▼❑What This episode is about...
▼❑In this episode...
•❑Energy transformations in the cell
•❑energy in general and energy transformations in the cell
•❑ADP and ATP
•❑How ATP is made in a cell - especially in the process called Cellular respiration, but also in other processes.
•❑How plants make glucose in photosynthesis (to get glucose for Cellular respiration)
•❑How plants and animals store their energy.
▼❑Energy is VERY important in a cell – it is needed for reproduction, repairing of organelles in a cell, growth, movement, AND synthesis of biomolecules - especially proteins (including enzymes!!!) but also nucleic acids and other macromolecules.
▼❑ listener feedback and comments
▼❑Energy in general
▼❑Energy - the capacity to do work
what we are really talking about here, when we say "Energy is the ability to do work" is that energy is the ability to make things happen that couldn't happen otherwise.. the ability to organize materials in a way that wouldn't happen spontaneously (ball doesn't roll up a hill, proteins don't synthesize themselves, damaged organelles won't be repaired.....
•❑There are different forms of energy: Potential energy, kinetic, heat, light, sound. We are most concerned with chemical energy (Cellular respiration.. ATP...) but also interested in light for photosynthesis.
▼❑Second law of thermodynamics.... every time energy is changed from one form to another, some is lost from the system as heat. chemical transformations are never 100% efficient. (that's why a car motor gets hot...
•❑The heat of your body comes from your metabolic processes that release energy.
•❑in chemical energy the energy is contained within the bonds. If you break a bond, the energy that was holding the atoms together are released as energy and some of that can be used by the cell to do work..... BUT Chemical transformations are never 100% efficient.
•❑Exergonic vs Endergonic (or energy releasing/downhill reactions.. vs energy requiring/uphill reactions)
•❑Catabolic vs Anabolic
▼❑ATP and ADP
▼❑ATP and ADP stand for.... Adenosine.. tri/di Phoshphate..
▼❑structure of each of these. Adenosine group - with either three or two phosphate ions.
▼❑ATP is the energy currency of the cell.. it's how the cell shifts energy around in the cell.
•❑shifts energy from one place in the cell where its made, to another place in the cell where it's needed.
▼❑ATP produced in the mitochondria (mostly)
▼❑this is anabolic and therefore requires energy.. That energy comes from a cellular respiration in the mitochondrion. The energy given off by cellular respiration is used to take 36 ADP molecules, and bind another phosphate on the end to make ATP. (remember the energy is in the bonds!)
•❑Now all this ATP is accumulating in and around the mitochondrion - so that means there is a very high concentration of ATP in the mitochondrion. HIGH CONCENTRATION!!! we know about that!! so what will happen is the ATP will diffuse from the mitochondrion to places in the cell where the concentration of ATP is lower.
•❑And you know where in the cell the concentration of ATP is the VERY lowest??? - well it will be any place where ATP is being broken down!! A great example is at the ribosomes. That is where proteins are being made!! Making proteins is anabolic, so it must be endergonic (it uses energy). That energy comes from breaking that 3rd phosphate off ATP - the energy in the bond comes out (and SOME of it can be used to join amino acids together with peptide bonds)...
•❑So around the ribosome there is this accumulation of ADP and extra phosphate ions (that have been broken off the ADP) So do you see?? there is a HIGH CONCENTRATION of ADP and Phosphate around the ribosome. You can see what's going to happen, can't you?? That ADP and phosphate will diffuse from the ribosomes where they have a high concentration to other places in the cell where there is a low concentration of ADP and phosphate.
•❑And you know where the concentration of ADP and phosphate is the lowest?? (this is cool isn't it?) Yes! it's the mitochondrion. Why is the concentration of ADP low at the mitochondrion? Because everytime an ADP gets to the mitochondrion, it is changed into something else and isn't ADP anymore. It gets changed into ATP. So the ADP is constantly being used up!!! and the concentration stays low.
▼❑Cellular Respiration - the process that happens in mitochondrion
▼❑Dont get bamboozled !!
•❑Most text books make cellular respiration look REALLY confusing. they have diagrams of arrows and little spinning wheels, -- it looks like you need a degree in mechanical engineering to understand it!!
▼❑It IS a complex process
•❑but VCAA says you don't need to know all the fine details of, say Krebs cycle.
•❑Im going to tell you what I think you need to know. (of course you could know more - and that would make me proud of you - if you want to understand it because you just aren't satisfied not knowing - then i like that - When you learn because you want to understand and not just because you are going to sit an exam, I think you learn in a whole new way - and the truth is that you probably end up doing better on the exam too. So I am NOT saying you shouldn't bother to learn all the nuts and bolts of cellular respiration, just that some students get frustrated and confused by it, and so i want to simplify your life by telling you what i think you really need to know and understand for the exam.
▼❑Equation for cellular respiration.
▼❑C6H12O6 + 6O2 –> 6CO2 + 6H2O
•❑commit them to memory. - YOU MUST KNOW THIS BY HEART.
▼❑3 stages of cellular respiration.
▼❑Glycolysis
•❑biochemical pathway of its own.
•❑breaks glucose 6C to two pyruvate 3C
•❑happens in the cytoplasm (not mitochondrion)
•❑does NOT require oxygen.
•❑produces 2 ATP molecules.
