Organic Compounds and Cell Membranes - Practice Flashcards

A comprehensive set of Q&A flashcards covering organic compounds essential to life and the structure/function of cell membranes and transport mechanisms, based on the provided lecture notes.

What are macronutrients and why are they important?

Macronutrients are nutrients the body needs in large quantities to provide energy and maintain structure and function of body systems (the three main macronutrients are carbohydrates, fats, and proteins).

What does the term carbohydrate mean and what is its general composition?

The term carbohydrate means 'hydrated carbon'; a molecule made of carbon, hydrogen, and oxygen, with hydrogen and oxygen in roughly the same 2:1 ratio as in water (generic formula (CH2O)n).

What are the three forms of carbohydrates important in the body?

Monosaccharides, disaccharides, and polysaccharides.

What is a monosaccharide?

A monosaccharide is the monomer of carbohydrates.

Name the three hexose monosaccharides and identify which is most common.

Glucose, fructose, and galactose; glucose is the most common.

Name the two pentose monosaccharides.

Ribose and deoxyribose.

What is a disaccharide?

A disaccharide is a pair of monosaccharides.

Name the three disaccharides.

Sucrose (glucose + fructose), lactose (galactose + glucose), maltose (glucose + glucose).

What is a polysaccharide?

A long chain of monosaccharides

What is stored for a polysaccharides

starches are polymers of glucose stored in plants, glycogen is a polymer of glucose stored in animals.

What are triglycerides and what are they commonly called?

Triglycerides are a common dietary lipid group; they are fats (solid) or oils (liquid) formed from glycerol backbone and three fatty acids.

What is a phospholipid and its key structural feature?

A phospholipid is generated from a diglyceride with a third binding site occupied by a charged phosphate group; the head is polar and hydrophilic, while the tails are nonpolar and hydrophobic.

Which part of a phospholipid is hydrophilic and which is hydrophobic?

The phosphate-containing head is hydrophilic; the fatty acid tails are hydrophobic.

What are sterols and give an example?

Steroids are four interlocking hydrocarbon rings; cholesterol is an example and the basis for all steroids formed in the body.

What is dehydration synthesis?

A set of synthesis reactions in which a new compound forms with the elimination of water.

What is a phospholipid’s common structural representation?

A glycerol backbone with two fatty acid chains (nonpolar tails) and a phosphate-containing head (polar).

What is the role of cholesterol in membranes?

Cholesterol inserts into the phospholipid bilayer and, depending on temperature, helps regulate membrane fluidity: at high temperatures it makes membranes less fluid; at low temperatures it prevents freezing and maintains fluidity.

What are proteins and what elements do they typically contain?

Proteins are organic molecules composed of amino acids; they contain carbon, hydrogen, oxygen, nitrogen, and often sulfur.

What are amino acids and what groups do they possess?

Amino acids have an amino group, a carboxyl group, a hydrogen, and a variable R group attached to a central carbon (alpha carbon).

What are peptide, polypeptide, and protein?

A peptide is a short chain of amino acids; a polypeptide is a longer chain of amino acids; a protein contains one or more polypeptides.

What is the cell?

The smallest unit of life and the basic structural and functional unit of all known organisms.

What do hepatocytes and myocytes illustrate in cellular function?

Hepatocytes perform liver functions; myocytes are capable of contracting.

What is the cell membrane and its primary function?

The plasma membrane that surrounds a cell, providing a protective barrier and regulating what enters and leaves; it is semipermeable.

What is the structure of the cell membrane bilayer?

Two adjacent layers of phospholipids; hydrophilic heads face the intracellular and extracellular fluids, while hydrophobic tails face inward, forming a nonpolar core.

Which molecules can freely cross the lipid bilayer?

Small, nonpolar molecules such as oxygen and carbon dioxide.

How do water molecules cross the membrane?

Water (small polar molecules) can cross slowly without transport proteins.

What happens with large polar molecules and ions crossing the membrane?

They generally require help from transport proteins and often cannot cross the nonpolar core easily.

What are the two major types of membrane proteins and their roles?

Peripheral and integral proteins; they include channels and carriers that assist transport across the membrane.

What are ion channels and what determines their selectivity?

Ion channels are pores that allow specific charged particles to cross in response to gradients; selectivity is influenced by charge (electrochemical exclusion) and pore diameter.

What is a ligand-gated channel?

A channel that opens when a signaling molecule (ligand) binds to the extracellular region, allowing ions to cross; common in neurons.

What are leakage channels?

Randomly gated channels that open and close, contributing to the resting membrane potential.

What is a carrier protein and how does it differ from a channel?

Carrier proteins move molecules across membranes and can move substances against the concentration gradient, unlike channels which provide a pore for passive flow.

What are glycoproteins and glycolipids and what is glycocalyx?

Glycoproteins and glycolipids have sugars attached and are involved in signaling and cell recognition; the glycocalyx is the surface layer formed by these molecules.

What is the role of phospholipids in cell membranes?

Phospholipids form a bilayer that provides structure and a barrier; their polar heads interact with water while nonpolar tails form the interior.