidized and Reduced
reduced forms captured free energy which in converted to ATP in the final stage of respiration: The electron transport chain.
NADH and FADH2
carry energy in bonds
NADH produced throughout cellular respiration
FADH2 produced during krebs cycle
ETC- redox reactions
NADH is oxidized (NAD+ + H)
FADH2 is oxidized to produce ATP ( FAD + 2H+)
ATP synthesis driven by donated e-
Glycolysis- where does it take place
cytosol of the cell
How many steps in glycolysis and what is it doing?
10 steps converts glucose to pyruvate
molecule of glucose is converted to 2 pyruvate molecules over a series of enzyme catalysed reactions
process also converts 2 net ATP and 2 NADH
what are the two ¨stages” of glycolysis
- Energy investment (phosphorylation)
and - Energy payoff (oxidation)
Step 1 glycolysis
glucose gains phosphate from ATP
Step 2 glycolysis
G6P rearranged in F6P
Step 3 glycolysis
Another ATP is used and phosphate is given to F6P
Step 4 glycolysis
F1,6-BP split into DHAP + G3P
Step 5 glycolysis
DHAP rearranged to isomer G3P
→ 2 G3P at end step 5
Step 6 glycolysis
2 e- and 2H+ removed from each G3P.
NAD+ accepts e- and becomes reduced NADH.
Step 7 glycolysis
1 phosphate transferred to ADP (creates ATP) and 3PG
Step 8 Glycolysis
Phosphate “moved” from 3rd carbon to 2nd carbon to create 2PG
Step 9 Glycolysis
e- moved from one part of molecule to another.
Water removed creates PEP
Step 10 Glycolysis
Removed
and used to phosphorylate ADP
What are the ATP´s used, produced and how many NADH in glycolysis
e investment phase 2 atp used, e pay off phase 4 atp produced and e pay off 2 NADH made
What happens after Glycolysis when oxygen is present?
- Oxygen is Present
The hydrogen acceptors (NADH, and FADH2) and pyruvate enter the mitochondria for the Krebs Cycle. ‘Aerobic Respiration’
What happens after glycolysis when oxygen is not present?
- Insufficient Oxygen
The pyruvate stays in the cytoplasm where it is converted to lactic acid or ethanol in anaerobic respiration
Pyruvate possible pathways?
- Ethanol Fermentation
- Lactic acid fermentation
- Pyruvate oxidation
Ethanol fermentation
Pyruvate + NADH + H+ –> ethanol + CO2 + NAD+
occurs when there is not enough energy to go through link reaction
Lactic acid fermentation
Animal cells- temporary lack of oxygen
pyruvate + NADH + H+ –> lactic acid + NAD+
What is the point of Lactic acid fermentation and ethanol fermentation
Both fermentation steps above do NOT directly create any high energy (ATP) compounds but they do both release NAD+ to allow the cell to continue glycolysis
Coenzyme A-
carrier that helps enzymes hold and modify molecules
- contains a sulphur and hydrogen group (-SH)
result:
Co-ash (unbonded co enzyme A)
-COA (attached to another molecule)
Pyruvate oxidation
pyruvate + NAD+ + CoA-SH
–> acetyl-CoA + NADH + H+ + CO2
oxygen present- mitochondria
How is pyruvate converted to acetyl
2 x CO2 molecules diffuse out the mitochondria, through cell membrane and into the blood
Co-A joins with acetylCOA
products; 2 acetyl co-A, 2 NADH
Whats really happening in pyruvate oxidation- steps
pyruvate is oxidized
loses e- + H+ to NAD+
NAD+ becomes reduced NADH (gains e- + H)
pyruvate has carboxyl group removed (co2 released- waste)
NADH -goes to e transport chain
Attaches to acetyl to form acetyl CoA
Pyruvate Oxidation Products
Products:
2 acetyl-CoA
2 NADH
2 CO2
2 H+
Pyruvate Oxidation Reactants
Reactants:
2 pyruvate
2 NAD+
2 CoA
Does krebs cycle require oxygen?
Yes
Where does the krebs cycle occur?
mitochondrial matrix
cycle is 8 steps each enzyme controlled
What happens in krebs (very basic explanation)
Acetyl groups are oxidized (to CO2)
ATP NADH and FADH2 are synthesized
Krebs tally
link: 2 NADH
ATP- 2
NADH 6
FADH2 2
(doubled because 2 acetyl co-A)
Oxidation of NADH (ETC)
NADH is oxidized by NADH dehydrogenase (complex 1). The electrons from NADH move into the NADH dehydrogenase complex, reducing it, NAD+ and 2 H ions are produced. NAD+ recycled
Movement of Electrons ETC
electrons are shuttled from NADH dehydrogenase to Cytochrome b-c complex 3 by (UQ) ubiquinone (mobile)
Movement of Hydrogen ions ETC
e- are moving from higher to lower energy, so energy is available to send 4 H+ ions across the membrane against a concentration gradient
Electrons pt 2 ETC
e- are shuttled from cytochrome b-c (complex 3) to cytochrome oxidase (complex IV) by cytochrome c
Movement of Hydrogens 2 ETC
more energy from e- moving down the ETC becomes available for 4 more H+ to cross the membrane.
Final Electron Acceptor ETC
2 electrons are combined with hydrogen ions and oxygen to form water
Movement of hydrogen 3 ETC
2 final hydrogen ions are moved across a membrane
Formation of ATP ETC
H+ ions pass through ATP synthase down its concentration gradient. For every 4H+, 1 molecule of ATP is synthesized. (oxidative phosphorylation)
the energy from oxidation of 1 NADH pumped 10 H across the membrane, as a result 2.5 (3) ATPS will be produced from each NADH
Oxidation of FADH2
complex 2 is a peripheral membrane protein called succinate dehydrogenase that oxides FADH2 transferring electrons to ubiquinone. Because it starts later in the ETC only 6 H+ ions are transported across the membrane
energy from oxidation of FADH2 pumped 6 H+ across the membrane. As a result, 1.5 (2- rounded) ATPS will be produced from each FADH2.
What does Glycolysis produce (tally)
2 ATP
2 NADH
What does Krebs + Link produce (tally)
6 CO2
2 ATP
8 NADH
2 FADH2
