AP Biology Unit 1: The Chemistry of Life

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Questions and Answers

Which of the following macromolecules serves primarily as structural support in plant cells?

Cellulose (correct)

Glycogen

Starch

Chitin

What is the bond type called that forms between two monosaccharides to create a disaccharide?

Glycosidic linkage (correct)

Ionic bond

Peptide bond

Hydrogen bond

Which of these carbohydrates is primarily used for energy storage in animals?

Cellulose

Fructose

Sucrose

Glycogen (correct)

Which carbohydrate has a 1,4 beta linkage, making it indigestible to humans?

Cellulose Signup and view all the answers

Which of the following correctly describes the composition of carbohydrates?

Composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio Signup and view all the answers

What type of bond primarily stabilizes the alpha helix and beta pleated sheet structures in proteins?

Hydrogen bonds Signup and view all the answers

Which of the following characteristics contributes to the tertiary structure of proteins?

Interactions between R groups Signup and view all the answers

What is a common characteristic of hydrophobic R groups in amino acids?

They contain primarily carbon and hydrogen. Signup and view all the answers

Which of the following statements correctly describes the quaternary structure of a protein?

It can consist of multiple polypeptide chains coming together. Signup and view all the answers

Which component of nucleic acids is responsible for their overall negative charge?

Phosphate groups in nucleotides Signup and view all the answers

What is the primary structure of proteins composed of?

A long string of amino acids Signup and view all the answers

What type of bond forms between adjacent amino acids?

Peptide bond Signup and view all the answers

Which statement about the R group of amino acids is true?

It determines the functional properties of the amino acid. Signup and view all the answers

What type of bond is involved in the stabilization of protein tertiary structure?

All of the above Signup and view all the answers

What are the two functional groups present in all amino acids?

Carboxylic acid and Amine group Signup and view all the answers

What is the difference between the sugar found in DNA and RNA?

RNA contains ribose while DNA contains deoxyribose. Signup and view all the answers

Which pair of nitrogenous bases is correctly matched with the number of hydrogen bonds they form?

Adenine and Thymine - two bonds Signup and view all the answers

What characteristic distinguishes purines from pyrimidines?

Purines include Adenine and Guanine; pyrimidines include Cytosine and Thymine. Signup and view all the answers

Which statement correctly describes the orientation of DNA strands?

One strand runs from 5' to 3' while the other runs from 3' to 5'. Signup and view all the answers

Which of the following is true regarding the structure of lipids?

Lipids are primarily made up of carbon, hydrogen, and often oxygen. Signup and view all the answers

Study Notes

Macromolecules

Four macromolecules (carbohydrates, proteins, nucleic acids, lipids) are crucial for biological processes.
Each has a unique structure and function.

Carbohydrates

Composed of carbon, hydrogen, and oxygen (1:2:1 ratio).
Monomer: monosaccharide (e.g., glucose, fructose, galactose).
Polymer: polysaccharide.
Glucose structure: ring structure; chemical formula C₆H₁₂O₆.
Dehydration reaction joins two monosaccharides to form a disaccharide (e.g., sucrose, lactose, maltose).
Bond between monosaccharides: glycosidic linkage.
Polysaccharides: cellulose (plant cell walls, structural), chitin (fungi cell walls, exoskeletons), starch (plant energy storage), glycogen (animal energy storage).
Starch and cellulose differ in glycosidic linkage (alpha-1,4 for starch; beta-1,4 for cellulose) - allowing us to break one but not the other.
Symbiotic relationships exist (termite gut microbes breaking down cellulose).

Proteins

Composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
Monomer: amino acid.
Amino acid structure: central carbon bonded to an amino group (NH₂), a carboxyl group (COOH), a hydrogen atom, and a variable R group.
Peptide bond forms between the carboxyl group of one amino acid and the amino group of the next.
Directionality: N-terminus (amino end) to C-terminus (carboxyl end).
Protein structure levels:
- Primary: linear sequence of amino acids.
- Secondary: alpha helix or beta-pleated sheet (hydrogen bonds in the protein backbone).
- Tertiary: 3D structure formed by various bonds (covalent, ionic, hydrogen, van der Waals, hydrophobic interactions) between R groups.
- Quaternary: multiple polypeptides forming a larger protein (e.g., collagen, hemoglobin).
R groups can be hydrophobic, hydrophilic, or charged.
Hydrophobic R groups fold inward, while hydrophilic ones fold outwards.
- Charged ones can form ionic bonds with water or other polar molecules.

Nucleic Acids

Composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus (in phosphate groups).
Monomer: nucleotide.
Nucleotide structure: phosphate group, nitrogenous base (adenine, guanine, cytosine, thymine/uracil), and a pentose sugar (deoxyribose/ribose).
Phosphodiester linkage joins nucleotides.
Directionality: 5' end (phosphate) to 3' end (hydroxyl).
DNA structure: double helix; antiparallel strands; base pairing (A-T with two hydrogen bonds; C-G with three hydrogen bonds).
RNA structure: single-stranded; contains uracil instead of thymine.
Differences between DNA and RNA: sugar type (deoxyribose vs. ribose) and strandedness.

Lipids

Composed of carbon, hydrogen, and oxygen.
Non-polar.
Not polymers (no repeating monomer units).
Types:
- Fats (triglycerides): glycerol backbone + 3 fatty acids linked by ester bonds.
  - Saturated fats (all single bonds) are solid at room temperature.
  - Unsaturated fats (at least one double bond) are liquid at room temperature (oils).
- Phospholipids: glycerol backbone + 2 fatty acids + phosphate group.
  - Amphipathic (polar head, non-polar tails).
  - Form bilayers in water.
- Steroids: four fused carbon rings (e.g., cholesterol, hormones). Key roles in cell signaling.

Water Properties

Polar covalent bonds (unequal electron sharing).
Hydrogen bonds between water molecules.
Cohesion: water molecules attracted to each other.
Adhesion: water molecules attracted to other polar substances.
Capillary action: combined effect of cohesion and adhesion.
Surface tension: resistance to increase in surface area due to hydrogen bonds.
Water is a universal solvent.
High specific heat: resists changes in temperature.
Ice is less dense than liquid water (hydrogen bonds stabilize crystal structure).
Evaporative cooling: heat absorbed to change water from liquid to gas phase.
pH: negative logarithm of hydrogen ion concentration (inverse relationship); pH scale (acidic/basic), significant for biological systems.

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Description

This quiz explores the four key macromolecules: carbohydrates, proteins, nucleic acids, and lipids. Each macromolecule's structure and function play vital roles in biological processes, from energy storage to genetic information. Test your knowledge on their compositions and interactions!