Bio106

Front 1

Name the three pathways of Vitamin C synthesis

Back 1

Smirnoff Wheeler pathway, myo-inositol pathway, D galacturonate pathway

Front 2

Smirnoff Wheeler Pathway

Back 2

Begins with D-mannose , goes through L-galactose and finishes at L- galactone - 1,4 - lactone.

Thought to be the predominant pathway.

Front 3

Myoinisitol pathway

Back 3

Important in kiwifruit because of the presence of lots of inisitol 1 phosphate. Starts at inisitol 1 phosphate and goes to myoinisitol.

Front 4

D-galacturonate pathway

Back 4

Starts with D-glucose goes to galacturonate and eventually meets up with the Smirnoff Wheeler pathway.

Front 5

What is Vitamin C important for in plants?

Back 5

Plant growth - cell division, vitamin C at the transition between G1 and S phases.

Photosynthesis.

Response to abiotic and biotic stress - neutralisation of ROS free radicals.

Front 6

Ascorbate peroxidase

Back 6

Detoxifies H2O2 produced in chloroplasts.

Ascorbate + H2O2 = 2H2O + DHA

Front 7

Dehydroascorbate acid reductase

Back 7

DHA to ascorbate.

Healthy leaves will have 10% DHA and 90% ascorbate.

Front 8

What is a secondary metabolite?

Back 8

Produced by specific plant species often as anti-feeding or defense compounds. eg: Willow and Saylicylic acid.

Defense against plants, herbivores, bacteria, fungi and insects. Also play a role in fertility attractants.

Front 9

What is an Alkaloid?

Back 9

Organic Nitrogenous bases found mainly in plants and are usually water soluble which allows easy isolation and purification. Poison, narcotics, stimulants and medicines. More than 10000.

Front 10

Caffine

Back 10

Alkaloid. Competitive inhibition of phosphodiesterase leads to increased cAMP = adrenaline release. This then stimulates the CNS which dilates bronchi and relaxes smooth muscle, induces diuresis.

Is also a pesticide and improves memory for pollinators.

Front 11

Theobromine and Theophylline

Back 11

Alkaloid. From the plant theobroma cacao - cocoa plant. Have more diuretic activity ( increased passing of urine) and a good muscle relaxant. Most in dark chocolate.

Front 12

Nicotine

Back 12

Alkaloid - derived from tryptophan. Extremely toxic - 50mg of nicotine will kill. Very powerful insectiside. Not the same as nicotinic acid (vit B3) this lowers cholesterol and triglyceride concentrations by inhibiting their synthesis.

Front 13

Pilocarpine and Histamine

Back 13

Alkaloids - derived from histadine. Pilocarpine - treat dry mouth by stimulating production of saliva and sweat.

Histamine - responsible to allergy response and can be found in tomatoes and pumpkins.

Front 14

Opiates

Back 14

Alkaloid - derived from tyrosine. Sourced from the dried latex of a poppy. Include codeine and morphine which are both analgesics. Have a complex structure. Misuse/ addiction can lead to cardiac or respiratory arrest or coma.

Front 15

Morphine

Back 15

Extremely effective painkiller but also highly addictive. prolonged effects of use affects the amount of neurotransmitter receptors causing chemical dependency.

Front 16

EMS mutagenesis

Back 16

Produces random mutations in the genetic material by guanine alkylation - G-C ultimately becomes A-T which changes the sequence = point mutation.

Front 17

Glucosinolate

Back 17

Derived from glucose contains N and sulfur. Is water soluble. example = Sulforaphane which has anticancer properties and helps treat autism.

Front 18

Palmitic acid

Back 18

No double bonds C16

Front 19

Stearic acid

Back 19

No double bonds C18

Front 20

Oleic acid

Back 20

One cis double bond at C9, C18

Front 21

Linoleic acid

Back 21

Linoleic acid is a omega 6 fatty acid (polyunsaturated) it has 18 carbons and two double bonds at C9 and C12. Abundant in many vegetable oils.

Front 22

Arachidonic acid

Back 22

4 double bonds c20. polyunsaturated. Saturated equivalent is Arachadic.

Front 23

Triglycerides

Back 23

The main storage for of fats - average person has storage for up to 30 days. There are composed of 3 fats that have been esterified to glycerol forming a triglyceride. Carbon chains are in a highly reduced form meaning they do not contain much O2. Very dense energy wise.

Front 24

Phosopholipids

Back 24

Base is phosphotidic acid. C3 has a phosphate group instead. Can have a range of head groups. Phosphitolcholine ethanolamine and serine are the main ones for membranes. Others for different uses and tissues.

Front 25

Free Fatty Acids

Back 25

Are carried by Serum Albumin in the blood stream - can bind up to 4 at a time. Can be directly absorbed by cells. And in the starved state can be generated by the hydrolysis of triglycerides in adipose tissue.

