basics of biochem

Question 1

what is metabolism

Answer 1

the overall process through which living organisms acquire and use free energy to carry out their various functions

Question 2

what are the 2 categories of metabolism

Answer 2

• catabolism = the degredation of nutrients to salvage their components +/ or generate their energy
• anabolism = the biosynthesis of new molecules from simpler components

Question 3

what are metabolic pathways

Answer 3

a series of connected enzymatic reactions that produce specific products many are branched and interconnected
in general catabolic and anabolic pagthways are related: complex metaboites broken down into simpler compounds with energy released in the form of ATP

Question 4

what allows interconversion of metabolites in degradative and biosynthetic oathways to be catalysed quickly enough to be compatabile with living

Answer 4

enzymes

Question 5

list categories of enzymatic reactions

Answer 5

• oxidations - reductions (redox)
• transfer of chemical groups
• hydrolysis
• removal of chemical groups
• linking two groups together
• isomerisation

Question 6

sequence the role of enzymes in catabolism

Answer 6

Question 7

how are metabolic pathways controlled

Answer 7

• intrinsic regulation = feed forward and feedback mechanisms which are reactions which self regulate to respond to changes in the levels of substrates or products
• extrinsic control = cell in a multicellular organism changing its metabolism in response to signals from other cells
• increasing or decreasing enzyme pathway in response to signals

Question 8

what do negative feedback loops rely on

Answer 8

detecting change in a body parameter then ectivating mechanisms to restore the parameter bad to the original or ideal. they are responsible for maintaining homeostasis

Question 9

where does energy come from

Answer 9

the breakdown of glucose, fatty acids and amino acids into acetyl CoA
- can the neter the TCA cycle to produce more energy as ATP or NADH/FADH2 (further processed through oxidative phosphorylation into ATP)

Question 10

what are the by-products of the TCA cycle

Answer 10

CO2 - expired by the lungs (transported by blood)

Question 11

what does ATP do

Answer 11

provides the energy that drives most of the energy consuming processes in the cell (i.e, muscle contraction, active transport etc)

Question 12

once ATP is used as energy, what happens to ir

Answer 12

converted back to adenosine diphosphate (ADP) and inorganic phosphat

ATP-ADP cycle

Question 13

what are the 2 key aspects of metabolism

Answer 13

• krebs cycle = allows release of stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and amino acids into ATP, NADH and FADH2 and carbon dioxide
• oxidative phosphorylation = the process where ATP is produced due to the transfer of electrons from NADH and FADH2 to oxygen via a series of electron carriers. this takes place in mitochondria

Question 14

discuss the role of the krebs cycle in catabolism

Answer 14

• the oxidatiion of fuels to generate ATP is called respiration
• kreb cycle is a series of reactions that completes the oxidation of fuels to CO2
• electrons lost from the fuels during oxidative reactions are transferred to O2 by a series of proteins in the electron transport chain
• the energy of electron transfer is used to convert ADP to Pi to ATP by a process known as oxidative phosphorylation
• 8 steps
• each turn in the cycle results in the regeneration of oxaloacetate and the formation of 2 molecules of CO2

Question 15

what is substrate level phosphorylation

Answer 15

as a glucose molecule is gradually broken down some of the breakdowns steps release energy that is directly captured as ATP. in these steps a phosphate group is transferred from a pathway intermediate straight to ADP = process known as substrate level phosphorylation

Question 16

explain the entire process of oxidative phosphorylation starting with the breakdown of glucose

Answer 16

electrons from glucose are transferred to small molecules known as electron carriers. The electron carriers take the electrons to a group of proteins in the inner membrane of the mitochondrion, called the electron transport chain. As electrons move through the electron transport chain, they go from a higher to a lower energy level and are ultimately passed to oxygen (forming water).

As an electron passes through the electron transport chain, the energy it releases is used to pump protons out of the matrix of the mitochondrion, forming an electrochemical gradient. When theyflow back down their gradient, they pass through an enzyme called ATP synthase, driving synthesis of ATP. This process is known as oxidative phosphorylation. The diagram below shows examples of oxidative and substrate-level phosphorylation.

Question 17

what is cellular respiration

Answer 17

when organic fuels like glucose are broken down using an electron transport chain

Question 18

explain why ruminant metabolism is compicated

Answer 18

Whilst the plant material that ruminants eat is around 75% carbohydrate, this carbohydrate is typically complex polysaccharides, primarily cellulose (most abundant), hemicellulose, pectins, fructans and starches. The complex carbohydrates are held intracellularly or in the plant cell wall. As such, they can only be accessed by fermentation by the rumen biota. There is very little breakdown into glucose and most of the glucose present is used by the rumen microflora as a substrate. Very little glucose is produced or absorbed by digestion in ruminants (<10%). Instead, VFAs (volative fatty acids or short-chain fatty acids) are produced in the GI by microbial fermentation of the polysaccharides.

The volatile fatty acids (VFA) including acetate, propionate and butyrate are produced in large amounts through ruminal fermentation and are important for providing over 70% of the energy supply in ruminants. They are rapidly absorbed through the rumen epithelium and are often metabolised by the ruminal or large intestinal epithelium before reaching the portal blood. Most of the butyrate is converted to ketone bodies or CO2 by the epithelial cells. Although species differences exist, acetate is used principally by peripheral tissues, especially fat and muscle.

Propionate is largely converted to glucose and is responsible for producing 50% to 60% of the glucose. Propionate, enters into the liver via portal vein to generate energy through the TCA cycle. Propionate is one of the key VFAs and is considered an important glucose precursor. In the hepatocytes propionate can be converted through several steps (first, propionyl CoA which requires biotin then into, Methylmalonyl CoA which requires B12) into succinyl-CoA which can insert on the Krebs cycle directly and generates ATP through the same routes as acetyl-CoA.

Question 19

what is resting metabolic rate

Answer 19

measure of the energy required to maintain life (functioning of organs and biological pathways)

Question 20

BMR is affected by which factors

Answer 20

• body size
• age
• sex
• species
• body temp (increasing BMR in fever)
• ambient temp
• thyroid hormone secretion
• pregnancy and lactation
• growth
• genetics
• proportionate to the amount of metabolically active tissue and to lean body mass

Question 21

Energy comes from the breakdown of glucose, fatty acids and amino acids into which compound?

Answer 21

acetyl CoA

Question 22

A chemical reaction which breaks down compounds into constituent parts is known as…..

Answer 22

catabolism

Question 23

Which process is described as the process where ATP is produced due to the transfer of electrons from NADH and FADH2 to oxygen via a series of electron carriers. This takes place in the mitochondria?

Answer 23

oxidative phosphorylation