Lipid Concepts Flashcards

Question

What **properties** lead to a **fatty acid** having a **higher melting point**?

Answer 1

- **Unsaturated** / less double bonds. - **Longer** hydrocarbon chain. ## Footnote An **unsaturated** fatty acid is **straight-chained**, and so molecules pack together more efficiently to increase intermolecular attractions (VdWs) along the hydrocarbon chains. **Longer chains** mean **greater surface area** for intermolecular attractions (VdWs).

Answer 2

**True** ## Footnote This is because they have a **hydrophilic head** as well as their **hydrophobic tail**, however the hydrophobic tail dominates.

Answer 3

A reaction that converts **esters** (can be derived from fatty acids) into **soap** when combined with an **aqueous alkali** (e.g. NaOH).

Answer 4

**Free fatty acids** are **toxic** and disrupt the **pH** due to being weak acids.

Answer 5

'**Backbone structures**' containing **OH** groups, such as... - **Alcohol** - **Glycerol** - **Sphingosine** - **Cholesterol** - **Amino acids**

Answer 6

**Fatty acids** that **cannot** be **synthesised**, but are **required** for certain **biochemical processes**, and so must be obtained via **diet**. ## Footnote For example, **linoelic acid** (18 : 2 , Δ^9,12), also known as **ω-6** as the first double bond occurs at the 6th carbon when you count from the ω end. Similarily ω-3 (or **α-linoelic acid** , 18 : 2 , Δ^6,9,12) is named for the same reason.

Answer 7

**Esters** made up of a **polar glycerol** 'head' and 1-3 **non-polar fatty acid chain(s)**. ## Footnote Each of the **fatty acid chains** may be different lengths/types to each other. The naming is based on the number of chains (**mono**- , **di**- , **tri**- ).

Answer 8

**Triglyceride** ## Footnote (i.e. **fat**)

Answer 9

- **Neutralises** fatty acids. - Major **long-term energy store** in animals.

Answer 10

**True** ## Footnote This is simply because there is such a large variety of fatty acid chain types/lengths.

Answer 11

~**85%** ## Footnote **Adipocyte** triglyceride storage is very efficient and has **more calories per gram** than carbohydrates or proteins. And, **adipose tissue** is only ~15% **water**, so cells can pack very closely together (whereas muscle is ~80%).

Answer 12

**Large globules** of **lipid droplets** ## Footnote These squeeze the cytoplasm into a thin layer, and cause the nucleus to be flattened and forced to the periphery.

Answer 13

A **single phospholipid layer** with lots of **triglycerides** contained within.

Answer 14

- **Glycogen** - **Epinephrine** (adrenaline) - **Adrenocorticotropic hormone** (ACTH). ## Footnote These are secreted by other cells.

Answer 15

It acts as **insulation** and forms layers under the skin, so it helps in trapping heat in cold environments.

Answer 16

**Brown adipose** ## Footnote It utilises a protein called **thermogenin**.

Answer 17

**Hormones** secreted by **adipocytes** which help modulate **apetite**/**satiety**, **energy expenditure**, and **related metabolic pathways**.

Answer 18

Lipids made up of a **glyceride** with a **phosphate group** bound to the polar glycerol head group, and **two fatty acyl chains**. ## Footnote (e.g. **phosphatidic acid**).

Answer 19

- Component of cellular **membranes**. - **Precursors** for the biosynthesis of other lipids. - Influence **membrane curvature**. - **Signalling** roles.

Answer 20

It can be **esterified** with the OH of another **polar head group**. ## Footnote For example, **choline** as a head group in **phosphatidylcholine**, which is a common constituent of **cell membranes**.

Answer 21

**Phosphatidylcholine**

Answer 22

**Phosphatidylethanolamine** ## Footnote **Ethanolamine** is the **polar head** added to the **phosphatidic acid**.

Answer 23

**Glycoglycerolipids** ## Footnote It constitutes about **half** of the **chloroplast membrane lipids**.

Answer 24

A type of lipid made up of a **sphingoid base** and a single, long **hydrocarbon tail**. ## Footnote They are major constituents of the **plasma membrane**. A **sphingoid base** is made up of **sphingosine** (an 18-carbon amino alcohol) - it has an **amino group** and a **terminal hydroxyl**. The **fatty acid residue** binds to the **amine group** of the **sphingosine** via an **amide bond**.

