Structure and Role of Lipids

Question 1

What is a lipid

Answer 1

Heterogeneous group of water insoluble (immiscible) molecules that are soluble in non polar solvents

Question 2

Which lipids are the major source of energy

Answer 2

TAG

Question 3

Which lipids are involved in cell signaling

Answer 3

DAGs

Question 4

What are fatty acids

Answer 4

Amphipathic long chain hydrocarbons with a carboxylic acid head group

Question 5

How are fatty acids classified

Answer 5

Based of number of C atoms and whether the FA is saturated

Question 6

What are cis-conformation fatty acids

Answer 6

Fatty acids with functional groups on same side resulting a a kink

Question 7

What are trans conformation fatty acids

Answer 7

Fatty acids with functional groups on opposite sides resulting in a linear fatty acid

Question 8

What is the alpha carbon

Answer 8

The first one next to a functional groups

Question 9

How are free fatty acids transported in blood

Answer 9

Non-esterified form conjugated to albumin

Question 10

How long are short chain fatty acids

Answer 10

2-6 carbons

Question 11

How long are medium chain fatty acids

Answer 11

6-12 carbonss

Question 12

How long are long chain fatty acids

Answer 12

12-21 carbons

Question 13

How long are very long chain fatty acids

Answer 13

21+ carbons

Question 14

What are essential fatty acids

Answer 14

Fatty acids that we are unable to synthesise effectively and have multiple unsaturated C=C bonds

Question 15

What are the two key essential fatty acids

Answer 15

w-3 fatty acid/ alpha linolenic (18:3)
w-6 fatty acids/ linoleic acid (18:2)

Question 16

What are the functions of the essential fatty acids

Answer 16

Precursors for many biomolecules and for membrane stability (eicosanoid and endocannabinoids/ signalling molecules)

Question 17

What are glycerolipids

Answer 17

Lipids with a glycerol backbone esterified to 1,2 or 3 fatty acids (MAG, DAG, TAG)

Question 18

What are glycerophospholipids

Answer 18

Polar, amphipathic compounds based on DAGS with a charged head group (phosphate) which can be linked to other functional groups

Question 19

What causes glycerophospholipid derivatives

Answer 19

Large range of head groups attached to phosphate so have distinct biological properties

Question 20

What are sphingophosphlipids

Answer 20

Phospholipids where the backbone is the amino alchemical sphingosine and has a long chain hydrophobic chain complexed to a FA by an amide linkage to produced ceramide, the ceramide is the esterified to a choline head group (phosphocholine) (to produce Sphingomyelin)

Question 21

What are glycoshingolipids

Answer 21

Have a ceramide backbone but no phosphate linkage e.g. cerebrosides and gangliosides

Question 22

How are triacylglycerols produced

Answer 22

Addition do new acyl group to DAG by diglyceride acyltransferase (DGAT)

Question 23

Where is the major store for triacylglycerols

Answer 23

Cytoplasm of white adipose tissue

Question 24

How much energy do triacylglycerols yield

Answer 24

6x more than equivalent masses of protein ans carbohydrates

Question 25

How long can triacylglycerols be stored

Answer 25

Weeks (long term)

Question 26

What are the two types of fat stores

Answer 26

White and brown adipose tissue

Question 27

How is TAGS stored in white adipose tissue

Answer 27

Fat stored as a single droplet (energy store)

Question 28

How is TAGs stored in brown adipose tissue

Answer 28

Fat stored as multiple droplets with more mitochondria for body temp maintenance

Question 29

What are sterols/steriods

Answer 29

Biologically active compounds with four rings arranged in a specific molecular configuration

Question 30

What is the function of sterols/steriods

Answer 30

Component of cell membrane to alter fluidity Signalling molecules

Question 31

What are examples of steroids

Answer 31

Cholesterol, testosterone, dexamethasone

Question 32

Which fat soluble vitamins are involved in cell signaling

Answer 32

A and D

Question 33

Which lipids are components of cell membranes

Answer 33

Phospholipids/ glycerophospholipids, sterols, sphingolipids

Question 34

Which lipids are involved in cell signaling

Answer 34

Sterols, DAG, phosphatidylcholine (glycerophospholipid derivative)

Question 35

What are the function of lipids in cell membranes

Answer 35

Separation of different fluid compartments (e.g. organelles) Selective transport Signal transduction

Question 36

What % of membranes are lipids

Answer 36

40-60%

Question 37

How is the packing of lipids in cell membrane affected by amount of unsaturation

Answer 37

Double bonds cause more kinks push lipids apart making the membrane looser and more fluid (Liquid disordered/ ld) Fewer double bonds so less kinks and less fluid or liquid ordered /lo

Question 38

What are lipid rafts

Answer 38

The liquid ordered regions of membrane that are involved in endocytosis, cell polarity and cell signalling transduction

Question 39

What % of membrane lipid is cholesterol

Answer 39

30%

Question 40

What is the function of cholesterol in membranes

Answer 40

Packs in between lipids to improve packing and contribute to stability of membrane by regulating fluidity through degree of packing

Question 41

Why do animal cells not have cell walls

Answer 41

Cholesterol maintains integrity of membrane with flexibility

Question 42

Which part of membranes are cholesterol rich

Answer 42

Lipid rafts