E+R Flashcards
Why do living organisms need energy?
To work!
Anabolic reactions in organisms
Eg: protein synthesis, synthesis
of glycogen (glycogenesis), DNA
replication, polymerisation
work done by organisms example
Anabolic reactions
Active transport
Movement
Maintenance of a constant body temperature
Bioluminescence / electrical
discharge
Movement in organisms
Eg: Muscle contraction,
cilia/flagella, movement of
chromosomes
Active transport in organisms
Eg: Na+- K+ pump, movement of
vesicles in exo/endocytosis
Maintenance of a constant body
temperature in organisms
in “warm-blooded animals”
i.e. endotherms
Bioluminescence / electrical
discharge in organisms
E.g. in jellyfish, electric eels
ATP
Adenosine triphosphate
* It is a phosphorylated nucleotide
ATP 3 components
1) Adenine (organic, nitrogenous base)
2) Ribose sugar (pentose sugar)
3) Three phosphate groups
adenosine (nucleoside)
adenine + ribose sugar
ATP
Characteristics of ATP:
- Small
- Water-soluble
→ Easily transported around the cell - Readily hydrolysed / lose phosphate to release energy
- Small packets of energy released at one time
- ATP can be synthesised and broken down quickly
→ High turnover rate
This makes it ideal as an energy currency
in all organisms
Roles/Functions of ATP:
a) The universal link/intermediate energy molecule
* Between energy-giving reactions and energy-requiring reactions
- Example of energy-giving reactions: aerobic respiration aka
complete oxidation of glucose
→ Gives a large quantity of energy of 2870 kJ per mole of glucose
Hydrolysis of ATP →
Energy
why are energy transfers considered inefficient
→Excess energy is lost at different stages in the multi-step reaction
→As thermal/heat energy
ATP is the energy
currency’ of the cell
* Energy giving/yielding-reactions are linked to production of ATP
first, then energy-requiring reactions
- Energy storage molecules
store energy in the form of chemical
potential energy
short term energy storage
glucose, sucrose
long term energy storage
glycogen, starch,
triglyceride
ATP AKA
Immediate donor of energy
why is ATP called immediate source of energy
To reactions requiring energy
Hydrolysis of ATP →
Energy
Chemical equation of ATP hydrolysis:
At rest, we use about
40kg of ATP in 24hours
Removal of 1st phosphate group from
ATP → ADP
→30.5 kJmol-1 energy released
Removal of 2nd phosphate group from
ADP → AMP
→30.5 kJmol-1 energy released
Removal of last phosphate group from
AMP → Adenosine
→14.2 kJmol-1 energy released
ATP is synthesized from
energy-yielding reactions
* E.g. oxidation of glucose in cellular respiration OR light
dependent stage in photosynthesis
* In a series of reactions
What is respiration?
- Process where….
- Organic molecules
(such as glucose, amino acids, glycerol, fatty acids) - Are broken down in a series of stages
- To release energy
- Which is used to synthesise ATP
two types of respiration
1) Aerobic respiration
2) Anaerobic respiration
Aerobic Respiration
- Breakdown of organic molecules
(i.e. glucose, but fatty acids, glycerol and
amino acids too!) - To release energy
- Which is used to synthesise ATP
- In the presence of oxygen
4 stages in aerobic respiration of glucose
1) Glycolysis
2) Link Reaction
3) Krebs Cycle
4) Oxidative Phosphorylation
glycolysis location
cytoplasm
link reaction location
Mitochondrial matrix
krebs cycle location
Mitochondrial matrix
oxidative phosphorylation location
Inner mitochondrial membrane / cristae
Oxidation of Glucose
IRL oxidation of glucose in cellular respiration is a
multi-step reaction
* Each step: releasing a small quantity of energy
(ATP)
Why use small, multiple steps?
1)Allow precise control
2) Cells could not fully harness total energy released if all were made available at one instan
Why doesn’t the reaction happen easily?