Answer 25

Via an **amide bond** to the **amine group** on **C₂** of the **sphingosine**. ## Footnote This is known as a **ceramide**.

Answer 26

A **central sphingolipid** that is made up of a **fatty acyl chain** bonded to a **sphingosine**. ## Footnote It is a **precursor** for other lipids such as **sphingomyelin** and **glycosphingolipids**.

Answer 27

A long-chain, unsaturated **amino alcohol**. ## Footnote Its backbone is made up of **18 carbons**.

Answer 28

Through its **reversible phosphorylation** to form **sphingosine-1-phosphate**.

Answer 29

A more complex **sphingolipid** formed from the **esterification** of **ceramide** and a **polar phosphorylcholine** head group. ## Footnote In higer animals, **sphingomyelin** makes up some of the **brain** and nerve tissue **plasma membranes**. It is similar in size and shape to **phosphatidylcholine**, but they are distinguished by their differing **fatty acid** components.

Answer 30

A more complex **sphingolipid** formed from the **esterification** of **ceramide** and a **polar sugar** head group. ## Footnote The type of sugar defines the type of glycosphingolipid.

Answer 31

A type of **glycosphingolipid** in which the **sugar head group** is a **monosaccharide**. ## Footnote (e.g. glucose or galactose)

Answer 32

A type of **glycosphingolipid** in which the **sugar head group** is a **complex oligosaccharide**. ## Footnote (e.g. sialic acid). **Gangliosides** are important constituents in **muscle** and **nerve membranes**.

Answer 33

Because they are comprised of **complex oligosaccharides**.

Answer 34

A **broad class** of compounds defined by having a **steroid nucleus** in their base structure. ## Footnote A **steroid nucleus** describes **three 6C rings** with **one 5C ring**, and an **OH** attached to one of the **6C rings**.

Answer 35

A **base structure** of all **steroids** that is made up of **three 6C rings** with **one 5C ring**, and an **OH** attached to one of the **6C rings**.

Answer 36

**Cholesterol** ## Footnote It is comprised of the **steroid nucleus** with a short branched **hydrocarbon tail**.

Answer 37

It is a **constituent** of **plasma membranes** that serves a role in **regulating fluidity**. ## Footnote During this, it has **amphipathic properties** whereby its **hydroxyl** head orients towards the external **aqueous** environment, and its hydrophobic regions insert into the membrane.

Answer 38

It forms **hydrogen bonds** with the **hydrophilic heads** of adjacent **phospholipids**. ## Footnote This combined with the disruption of the close packing of the hydrocarbon tails helps make the membrane more fluid.

Answer 39

By regulating the **level** of **cholesterol** present.

Answer 40

Lipid molecules found in **cell membranes** and built on a **phosphatidylglycerol core** that extend into the **extracellular space** and may act as **anchors** for proteins or as **signalling tags**. ## Footnote This is imprtant for **tissue specificity**, **cell-cell** interactions, and **tissue immunity**.

Answer 41

A lipid with a **ceramide backbone** and a **polar head group** made up of **phosphate** bound to another **polar group**. ## Footnote (e.g. **choline**)

Answer 42

Lipids formed from **≥ 2** five carbon molecules called **isoprene**. ## Footnote These are typically linked '**head-to-tail**' to form straight chains. **Terpenes** are a vast group predominantly produced by **plants** (but also insects and some animals too).

Answer 43

Their **flavour**, **colour**, and/or **odour**.

Answer 44

**Two** ## Footnote **C₁₀** Since there is at least **two or more isoprene units** required in a terpene molecule - two is the lowest number and where it starts counting from. Many of these have characteristic odours/flavours, and may have funcitons as **defensive agents** or **pheromones**.

Answer 45

**Three** ## Footnote **C₁₅**

Answer 46

**Four** ## Footnote **C₂₀** One important diterpene includes **retinal** which is a visual pigment of **rhodopsin**. **Phytol** is a component of **chlorophyll**.

