Biology 1113: Lecture 6 (lipids) Flashcards
What is the primary unifying characteristic of lipids?
They do not dissolve easily in water (hydrophobic due to nonpolar C-H chains/rings).
What are the three main categories of lipids?
Triglycerides (fats): Energy storage.
Phospholipids: Cell membranes.
Steroids: Hormones and cell membrane components.
Do lipids have true monomers?
No, they are defined by their hydrophobicity rather than specific monomers.
What is a triglyceride made of?
Glycerol + 3 fatty acids.
How do fatty acids differ?
Length (number of carbons).
Number of double bonds (saturation).
What is the difference between saturated and unsaturated fatty acids?
Saturated: No double bonds, straight chains, solid at room temperature.
Unsaturated: At least one double bond, kinked chains, liquid at room temperature.
What are trans fats, and why are they harmful?
Fats with trans double bonds created artificially (e.g., hydrogenation).
They are solid at room temperature, hard to digest, and linked to health issues like heart disease.
Why do triglycerides store more energy than carbohydrates?
They contain more C-H bonds, which store more energy.
What is the structure of a phospholipid?
Glycerol + 2 fatty acids + a phosphate group with a polar head.
What does ‘amphipathic’ mean?
Molecules with both hydrophobic (nonpolar) and hydrophilic (polar) regions.
Why are phospholipids important in cell membranes?
They form bilayers, with hydrophobic tails inward and hydrophilic heads outward, creating a selective barrier.
What is the structure of steroids?
Four fused rings of carbon and hydrogen.
What is the most common steroid, and what are its functions?
Cholesterol:
Component of cell membranes.
Precursor for steroid hormones (e.g., testosterone, estrogen).
What are essential fatty acids?
Fatty acids humans cannot produce (e.g., omega-3 and omega-6) and must obtain through diet.
Why are essential fatty acids important?
They are necessary for phospholipid synthesis, brain function, and heart health.
Why do organisms store energy in both lipids and carbohydrates?
Lipids: Long-term, high-energy storage (9 calories/gram).
Carbohydrates: Short-term, quick energy source (4 calories/gram).
Why is glycogen preferred for short-term energy storage?
It is water-soluble and stored in the liver and muscles for quick access.
What determines membrane permeability?
Saturation of fatty acids (unsaturated increases fluidity).
Temperature (higher temperature increases permeability).
What types of molecules easily pass through a lipid bilayer?
Small, nonpolar molecules (e.g., gases like O2).
What types of molecules cannot pass through without assistance?
Large or charged molecules (e.g., ions).
How do phospholipids form membranes?
Their amphipathic nature causes them to spontaneously form bilayers or micelles in water.
Why are lipids defined by their physical properties?
They are characterized by hydrophobicity rather than specific monomers.
Why are most phospholipids unsaturated?
The kinks from double bonds increase membrane fluidity and permeability.
What is the role of temperature in membrane fluidity?
Higher temperatures increase fluidity, while lower temperatures decrease it.
What are the risks associated with trans fats?
Increased risk of heart disease, diabetes, and obesity.
Difficult for enzymes to digest properly.
What are omega-3 and omega-6 fatty acids, and where are they found?
Types of essential unsaturated fatty acids.
Found in fish, nuts, and seeds.
