Lect3: Chemistry for Human Physiology a&p

What are the two main parts of an atom?

Nucleus + electron cloud

What does the nucleus contain?

Protons (+) and neutrons (neutral)

What does the electron cloud contain?

Electrons (−)

What part of an atom forms bonds?

Electrons

How can electrons form bonds?

By interacting or sharing with electrons of another atom

What is O₂?

Two oxygen atoms bonded together

What is a covalent bond?

A bond where atoms share electrons

What is a nonpolar covalent bond?

Electrons are shared equally.

What is a polar covalent bond?

Electrons are shared unequally.

Why are electrons shared unequally in a polar bond?

They spend more time near the more electronegative atom.

What happens to charge in a polar molecule?

Unequal sharing creates partial positive (δ+) and negative (δ−) charges.

Is O₂ polar or nonpolar?

Nonpolar

Is water (H₂O) polar or nonpolar?

Polar

What do polar molecules often contain?

Electronegative atoms

What is electronegativity?

An atom’s ability to attract electrons

What are the most electronegative atoms to know for anatomy?

F, O, N, Cl, S, P

What mnemonic helps remember F, O, N, Cl, S, P?

“Phone Calls P”

In a polar bond, which atom becomes partially negative (δ−)?

The more electronegative atom

Which atom becomes partially positive (δ+)?

The less electronegative atom

What is an ionic bond?

A bond where electrons are given or taken (transferred).

What happens when an atom loses an electron?

It becomes a positive ion (cation).

What happens when an atom gains an electron?

It becomes a negative ion (anion).

What is a cation?

Positive (+) ion
Think: “CATS make me feel positive”

What is an anion?

Negative (−) ion

What are ionic bonds associated with in anatomy?

Charge

What are ions called when dissolved in water/body fluids?

Electrolytes

Where are electrolytes found in the body?

Interstitial and intracellular fluids

What happens in a REDOX reaction?

Electrons are transferred between substances.

What is oxidation?

Loss of electrons

What is reduction?

Gain of electrons

What does OIL RIG mean?

Oxidation Is Loss, Reduction Is Gain

In MgCl₂ formation, what happens to magnesium (Mg)?

Mg loses electrons → oxidized

In MgCl₂ formation, what happens to chlorine (Cl)?

Cl gains electrons → reduced

What is a hydrogen bond?

Attraction between opposite partial charges

Are hydrogen bonds true electron-mediated bonds?

No, they are attractions between charges

Hydrogen bonds typically occur between what type of molecules?

Polar molecules

What charge does hydrogen have in a polar molecule?

Slightly positive (δ+)

What does the slightly positive hydrogen attract?

A slightly negative (δ−) electronegative atom

What is an example of hydrogen bonding?

Attraction between water molecules

How many hydrogen bonds can one water molecule form?

Up to 4 hydrogen bonds

Why can water form multiple hydrogen bonds?

Its polar charges attract nearby water molecules

What attracts during hydrogen bonding in water?

δ+ hydrogen of one water molecule attracts δ− oxygen of another

What can water dissolve (solubilize)?

Polar or charged substances

What does hydrophilic mean?

Water-attracting; dissolves/interacts well with water

Why can water dissolve ions and polar substances?

Because water is polar

What is a hydration layer?

A layer of water molecules surrounding a charged or polar substance.

How does water orient around ions?

Oxygen (δ−) faces positive ions; hydrogen (δ+) faces negative ions

Why is water polar?

Oxygen is partially negative (δ−) and hydrogens are partially positive (δ+)

Why is water called a universal solvent?

It dissolves many polar and ionic substances

Why is water important for cellular reactions?

It provides a liquid medium for metabolic and chemical reactions

How does water help with transport in the body?

Helps transport nutrients and waste

What does it mean that water has a high specific heat?

It can absorb/release lots of heat with little temperature change

Why is water’s high specific heat important?

Helps stabilize body temperature

What does high heat of vaporization mean?