Answer 47

**Six** ## Footnote **C₃₀**

Answer 48

**Squalene** & **lanosterol**.

Answer 49

**Esters** of long-chain **monohydroxy alcohols** with long-chain **fatty acids**. ## Footnote They are **insoluble** in water.

Answer 50

**R₁-C(=O)-O-R₂** ## Footnote The **fatty acid** is **R₁**, and the **alcohol** is the **second R group**.

Answer 51

It helps comprise **protective coatings** to make things **water-repellent**. ## Footnote This could be **leaves**, **stems**, **fruit** (plants), or even **fur** and **skin** (animals).

Answer 52

A **hard wax** called **carnauba wax**.

Answer 53

A **wool wax** used in **cosmetics**.

Answer 54

**Glycerophospholipids** & **sphingolipids**. ## Footnote For example, their breakdown can generate **secondary chemical signals** that act **locally** (on same cell or neighbouring), usually by triggering **reaction cascades**.

Answer 55

Due to their significant **hydrophobicity**, lipids in polar solvents such as water will **associate** (aggregate) in a way that minimises exposure of their hydrophobic regions and orients their **hydrophilic** regions to be in contact with surrounding **polar solvent molecules**. ## Footnote For example, **monolayers**, **bilayers**, and **micelles**.

Answer 56

...form **orderly structures spontaneously**. ## Footnote Rarely does a lipid exist as a **monomer** in a polar solvent.

Answer 57

A **single layer** of lipids on the **surface** of an **aqueous solution**.

Answer 58

A formation of lipids in which there are **two layers**, each having the **hydrophilic** (head) regions oriented outwards towards the **polar solvent** and the **hydrophobic** (tail) regions oriented inwards between the two layers. ## Footnote This is the **most stable** structure for **phospholipids**, and makes up **cell membranes**.

Answer 59

**Spherical structures** formed by **single-tailed** lipids in an **aqueous solution**. ## Footnote For example, **fatty acids** or **monoacylglycerol** etc.

Answer 60

The **minimum concentration** of **fatty acids**/single-tailed lipids in an aqueous solution required for **micelles** to begin forming. ## Footnote At lower **concentrations**, such lipids/fatty acids will instead form **monolayers**.

Answer 61

They have **two fatty acyl chains**, which don't pack together as well as **monoacylglycerols** or single **fatty acids** in a **micellular formation**.

Answer 62

**Dietary** & **adipose tissue**. ## Footnote Modern diets tend to be high in fat.

Answer 63

**Fatty acids** need to be **transported** to the appropriate cells for catabolism. ## Footnote (e.g. heart, liver, muscle)

Answer 64

**Long chain** ## Footnote (i.e. about 16 - 20 carbons)

Answer 65

**Hydrolysis** of **dietary triglycerides** by **acid-stable lipases** in the **stomach**. ## Footnote However, this is not very effective and only a small amount is hydrolysed.

Answer 66

Large amounts of **lipases** (and **estarases**) contained within **pancreatic fluid** continue to **hydrolyse** the fats into **monoglycerides** and **fatty acids**. This is assisted by **bile** secretions from the **gall bladder**, which **emulsify fat globules** to further promote hydrolysis. ## Footnote **Bile** is made up of compounds derived from **cholesterol**, and is synthesised in the **liver**, and stored in the **gall bladder**.

Answer 67

Compounds derived from **cholesterol**. ## Footnote For example **cholic acid**.

Answer 68

**Surfactant**/**detergent**/**emulsifier**. ## Footnote It **emulsifies fat globules** and **promotes hydrolysis** of these into **monoglycerides** and **fatty acids** via **pancreatic lipases** and **esterases**.

Answer 69

It is synthesised in the **liver**, stored in the **gallbladder**, and excreted from there into the **small intestine**.

Answer 70

**Aggregates** of **lipolytic products** formed in the **small intestines**, which act as a **lipid shuttle** that carries these compounds to absorptive cells (to then become chylomicrons). ## Footnote They are typically comprised of **monoglycerides**, **fatty acids**, **bile**, **phospholipids**, **cholesterol**, and **protein**.

