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Biomolecules > Lipids > Flashcards

Lipids Flashcards

1
Q

Lipids- Key points

A
  • defined as water insoluble due to their Hydrophobic (non-polar) nature.
  • Many lipids e.g. excluding triglycerides are amphipathic, meaning they possess both hydrophilic (polar) and hydrophobic (non-polar) regions.
  • Monomer = fatty acid
    polymer= lipid
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2
Q

Main functions of lipids.

A
  • energy storage, as triglycerides store energy efficiently in fat tissues.
  • Function as signalling molecules, such as hormones (e.g., steroids) and lipid-derived messengers (e.g., prostaglandins), which play critical roles in regulating physiological processes.
  • insulation and protection, e.g. myelin sheaths around nerve fibres.
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3
Q

where is most adipose tissue (consisting of the specialised cells adipocytes).

triacylglycerols coalesce as fat droplets. where are these found?

A

most adipose tissue occurs just under the skin and in the abdominal cavity.

These droplets are sometimes seen near mitochondria in cells that rely on fatty acids for metabolic energy.

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4
Q

what is the name given to the class of lipids that are not derived by Fatty acids? List them (3)

A

Isoprenoids

  • Steroids
  • Lipid vitamins
  • Terpenes
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5
Q

what are the 5 classes of fatty acids.

Everyone, Goes, To, Wendys, Shop

A
  • Eicosanoids
  • Glycerophospholipids - cell membrane form
  • Triacylglycerols (OR triglycerides) - fat storage
  • Waxes (bee/ear wax)
    -Sphingolipids (cell membranes)
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6
Q

Examples of Phospholipids

A

Phosphatidyl-ethanolamines

Phosphatidyl-serines

Phosphatidyl-Choline

Phosphatidyl-inositols

Other Phospholipids

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7
Q

Examples of Glycerophospholipids

A

Cerebrosides
Gangliosides

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8
Q

Revise Diagram Showing different types Lipids

A

PP

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9
Q

Key points of isoprenoids, waxes, steroid hormones, eicosanoids, gangliosides.

add function of isoprenoid

A

Isoprenoid- five carbon- FUNCTION

Waxes in cell walls, exoskeletons, and skins protect the surfaces of
some organisms.

steroid hormones regulate and integrate a host of metabolic activities in animals.

eicosanoids participate in the regulation of blood pressure, body temperature, and
smooth-muscle contraction in mammals.

Gangliosides and other glycosphingolipids
are located at the cell surface and can participate in cellular recognition.

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10
Q

How many carbon bonds do most abundant fatty acids have.

A

12-20 carbon atoms.
even numbers only e.g. 12, 14, 16, etc

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11
Q

How do you differ fatty acids?

A
  • in the length of their hydrocarbon tails
  • the number of
    carbon–carbon double bonds,
  • the positions of the double bonds in the chains,
  • the number of branches.
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12
Q

what do all fatty acids have?

A

All fatty acids have a carboxyl group (—COOH) at their “head.” The pK
a of this group is about 4.5 to 5.0 so it is ionized at physiological pH (7.37 and 7.42).
(—COO-).

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13
Q

Relationship between hydrocarbon tails and melting points.

A

As the lengths of the hydrocarbon tails increase, the melting points of the SATURATED fatty acids also increase. The number of van der
Waals interactions among neighboring hydrocarbon tails increases as the tails get longer so more energy is required to disrupt the interactions.

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14
Q

Melting points of saturated and unsaturated fatty acids.

A

unsaturated fatty acids have a much lower melting point, they have a shorter hydrocarbon chain e.g. why butter is solid in room temperature and olive oil is liquid.

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15
Q

Structure of lipids.
+ Display formula

A

BOOK

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16
Q

which part of the lipids are saturated/ unsaturated.

A

BOOK

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17
Q

difference between cis and trans UNSATURATED fatty acid.

A

Cis is most common naturally occurring in both saturated and unsaturated.

