Biochemistry Chapter 9: Lipid Metabolism

Question 1

Answer 1

Glycerol ( 1,2,3 propanetriol )

Question 2

arachidonic acid is important as a precursor for the biosynthesis of

Answer 2

eicosanoid signaling molecules

Question 3

types of eicosanoids

Answer 3

prostaglandins, thromboxanes, and leukotrienes.

Question 4

What are fatty acids?

Answer 4

long-chain carboxylic acids

Question 5

What are triglycerides/ triacylglycerols?

Answer 5

formed by 3 FAs esterified to a 3-carbon glycerol backbone. Main role is to provide energy.

Question 6

What are phospholipids/fatty acid derivatives?

Answer 6

Large category including phospholipids and sphingolipids; play structural/signaling roles.

Question 7

What is Cholesterol and its derivatives:

Answer 7

Four-ring structure. Cholesterol contributes to fluidity of plasma membrane; steroid hormones are derived from cholesterol

Question 8

What are Eicosanoids?

Answer 8

Eicosanoids are not hormones in the classical sense (like insulin or cortisol), but they act as local signaling molecules with hormone-like functions.

Derived from arachidonic acid; have 20 carbons and a 5-carbon ring

Question 9

prostaglandins

Answer 9

Eicosanoid that modulate inflammation

Question 10

Thromboxanes

Answer 10

Eicosanoids involved in clotting

Question 11

More double bonds in fatty acids means what for melting/boiling pts?

Answer 11

More unsaturated and lower melting/boiling point = greater contribution to fluidity of membrane.

Question 12

Beta oxidation

Answer 12

Fatty acid broken down into acetyl-CoA (2-carbon) units in the mitochondria

Question 13

What are the fate of acteyl-CoA products from beta-oxidation?

Answer 13

are fed into the citric acid cycle or used to produce ketone bodies in the liver. Ketone bodies are formed in the liver and sent to provide energy to other cells, where they are broken back down into acetyl-CoA (think of ketone bodies as an acetyl-CoA delivery service

Question 14

Carnitine shuttle moves activated FAs

Answer 14

into the mitochondria

Question 15

Four major steps in beta oxidation

Answer 15

A C=C double bond is formed between C2 and C3, and FAD → FADH₂.

An OH group is added to C3.
C–OH → C=O at C3, coupled with NAD⁺ → NADH.

Molecule is broken up, generating acetyl-CoA and a shorter acyl-CoA.

Ketone body formation upregulated in starvation and untreated diabetes

Question 16

What is the building block of fatty acid synthesis?

Answer 16

Acetyl-CoA is the ultimate building block, but malonyl-CoA (a three-carbon compound generated by carboxylating acetyl-CoA) is the intermediate that transfers two-carbon units to an extending chain.

Question 17

Fatty Acid synthesis takes place in the

Answer 17

cytosol

Question 18

What is the cholesterol synthesis pathway?

Answer 18

Built from mevalonate → repeating isoprene units → squalene → cholesterol; mevalonate is limiting step

Question 19

What are chlyomicrons?

Answer 19

Least density; first transporters of triacylglycerols to tissue.

Question 20

Very-low-density lipoprotein (VLDL)

Answer 20

Transport triacylglycerols from liver to tissue.

Question 21

Low-density lipoprotein (LDL)

Answer 21

Transport cholesterol to tissue; high levels associated with risk of cardiovascular disease

Question 22

High-density lipoprotein (HDL)

Answer 22

Transport cholesterol from tissue to liver; high levels are cardioprotective

Question 23

Goal of Fatty Acid Synthesis

Answer 23

To create fatty acids, which are stored as triglycerides for energy reserves or used in membrane formation

To produce phospholipids and cholesterol for cellular structures and signaling molecules

Question 24

Location of Fatty Acid Synthesis

Answer 24

Cytoplasm:
Fatty acid synthesis primarily occurs in the cytoplasm of cells, particularly in the liver and adipose tissue.

Smooth Endoplasmic Reticulum:
Final steps of triglyceride synthesis, phospholipid synthesis, and cholesterol synthesis occur here

Question 25

Inputs/Outputs for Fatty Acid Synthesis

Answer 25

Inputs CO₂ (Carbon Dioxide) – Released during the formation of malonyl-CoA from acetyl-CoA. CoA (Coenzyme A) – Released when acetyl-CoA and malonyl-CoA are incorporated into the growing fatty acid chain. NADP⁺ (Nicotinamide Adenine Dinucleotide Phosphate, oxidized form) – Generated from the oxidation of NADPH used in the reduction steps. H₂O (Water) – Released during the dehydration step of the elongation cycle. Outputs Fatty Acids: 1) Synthesized as long-chain fatty acids like palmitic acid (16:0). 2) Triglycerides (Triacylglycerols): Fatty acids combined with glycerol to form energy-storage molecules. 3) Phospholipids: Essential for membranes and signaling. 4) Cholesterol: Used for steroid hormones, bile acids, and membrane fluidity.

