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Biology Exam I: Ch. 3 & 4

Biology Exam I: Flashcards for Chapters 3 & 4 only!
Describe how and why hydrogen bonds form in water.
Hydrogen bonds are the bonds between two polar molecules - one with a partial positive charge and one with a partial negative charge; water is perfect for this because it has the partial negative of Oxygen and the partial positive of Hydrogen.
What are emergent properties of water?
Special abilities water takes on when combined with itself (only works with large amounts of molecules, not just a single molecule)
What two properties of water do plants take advantage of, to move water against gravity, explain?
Cohesion and Adhesion.
Cohesion - waters ability to stick to ITSELF (other water molecules)
Adhesion - waters ability to stick to OTHER THINGS that are POLAR
Be able to recreate hydrogen bonding in water.
(see p. 1 slide 4 in ch. 3)
Describe surface tension and give an example relating to living organisms.
Hydrogen bonds in water hold each other together stronger than they'd bond to the air, for example. Ex: Jesus Christ lizard can walk on water because of it's surface tension; a dragonfly has non-polar exoskeleton so water beads on it
What is specific heat?
Resistance to change in temperature
How does waters specific heat compare to other solvents specific heat? What properties does it have that allows this? What affect does this have on the climate?
Waters specific heat is much higher that that of other solvents; this is because of hydrogen bonding; this keeps temperatures of places near/on bodies of water consistent
What is heat of vaporization? How does it relate to evaporative cooling? What affect does it have on living organisms?
Heat required to convert 1g of liquid into a gaseous state (high); Evaporative cooling is the warmest molecules of a liquid leave as a gas; allows us to sweat, or release heat so we don't die
Why is water in the solid phase less dense? How does this support life?
Hydrogen bonds keep the molecules spread out, so they don't pack together, making them less dense.
The floating ice insulates the body of water underneath it; if ice sank, then all the bodies of water would freeze solid, making life unlivable.
Describe the terms: solvent, solute, and solution.
Solvent: Substance doing the dissolving (water)
Solute: Substance being dissolved (sugar or salt)
Solution: homogenous mixture (product of solvent & solute)
What is the Universal Solvent?
What are the differences between a hydrophilic and hydrophobic substance?
Hydrophilic - attracted to water; polar or ionic; has charge
Hydrophobic - repels water; nonpolar; no charge
What is the pH scale?
pH is the measurement used to quantify the H⁺ ion concentration in an aqueous (water) solution
How do acids and bases affect pH?
Acids raise the concentration of H⁺ ions in an aqueous solution (decreases the pH number)
Bases lower the concentration of H⁺ ions (increases the pH number)
What are the molar concentrations of hydrogen and hydroxide ions in one liter of pure water?
H⁺ = 10⁻⁷ and OH⁻ = 10⁻⁷ Equation: [H⁺][ OH⁻] = 10⁻¹⁴ (always = to 14)
Be able to calculate the molar concentrations of hydrogen and hydroxide ions from a given pH value or vice versa.
Ex: pH = 12, What is the molar concentration of H⁺? OH⁻? H⁺ is 1 x 10⁻¹², OH⁻ is 1 x 10⁻².
What is a buffer?
Buffers are molecules that resist change in pH; they either release H⁺ to lower the pH or take up H⁺ to raise the pH
Organic molecules must always contain what?
Carbon and Hydrogen
Why is carbon the basic building element of life?
Because it can bond to 4 other atoms (tetravalent - 4 valence electrons)
How many valence electrons does carbon have? How many single covalent bonds can it form?
4 and 4
What are primary producers?
Fix C from atmospheric CO₂ (ex: Plants w/ photosynthesis)
What is a hydrocarbon? Polar or non-polar?
Organic molecules composed solely of Carbon and Hydrogen; Nonpolar covalent bond so they resist/repel water (ex: fat)
What are the different types of isomers (changes) and how are they different?
1.) Structural - changes structural form; same formula, different structure
2.) Geometric - differ in spatial arrangement due to inflexibility of double bond (two types: cis and trans) 3.) Enantiomers - mirror images of each other
Does form impact function?
What are functional groups? Names?
Small organic molecules with great effects:
Hydroxyl, Carbonyl, Carboxyl, Amino, Sulfhydryl, Phosphate, and Methyl
Do the functional groups have an impact on life? Give an example.
Yes. Ex: tiny tag from a functional group determines whether we are males or females
Hydroxyl, Carbonyl, Carboxyl, Amino, Sulfhydryl, Phosphate, and Methyl
Draw functional group structure and give molecular formula for: Hydroxyl.
Hydroxyl (polar, form hydrogen bonds, polar solvents)
−OH (may be written HO-)
Ex: Alcohols, such as Ethanol
Draw functional group structure and give molecular formula for: Carbonyl.
Carbonyl (>CO) (ketones, aldehydes, sugars); C double bonded to O



Ex: Acetone, the simplest ketone
Draw functional group structure and give molecular formula for: Carboxyl.
Carboxyl (-COOH) acidic properties, components of many biologically important molecules; C double bonded to O and single to OH



Ex: Formic acid or acetic acid
Draw functional group structure and give molecular formula for: Amino.
Amino (-NH₂) (acts as a base, amino acids); N single bonded to 2 H's


Ex: Glycine
Draw functional group structure and give molecular formula for: Sulfhydryl.
Sulfhydryl (−SH or HS−) (protein cross-linking, stabilizes structure)
Ex: Covalent bonding w/ other sulfhydryls (disulfide bridge)
Draw functional group structure and give molecular formula for: Phosphate.
Phosphate (−OPO₃²⁻) (acid: DNA, cell membrane, ATP); P double to O, single to O, 2 O⁻



Ex: glycerol phosphate
Draw functional group structure and give molecular formula for: Methyl.
Methyl (−CH₃) (sex hormones, DNA methylation (when it gets tagged onto your DNA); C single bonded to 3 H's

−C − H

Ex: 5-methyl cytidine
What scale is pH?
A log scale. Each change is 10 times. So when we go up or down, we add a zero to the end.

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