Front 26

Alpha - linoleic acid (ALA)

Back 26

Is an omega - 3 fatty acid (polyunsaturated). Is C18 and has three cis double bonds at C6, C9 and C12. Found in seeds like flaxseed, some nuts and vegetable oils. Essential fatty acid not produce din the body.

Front 27

EPA

Back 27

Omega 3 fatty acid. Has 20 carbons and 5 double bonds. Found mainly in cod liver and other fish oils aswell as seaweed and microalgae.

note that fish cannot produce this oil. Produces compound in our body above C20 like prostoglandins and hormones involved in homeostatis and inflammatory response.

Front 28

Sphinogolipids

Back 28

Comprised of amine-alcohol spingosine to which fatty acids are attatched. example is sphingomyelin which is important in nervous tissue and myelination of nerves (cerebroside -present in the sheaths of nerve fibres). Found in plants and animals.

Front 29

Soaps

Back 29

Result from the saponification of triglycerides with aqueous NaOH. Then precipitated with a metal ion. eg: Ca2+ or Mg2+ etc.

Front 30

Waxes

Back 30

Straight hydrocarbons and wax esters. ie bumblebees, orange roughy, and jojoba plant - seeds and leaves.

Front 31

Glycolipids

Back 31

Sphingosine and fatty acid + glucose or galactose unit. Many are derived from ceramides. Those that contain more than 3 sugars are called gangliosides (1,2 and 3).

Cerebrosides - contain no phosphate.

Front 32

Steroids

Back 32

A group of lipids that have a fused ring structure. of 3 six membered rings and 1 five membered ring. eg: cholesterol which has 27 carbons (4 rings) and is mainly non-polar, sex sterols and other hormones. Insects also use cholesterol in molting - cannot make it though.

Front 33

Ursolic acid

Back 33

Is the white blush found on apples. Is a derivative of Squalene like cholesterol. Is and anti-inflammatory and analgesic.

Front 34

Hopane

Back 34

Part of the membranes of bacteria, also derived from squalene.

Front 35

Bile salts

Back 35

Secreted from the gall bladder to help emulfsify lipids forming micelles which permit soluble enzymes (lipase) to hydrolyse triglycerides to fatty acids and glycerol. Have a hydrophillic and a hydrophobic face which detergent like properties.

Front 36

Short chain triglyceride absorption

Back 36

Can pass directly across the epithelial cells from the gut lumen into the blood stream, where they are then bound and transported by serum albumin.

Front 37

Long chained triglyceride absorption

Back 37

(C16 and above) Bound to fatty acid binding protein, then resesterifed to glycerol in the gut membrane. Then they are secreted into the blood in the form of Chylomicrons which can also be composed of phospholipids and cholesterol.

Front 38

Chylomicrons

Back 38

Are a form of lipoprotein that are rich in triacylglycerols. They travel first in the lymph then into the blood stream. Are assembled in the gut. They get smaller as they travel through the blood stream due to breakdown by lipases.

They are the lowest density form of lipoprotein.

Front 39

lipoprotein structure

Back 39

Have a coating composed of phospholipids, proteins and cholesterol that surrounds the storage area for triglycerides and cholesterol esters. VLDL's are the largest and LDL are the smallest (contain more cholesterol) and the most dense.

Front 40

HDL

Back 40

Do not contain much cholesterol in either the coating or in the centre. Are so called "good" cholesterol.

Front 41

Liberation of Fatty acids

Back 41

In response to the starved state: A hormone binds to a receptor on cell which activates adenyl cyclase. This in turn activates cAMP which activates protein kinase. This protein kinase activates triacylglycerol lipase and that breaks down triacylgylcerol into 3 fatty acids and glycerol.

Front 42

Fatty acid activation

Back 42

To make fatty acids more soluble they must be converted to their CoA- thioester form.

A thioester bond is formed between the carboxyl group of the FA and the thiol CoA-SH using the enzyme acyl CoA synthetase. The process requires 2 ATP.

Front 43

Carnitine Shuttle

Back 43

Acyl-CoA cannot cross the inner mitochondrial membrane so the acyl group is transferred to the carnitine shuttle and the CoA travels back out into the cytosol. Acyl- carnitine crosses the membrane and acyl is transferred back to CoA-SH.

Carnitine Palmitoyl transferase (CPT-1) has specifity for acyl groups between 14 and 18 Cs long.

Front 44

B oxidation

Back 44

A series of four reactions that cleaves 2 carbon units from the carboxyl end of fatty acids.

Front 45

Unsaturated fatty acid B oxidation

Back 45

Because they have a double bond require an extra enzyme. Most acids have cis double bonds and these must be changed to trans double bonds to undergo further B oxidation. This is done using an isomerase.

However missing a step means less energy yielded.

Front 46

How do camels go without water?

