Topic 12 - Respiration Flashcards
What is energy needed for? (2 things)
- Movement
2. Anabolic Reactions
What are examples of movement that energy is needed for? (3 things)
- Moving substances across membranes against the concentration gradient - active transport
- Transporting a protein from ribosome to Golgi Apparatus
- Contracting a muscle
What are anabolic reactions?
A chemical reaction which carries out the process of synthesising large molecules from smaller ones
Give 2 examples of anabolic reactions
- DNA Replication
2. Protein Synthesis
What is ATP known as?
The universal energy currency of cells
In all known organisms, what is ATP used for?
To supply energy
Where does energy from ATP mostly originate from?
Sunlight - Plants and photosynthetic organisms capture energy from sunlight and transfer it to chemical potential energy in organic molecules
What does ATP stand for?
Adenosine TriPhosphate
What type of nucleotide is ATP?
A phosphorylated nucleotide
Why is ATP the perfect energy currency? (3 things)
- Hydrolysis of an ATP molecule can be done quickly and easily in any part of the cell where energy is required
- Hydrolysis of 1 molecule of ATP releases a useful quantity of energy
- ATP is a relatively stable molecule in a range of pH that normally occurs in cells, doesn’t break down unless there’s a catalyst - ATPase
How is ATP made?
When a phosphate group combines with ADP
There are 2 ways to combine ADP with phosphate. What are they?
- Using energy provided directly by another chemical reaction - Substrate linked reaction
- Chemiosmosis - Takes place in the inner membranes of the mitochondria where it uses energy released by the movement of Hydrogen ions down their concentration gradient
How is ATP made in humans?
Made by respiration, by substrate linked reactions and chemiosmosis
How is ATP made in plants?
ATP is made in respiration and photosynthesis
Why do humans need to continuously breathe for respiration to happen?
To get oxygen which can oxidise the glucose and release energy so that ATP molecules can be synthesised
What is the main organic molecule used in respiration?
Carbohydrates, especially glucose
What is special about the brain cells and the respiratory substrate they can use?
Brain cells, along with other cells, can only use glucose as their respiratory substrate
What other respiratory substrates are there apart from glucose?
Proteins, fats, amino acids, glycerol, fatty acids
What are the 4 stages in breaking down glucose?
- Glycolysis
- Link Reaction
- Krebs Cycle
- Oxidative Phosphorylation
What occurs in glycolysis?
The splitting or lysis of glucose
Where does glycolysis occur?
The cyctoplasm
What are the reactants in glycolysis?
2 ATP molecules and 1 glucose (6C)
What are the products of glycolysis?
Net gain of 2 ATP molecules and 2 pyruvate molecules and reduced NAD
The first stage of glycolysis is phosphorylation. Wha happens here?
Phosphate groups are transferred from ATP to the glucose molecule. This raises the energy of the glucose molecule, making it easier for them to react because it makes the glucose molecule unstable.
How does the phosphorylation of the glucose molecules happen to end up producing 2 molecules of triose phosphate?
- 2 ATP molecules are used for each molecule of glucose
- The donation of the first phosphate group forms glucose phosphate
- The atoms of the glucose phosphate are rearranged to form fructose phosphate
- The 2nd ATP molecule donates another phosphate
- This forms fructose bisphosphate (6C)
- Fructose bisphosphate breaks down
- This produces 2 molecules of triose phosphate ( 2 X 3C)
How does glycolysis work from 2 triose phosphate molecules turning into 2 pyruvate and a net gain of 2 ATP?
- The hydrogen is removed from the triose phosphate
- The hydrogen is transferred to a carrier molecule NAD
- The triose phosphate is oxidised
- The NAD is now reduced NAD
- 2 molecules of reduced NAD produced for each molecule of glucose entering glycolysis
- Triose phosphate is converted into pyruvate (3C)
- During this, 2 ATP is produced by transferring a phosphate group from a substrate to an ADP molecule - substrate linked phosphorylation
What does a pyruvate molecule have a lot of?
Chemical potential energy
What happens to the pyruvate produced in glycolysis if oxygen is available in the cells?
The pyruvate moves through the 2 membranes making up the mitochondrial envelope by active transport (small amount of ATP used for this). Pyruvate enters the mitochondrial matrix
Where does the link reaction take place?
The mitochondrial matrix
What are the reactants in the link reaction?
Pyruvate (3C)
What are the products of the link reaction?
Acetyl CoEnzyme A
What happens in the link reaction to produce Acetyl Coenzyme A?
- Pyruvate produced from glycolysis enters the mitochondrial matrix
- Enzymes remove CO2 and H from pyruvate
- This is decarboxylation and dehydrogenation
- The remainder molecule combines with coenzyme A
- This produces acetyl coenzyme A
What is coenzyme A?
A complex molecule made of a nucleoside combined with a vitamin
Nucleoside = adenine + ribose
Vitamin = Pantothenic acid, Vitamin B5
What is coenzyme A needed for?
For an enzyme to catalyse a reaction. Coenzymes don’t take part in reactions themselves
What does the coenzyme do?
Carries and supplies acetyl groups needed for the conversion of oxaloacetate to citrate
How is reduced NAD produced int he link reaction?
The hydrogen that is removed from pyruvate is transferred to NAD, producing more reduced NAD
What is the word equation for the link reaction?
Pyruvate + CoA + NAD ————> Acetyl coA + CO2 + reduced NAD
Where does the Krebs Cycle take place?
Mitochondrial matrix
What are the reactants in the Krebs cycle?
2 Acetyl CoA
What are the products of the Krebs Cycle?
2 CO2, 1 Reduced FAD, 3 reduced NAD, 1 ATP
How is the 1 ATP in the Krebs cycle produced?
By the direct transfer of a phosphate group from one of the substrates int eh reactions to an ADP molecule
Substrate linked reaction
What is the Krebs Cycle known as?
A circular pathway of enzyme controlled reactions
What happens in the Krebs Cycle?
- Acetyl CoA (2C) combines with oxaloacetate (4C) to form citrate (6C)
- Citrate is decarboxylated and dehydrogenated in a series of steps
- This causes CO2 to be released as waste gas, and the release of Hydrogen which is accepted by the carriers FAD and NAD
- Reduced NAD and Reduced FAD produced
- Oxaloacetate is regenerated to combine with another acetyl CoA
Where does oxidative phosphorylation and the ETC take place?
Inner mitochondrial membrane
What is the ETC?
A series of membrane proteins called electron carriers held in the inner membrane (cristae)
How does the ETC work?
- Electron carriers are close to one another
- Electrons can easily be passed from one carrier to the next, along a chain
- Each carrier is first reduced (electron added to it)
- Then it’s oxidised (electron remover and passed on)
What are the reactions that take place in the ETC called?
Redox reactions
What happens in oxidative phosphorylation for an electron to be transferred to the first electron carrier in the ETC?
- Reduced NAD made in the cytoplasm in glycolysis passes through the mitochondrial envelope to the matrix
- Reduced NAD and reduced FAD made in the Krebs cycle and reduced NAD made int he link reaction passes into the inner membrane from the matrix
- The hydrogen being carried by reduced NAD and reduced FAD is removed
- Each hydrogen in made of a proton and electron
- The proton (aka H+ ion) and electron split apart
- The electron is transferred to the first electron carrier in a series of electron carriers