Trans fats are often industrially created during hydrogenation and are less common in nature.

cis unsaturated fatty acids
- the hydrogen atoms on either side of the double bond are on the same side of the carbon chain= kink or bend in the fatty acid chain, which prevents the molecules from packing closely together= lower melting point and are typically liquid at room temperature (e.g., olive oil)

Trans Unsaturated Fatty Acids
- the hydrogen atoms on either side of the double bond are on opposite sides of the carbon chain = a straighter chain, similar to saturated fatty acids, allowing the molecules to pack more tightly together= higher melting point and can be solid or semi-solid at room temperature.

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18
Q

what are free form fatty acids (FFAs)?

How are they formed

what can they do?

A

unesterified fatty acids resulting from the breakdown of triglycerides or phospholipids. as a result FFAs can provide rapid energy ,
- they are readily available for cellular metabolism and do not to be broken down from complex molceules.

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19
Q

How are free form fatty acids found while present in the body.

what can high concentration of free fatty acids cause?

A

Low concentration of free fatty acids due to their rapid metabolism and incorporation into other lipid forms.

high concentrations of free fatty acids could disrupt membranes.

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20
Q

How doe most fatty acids in biological systems exist?

A

Most fatty acids in biological systems exist as part of larger molecules, primarily through the formation of ester bonds, where the terminal carboxyl group of a fatty acid reacts with an alcohol group, such as that found in glycerol.

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21
Q

what 3 fatty acids are most abundant in mammalian cells? Include MOLECULAR FORMULAS! BE ABLE TO RECOGNISE !(BOOK)

(BOOK) Key points about stearate and palmitate
- hydrocarbon tail
- melting point

key points about oleate and linoleate.
- hydrocarbon tail
- bonds
- melting points

A

Oleate (18:1) - oleic acid
Palmitate (16:0) - palmitic acid
Stearate (18:0) - stearic acid

CHECK!! table for numbers

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22
Q

Some fatty acids are essential. what does this mean?

A

They cannot be synthesised.

Essential fatty acids (EFAs) are types of polyunsaturated fats that the body cannot produce on its own, meaning they must be obtained through diet.

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23
Q

what are the examples of essential fatty acids. Including carbon/bond numbers) + delta and molecular drawings.

A

Lionoleate
Linolenate
arachidonate

BOOK

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24
Q

What can fatty acids be modified into? what are they involved in?

A

Fatty acids, particularly those derived from arachidonic acid, can be modified to form important chemical mediators involved in inflammation and clotting.

A chemical mediator: a substance that helps to transmit or regulate biological signals in the body, typically by influencing the behavior of cells and tissues.

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25
Q

Examples of fatty acids that have been modified (Fatty acid derivatives).

Post The Letter

A

-Prostaglandins
-Thromboxanes
- Leukotrienes
BE FAMILAIR WITH STRUCTURES.

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26
Q

Triacylglycerols- Key points (4)

A
  • (Triglycerides) consist of three fatty acyl residues (fatty acids) esterified to a glycerol backbone.
  • partially Amphipathic (both hydrophobic and hydrophilic components)
  • Can form cell membranes
  • they are primarily stored in the form of fat droplets within the cell, particularly in adipocytes (fat cells).
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27
Q

what is the basic structure of Triacylglycerol’s + the glycerol molecule they are derived from.

A

BOOK- drawing

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28
Q

what class do phospholipids belong to?

A

Glycerophospholipids

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29
Q

what is the basic structure of phospholipid.+ including DRAWING.

A
  • glycerol backbone
  • Two fatty acyl groups
  • phosphate group
  • head group (polar)
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30
Q

Examples of Phospholipids. Names and Drawings

A

BOOK

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31
Q

What does each group of phospholipids (choline, serene,etc) have?

A

The same group but different tails. These can be analysed using the enzyme phospholipases(FOUND IN SNAKE VENOM)- they break down phospholipids.

e.g. Red blood cells contain at least 21 types of phosphatidylcholine.

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32
Q

Name the different types of phosphoLIPASES used to identify different tails.+ DIAGRAM IN BOOK.

A

A1- found in digestive system
A2- found in pancreatic juice and snake venoms
C- liberates diacylglycerol
D-converts phospholipids to phosphatides.

