Cell Biology and Biochemistry for Biomedical Engineering Students

What are the four major families of small organic molecules found in cells?

Amino acids, lipids, carbohydrates, and nucleotides.

What distinguishes organic molecules from inorganic molecules?

Organic molecules contain carbon-hydrogen (C-H) bonds, while inorganic molecules do not.

What is the primary function of fatty acid chains in cell membranes?

They form lipid bilayers that create selectively permeable boundaries.

What are the components of a phospholipid molecule?

A polar (hydrophilic) head group and two hydrophobic fatty acid tails.

How do triacylglycerols function in animal cells?

They serve as the main energy reserve, providing more than twice the energy per gram compared to carbohydrates.

What is the structure of DNA?

A double helix formed by two complementary strands running antiparallel, held together by hydrogen bonds between base pairs.

What are the differences between DNA and RNA?

DNA uses thymine (T) while RNA uses uracil (U), DNA has deoxyribose sugar while RNA has ribose, and DNA is usually double-stranded while RNA is single-stranded.

What role do hydrogen bonds play in DNA structure?

They hold the two strands together and provide stability while allowing for reversible replication and transcription.

What is the significance of ATP in cellular processes?

ATP stores energy in its high-energy phosphate bonds and releases energy upon hydrolysis to ADP and inorganic phosphate.

How does phosphorylation affect proteins?

It can induce conformational changes in proteins, altering their shape and function.

What is the role of motor proteins in cells?

They perform mechanical work by moving along cytoskeletal filaments.

What is the primary lipid stored in fat droplets within cells?

Triacylglycerol (TAG).

What is the hydrophilic part of a phospholipid molecule?

The polar head group that interacts with water.

What types of bonds stabilize the sugar-phosphate backbone in DNA?

Covalent bonds.

What is the function of nucleotides in DNA and RNA?

They serve as the building blocks for nucleic acids and are involved in the storage and transmission of genetic information.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have straight chains, while unsaturated fatty acids contain kinks due to double bonds.

How do cells utilize energy from ATP?

Energy is transferred to other molecules through phosphorylation.

What is the role of cholesterol in cell membranes?

Cholesterol plays an important role in membrane structure and fluidity.

What is the significance of the amphipathic nature of phospholipids?

It allows them to self-assemble into lipid bilayers, forming cell membranes.

What is the typical energy yield of triacylglycerols compared to carbohydrates?

Triacylglycerols provide more than twice the energy per gram compared to carbohydrates.

What are the nitrogenous bases found in DNA and RNA?

DNA contains adenine (A), thymine (T), cytosine (C), and guanine (G); RNA contains adenine (A), uracil (U), cytosine (C), and guanine (G).

What is the role of the hydrophobic tails in phospholipids?

They avoid water, contributing to the formation of lipid bilayers.

What is the primary role of lipids in cells?

They provide structure to cell membranes and serve as energy storage.

What are the three main types of macromolecules in cells?

Polysaccharides, proteins, and nucleic acids.

What are macromolecules made of?

They are polymers built by linking together repeating monomer subunits.

What type of bond links monomer subunits in macromolecules?

Covalent bonds.

What are the specific covalent linkages for each type of macromolecule?

Glycosidic bonds in polysaccharides, peptide bonds in proteins, and phosphodiester bonds in nucleic acids.

How do noncovalent interactions contribute to macromolecule stability?

They are individually weak but can collectively stabilize molecular interactions.

What factors influence the specificity and stability of noncovalent interactions?

Surface complementarity between molecules, including how well their shapes and chemical groups fit together.

What regulates chemical reactions in living systems?

Enzymes and signaling pathways tightly regulate chemical reactions to ensure specific products, proper metabolic balance, and controlled cellular function.

What is the consequence of unregulated chemical reactions in cells?

Unregulated reactions can disrupt homeostasis and threaten cell survival.

What is the mass of a mole in grams equivalent to?

The mass of a mole equals the molecule's molecular weight in daltons.

What is radiation therapy used for?

Radiation therapy is a common cancer treatment that uses high-energy radiation to damage the DNA of cancer cells to stop them from dividing.

What type of radiation is typically used in radiation therapy?

Gamma rays and X-rays are commonly used as they can penetrate deep into the body to reach tumors.

