Biology: Osmosis and Ionic Compounds

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Questions and Answers

What is the function of heparin in the body?

Provides tensile strength to connective tissue

Provides elasticity to cartilage

Acts as a natural anticoagulant by binding to antithrombin protein (correct)

Maintains skin flexibility

Which type of glycoconjugate is involved in cell-cell recognition and cell migration?

Glycoproteins (correct)

Lectins

Proteoglycans

Glycolipids

What is the function of keratan sulfate?

Found in the cornea and cartilage, but does not contain uronic acid (correct)

Involved in blood clotting

Maintains skin flexibility

Provides elasticity to cartilage

What is the main component of bacterial cell walls?

Peptidoglycan Signup and view all the answers

What is the function of selectins?

Involved in cell-cell recognition and signaling Signup and view all the answers

What is the function of dermatan sulfate?

Maintains skin flexibility Signup and view all the answers

What is the function of chondroitin sulfate?

Provides tensile strength to connective tissue Signup and view all the answers

What is the function of glycolipids?

Involved in cell-cell recognition and signaling Signup and view all the answers

What is the primary mechanism by which water dissolves salts such as NaCl?

By hydrating and stabilizing the Na+ and Cl- ions Signup and view all the answers

What is the characteristic of an amphipathic compound?

Having a hydrophilic head group and a hydrophobic tail Signup and view all the answers

What is the term for a solution that has a higher concentration of solutes than the cell?

Hypertonic Signup and view all the answers

What is the purpose of a buffer in a solution?

To resist changes in pH upon the addition of an acid or base Signup and view all the answers

What is the result of the reversible ionization of water molecules?

Hydrogen ions are formed and immediately hydrated to form hydronium ions Signup and view all the answers

What is the value of Keq in the equation for the ionization of water at a temperature of 25°C?

1.8 x 10-16 M Signup and view all the answers

What is the pH of a solution with a concentration of [H+] = 1 x 10^-7 M?

7 Signup and view all the answers

What is the defining characteristic of a strong acid?

It has a greater tendency to lose protons Signup and view all the answers

What is the role of a proton acceptor in an acid-base reaction?

It accepts a proton Signup and view all the answers

What is the purpose of a buffer system?

To maintain a relatively constant pH Signup and view all the answers

What is the general formula for carbohydrates?

(CH2O)n Signup and view all the answers

What is one of the functions of carbohydrates in the body?

To provide energy through oxidation Signup and view all the answers

What is an example of a biological buffer?

Hemoglobin Signup and view all the answers

What is the equation for the carbonate/bicarbonate buffer system?

H2CO3 = H+ + HCO3- Signup and view all the answers

What is the average weight of an amino acid?

110 Signup and view all the answers

What type of bonds stabilize the structure of an alpha helix?

Hydrogen bonds Signup and view all the answers

What is the primary structure of a protein?

The sequence of amino acid residues Signup and view all the answers

What type of protein has a repeated heptapeptide in its primary structure?

Keratin Signup and view all the answers

What is the function of a beta turn in a protein?

To connect the ends of two antiparallel sheets in a 180-degree turn Signup and view all the answers

What is the type of protein that has a quaternary structure consisting of two or more polypeptides?

Globular protein Signup and view all the answers

What is the non-amino acid part of a conjugated protein?

All of the above Signup and view all the answers

What is the type of bond that stabilizes the tertiary structure of immunoglobulins?

Disulfide bond Signup and view all the answers

What is the primary function of heat shock proteins?

To prevent denaturation and stimulate protein folding Signup and view all the answers

Which enzyme is responsible for catalyzing the reshuffling of disulfide bonds?

Protein disulfide isomerase Signup and view all the answers

What is the purpose of ion exchange chromatography?

To separate proteins based on their charge and binding affinity Signup and view all the answers

What is the main difference between proteins that migrate faster or slower in size exclusion chromatography?

Their size and shape Signup and view all the answers

Which of the following proteins is associated with the formation of brain plaques in Alzheimer's disease?