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33
Q

Difference between Phospholipids and triglycerides.

A

PHOSPHOLIPIDS
structure : 2 fatty acid tails, glycerol backbone, phosphate group with a polar head.

Amphipathic: both hydrophobic and hydrophilic parts. (CHECK)

Function: primarily forms cell membranes, creating a barrier that separates the inside of cell from the outside.

Role (in membranes) : essential for membrane fluidity and structure; supports membrane proteins and participates in signalling.

Bilayer formation: self-assembles into lipid bilayers in aqueous environments.

TRIGLYCERIDES

Structure: 3 fatty acid tails, glycerol backbone.

Hydrophobic: entirely hydrophobic, with no polar head group.

Function: primarily as an energy storage molecule in adipose tissue.

Role (in energy): provides a concentrated source of energy; can be broken down into fatty acids and glycerol for
energy use.

SUMMARY: Phospholipids are key components of cell membranes, while triglycerides are primarily energy storage molecules.

34
Q

what are plasmalogens?
- component of what?
- found where?

A

Class of Phospholipids

Important components of cell membranes

Found in the CNS, bacterial membranes, peripheral nerve, heart and muscle tissue.

35
Q

Linkage in plasmalogens? + DIAGRAM

A

Plasmalogens have a unique vinyl ether bond at the sn-1 position of the glycerol backbone instead of a standard ether or ester bond.

36
Q

what compounds/head groups are esterified to the phosphate group in plasmalogens.

A

The phosphate group in plasmalogens is esterified to head groups like ethanolamine or choline- contributes to their role in cell membrane dynamics and signaling.

37
Q

molecular formula of head groups ethanolamine and choline.

A

BOOK

38
Q

Sphingolipids - key points

class? role?
abundance?
high conc
low conc

A
  • A class of lipids- roles in cell membrane structure and function and signalling pathways.

Second most abundant in plant and animal membranes.
- high concentration in CNS.
- Not generally present in bacteria.

39
Q

what is the backbone of sphingolipids. + DIAGRAM

A

Backbone is Sphingosine
- unbranched C18 alcohol
- trans double bond (C4-C5)
- Amino group at C2
-Hydroxyl groups at C1 and C3.

40
Q

what is ceramaide?
how is it linked to sphingosine.
+ Diagram/formula

A

Type of sphingolipid

Fatty acid group linked to sphingosine via amide bond.

41
Q

what are gangliosides? (4)
- What is it?
- Hoe much ?
- where
- role

A

more complex glycosphingolipid e.g. GM2.

More than 60 varities.

Present on cell
surfaces (hydrocarbon
chains embed in
membrane)

role in cellular functions, particularly the nervous system.

42
Q

Structure of gangliosides.
-backbone
- fatty acid
- carbohydrate

A

Sphingolipid Backbone: Built on a sphingosine backbone.

Fatty Acid: Contain one fatty acid linked by an amide bond, forming a ceramide.

Carbohydrate Moiety: have complex oligosaccharide chains (3-10 monosacccharides) with one or more sialic acid residues, contributing to their unique properties.

43
Q

Functions of gangliosides.

A

Cell Signaling: They regulate cellular processes like growth,
differentiation, and apoptosis.

Cell Recognition: They facilitate cell-cell recognition and communication, aiding in tissue development and immune responses.

Neuronal Function: In the nervous system, they are crucial for synaptic transmission and may enhance neuroprotection.

44
Q

Effects of defects in lipid metabolism and lipid biosynthesis.

A

can range from minor to lethal.
e.g. fatty liver disease, cardiovascular, neurological disorders, skin disorders.

45
Q

Isoprenoids -Steroids -key points
- location
- isoprenoid relation
- ring structure
- Biosynthesis

A

lOCATION:
found in eukaryotic (and some bacterial) membranes. key components that influence membrane fluidity and stability.

ISOPRENOID RELATION:
steroids are a type of Isoprenoid so their structure is related to isoprene 5 carbons (C5H8) (WHICH IS THE BUILDING BLOCK OF ISOPRENOID COMPOUNDS).