Question 26

Beta Oxidation Goals

Answer 26

To break down fatty acids into acetyl-CoA, which can enter the Krebs cycle for ATP production. To produce ketone bodies during fasting or starvation for use as an alternative energy source.

Question 27

Location of Beta Oxidation

Answer 27

Mitochondria: Beta-oxidation occurs in the mitochondrial matrix. Liver: Produces ketone bodies during prolonged fasting. Adipose Tissue: Releases free fatty acids into the blood when triglycerides are broken down.

Question 28

starvation and untreated diabetes mellitus can lead to the overproduction of

Answer 28

ketone bodies

Question 29

Ketoacidosis

Answer 29

High levels of ketone bodies D-β-hydroxybutyrate and acetoacetate (acidic) in the blood, leading to a drop in blood pH known as diabetic ketoacidosis. can detect on patient's breath because acetone accumulates to a noticable level

Question 30

True or false: Lipids can absorb visible light

Answer 30

False they lack conjugated double bonds or other chromophores that interact with photons in the visible spectrum (wavelengths ~400–700 nm)

Question 31

Chylomicrons

Answer 31

lipoprotein particles that transport dietary lipids (mostly triglycerides) from the intestine to other parts of the body via the lymphatic and circulatory systems.

Question 32

lipoprotein density compares what to what

Answer 32

Lipid to protein. therefore the LEAST dense has the highest ratio of lipids to proteins

Question 33

Order of density from least to greatest lipoproteins

Answer 33

VLDL < IDL < LDL < HDL

Question 34

VLDL journey

Answer 34

VLDL starts off with high fat ratio, unloads fat content as it continues and eventually becomes LDL which can exist easier in the blood stream

Question 35

LDL contains more ________ than triglycerides

Answer 35

cholesterol

Question 36

Job of LDL

Answer 36

Deliver cholesterol to tissues that need it

Question 37

HDL job

Answer 37

Pick up stray cholesterol and taking it back to the liver

Question 38

Fatty acid catabolism consists of what 2 steps

Answer 38

lipolysis (fatty acid molecule mobilized from storage) and beta oxidation

Question 39

True or false: even number FA chain beta oxidation is easier than odd number

Answer 39

true

Question 40

Acyl CoA vs acteyl CoA

Answer 40

Acyl-CoA is a broader term referring to any molecule where a fatty acid chain (the "acyl group") is attached to coenzyme A (CoA), while acetyl-CoA is a specific type of acyl-CoA where the acyl group is a two-carbon acetic acid

Question 41

Major steps of beta oxidation

Answer 41

1) Oxidation 2) Hydration 3) Oxidation 4) Thiolysis

Question 42

Inputs and outputs of beta oxidation

Answer 42

**Inputs** 1. **Fatty Acids**: - Released from triglycerides stored in adipose tissue. 2. **NAD⁺**: Electron carrier for oxidation reactions. 3. **FAD**: Electron carrier for dehydrogenation steps. 4. **ATP**: Required to activate fatty acids for transport into mitochondria. (needed to activate the fatty acid, before beta oxidation) **Outputs** 1. **Acetyl-CoA**: - Fed into the Krebs cycle for ATP production or used to generate ketone bodies. 2. **NADH** and **FADH₂**: - High-energy electron carriers for the electron transport chain. 3. **Ketone Bodies** (during fasting): - Acetoacetate, β-hydroxybutyrate, and acetone (used by tissues like the brain and muscles).

Question 43

enzyme that hydrolyzes stored triglycerides in adipose tissue into free fatty acids and glycerol, regulated by hormones like epinephrine and insulin to control fat mobilization.

Answer 43

hormone sensitive lipase

Question 44

Fats produce approx how much ATP per carbon?

Answer 44

About 7n ATP, where n = number of carbons

Question 45

Why are fats high energy?

Answer 45

Because they are highly reduced

Question 46

Most abundant fatty acid in the body

Answer 46

palmitic acid (C16:0)

Question 47

Fatty acid synthesis is accomplished by fatty acid synthase, a large enzymatic complex with multiple active sites and a long acyl carrier arm that moves the growing fatty acid between these active sites. This type of synthetic mechanism increases catalytic efficiency how?

Answer 47

increases catalytic efficiency by limiting substrate diffusion. Fatty acid synthase has which has highly specific substrates. By preventing intermediates from diffusing away and having to diffuse back into the next active site, fatty acid synthase is able to more efficiently conduct the sequential reactions necessary to form a complete fatty acid.

Question 48

Malonyl-CoA

Answer 48

is a key intermediate in fatty acid synthesis and an inhibitor of β-oxidation, formed from acetyl-CoA by acetyl-CoA carboxylase (ACC). 🚀

Question 49

Steps of fatty acid synthesis

Answer 49

1) Transacylation 2) Condensation 3) Reduction 4) Dehydration 5) Reduction