▼❑Krebs cycle
•❑in the center of mitochondrion (the matrix)
•❑2 ATP molecules
•❑doesn't use oxygen, but it won't happen if there is no oxygen available.
▼❑at the end all Carbon and Oxygen is gone. as CO2 - and all we have left is Hydrogen.
▼❑Electron transport
•❑takes place on the folded inner membrane - cristae,
•❑cytochromes (enzymes) embedded in the membrane.
•❑requires oxygen. (the Oxygen combines with the Hydrogen to make water!!!)
▼❑32 ATP
•❑some texts say 34 - which is true for some cells - but in most cells it is 32
▼❑Anaerobic respiration (if oxygen is not available.)
•❑"cellular respiration" should only be used for AEROBIC cellular respiration. confusing because some people talk about anaerobic cellular respiration....
•❑basically glycolysis! that's why we get 2 ATP. (no oxygen... game over)
▼❑Cant leave it as pyruvate. A cell needs to convert it to something else.
•❑Animal cells convert it to lactic acid.
▼❑plants convert it to - ethanol and carbon dioxide. (We give it a special name: fermentation).
•❑The reason for the difference is that plants have a different enzyme to animals.
•❑Anaerobic respiration is 1/18th as efficient as cellular respiration. (it is very wasteful of glucose)
•❑Anaerobic respiration is FASTER than cellular respiration. (it is very quick!)
▼❑Can only be sustained for a short period of time.
•❑well that's true for animals. - but some bacteria can sustain it indefinitely - anaerobic bacteria for example.
▼❑Photosynthesis - the process that happens in chloroplast
▼❑purpose of photosynthesis
•❑capture radiant (light) energy and convert it to chemical energy (bonds) in glucose.
•❑some people think that plants do photosynthesis to make glucose and oxygen for animals. But no - plants don't do anything for us! They do make oxygen - and it's very lucky for us that they do - but that's not why they are doing it!! So what are they doing it for? YES to make glucose for themselves!! For their own cellular respiration. because plants need ATP too. so they also have to do cellular respiration to get ATP. But unlike you and i - they can't go to the pantry and get a mars bar when they are hungry - they have to make their own glucose - and photosynthesis is how they do it.
▼❑Pigments involved are called chlorophylls - chloro (green) phyll (leaf) in chloroplasts - green plastids.
•❑absorb red and blue light (not green)
▼❑Chloroplasts - need to know structure of grana and stroma.
•❑big organelle (much bigger than a mitochondrion!) - getting close to being as big as a nucleus!
▼❑Equation for photosynthesis
•❑6CO2 + 12H2O –> C6H12O6 + 6O2 + 6H2O
▼❑sometimes written as: 6CO2 + 6H2O –> C6H12O6 + 6O2
•❑commit them to memory. - YOU MUST KNOW THIS BY HEART.
▼❑2 stages of photosynthesis (it is also a biochemical pathway)
▼❑Light Dependant reactions.
•❑splitting of water 12 water taken in. H are kept. O are released as O2.
▼❑Light Independant reactions.
•❑H is combined with the Cs and Os to make glucose and CO2
•❑18 ATP made in light dependent stage, but all 18 ATP are used in light independent stage.
▼❑Factors affecting the rate of photosynthesis
•❑light intensity
•❑Carbon dioxide conc.
•❑temperature (enzymes have optimum temp and all chem reactions go faster at higher temperatures.)
▼❑chlorophyll concentration - not enough nitrogen for the plant to make chlorophyll.
•❑Limiting factors: one of these things is the limiting factor for the reaction.
▼❑Cellular resp and photosynthesis rates.
▼❑Misconception: Photosynthesis happens during the day and cellular respiration happens at night.
•❑respiration constant. photosynth rises and falls. light-compensation point is the point at which the rates are equal.
•❑Carbon dioxide conc.
•❑temperature (enzymes have optimum temp and all chem reactions go faster at higher temperatures.)
▼❑chlorophyll concentration - not enough nitrogen for the plant to make chlorophyll.
•❑Limiting factors: one of these things is the limiting factor for the reaction.
▼❑Storage of energy
•❑plants store their glucose as starch - especially in their roots (think about a carrot or potato)
▼❑animals store their glucose as glycogen (animal starch)
•❑be careful of the glucy glycy, glicky words glucose, glycogen, glycerol, glycolysis
•❑glycogen is stored as glycogen, in liver and skeletal muscles.
•❑when glycogen stores are full, energy is stored as fat in adipose tissues. - higher energy content per weight. it's a more useful storage molecule.
•❑Why do we need to store our excess glucose as anything? - needs to be something insoluble in water so as not to cause an osmotic gradient into the cell.
▼❑RELEVANT EXAM QUESTIONS
•❑VCE BIOLOGY EXAM 1, 2006: Multiple choice question 2
•❑VCE BIOLOGY EXAM 1, 2002: Multiple choice question 13
•❑VCE BIOLOGY EXAM 1, 2003: Multiple choice questions 10 - 13
•❑VCE BIOLOGY EXAM 1, 2006: Short answer question 4
•❑VCE BIOLOGY EXAM 1, 2005: Short answer question 3
•❑VCE BIOLOGY EXAM 1, 2004: Short answer question 3 (e - g)
•❑HSC BIOLOGY EXAM, 2006: Short answer question 33.
•❑HSC BIOLOGY EXAM, 2005: Short answer question 32