5.7 Respiration Flashcards
What happens in respiration?
Respiration is a process the occurs in living cells and releases the energy stored in organic molecules such as glucose.
What is the energy from repiration immedieatly used for?
The energy is used to synthesis molecules of ATP from ADP and inorganic phosphate.
What is ATP used for?
ATP in cells can be hydrolysed to release energyneeded to drive biological processes.
What organisms respire to obtain energy?
Microorganisms (eukaryotes and prokaryotes), plants, animals, fungi and protoctists.
Why do living organisms need to respire?
Via respiration, energy is released from organic molecules, which can be used to make ATP to drive biological processes.
What processes do living organisms need energy for?
- Active transport
- Endocytosis
- Exocytosis
- Synthesis of large molecules e.g. proteins
- Dna replication
- Cell division
- Activation of chemicals
What are the chemical reactions that take place within living cells collectivly known as?
Metabolism or metoblic reactions
What reactions synthesis small moecules to big molecules?
Anabolic reactions are metabolic reactions where large molecules are synthesised from smaller molecules.
What reactions invove the hydrolysis pf large molecules to smaller ones?
Catabolic reactions involving the hydrolysis of large molecules to smaller ones.
What is ATP the intermegiary molecule between?
ATP is the standard intermediary between energy-releasing and enrergy-consuming metabolic reactions.
What is the structure of ATP?
When is ATP reatively stable, what does this mean for the molecule?
ATP is relatively stable in solution, this means it can easily be mived from place from place to place within a cell.
Whsat is ATP readily hydrolysed by?
ATP is readily hydrolysed by enzyme catalysis.
What is the energy-releasing hydrolysis reaction of ATP paired with?
THe energy-releasing hydrolysis of ATP is coupled with an energy-consuming metabiolic reaction.
What is ATP hydrolysed to? What happens in this process?
ADP and P. A small qunatity of energy is released for use in the cell.
Why is energy being produced in small quanitites of energy good?
Cells can ontain energy they need for processes in small mangeable amounts that will not cause damage or be wasteful.
What is reffered to as the universal energy currency? Why is it reffered to like this?
ATP because it occurs in all living cells and is a source of energy that can be used by cells in small amounts.
What ways is the energy from the hydrolysis of ATP released by?
- Thermal energy
- Chemical potential energy
Why is energy released from the hydrolysis of ATP as thermal energy significant?
It enables living organisms to stay warm and enables their enzyme-catalysed reactions to proceed at ot near their optimum rate.
Every time ATP is hydrolysed, roughly, how much energy is released?
30.5kJ mol^-1
What is glycosis?
Glycosis is the first stage of respiration; a 10-stage metabolic pathway that converts glucose to pyruvate.
It is the biochemical pathway.
Where does gylcosis occur?
In the cytoplasm of all organisms that respire.
During glycosis, what coenzyme catalyses some of the reactions?
NAD
What are the 3 main stages of glycosis?
- Phosphorylation of glucose to hexose biophosphate.
- Splitting each hexose biophosphate molecule into 2 triose phosphate molecules.
- Oxidation of triose phosphate to pyruvate.
What do enzymes the catalyse oxudation and reduction reactions need help from?
Coenzymes that accept the hydrogen atoms removed during oxidation.
What is the full name of the coenzyme NAD?
Nicotinamide adenine dinucleotide
Describe the molecule NAD?
NAD is a coenzyme. It is a non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions. NAD oxidises substrate molecules during glycosis.
What id NAD sythesised from?
NAD is synthesis is synthesised in living cells from nicotinamide (vitimin B3), the 5-carbon sugar ribose, the nucleotide base adenine and 2 phosphoryl groups.
What is the structure of NAD?
The nicotinamide ring in NAD can accept 2 hydrogens, what does the NAD become?
Reduced NAD.
What does reduced NAD do?
Reduced NAD carries protons and electrons to the cristae of mitochondria and delivers them to be used in oxidative phosphorylation for the generation of ATP from ADP and P.
What happens when reduced NAD gives up the protons and electrons that it accepted in 1 of the first 3 stages of respiration?
It becomes oxidised and can be reused to oxidise more substrate, in the process of becoming reduced again.
How many carbons does glucose have?
6 carbons, hexose sugar.
What happens in phosphorylation in glycolysis?
- One molecule of ATP is hydrolysed and the released phosphoryl group is added to glucose to make hexose monosulphate.
- Another molecule of ATP is hydrolysed and the phosphoryl group added to the hexose phosphate to form a molecule of hexose biopholphate. This sugar has one phosphate group at carbon one and six.
What happens during splitting the hexose bisphophate in glycolysis?
Each molecule of hexose bisphosphate is split into 2 three-carbon molecules, triose phosphate, each with a phosphate group attatched.
What happens during the oxidation of triose phosphate to pyruvate in glyolysis?
- Dehydrogenase enzymes, aided by coenzyme NAD, remove hydrogens from triose phosphate.
- The 2 molecules of NAD accept the hydrogen atoms (protons and electrons) and become reduced.
- At this stage, 2 molecules of NAD are reduced for every molecule of glucose undergoing this process. Also, at this stage, 4 molecules of ATP are made for every triose phosphate molecules undergoing oxidation.
