Metabolism Flashcards
metabolism is the …
…sum of anabolism and catabolism
Glycolysis is the almost…
…universal system of deriving usable energy from glucose
anabolism refers to …
…building up macromolecules to provide the cell with functional molecules
catabolism refers to …
breaking down macromolecules to obtain their component parts and utilise their energy
Glycolysis is the metabolic …
…pathway that converts glucose into pyruvate.
What is pyruvate?
Pyruvate—three carbons—is converted to acetyl CoA, a two-carbon molecule attached to coenzyme A
Energy is in the form of …
…ATP
the basis of energy flow is through …
…glycolysis, the TCA cycle (Krebs Cycle) and electron transport. Throughout these processes is the production of ATP.
the cell contains a large number of …
…biologically important molecules – proteins, nucleic acids, carbohydrates and lipids
What are the three main parts of cellular respiration?
- glycolysis
- TCA cycle/Krebs cycle/Citric acid cycle.
- Electron transport chain
What does glycolysis yield?
yields NADH and ATP and the formation of pyruvate, which is then processed releasing nadh AND co2
What does TCA cycle/Krebs cycle/Citric Acid Cycle do?
the main source of energy for cells and an important part of aerobic respiration. The cycle harnesses the available chemical energy of acetyl coenzyme A (acetyl CoA) releasing NADH / FADH2
What does electron transport chain do?
harnesses NADO and FADH2, which are then used to produce ATP via establishment of a proton gradient.
Krebs cycle can be defined as…
…a combination of biochemical reactions via oxidation of acetyl Co-A to release the stored energy.
NADPH is produced in…
…glycolysis.
In the electron transport chain…
- electrons are passed from one molecule to another, and energy released in these electron transfers is used to form an electrochemical gradient.
- In chemiosmosis, the energy stored in the gradient is used to make ATP.
during times when energy is not being used rapidly the cell builds up…
…carbon skeleton bio-polymers (lipids and carbohydrates) which can be utilised for energy later (energy storage)
How are lipids stored?
lipids are mainly stored as triacylglycerol – in animals specialised cell types are used to store lipids though most cells have some lipid storage – consist of fatty acids and glycerol
Triacylglycerols, or triglycerides are the main components of…
- animal (including human) fat, most of which is concentrated in adipose tissue.
- also vegetable oils.
Triacylglycerols, or triglycerides constitute…
…90% to 95% of dietary fat.
What are the two main stores of energy?
Cholesterol and fatty acids are two of the main stores of energy.
WHere does fatty acid synthesis occur?
in the cytoplasm
Where is the starting point of fatty acid synthesis?
is citrate from the TCA cycle (mitochondria)
Where is citrate exported to?
the cytoplasm where it is converted back to oxaloacetate and Acetyl-CoA with the loss of energy by hydrolysis of ATP.
Fatty acids are a major component of…
…membranes
In addition to being the major component of membranes, fatty acids are important…
…energy storage molecules
What is ATP hydrolysis?
the catabolic reaction process by which chemical energy that has been stored in the high-energy phosphoanhydride bonds in adenosine triphosphate is released after splitting these bonds,
ATP can be hydrolyzed to…
…ADP and Pi by the addition of water, releasing energy
commitment to fatty acid synthesis involves …
…the formation of malonyl CoA
Malonate group of malonyl-CoA is transferred to …
…Acyl carrier protein
Co-enzyme A is exchanged for …
…Acyl Carrier Protein – linked via sulphur bond
Describe the beginnings and initiation of fatty acid biosynthesis.
- fatty acid synthesis occurs in the cytoplasm
- Citrate is exported to the cytoplasm where it is converted back to oxaloacetate and Acetyl-CoA with the loss of energy by hydrolysis of ATP
- Malonyl CoA is formed to commit to fatty acid synthesis.
- Malonate group of malonyl-CoA is transferred to Acyl carrier protein
- Co-enzyme A is exchanged for Acyl Carrier Protein – linked via sulphur bond
- at this point we have a four carbon atom skeleton
- this is then further processed and fed back into a cycle where it again reacts with malonyl CoA to add two more C atoms onto the growing fatty acid skeleton
the elongation cycle is a …
…series of chemical reactions
What are the steps of the elongation cycle?
1 – condensation – Carbon dioxide is released
2 – reduction – hydrogen added to carbonyl group on 3C
3 – dehydration – water is removed and C=C bond formed
4 – reduction – hydrogen atom added to 2C – removal of C=C bond
5 – condensation 2 – malonyl-CoA reacts and CO2 is released.
What catalyses fatty acid synthesis?
Synthesis of fatty acids is catalyzed by the multi-subunit enzyme fatty acid synthase
the long chain carbons of fatty acids are assembled …
…in a repeating five-step sequence.
What holds reaction intermediates in place?
Reaction intermediates are held in place by ACP protein (acyl carrier protein), which acts like a tethered-arm swinging intermediates through the correct sequence of active sites within the protein.
What is Fatty acid synthase (FAS)?
- an enzyme catalyzing the synthesis of fatty acids.
- Itsa housekeeping protein, producing fatty acids that can be used for energy storage, membrane assembly and repair, and secretion in the form of lipoprotein triglycerides.