Amyloid-β protein Signup and view all the answers

What is the primary function of chaperonins?

To facilitate folding of proteins Signup and view all the answers

What is the purpose of differential centrifugation?

To isolate specific organelles from a cell Signup and view all the answers

Which of the following is NOT a type of column chromatography?

Differential centrifugation Signup and view all the answers

Study Notes

Water and Salts

Water dissolves salts like NaCl by hydrating and stabilizing Na+ and Cl- ions, weakening electrostatic interactions between them.
Amphipathic compounds have a hydrophilic or polar head group and a hydrophobic tail, usually a hydrocarbon.

Osmosis

Osmosis is the movement of water across a semi-permeable membrane driven by differences in osmotic pressure.
Types of osmotic systems:
- Isotonic: balanced, no net water movement
- Hypotonic: diluted solution, water moves into the cell (RBC cell wall may burst)
- Hypertonic: concentrated solution, water moves out of cells (shrinking)

Buffers, Weak Acids, and Bases

Buffers: aqueous systems that resist a change in pH upon the addition of an acid or base, consisting of a weak acid (proton donor) and its conjugated base (proton acceptor).
Ionization of water:
- Water molecules undergo reversible ionization to yield a hydrogen ion (a proton) and a hydroxide ion.
- Hydrogen ions formed in water are immediately hydrated to form hydronium ions (H3O+).
Example: calculating the concentration of H+ in water using Keq.

Acids and Bases

Acids: proton donors, strong acids disassociate fully in aqueous solutions to give H+ ions.
Bases: proton acceptors, strong bases disassociate fully in aqueous solutions to give OH- ions.
Acid-base pairs: a proton donor and corresponding proton acceptor make up a conjugate acid-base pair.

Biological Buffers

Examples of biological buffers:
- Hemoglobin
- Proteins (histidine)
- Carbonate/bicarbonate system: H2CO3 = H+ + HCO3-
- Phosphate buffer system: H2PO4- = H+ + HPO42-

Carbohydrates

Carbohydrates are polyhydroxy aldehydes, ketones, or substances that yield such compounds.
Functions of carbohydrates:
- Energy yielding (by oxidation of carbohydrates)
- Insoluble carbohydrates serve as structural and protective elements
Types of carbohydrates:
- Glycoconjugates: carbohydrate joined to protein or lipid
- Peptidoglycan: linear (acetylglucosamine + acetylmuramic acid), hetero, cross links, forms strong sheath, present in bacterial cell wall
- Proteoglycans: macromolecules in ECM or cell surface, in connective cartilage tissues, do non-covalent interactions (strength) between cells and ECM
- Glycoproteins: carbohydrate + protein, in out face of plasma membrane, ECM, and blood
- Glycolipids: membrane proteins (hydrophilic part is an oligosaccharide), intercellular communication

Proteins

Primary structure: sequence of amino acid residues
Secondary structure: residues giving rise to recurring structural proteins, e.g., a-helix and B-conformations
- a-helix: hydrogen bonding stabilizes the structure
- B-helix: backbone is extended as a zig-zag rather than helical in the form of sheets known as pleats
Tertiary structure: 3D folding of polypeptide
Quaternary structure: 2 or more polypeptides
Interactions that stabilize the tertiary structure:
- Disulfide bonds: covalent linkage formed from SH of 2 cysteines forming cystine
- Heat shock proteins: hsp70 binds and hydrolyses ATP
- Chaperonins: facilitate folding
Diseases related to protein misfolding:
- Alzheimer's: Amyloid B protein (formation of brain plaques)
- Parkinson's: a-synuclein

Separation and Purification of Proteins

Methods:
- Column chromatography:
  - Ion exchange chromatography: based on charge
  - Size inclusion chromatography/gel filtration: based on size
  - Affinity chromatography: based on binding specificities

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Description

Understand the process of osmosis, ionic compounds, and amphipathic molecules. Learn how water dissolves salts and the effects of osmotic pressure.