BIOC 3021 Exam 2

What is the basic structures of lipids?

A group of hydrophobic molecules which contain the following

• fatty acids

• triglycerides

• phospholipids

• steroids

What is the basic structure of fatty acids?

 long hydrocarbon chains with a carboxyl group (-COOH)

• hydrophobic tail (nonpolar)

• hydrophilic head (polar)

What are the functions of fatty acids and lipids?

• energy storage

• cell membrane structure

• insulation & protection

• signalling molecules (hormones like epinephrine & norepinephrine)

What is the difference between a saturated and unsaturated fatty acid and lipid?

Saturated fatty acids:

• no double bonds

• straight chains allows for tight packing

• solid at room temperature

Unsaturated fatty acids:

• one or more double bonds

• kinks in the chain mean looser packing

• liquid at room temperature (oil)

What is the chemical notation used for a saturated fatty acid?

Format: C:D

• C = number of carbons

• D = number of double bonds

Examples:

• 18:0 → saturated w/ 18 carbons

What is the chemical notation used for an unsaturated fatty acid?

Format: C:D

• C = number of carbons

• D = number of double bonds

Examples:

18:1 → monounsaturated w/ 18 carbons & 1 double bond

What is a triglyceride?

• three fatty acids with a glycerol body

the main energy storage form in animal

How are the properties of a triglyceride dependent on its structure?

If a triglyceride is/has _____, then it is/has _____

• more saturated, more solid

• more unsaturated, more fluid

• longer chains, a higher melting point

What is a phospholipid?

• two fatty acids with a glycerol body and a phosphate head

• amphipathic

  • hydrophobic tails

  • hydrophilic head

What is a phospholipid’s role in cell membranes?

forms bilayers that make up cell membranes

What is a glycolipid?

• lipids plus a carbohydrate group

• found on the outer membrane

What is a glycolipid’s role in cell membranes?

• found on the outer membrane

• functions of cell signalling and cell recognition

What is the general structure of a sterol or steroid?

4 fused carbon rings with a hydrophobic core

What is the importance of cholesterol in membranes and as a precursor to other molecules?

To maintain membrane fluidity. It is also a precursor for steroid hormones, vitamin D, and bile acids.

Which of the following statements is false regarding the fatty acid below.

CH₃CH₂CH₂CH₂CH₂CH=CHCH₂CH=CHCH₂CH₂CH₂CH₂CH₂CH₂CH₂-COOH

It is an omega-3 fatty acid

Storage lipids in animals are mainly in the form of _______ which contain predominantly ____ fatty acids.

fats (solids); saturated

Select the correct answer for each of the following

1. unsaturated fatty acid

2. saturated fatty acid

3. C16:0 fatty acid

4. Lipid

an oil; a solid; a very common fatty acid; triglyceride

To what family of molecules does cholesterol belong?

sterol

Which of the following is not found in cell membranes

triglycerides

The correct order for these three processes leading from a fatty acid molecule in a cell needing energy to high energy molecules capable of meeting that energy need is

 

1. Activation by reaction with Coenzyme A

2. Oxidation to acetyl CoA and reduced coenzymes

3. Transport from cytosol into the mitochondria

1, 3, 2

Which of the following molecules is not a signaling molecule that interacts with a receptor on the surface of the cell causing a biochemical response to occur inside the cell?

cAMP

Metabolism of a C12:0 fatty acid by β-oxidation produces _____ Acetyl CoA and ______ FADH₂ and NADH total.

6; 10

The glucose transporter is an example of ________ transport that moves glucose across the plasma membrane _________ a concentration gradient.

passive; in the direction of

What are the main types of membrane transport?

1. Passive Transport: Moves substances down their concentration gradient without energy (e.g., Simple Diffusion, Facilitated Diffusion).

2. Active Transport: Moves substances against their gradient using energy (e.g., Primary Active Transport like the $Na^{+}/K^{+}$ pump, and Secondary Active Transport).

What is an example of a channel protein?

Aquaporins (for water) or Ion Channels (e.g., Voltage-gated $Na^{+}$ channels). Unlike carriers, channels provide a hydrophilic pore for rapid passage

What are the general functions of membrane proteins?

Transport: Moving ions/molecules across the membrane.

Receptors: Sensing external signals (cell signaling).

Enzymes: Catalyzing reactions at the membrane surface.

Cell Recognition: Identifying the cell to the immune system.

Structural Support: Linking the cytoskeleton to the extracellular matrix.

What is the GLUT transporter and how does it operate?

It is a facilitated diffusion carrier for glucose. It operates by changing shape (conformation) when glucose binds, moving it from high concentration (usually outside) to low concentration (inside) without using ATP.