Answer 71

**C₁** & **C₃** ## Footnote The **monoglycerides** are further hydrolysed by **intestinal lipases** in the small intestine.

Answer 72

A **lipoprotein aggregate** formed in the cells of the **small intestine**. ## Footnote It is the **largest**, **lowest density**, **highest** in **triglycerides**, and **lowest** in protein of the **lipoproteins**.

Answer 73

The binding **apolipoprotein II** on the surface of the chylomicron. ## Footnote The **lipprotein lipase** is anchored to the **surface** of **endothelial cells**.

Answer 74

- **Diffuse** into endothelial cells and then enter **capillaries** proximal to **liver**, **muscle**, or **adipose** tissues for **absorbtion** and then **energy production**. - **Bind** to **albumin** and be **transported** via the **bloodstream** to more **distant cells**.

Answer 75

It **activates** the fatty acid and essentially labels it for **degredation** before it is transported into the mitochondria.

Answer 76

**Acyl-CoA synthetase** ## Footnote As the enzyme name suggests, this requires **ATP**.

Answer 77

**Short-chain fatty acids** may be transported directly as **free fatty acids**, while **long-chain fatty acids** CANNOT.

Answer 78

- **Carnitine acytransferase I** - **Acyl** group of the **fatty acyl-CoA** is transferred to the **OH** of **carnitine** to form **acylcarnitine**, which then diffues into the mitochondrial **intermembrane space**.

Answer 79

- **Acylcarnitine translocase** - **Transports acylcarnitine** into **matrix**. - This is coupled with the transport of **carnitine** from the **matrix** to the **cytosol**. ## Footnote This enzyme is found on the **inner mitochondrial membrane**.

Answer 80

- **Carnitine acyltransferase II** -

Answer 81

**Acyl-CoA transport** into the mitochondria. ## Footnote (Specifically, at **carnitine acyltransferase I**)

Answer 82

**Malonyl-CoA** ## Footnote (i.e. a **precursor** to **fatty acid synthesis**)

Answer 83

**Acetyl-CoA Carboxylase** (ACC)

Answer 84

- **Activation** (forms fatty acyl-CoA) - **Transport** (into mitochondria via carnitine for LCFA) - **β-oxidation** (in mitochondria) - **TCA cyle** (metabolite acetyl-CoA fed into this)

Answer 85

- **Oxidation** - **Hydration** - **Oxidation** - **Cleavage** ## Footnote It is called **β-oxidation** since the **βC** is **oxidised** to allow for multiple rounds of cleavage.

Answer 86

- **Acyl-CoA dehydrogenase** - **Oxidation** (dehydrogenation) of **acyl-CoA** in which the **C_α-C_β** bond is converted to a **trans double bond** to form **trans-Δ²-enoyl-CoA**. - Coupled with the **reduction** of the **FAD prosthetic group** to **FADH₂**. ## Footnote **Acyl-CoA DH** has different **isoforms** depending on the lenght of the **fatty acyl-CoA chain**. The **2e^-** of **FADH₂** can then be taken to the **ETC** via **ETF** (electron-transferring flavoprotein) to **ubiquinone** (**Q**).

Answer 87

- **Enoyl-CoA hydratase** - Stereospecific **hydration** of the **trans double bond** (**C_α=C_β**) to yield **L-β-hydroxyacyl-CoA**.

Answer 88

- **L-β-hydroxyacyl-CoA dehydrogenase** - **Oxidation** (dehydrogenation) of **L-β-hydroxyacyl-CoA** to **L-β-ketoacyl-CoA**. - Coupled with **reduction** of **NAD⁺** to **NADH**. ## Footnote It can now undergo cleavage between the alpha and beta carbon. The **NADH** can deposit its electrons to the **ETC**.

Answer 89

- **Thiolase** - **Cleavage** of the **C_α-C_β** bond and attachement of **CoASH** to the shorter fragment to release **acetyl-CoA**, whilst the main chain is **shortened** by **2C** before enetering the next round of oxidation. ## Footnote This occurs via a **fatty acyl-CoA enzyme-cysteine thiolester intermediate**.