Molecular Biology - 2.8 Cell Respiration Flashcards
Respiration
understanding and 2 types
Understanding = cell respiration is the controlled release of energy from organic compounds to produce ATP. ATP from cell respiration is immediately available as a source of energy in the cell
= Respiration is the controlled release of energy from food (eg. carbohydrates, fats, protein) to produce ATP - the ATP is in the carbon bonds and it is the breaking of these bonds that releases the energy
Two types of respiration:
- Aerobic respiration
- Anaerobic respiration (fermentation)
Role of energy in a cell
All cells need energy for cell processes (eg. active transport, cell division, making proteins) - use energy in the form of ATP (adenosine triphosphate) (it can diffuse anywhere and releases its energy very quickly) - each cell produces its own ATP from foods.
ADP -> ATP (process and explanation)
ADP <- ATP
ATP = the universal energy molecule and exists in 2 states:
- Adenosine diphosphate (ADP)
- Adenosine triphosphate (ATP)
ADP = the empty energy carrier, when it adds another phosphate it = ATP and carries the unstable energy in the last high energy phosphate bond (= PHOSPHORYLATION)
When ATP gives up its energy it loses a phosphate = ADP and has to go back to the cytoplasm/mitochondria to be recharge by the process of RESPIRATION
Aerobic Respiration
understanding, equation(s), processes
Understanding: Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose
(this occurs in the cytoplasm and in the mitochondria = USES oxygen)
MUST KNOW THE EQUATION!!!! (balanced and word):
- C6H12O6 + 6O2 –(enzymes)–> 6CO2 + 6 H2O + 38 ATP
- glucose + osygen –(enzymes)–> carbon dioxide + water + energy
Processes:
- Glycolysis
- Krebs Cycle
- Electron Transport Chain
Glucose -> pyruvate -> Acetyle co-enzyme A -> krebs cycle -> CO2 + H2 -> H2 + O2 -> H2O
Glycolysis (aerobic respiration)
- In depth breakdown in 8.2 - Aerobic respiration detail (go to there don’t bother with these)
- Occours in the CYTOPLASM
- Produces 2 ATP
- Glucose is broken into 2, 3 carbon private molecules releasing H2 and Co2 (including ACETYL CO-ENZYME A (this then enters the mitochondria) formation which is 2 carbon molecule in the matrix
Glycolysis breaks down glucose (6-C) into two molecules of pyruvate (3C), and also produces: Hydrogen carriers (NADH) from an oxidised precursor (NAD+) A small yield of ATP (net gain of 2 molecules)
Krebs Cycle (aerobic respiration)
- In depth breakdown in 8.2 - Aerobic respiration detail (go to there don’t bother with these)
- occurs in the MATRIX of the MITOCHONDRIA
- Produces 2 ATP
- A series of relations breaks up these molecules into H2 and CO2
Electron Transport Chain (aerobic respiration
- In depth breakdown in 8.2 - Aerobic respiration detail (go to there don’t bother with these)
- occurs ON the increased surface area of the folded CRISTAE surface
- produces 34 ATP
- H2 (from krebs cycle) combines with O2 to produce water
Fatty acids in aerobic respiration
when glucose (used in glycolysis) is in short supply = other molecules (eg fats/proteins) are used
- Fats are broken down into fatty acids and glycerol -> glycerol (part of a triglyceride) enters glycolysis (ie same as glucose)
- Fatty acids enter by combining directly with ACETYL COENZYME A.
- Proteins (amino acids) enter glycolysis by combining directly with PYRUVATE
Anaerobic Respiration
understanding, equation(s), processes
Understanding = Anaerobic cell respiration gives a small yield of ATP from glucose
If there is no oxygen (ie anaerobic = no O2) then ONLY glycolysis occurs
- takes place in the cytoplasm
- only produces 2 ATP
- only glucose can be used
The purpose of anaerobic respiration is to restore stocks of NAD+ – as this molecule is needed for glycolysis
By restoring stocks of NAD+ via anaerobic pathways, the organism can continue to produce ATP via glycolysis
Anaerobic Respiration - in PLANTS
pyruvate is converted to ethanol alcohol and carbon dioxide
- glucose -> pyruvate -> ethanol alcohol + carbon dioxide
Common in: bacteria, fungi, yeast, seeds of plants
Glycolysis breaks down glucose (6-C) into two molecules of pyruvate (3C), and also produces: Hydrogen carriers (NADH) from an oxidised precursor (NAD+) A small yield of ATP (net gain of 2 molecules)
The conversion of pyruvate into lactic acid (animals) or ethanol and CO2 (plants / yeasts) is REVERSIBLE Hence, pyruvate levels can be restored once oxygen is present and a greater yield of ATP may be produced aerobically
Anaerobic Respiration - in ANIMALS
Pyruvate is converted to lactic acid (lactate)
- glucose -> pyruvate -> lactic acid
When the individual stops exercising, oxygen levels will increase and lactate will be converted back to pyruvate
- very few animals can use anaerobic metabolism as their only method of getting energy (a few (eg. the tapeworm) w/ VERY LOW ENERGY REQUIREMENTS can get away with it
It is the accumulation of lactic acid that causes fatigue in muscles and may cause pain - Lactate production is used to maximize the power of muscle contractions
The conversion of pyruvate into lactic acid (animals) or ethanol and CO2 (plants / yeasts) is REVERSIBLE Hence, pyruvate levels can be restored once oxygen is present and a greater yield of ATP may be produced aerobically
Aerobic Respiration vs Anaerobic Metabolism/Respiration
Aerobic Respiration
- Takes place in most organisms/cells
- Products are CO2 and H2O
- High energy production (ie. 38 ATP from ONE glucose molecule)
- O2 is NEEDED
- Takes place in the cytoplasm and the mitochondria
- SLOW (eg. marathon runner)
Anaerobic Metabolism/Respiration
- Takes place in some bacteria/fungi
- Products = lactic acid (animals) and ethanol/CO2 (plants)
- Low energy production (2 ATP from ONE glucose molecule)
- O2 is NOT needed
- Takes place ONLY in the cytoplasm
- FAST (eg. sprinter)
Fermentation (yeast)
Anaerobic respiration (fermentation) involves the breakdown of carbohydrates in the absence of oxygen
In yeasts, fermentation results in the production of ethanol and carbon dioxide – which can be used in food processing:
Bread – Carbon dioxide causes dough to rise (leavening), the ethanol evaporates during baking
Alcohol – Ethanol is the intoxicating agent in alcoholic beverages (concentrations above ~14% damage the yeast)
Bacterial cultures can also undergo fermentation to produce a variety of food products
Yogurt / Cheese – Bacteria produce lactic acid anaerobically, which modifies milk proteins to generate yogurts and cheeses
Skill: Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer
Carbon dioxide production can be measured with a data logger or by pH changes if the specimen is immersed in water
When an alkali is included to absorb CO2, oxygen consumption can be measured as a change in pressure within the system
The pressure change can be detected with a data logger or via use of a U-tube manometer
Factors which may affect respiration rates include temperature, hydration, light (plants), age and activity levels
An increase in carbon dioxide levels will indicate an increase in respiration (CO2 is a product of aerobic respiration)
A decrease in oxygen levels will indicate an increase in respiration (O2 is a requirement for aerobic respiration)