Why are alpha particles not useful for radiation therapy?

Alpha particles are large and heavy, stopping quickly in tissue and cannot travel far.

What are beta particles and their use in therapy?

Beta particles are small and can travel a moderate distance, making them sometimes useful for targeted therapies.

How do you calculate the number of moles in a sample?

To find moles, divide the mass of the sample by its molar mass.

What is the atomic mass of oxygen in grams per mole?

The atomic mass of oxygen is 16 g/mol.

How many atoms are in 48 grams of oxygen?

48 grams of oxygen equals 3 moles, which corresponds to 1.8 × 10²⁴ atoms.

What elements primarily compose the human body?

The human body is mainly composed of hydrogen (H), carbon (C), nitrogen (N), and oxygen (O), accounting for about 96% of total atoms.

What type of bonds are stronger: covalent or noncovalent?

Covalent bonds are much stronger than noncovalent interactions.

What are the strongest noncovalent forces?

Electrostatic attractions, also known as ionic bonds or salt bridges, are the strongest noncovalent forces.

What are some examples of weaker noncovalent interactions?

Weaker noncovalent interactions include hydrogen bonds, hydrophobic interactions, and van der Waals attractions.

How does an ionic bond form?

An ionic bond forms when one atom transfers electrons to another, creating oppositely charged ions.

What happens to an atom that loses electrons?

The atom that loses electrons becomes a positively charged cation.

What happens to an atom that gains electrons?

The atom that gains electrons becomes a negatively charged anion.

What are van der Waals forces?

Van der Waals forces are weak noncovalent interactions that occur when two molecules are very close together.

What role do van der Waals interactions play in biological systems?

While individually weak, many van der Waals interactions can help stabilize protein folding, enzyme-substrate binding, and molecular packing.

What percentage of a cell's mass is composed of water?

About 70%.

How do water molecules affect ionic bonds in cells?

Water molecules surround and shield charged ions, weakening ionic bonds and making them relatively weak and unstable compared to covalent bonds.

When are ionic bonds most stable in biological systems?

Ionic bonds are most stable when part of a larger molecule or in regions with low water exposure.

Where are strong ionic bonds most likely to occur in proteins?

Deep inside a protein's core, where water is excluded.

What is a covalent bond?

A covalent bond is formed when two atoms share electrons in their outer shells.

How does covalent bonding differ from ionic bonding?

Covalent bonding involves sharing electrons, while ionic bonding involves the transfer of electrons.

What characterizes a double covalent bond?

A double covalent bond involves two pairs of shared electrons, making it shorter and stronger than a single bond.

How does a double bond affect the shape of biological molecules?

It restricts rotation, affecting the shape and geometry of the molecules.

What is a polar covalent bond?

A polar covalent bond forms when electrons are unequally shared between atoms due to differences in electronegativity.

How does electronegativity affect water's molecular structure?

In water (H₂O), oxygen is more electronegative than hydrogen, pulling shared electrons closer and creating partial charges.

What types of molecules have nonpolar covalent bonds?

Molecules like O₂, CH₄, and C₃H₈, which involve atoms with similar electronegativity.

Why is water essential for chemical reactions in cells?

Water stabilizes molecules, facilitates bond formation and breaking, and supports proper protein and enzyme function.

What role do hydrogen bonds play in biological molecules?

Hydrogen bonds are important noncovalent bonds that enhance solubility and stability of macromolecules in water.

What determines the solubility of a molecule in water?

The presence of polar or charged functional groups that can form hydrogen bonds with water.

Which functional groups increase a molecule's solubility in water?

-OH (hydroxyl) groups, -COOH (carboxyl) groups, and -SH (sulfhydryl) groups.

How do -COOH groups affect solubility?

They can ionize into -COO⁻ and H⁺, making them strongly hydrophilic.

What is the effect of -SH groups on solubility?

They are polar and can form weak hydrogen bonds, enhancing solubility.

What is the significance of maintaining a narrow temperature range in living systems?

It preserves molecular stability and activity during chemical reactions.

What happens to ionic bonds on the surface of proteins or in the cytoplasm?

Ionic bonds are usually weaker due to constant interaction with water molecules.

What enhances the solubility of macromolecules in water?