How are triacylglycerol synthesised?
- fatty acids are added onto the glycerol-3-phosphate backbone until all 3 carbon atoms of glycerol are linked to an acyl chain
- the reactions are dehydration reactions – H is removed from glycerol and the OH removed from the fatty acid, which forms an ester bond
What is a triacylglycerol?
Triacylglycerols are the form in which fat energy is stored in adipose tissue. Triacylglycerols are sometimes referred to as triglycerides.
How are lipids (fatty acids and triglycerols) broken down?
- breakdown of triacylglycerol and fatty acids is essentially the reverse process.
- oxidation of fatty acids releases acetyl CoA which feeds back into the TCA cycle in a process known as beta-oxidation
Enzymes involved:
1. Acyly dehydrogenase
2. Enoyl hydratase
3. β hydroxyacyl dehydrogenase
4. β ketoacyl thiolase
What is glycogen?
Glycogen is the molecular form of carbohydrates stored in humans and other mammals
How are carbohydrates bound to one another?
Carbon 1 on the first carbohydrate bound to second carbohydrate at carbon 4. Hence its called 1-4 glycosidic bond.
How are carbohydrates built up?
1) Phosphate group of glucose-6-phosphate rearranged to form glucose-1-phosphate
2) glucose-1-phosphate is then converted to UDP-glucose via the addition of uridine triphosphate (UTP)
3) Pyrophosphate (PPi) released which provides the energy for the reaction
4) UDP-glucose is then added to the growing chain of glycogen resulting in the loss of UDP
5) branching increases the solubility and speed of access during catabolism
6) branching enzymes form branches from α1-6 glycosidic bonds using a small oligomer of the growing glycogen chain
How are carbohydrates broken down?
1) Inorganic phosphate is added
2) glycogen is catabolised by the release of the 1-4 glycosidic bond from the glycogen chain
3) this is converted to glucose-1-phosphate due to glycogen phosphorylase
4) phosphoglucomutase causes reconversion to glucose-6-phosphate
5) the cell therefore has an easily accessible store of glucose which can be fed back into glycolysis if needed to produce usable energy (in the form of ATP) when required.
How many amino acids are there?
20
What do amino acids contain?
- an amine group, a carboxylic acid group and an R group.
- it is the R group that determines the chemistry of the particular amino acid
Describe the relationship between the cell and amino acids.
- amino acids can be taken up by the cell or manufactured by the cell itself
- in animal cells this is dependent on which amino acid it is
Can amino acids be made by the body?
- some are able to be synthesised and others not (ESSENTIAL VS NON-ESSENTIAL)
- Essential amino acids cannot be made by the body. As a result, they must come from food.
Describe amino acid degredation.
It is necessary because, unlike fats and carbohydrates,excess amino acids cannot be stored. The majority of amino acid degradation occurs in the liver and skeletal muscle. Common end products include: ammonia, which enters the urea cycle.
Function of amino acid’s carbon skeleton?
The carbon skeletons of amino acids are fragmented to form only a few end products; all of them are intermediates of either glycolysis or the TCA cycle.
How does amino acid synthesis take place?
synthesis takes place again via intermediates linked to glycolysis and the TCA cycle
What is the source of the amino acid glutamate?
the source of the amino acid glutamate is a-ketoglutarate (aKG), an intermediate of the TCA cycle. The reaction is catalysed by glutamate dehydrogenase
What can glutamate be further converted into?
glutamine
how is glutamate further converted into glutamine?
glutamate can be converted further to glutamine by the action of glutamine synthetase and the addition of an amide group onto the terminal C of the carboxylic acid group
The reaction causing glutamate to be further converted into glutamine is…
…reversible.
What determines which direction the glutamate and glutamine reaction runs in?
- the reaction is reversible – the energy state of the cell (i.e. the amount of ATP and GTP) determines which direction the reaction runs
- in conditions of high GTP/ATP the reaction runs forwards – biosynthesis
- in conditions of low ATP/GTP the reaction runs backwards - catabolism
Amino acids can be…
…synthesised or absorbed by the cell (essential amino acids)
What does protein synthesis utilize?
protein synthesis utilises amino acids attached to tRNA molecules in translation
Describe peptide bonds.
A peptide bond is a kind of linkage between two amino acids. It is also known as an amide bond.A peptide bond connects two amino acids, forming a dipeptide, and is associated with the loss of a water molecule. This process is called a condensation reaction
This is how we build up proteins
Describe protein synthesis
Dna structure converted to RNA. RNA provides the code for the trna. Trna has a 3 base sequence (carries an amino acid in). Amino acids join by peptide bond and the removal of a water molecule in a condensation reaction, resulting in the formation of a dipeptide/polypeptide.
How are proteins deconstructed?
- proteins are degraded in the cell by proteases – the amino acids are either reused for protein synthesis or broken down and the carbon skeletons used for energy production and the nitrogen groups removed from the cell as urea
- this ensures the cell retains nitrogen balance and doesn’t lead to excess ammonia (nitrogen homeostasis)
- there are pathways for the removal of all amino acids by conversion of carbon skeletons to intermediate molecules of glycolysis and the TCA cycle