Because….glucose is quite a stable substance
→It requires a high activation energy for
reaction to take place
how to overcome reactions not happening easily
a) Usage of enzymes to lower activation energy
b) Raising energy level of glucose by
phosphorylation
→More reactive
glycolysis steps
glyco
glycolysis at cytoplasm
- Lysis of glucose
- Multi-step process
- Involves many enzymes at each step
initial reactants of glycolysis
- 1 Glucose (6C)
- 2 ATP
- 4 ADP, 2 NAD
Final products per molecule of glucose:
- 2 Pyruvate (3C)
- 2 NADH
- 4 ATP →But 4 - 2 = net gain of 2 ATP only
Hydrogen Carrier Molecules aka
hydrogen acceptor
3 hydrogen acceptor molecules
NAD
NADP
FAD
NAD
nicotinamide adenine
dinucleotide
(used in respiration)
NADP
nicotinamide adenine
dinucleotide phosphate
(used in photosynthesis)
FAD
flavin adenine dinucleotide
(used in respiration)
hydrogen acceptor molecules are called
coenzymes
coenzymes
a non-protein
complex organic substance that is
required for an enzyme’s activity.
NAD full form
Nicotinamide Adenine Dinucleotide
NAD is a
coenzyme
NAD is a H carrier molecule used in
respiration
structure of NAD
- Two linked nucleotides
- Both have ribose sugar and a phosphate group each
- 1 has adenine base, the other nicotinamide ring
- Nicotinamide ring – accepts H
function of NAD
- H carrier molecule in respiration
- Carry hydrogens from all stages of respiration (Stage 1 2 3)
- To take part in oxidative phosphorylation (Stage 4) where
most ATP is synthesised
reduced NAD
NADP full form
Nicotinamide Adenine Dinucleotide Phosphate
NADP is a
coenzyme
NADP is used in
photosynthesis
NADP is a different form of
NAD
structure of NADP
- Similar to NAD
NAD - But has a phosphate group instead of H on carbon 2 on ribose ring with adenine
FAD full form
Flavin Adenine Dinucleotide
FAD is a
coenzyme
FAD used in
respiration
FAD use
- Used to carry H produced in
Krebs Cycle (Stage 3) only
→Then used in oxidative
phosphorylation (Stage 4)
structure of FAD
- Two linked nucleotides
- One nucleotide with phosphate, ribose and adenine
- Another nucleotide with phosphate, ribitol and flavin
Link reaction steps
link reaction
What is coenzyme A?
- Complex molecule
- Made of a nucleoside (adenine + ribose) and a vitamin (pantothenic acid)
function of coenzyme A
- Carry acetyl groups (2C) to Krebs Cycle (Stage 3)
inital reactants of link reaction
- 1 Pyruvate (3C)
- 1 NAD
- 1 CoA
final products per molecule of pyruvate in link reaction
- 1 Acetyl CoA (2C)
- 1 NADH
- 1 CO2 → waste gas, released
1 molecule of glucose is oxidised by link reaction into
2 pyruvate
final products per molecule of glucose
- 2 Acetyl CoA (2C)
- 2 NADH
- 2 CO2 →waste gas, released
krebs cycle AKA
citric acid cycle / tricarboxylic acid cycle
krebs cycle is a
enzyme controlled pathway
krebs cycle steps
1) Acetyl coenzyme A (2C)
→combines with oxaloacetate (4C)
→To form citrate (6C)
→CoA removed and can be used again in
Link Reaction (Stage 2
2) Citrate (6C) goes through series of dehydrogenation and decarboxylation
→7steps, by products of each step are
1. Nothing
2. Reduced NAD and CO2
3. Reduced NAD and CO2
4. ATP
5. Reduced FAD
6. Nothing
7. Reduced NAD
3) Oxaloacetate (4C) regenerated
→Can combine with another acetyl CoA
→Kreb cycle continues
oxaloacetate
4C
Acetyl CoA
2C
citrate
6C
Initial reactants: of krebs cycle
- 1 Acetyl CoA (2C)
- 1 Oxaloacetate (4C)
- 1 ADP, 3 NAD and 1 FAD
Final products per molecule of acetyl CoA:
(This is 1 turn of the Krebs Cycle)
- 3 NADH
- 1 FADH2
- 2 CO2 → waste gas, released
- 1 ATP
- Oxaloacetate (4C) → regenerated
Final products per molecule of glucose:
(This is 2 turns of the Krebs Cycle)
- 6 NADH
- 2 FADH2
- 4 CO2 →waste gas, released
- 2 ATP
- Oxaloacetate (4C) → regenerated twice