What are the products of glycolysis?
- 2 molecules of ATP, 4 have been made but 2 were used to ‘kick start’ the process
- 2 molecules of reduced NAD
- 2 molecules of pyruvate
What are the 4 stages of respiration of glucose?
- Glycoysis
- The link reaction
- The Krebs cycle
- Oxidative phosphorylation
In what conditions does the last 3 stages of respiration occur in?
Anaerobic conditions.
Under anerobic conditions, what happens to the pyruvate molecules from glycoysis?
The pyruvate molecules are actively transported into the mitochondria for the link reaction.
In the absencde of oxygen pyruvate is converted in the cytoplasm to lactate or ethanol. In this process, the reduced NAD molecules are reoxidised so glycoysis can continue to run, genewrating 2 molecules of ATP for every glucose molecule metabolised.
Why do living organisms have low levels of NAD in their cells although they use many molecules of it through the day?
It is continually being recycled – reduced and then reoxidised.
Why is NAD described as a nucleotide derivative?
It contains adenine, ribose sugar and phosphoryl groups, and therefore is derived from two nucleotides.
Explain how glycolysis involves oxidation, although its an anerobic process.
Oxidation involves removal of hydrogen atoms from substrate molecules.
What is the role of NAD during glycolysis?
It removes hydrogen atoms from triose phosphate molecules, oxidising triose phosphate to pyruvate.
Why is the net gain of ATP 2 molecules per molecule of glucose undergoing glycolysis, although 4 molecules of ATP are madde?
Two molecules of ATP are used at the beginning of glycolysis and four are produced, giving a net gain of 4 – 2
= 2.
Alcohol is metabolised in the liver. It is oxidised, by dehydrogenation, to ethanal. Ethanal is then oxidised to ethanoate (acetate). Why may people who drink regularly be deficient in NAD?
The NAD being used to oxidise ethanol (ethyl alcohol) and ethanal is not available for use in respiration.
What is cristea?
Inner highly-folded moitovhondrial membrane.
What is the mitochondrial matrix?
Fluid- filled inner part of mitochondria.
Describe the shape of a mitochondrion?
Mitochondria may be rod-shaped, thread like or spherical with diameters of 0.5-1.0μ and lengths of 2-5mμ.
Why can we say a michochndria has an envolope?
All mitochondria have an inner and an outer phospholipid membrane making up the envolope.
Describe a mitochondia’s envolope?
The outer membrane is smooth, and the inner memebrane is folded into cristae, giving it a larger surface area.
What is embedded in the inner membrane of a mitochondia, what does this allow?
Embedded in the inner membrane are proteins that transport electrons, and protein channels channels associated with ATP sythase anzymes that aloow protons to diffuse through them.
What is between the inner and outer mitochondrial membranes, between the envolope?
Intermembrane space.
Describe the mitochondrial matrix?
The mitochondrial matrix, enclosed by the inner membrane , is semi-rigid and gel-like; it contains mitochondrial ribosomes; looped mitochondrial DNA and enzymes for the link reaction and the Krebs cycle.
What occurs iin the matrix in a mitochondria?
The link reaction and the Krens cycle.
What does the matrix in a mitochondria contain?
- Enzymes that catalyse the link reaction and the Krebs cycle.
- Molecules of the coenzyme NAD and FAD.
- Oxaloacetate- the 4-carbon compound that accepts the actyl group from the link reaction.
- Mitochondrial DNA- some of which codes for mitochondrial enzymes and other proteins.
- Mitochondrial ribosomes
Describe the outer mebrane of a mitochondria.
The phospholipid composition of the outer membrane around other organells in eukaryotic cells. It contains proteins, some of which form channels or carriers that allow the passage of molecules, such as pyruvate, into the mitochondrion.
Describe the inner membrane of a mitochondrion.
The lipid composition differs from that of the outer membrane. The lipid layer is less permeable to small ions such as hydrogen ions (protons); also, the folds, cristae, in the inner membrane give a large surface area forthe electron carriers and ATP synthase emzymes embedded in them.
On the inner membrane of a mitochondrion, how are electron carriers and protein complexes arranged?
They’re arranged in electron transport chains. These chains aare involved in the final stage of aerobic respiration, oxidative phophorylation.
What is the the innermembrane space in a mitochondrion involved in?
Oxidative phosphorylation.
Why is significant that the inner membrane of a mitochondrion is close contact to the mitochondrial matrix?
So the molecules of NAD and FAD can easiy deliver hydrogens to the electron transport chain.
What is decarboxylation?
Removal of a carboxyl group from substrate molecule.
What is dehydrogenation?
Removal of hydrogen atoms from a substrate molecule.
What is substrate-level phosphorylation?
Production of ATP from ADP and P during glycolysis and the kreb cycle.
After glycolysis, where is pryuvate transported?
Pyruvate is transported arcoss the outer and inner mitochondrial membranes via specific pyruvate-H+ symport.
What process is pyruvate tranported into a mitochondria after glycolysis?
Via specific pyruvate-H+ symport, a transport protein that transports two ions or mo
lecules in the same direction, into the matrix.