It takes lots of energy to turn water into gas

How does evaporation help cool the body?

Sweating removes heat as water evaporates

What type of bond is Na⁺ — Cl⁻?

Ionic bond

What type of bond is Cl—Cl?

Nonpolar covalent bond

What type of bond is O—H ··· O—H?

Hydrogen bond (the ··· between molecules)

What type of bond is H—Cl?

Polar covalent bond

In H₂O ··· H₂O, how many of each bond type are present?

4 covalent bonds, 1 hydrogen bond, 0 ionic bonds

Why is water polar?

Oxygen is partially negative (δ−) and hydrogens are partially positive (δ+)

Why is water called a universal solvent?

It dissolves many polar and ionic substances

How does water help support life?

Provides a liquid medium for cellular reactions and helps transport nutrients and waste.

What is high specific heat?

Water absorbs/releases lots of heat with little temperature change.

What is high heat of vaporization?

It takes lots of energy to turn liquid water into gas

How does water help regulate temperature?

Stabilizes body temperature and provides cooling through evaporation (sweating).

What is metabolism?

Building and breaking down molecules in the body.

What are catabolic reactions?

Break down molecules and release energy.

What are anabolic reactions?

Build molecules and require energy

What happens to bonds during catabolism vs. anabolism?

Catabolism breaks bonds; anabolism forms bonds

What is dehydration synthesis?

Removes water to form a new bond.

What is hydrolysis?

Adds water to break a bond.

What biomolecules use dehydration synthesis and hydrolysis?

Carbohydrates, proteins, lipids, and nucleic acids

Dehydration synthesis vs. hydrolysis?

Dehydration = builds; Hydrolysis = breaks down

What is a Brønsted-Lowry acid?

Donates H⁺ (protons)

What is a Brønsted-Lowry base?

Accepts H⁺ (protons)

What does pH measure?

Concentration of H⁺ ions in a solution

Acid vs. base?

Acid = gives H⁺; Base = takes H⁺

What does pH measure?

H⁺ concentration in a solution.

What happens to H⁺ as pH increases?

H⁺ decreases

What happens to H⁺ as pH decreases?

H⁺ increases

How much does H⁺ concentration change with each pH unit?

10×

What does a 2-unit pH change represent?

100× change in H⁺ concentration

What pH is neutral?

7

What pH is acidic?

Below 7

What pH is basic (alkaline)?

Above 7

As pH decreases, what happens to acidity and H⁺?

Both increase

Saliva = pH 6.2 and spleen = pH 7.2. Which is more acidic and by how much?

Saliva; 10× more H⁺

Saliva = pH 6.2 and stomach = pH 4.2. Which is more acidic and by how much?

Stomach; 100× more H⁺

The stomach normally has a much lower pH than most other parts of the body. Why is this useful?

A. It helps the stomach absorb more water

B. The acidic environment break down food

C. It prevents the stomach from moving

D. It makes the blood more acidic

B. The acidic environment break down food

Stomach fluid = pH 2 and urine = pH 5. How much more H⁺ does stomach fluid have?

1,000× more H⁺

If the urine sample contains 8mg of H+, how many mg of H⁺ does the stomach fluid sample contain?

A. 24 mg

B. 240 mg

C. 800 mg

D. 8,000 mg

D. 8,000 mg

What is the job of a buffer?

Resists sudden changes in pH

What does a buffer do when there is too much acid (H⁺)?

Accepts H⁺

What does a buffer do when there is too much base (too little H⁺)?

Donates H⁺

What is an example of a buffer?

Phosphate buffer

Which direction does the phosphate buffer reaction shift?

Too much H⁺ → left; too little H⁺ → right

What is the main blood buffer system?

Carbonic acid–bicarbonate buffer system

What equation should you memorize for the blood buffer system?

H₂CO₃ ⇌ H⁺ + HCO₃⁻

What is H₂CO₃?

Carbonic acid