Stable interactions between water and the macromolecule's surface groups through hydrogen bonds.

What role does water's high boiling point and heat capacity play in organisms?

They help regulate temperature and allow sweating to release excess energy.

How does water provide protection in cells?

It acts as a protective matrix, shielding cells from temperature extremes and supporting their framework.

What ions does water dissociate into, and why is this important?

Water dissociates into H⁺ and OH⁻ ions, which are essential for maintaining pH balance and driving biochemical reactions.

What are hydrophobic interactions?

They occur between non-polar molecules or groups that lack charged or polar functional groups.

What types of bonds characterize non-polar groups?

Non-polar groups primarily contain C-C and C-H bonds.

What functional groups are considered polar and can form hydrogen bonds?

-OH (hydroxyl), -SH (sulfhydryl), and -NH2 (amino) groups.

What are lipids and what type of bonds do they contain?

Lipids, such as fats and waxes, are mostly non-polar molecules containing many non-polar covalent bonds.

Why are lipids generally hydrophobic?

They lack significant amounts of polar bonds or charged groups.

What is the significance of hydrophobic interactions in proteins?

They help stabilize protein structure by clustering non-polar side chains away from water.

What are amphipathic molecules?

Molecules that contain both hydrophilic (water-loving) and hydrophobic (water-fearing) parts.

What is the structure of lipids (fatty acids) in relation to water?

They have a polar carboxyl group that interacts with water and a nonpolar hydrocarbon chain that avoids water.

How do sugars interact with water?

Sugars, which have many hydroxyl (-OH) groups, can form hydrogen bonds with water, making them highly water soluble.

What does the pH scale measure?

The concentration of hydrogen ions [H⁺] in a solution.

How is pH calculated?

pH = -log₁₀[H⁺], making it a logarithmic scale.

What does a shift from pH 4 to pH 6 indicate?

The solution becomes 100 times more basic, as it moves from a more acidic to a more basic condition.

What are buffers and how do they function?

Buffers are mixtures of a weak acid and its conjugate base that resist changes in pH.

Why are sugars different from non-polar molecules like fats?

Sugars have a large number of polar functional groups, making them highly soluble in water.

What happens to non-polar groups in an aqueous environment?

They cluster together to minimize their exposure to water.

What is the significance of the dual nature of amphipathic molecules in biology?

It is key to many biological processes, including the formation of cell membranes.

What is the relationship between pH and acidity?

Lower pH values correspond to higher [H⁺] (more acidic), while higher pH values correspond to lower [H⁺] (more basic).

What is the role of substances that can accept or donate protons in a solution?

They stabilize [H⁺] concentration, essential for maintaining near-neutral pH required for cellular processes.

What are polysaccharides and their biological roles?

Polysaccharides are long chains of sugar monomers that serve important structural roles and can have different biological functions depending on their linkage.

Give examples of durable structural polysaccharides and their functions.

Cellulose in plant cell walls and chitin in insect exoskeletons provide strength and rigidity.

How do carbohydrates contribute to catalytic functions?

When bound to proteins or enzymes, such as glycoproteins and glycolipids, carbohydrates help with recognition and activity.

What are artificial organs?

Human-made devices designed to replace or support the function of failing natural organs.

What are some examples of artificial organs?

Artificial limbs (prosthetics), artificial bladder, neurostimulators (deep brain stimulators), and artificial heart.

What is biocompatibility in the context of artificial organ development?

Biocompatibility is the major challenge, requiring organs or tissues to be built from living cells.

What are two major strategies to increase biocompatibility in artificial organs?

1. Tissue engineering with enhanced cell culture on a 3D patterned substrate (scaffold). 2. Making replacement organs that self-assemble into 3D aggregates known as organoids.

What are some types of biomaterials used in tissue engineering?

Metals, ceramics, polymers, composites, sponges, sheets, fibers, and hydrogels.

What characteristics should biomaterials possess for tissue engineering?

They should be non-cytotoxic, non-thrombogenic, non-immunogenic, bio-resorbable, bio-responsive, and bio-active.

What is the deadline for Project #1 in the course?

October 3, 2025, by 11:59 PM.

What is the main task for Project #1?

Research the engineering and biology behind a current biomedical innovation and report findings in a short video essay.