FUSED RING STRUCTURE:
Steroids contain four fused rings: three six-membered carbon rings and one five-membered carbon ring- arrangement is critical for their biological activity.

BIOSYNTHESIS:
Steroids are derived from squalene (linear intermediate=straight chain), a triterpene formed through the assembly of multiple isoprene units. Squalene is then converted through a series of enzymatic reactions to produce various steroid molecules.

46
Q

Be able to identify a squalene and different steroid structures. + MOLECUALR formula of isoprene.
POWERPOINT

A

BOOK

47
Q

what is cholesterol vital for? Where is it NOT PRESENT.

A
  • Vital for eukaryotic membranes fluidity.
  • absent in prokaryotes, protists and fungi.
48
Q

what does fungi have instead of Cholesterol.

A

Ergosterol - similar role to cholesterol.

49
Q

structure of Cholesterol- what can you use to identify them.
4

A
  • its a sterol (has a OH at C3)-(makes cholesterol amphipathic)
  • has a hydrocarbon side chain length
  • has 3 methyl (-CH3) groups at C10, C13 and C17)
  • has one double bond between carbons 5 and 6 in the steroid ring structure, which affects its rigidity and fluidity within cell membranes.
50
Q

what is fatty acid synthesis?
what is it attached to?

A

Repetitive addition of two-carbon units to a growing hydrocarbon chain. This growing chain is attached to acyl carrier protein (ACP).

51
Q

Role of ACPs in fatty acid synthesis?

A

serves as a molecular “carrier” that facilitates the transfer and elongation of the fatty acid chain during biosynthesis.

52
Q

Where does Fatty acid synthesis occur?

A

in the cytosol where its hydrophobic so ACP shields the fatty acids.

53
Q

where does fatty acid syntehss occur in adult mammals?

A

liver cells and adipocytes

54
Q

what are the three steps of fatty acid synthesis?

A
  1. Production of acetyl ACP (2C) and malonyl ACP (3C).
    Acetyl CoA to Acetyl ACP
    Malonyl CoA to Malonyl

via the Enzyme = Acetyl/Malonyl-transacylase.

  1. Initiation – condensation of acetyl and malonyl groups to produce 4 carbon (C4) precursor and CO2.
  2. Elongation – acyl group on ACP extended by C2 units from malonyl ACP.

Condensation: Acetyl-CoA and malonyl-CoA combine, releasing CO₂.
Reduction: NADPH is used to reduce the beta-keto group to a hydroxyl group.
Dehydration: Water is removed, forming a double bond.
Second Reduction: The double bond is reduced again by NADPH, yielding a saturated acyl group.

55
Q

Fatty acid extension

A

Produces 16- 18- carbon fatty acids.

limited by the size of enzyme active site.

Extended further by elongases.

56
Q

what is the intermediate involved in the synthesis of triacylglycerol and phospholipids

A

Phosphatidate

57
Q

what is esterification

A

Esterification is a chemical reaction in which an acid (typically a carboxylic acid) reacts with an alcohol (OH group) to form an ester and water

58
Q
A

Formation of Glycerol-3-Phosphate: The backbone, glycerol-3-phosphate, is formed from either glucose (via glycolysis) or glycerol.

Addition of Fatty Acids: Fatty acids are activated to form acyl-CoA.

Esterification: Two fatty acyl-CoA molecules are added to glycerol-3-phosphate to form phosphatidic acid.

Dephosphorylation: Phosphatidic acid is dephosphorylated to form diacylglycerol (DAG).

Final Esterification: A third fatty acyl-CoA is added to DAG to form triacylglycerol (TAG).

59
Q

Phospholipid Synthesis.

A

Formation of Glycerol-3-Phosphate: glycerol-3-phosphate id formed by glucose or glycerol

Addition of Fatty Acids: Fatty acids are activated to form acyl-CoA.

Esterification- Two fatty acyl-CoA molecules are added to glycerol-3-phosphate to form phosphatidic acid.

Head Group Attachment:

Phosphatidic acid can be converted to CDP-diacylglycerol by removing a phosphate group.