What are the key features of the Na/K pump?

It is a primary active transporter that uses 1 ATP to move 3 Na ions OUT of the cell and 2 K ions IN. This maintains the cell's electrochemical gradient and resting potential.

What is the role of cAMP in cell signaling?

Cyclic AMP (cAMP) is a second messenger. When a hormone (like epinephrine) binds to a membrane receptor, it triggers the production of cAMP inside the cell, which then activates enzymes like Protein Kinase A to amplify the signal.

How do Insulin, Glucagon, and Epinephrine affect glycogen?

Insulin: Signals high blood sugar; inhibits glycogen degradation and stimulates glycogen synthesis (storage).

Glucagon & Epinephrine: Signal low energy or stress; stimulate glycogen degradation to release glucose into the blood for energy

Why do fats contain more energy per weight than carbohydrates?

1. Reduction State: Fats are more chemically reduced (saturated with hydrogens), meaning they have more high-energy electrons to give up during oxidation. 2. Anhydrous Storage: Fats are nonpolar and stored without water. Glycogen is polar and carries 2x its weight in water, making fats 6x more energy-dense by weight.

Describe the journey of dietary lipids from mouth to cells.

Bile Acids: Emulsify large fat globules in the small intestine.

Lipases: Enzymes that break triglycerides into free fatty acids.

Chylomicrons: Lipoprotein "packages" that transport these fats through the lymph and blood to tissues.

What are the three main steps of Fatty Acid Oxidation and their locations?

1. Activation: Conversion to Fatty Acyl-CoA (Cytoplasm; costs 2 ATP).

2. Transfer: Movement into mitochondria via the Carnitine transporter.

3. Beta-Oxidation: The actual breakdown into Acetyl-CoA units (Mitochondrial Matrix).

What is the ATP yield for a 6-carbon (6C) Fatty Acid?

44 ATP.

• Spins: (6/2) - 1 = 2 spins.

• Acetyl-CoA produced: 6/2 = 3 molecules.

• Energy: (2 spins x 5 ATP) + (3 Acetyl-CoA x 12 ATP) - 2 activation = 10 + 36 - 2 = 44.

What is the ATP yield for Palmitate (16C)

129 ATP.

• Spins: 7 spins (7 NADH, 7 FADH2).

• Acetyl-CoA: 8 molecules.

• Energy: (7 × 5) + (8 × 12) - 2 = 35 + 96 - 2 = 129.

What is the definition and location of Oxidative Phosphorylation?

It is the process where the energy from NADH and FADH2 oxidation is used to drive the synthesis of ATP. It takes place in the inner mitochondrial membrane.

How do the components of the Electron Transport Chain (ETC) operate?

Complexes I-IV and mobile carriers (Q and Cytochrome c) transfer electrons in a series of redox reactions. This flow of electrons provides the energy to pump protons (H+) from the matrix into the intermembrane space.

What is the "final electron acceptor" in cellular respiration?

Oxygen (O2). It accepts electrons and protons at the end of the ETC to form water (H2O).

How does ATP Synthase operate?

It acts as a molecular motor. Protons flow back into the matrix through its channel (down the gradient), causing a portion of the enzyme to rotate. This mechanical energy is used to catalyze the conversion of ADP + Pi → ATP

What are Reactive Oxygen Species (ROS) and how are they handled?

ROS are highly reactive oxygen byproducts of the ETC (like superoxide) that can damage DNA and lipids. Antioxidants (like Vitamin E or specific enzymes) detoxify ROS to prevent this damage.

What is UCP1 (Uncoupling Protein 1)?

Found in brown fat, it creates a "leak" in the inner membrane, allowing protons to bypass ATP synthase. Instead of making ATP, the energy from the gradient is released as heat (thermogenesis).

Proton Gradient Formation

The ETC uses the energy from electron transfers to pump protons across the inner membrane, creating a high concentration in the intermembrane space and a low concentration in the matrix.

Inhibitors of Electron Transport

They act as potent poisons (e.g., cyanide) by stopping electron flow, preventing the formation of the proton gradient and ATP.

Co-factors in Electron Transport

These include Cytochromes (heme groups with iron), Iron-Sulfur groups, and Coenzyme Q (ubiquinone). They operate by cycling between oxidized and reduced states (e.g., Fe+3 to Fe+2) to pass electrons.

NADH and FADH2 in the ETC

NADH enters at Complex I, while FADH2 enters at Complex II. Because FADH2 enters further down the chain, it pumps fewer protons and generates less ATP.

Aquaporin

A specialized channel protein that facilitates the rapid movement of water molecules across the cell membrane.