Module 3 - Cellular Respiration Flashcards
What is cellular respiration?
ATP Production in cells
What is ATP?
ATP is a rapid, short term energy storage and release molecule, converting back and forward to and from ADP
What is the importance of glucose?
Glucose is the body’s preferred and rapid energy source for the production of ATP - our immediate energy molecule
Glucose is the primary energy source of the brain and central nervous system. For this reason, glucose is tightly regulated
some ATP is manufactured in the cytosol, but mostly in the mitochondria
glucose is not needed for immediate use, it can be converted to glycogen storage for later use
when glycogen stores are full the liver can convert glucose into triglycerides for storage in adipose tissue
What happens when glucose burns in the air?
When anything “burns” in the air, oxygen is combining with atoms in its molecules. These are called oxidation reactions. Oxidations always release energy. In this case, heat energy.
How does glucose burn in the cell?
in cells, glucose (and other energy source molecules) is broken down gradually in a series of catabolic reactions. Like demolition, there are intermediate stages and intermediate molecules are produced on the way. Each molecule is the substrate for the next enyzme that produces the next intermediate molecule. In this way glucose is completely broken down to H2O and CO2. Instead of heat energy, chemical energy is collected bit by bit and used to manufacture ATP.
a series of reactions like this is called a METABOLIC PATHWAY!
examples of which are GLYCOLYSIS and KREBS CYCLE
How is chemical energy collected?
- used to produce ATP directly/immediately
Enzyme 1 –> ADP + P –> ATP
or
- collected by co-enzymes (NADH and FADH2) that are used later to manufacture ATP in the mitochondia in “ELECTRON TRANSPORT”
CELLULAR RESPIRATION TAKE HOMES
- chemical energy in the cell is collected when fuel molecules (such as glucose) are broken down
- each reaction requires its own enzyme
- the ultimate goal is to produce ATP from the energy
1. ATP can be produced directly during an enzyme reaction - ONLY SMALL AMOUNTS OF ATP ARE MADE THIS WAY
2. ATP can be produced in the mitochondria from energy collected by coenzymes. NADH and FADH2 in a process called ELECTRON TRANSPORT. MOST ATP is made this way
Glucose catabolism occurs in what 3 stages?
Glycolysis
Krebs Cycle
Electron transport
What is glycolysis?
doesnt require oxygen, takes place in cytosol for every glucose molecule: 2 ATP are produced directly 2 NADH are produced 2 pyruvic acids are produced
What is Krebs cycle?
in mitochondria, pyruvic acid is first converted to acetyl-coA, for every 2 pyruvic acids, 2 ATP are produced directly. A lot of NADH and FADH2 are produced. The CO2 we breath out is released here
What is electron transport?
like krebs, also in mitochondria
finally, all of the co-enzymes produced previously, NADH, FADH2, transfer their stored energy to manufacture ATP - a lot of ATP. about 28 ATP per 1 glucose molecule. It is also the only place in this whole process of cellular respiration where we use oxygen
the whole process of cellular respiration = glycolysis –> Krebs –> Electron transport, is aerobic cellular respiration since oxygen is ultimately required
What is anaerobic respiration?
if O2 is low in our blood, electron transport slows, Krebs cycle slows and suddenly our cels are short of ATP. however, remember that glycolysis produces 2 ATP? If we can keep just glycolysis running, we can at least produce some ATP. This metabolic trick is called anaerobic respiration. The downside is that it produces lactic acid that build up in our blood to toxic levels
increased levels of lactic acid cause muscle cramps and lower blood pH
once oxygen becomes available again the body converts lactic acid into pyruvate
Lipids and proteins are connected to the cellular respiration pathyway
Acetyl-CoA is one of the major crossroads for anabolic and catabolic pathways for proteins and lipids
WHat happens during the breakdown of triglycerides?
2 stages
- first triglycerides are split into glycerol and 3 fatty acids, this is called LYPOLYSIS
Glycerol can join the glycolysis pathway and on the the rest of cellular respiration
- FATTY ACID CATABOLISM, fatty acids are broken down into 2 carbon fragments and combined with coenzyme A = acetyl coa
many molecules of Acetyl CoA are produced from a single fatty acid and fed into the Krebb cycle. This is why lipids produce and store so much energy
What happens when we go without food?
As you know, after 24 hours of not eating, we deplete our glycogen stores. So we have now lost glucose from glycogen as a fast source of energy. Because we are catabolizing fat we have lots of acetyl-coa available. What next?
- Produce ketones from Acetyl Coa in the liver. Ketones are an important energy source and can be used to generate ATP in the brain, kidney and heart.
Note excessive ketone production can lead to the condition of ketoacidosis. Ketones are acidic and lower blood pH. This can lead to coma and death if untreated.
Triglycerides –> Acetyl CoA –> Liver —> ketone bodies used by the brain, kidney and heart
- manufacture new glucose called GLUCONEOGENESIS
Pyruvate –> gluconeogenesis –> Glucose (this is a bit like glycolysis but in reverse)
Gluconeogenesis is especially important in fasting/starvation to keep blood glucose within the normal range for the brain and CNS. THE BRAIN CANNOT FUNCTION WITHOUT GLUCOSE. IF BLOOD GLUCOSE LEVELS FALL TOO LOW WE CAN QUICKLY FALL INTO A COMA AND DIE