Various head groups (such as serine, ethanolamine, or choline) are added to form different phospholipids like phosphatidylserine, phosphatidylethanolamine, or phosphatidylcholine).

60
Q

Summary of synthesis of Triacgycerol and phospholipids

A

both pathways start with glycerol-3-phosphate and involve the addition of fatty acids, but they diverge in the final steps where either additional fatty acids or specific head groups are added.

61
Q

Sphingolipid Synthesis

(5)

A

Serine (C3) condenses with palmitoyl-CoA
to give 3-ketosphinganine.

  • 3ketosphinganine is Reduced to sphinganine using NADPH as a reducing agnet.
  • Fatty acyl group from acetyl-CoA is transferred to sphingosine to give N-acylsphinganine (dihydroceramide)- enzyme involved= dihydroceramide synthase.
  • Desaturated to give ceramide- involves the introduction of a double bond at C4 and C5, converting dihydroceramide to ceramide via the enzyme dihydroceramide desaturase.
  • Ceramide is the source of all other
    sphingolipids (sphingomyelin, glycophingo
    lipids and gangliosides).
62
Q

Cholesterol (sterol) synthesis- flow chart in BOOK.

A

Acetate (C2) to Isoprenoid (C5) to Squalene (C30) to Cholesterol (C27).

1) Acetyl CoA is produced from carbohydrates fats and proteins.

2) mevalonate pathway:
- Acetyl-CoA condenses to form acetoacetyl-CoA.

  • acetoacetyl-CoA combines with another Acetyl-CoA to form HMG-CoA.
  • HMG-CoA is converted to mevalonate by HMG-CoA reductase using NADPH as a reducing agent.

3) via a series of phosphorylation reactions, followed by decarboxylation, Mevalonate is converted to isopentyl diphosphate (isoprenoid units).

4) isopentyl diphosphate condenses to squalene.

5) Squalene cyclizes to produce lanosterol- cataylsed by squalene monooxygenase.

6) Via several demethylation and reduction , Lanosterol is converted into cholesterol- These reactions involve the removal of methyl groups and the introduction of double bonds and hydroxyl groups, facilitated by various enzymes in the ER.

63
Q

what enzyme is involved in the regulation of Cholesterol synthesis.

what can it be used for?

A

HMG-CoA reductase.

HMG-CoA reductase is the target of statin drugs, which are used to lower cholesterol levels.

64
Q

what are the regulation mechanism is cholesterol synthesis.

A

Regulation Mechanisms:

Phosphorylation: The activity of HMG-CoA reductase is influenced by phosphorylation, which can either activate or inhibit the enzyme.

Transcriptional Control: The gene expression of HMG-CoA reductase is regulated based on cellular cholesterol levels.

Degradation Control: The enzyme’s degradation rate is also adjusted in response to cholesterol levels, ensuring balance.

65
Q

what is lowering serum cholesterol level associated with?

A

with a reduced risk of coronary heart disease.

66
Q

what are the competitive inhibitors of HMG-CoA reductase?

A

STATINS.

67
Q

LDL and HDL cholesterol

A

LDL- bad cholesterol
HDL- good cholesterol

68
Q

what are statins used for ? what is its downside?

A

used for the treatment of hypercholesterolemia (high cholesterol levels) to lower LDL cholesterol and reduce the risk of cardiovascular diseases.

Downside: inhibition of HMG-CoA reductase also reduces the production of mevalonate, which is a precursor molecules, such as ubiquinone (coenzyme Q10)

Low Ubiquinone = low energy production= muscle pain/weakness

69
Q

why are fatty acids degraded?

A

Fatty acids store energy, so to get that energy they need to be broken down are degraded to generate energy and maintain metabolic balance.

70
Q

what is the degrading pathway for fatty acids and how does it work?

A

Fatty Acid B-oxidation.

1) Each cycle of β-oxidation removes two-carbon (C2) units from the fatty acid, which is then transferred to coenzyme A to form acetyl-CoA.

2) Acetyl-CoA enters the citric acid cycle (Krebs cycle) for energy production.