Back 46

The oxidation of fatty acids generates alot of water as hydrocarbons break down into CO2 and H2O. Camels store fat in their humps and this is how they stay hydrated.

Front 47

ketone bodies

Back 47

In starvation there may not be high enough levels of oxaloacetate to react with acetyl CoA. Instead acetyl-CoA can be converted to ketone bodies such as acetone, acetoacetone and B-hydroxybutarate. They are formed primarily by liver mitochondria and can even be used by the brain. we can go into a metabolic state ketosis.

Front 48

Ketosis

Back 48

Acidic blood and happens when two acetyl CoAs followed by a third form B- hydroxy B- methylglutaryl.This can then be broken down into acetone or acteoacetone which are water soluble and readily transported in the blood leading to acidic blood.

Front 49

Respiratory Quotient

Back 49

Is 1 in the post-prandial state/fed state. And is found by dividing the number of CO2s produced by the number of O2s that go into the oxidation.

Oxidation of glucose is 1, triglycerides is 0.71and protein is 0.82.

Front 50

When would we want to re-synthesize fatty acids?

Back 50

When there is a surplus of glucose acetyl - CoA can be used to resynthesize fatty acyl - CoAs. This usually occurs in the mammary glands or adipose tissue.

Front 51

Acetyl CoA to Malonyl CoA

Back 51

Is a carbon fixation reaction that is catalysed by acetyl-CoA carboxylase. Carboxylase is made up of 3 proteins: biotin carboxylase, biotin carrier protein and carboxylase transferase.

Note that malonyl CoA strongly inhibits Carnitine to prevent a futile cycle.

Front 52

Stage I fatty acid synthesis

Back 52

CoA-SH removed and replaced with ACP-SH in both malonyl and acetyl. Acetyl forms a thoiester bond with a phosphonthethiene cofactor. The acyl group is then passed to Ksase where it is linked via a thioester bond to a cystiene SH group.

Malonyl is attatched to an ACP then loses a CO2 and joins with modified acetyl- Cystine-SH to give Acetoacetyl ACP.

Front 53

Stage II Fatty Acid synthesis

Back 53

Reduction hydration, reduction to give Butaryl ACP. Using two reductase and dehydratase. In both reduction reactions NADPH is oxidised to NADP+.

Front 54

Stage III Fatty Acid synthesis

Back 54

Malonyl ACP can continue to be added to Butaryl ACP through the cycle of reduction dehydration and reduction. Can continue up to 16C which gives Palmitate. All occurs in cytosol.

Front 55

Long chain and unstaturated Fatty acid biosynthesis.

Back 55

Elongation of the acyl group occurs in both the mitochondria and the ER and uses acetyl CoAs, Malnoyl CoAs and NADPH.

Fatty acyl-CoA desaturase is an animal enzyme that catalyzes cis bond formation in stearic and palmitic acid. occurs in ER.

Front 56

Leptin

Back 56

Responsible for appetite suppression.

Front 57

Perilipin

Back 57

Binds to lipid droplets in adipose cells and stops deposistion of lipid. In a mutation these lipids are mobilized and we cannot keep fat on. Leptin + perilipin = a relatively normal mouse.

Front 58

Triacylglyceride synthesis

Back 58

Glycerol-3-phosphate accepts acyl chains from acyl-CoAs using transferase. 2 additions make phosphotidic acid and then phosphate is removed with hydrolysis and a third acetyl-CoA added = triacylglyceride.

Front 59

Phosphoacylglycerols

Back 59

Same up until phosphoditic acid and then one of the three esterified hydroxyl groups is replaced with phosphate. Phospahte group can be esterified to something like choline or inositol to form a phosphotidyl ester.

Front 60

Isoprenoid synthesis I

Back 60

Acetoacetyl-CoA with the addition of another acetyl-CoA gives HMG-CoA using a sythetase. This is then converted to mevalonic acid using HMG-CoA reductase, we have the reduction of thioester bond to give a primary alcohol.

Front 61

HMG-CoA Reductase

Back 61

Major regulatory enzyme in cholesterol biosynthesis, that is controlled hormonally by insulin and glucagon. Transcription and translation can be suppressed by the presence of cholesterol in cells. Major target for drugs such as statins that are taken to lower blood cholesterol.

Front 62

Isoprenoid synthesis II

Back 62

Mevalonate is pyrophosphorylated using two mole of ATP. ATP driven carboxylation and B elimination of phosphate ion gives IPP. Isomerization of double bond gived DMAPP. DMAPP is then coupled to two IPPs to give farnesyl pyrophosphate. (C15) Two of these are added together with the elimination of two elcetrons to give squalene (C30).

Front 63

Isoprenoid synthesis III

Back 63

Mainly in liver. Oxidosqualene which is the most complex single reaction enzyme known changes linear squalene 2,3 epoxide into complex multiple ring structures, eventually leads to cholesterol and cholesterol esters.