3) The remaining chain after the release of acetyl-CoA continues through further rounds of β-oxidation until the entire fatty acid is broken down into multiple acetyl-CoA units (this is called Oxidative pathway).

71
Q

Additional requirements for odd-numbered and unsaturated fatty acids.

A

Odd-numbered fatty acids produce one propionyl-CoA (a three-carbon unit) during degradation, which can be converted into succinyl-CoA to enter the citric acid cycle.

Unsaturated Fatty Acids: Additional enzymes are required to handle double bonds.

72
Q

Fatty acid B-Oxidation.
1) Location
2) Activation
3)Transport
4) Energy Production
5) Carbon Utilization

A

Occurs in the mitochondria of eukaryotic cells.

by combining with coenzyme A, forming acyl-CoA.

Acyl-CoA is transported across the mitochondrial membrane through a reversible reaction with carnitine.

β-oxidation is a vital source of ATP for energy generation.

The carbon units generated can also be used in the synthesis of amino acids.

73
Q

what are ketone bodies produced by and when?

A

produced from Acetyl-CoA when carbohydrate are scarce, providing an alternative energy source.

74
Q

where are ketone bodies synthesized?

A

in the liver of mammals.

75
Q

what the role of ketone bodies?

A

Ketone bodies serve as a major source of energy for peripheral tissues, especially during fasting or prolonged exercise.

76
Q

property of Ketone bodies

A

They are considered “water-soluble lipids,” allowing them to easily circulate in the bloodstream.

77
Q

ketone bodies during starvation.

A

Ketone bodies are produced in large amounts during starvation, helping to provide fuel for brain cells, which can utilize them when glucose is limited.

78
Q

what reaction can convert phosphatidylethanolamine to phosphatidylcholine

A

Mythlation

79
Q

What are the two lipid (membrane) phases.

Tm= melting temperature

A

Gel phase (T<Tm)
- lipid molecules are tightly packed.
- fatty acid chain extend and ORDERED (Low chain disorder)
- Thick bilayer
- crystalline structure= less permeable and less fluid membrane.

Liquid phase (T>Tm)
- lipid molecules are loosely packed and move freely.
- Fatty acid chains are DISORDERED and flexible= liquid state
-thin bilayer
- more permeable and fluid membrane.

80
Q

what happens when you put goldfish into cold water?

A

Induction of More Unsaturated Acyl Chains:

Low Temperatures: When the water temperature drops, goldfish respond by incorporating more unsaturated fatty acids into the lipid membranes of their cells, particularly in vital organs such as the intestines and the brain. Unsaturated acyl chains have one or more double bonds, which create kinks in the fatty acid chains.

Mechanism: This adaptation helps to maintain membrane fluidity despite the cold. The kinks/bends prevent the lipids from packing too closely together, thus keeping the membrane more fluid and functional.

Preservation of Membrane Fluidity:
Adaptation Benefit: By adjusting the composition of their membranes to include more unsaturated fatty acids, goldfish can maintain proper membrane fluidity even in colder environments. This physiological flexibility ensures that their cells and tissues continue to function effectively, which is vital for survival in fluctuating temperatures.

81
Q

role of cholesterol in membrane phases?

Addition of cholesterol to a:

  • solid phase (gel phase) + Mechanism
  • liquid phase (fluid phase) + mechanism
A

Addition of cholesterol to solid
phase disrupts interactions of acyl
chains= reduces order and rigidity= less crystalline= More fluid.

Mechanism= cholesterol inserts itself between fatty acids chains of the phospholipids. This intercalation prevents the acyl chains from packing tightly, thus enhancing fluidity.

  • Addition of cholesterol to liquid
    phase= increases ORDER of acyl chains= stabilise membrane.

mechanism:
Cholesterol’s rigid ring structure interacts with the acyl chains, restricting their movement and brings order.

82
Q

Polar head group and Intercalation.

A

Cholesterol has a small polar head group (OH group)which aligns with the polar head groups of the phospholipids. This helps cholesterol to interrogate into the membrane structure.

Biomolecules (9 decks)

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