Lecture 8

BIOL 118 Exam 1

What defines an acid?

releases H⁺

What defines a base?

accepts H⁺

Is water an acid or a base?

both because it donates and accepts H⁺ (amphoteric)

neutral pH

7.0

acidic

pH < 7.0

basic

pH > 7.0

A change of 1 pH unit

10× change in acidity

high blood pH (too basic)

• Decrease ventilation

• CO₂ increases

• Carbonic acid increases

• pH decreases

low blood pH (too acidic)

• Increase ventilation

• CO₂ decreases

• Carbonic acid decreases

• pH increases

Which two organ systems can be involved in feedback loops of blood pH?

• Respiratory system

• Urinary (renal) system

Why does ventilation affect pH?

• More breathing → less CO₂ → fewer H⁺ → higher pH

• Less breathing → more CO₂ → more H⁺ → lower pH

Which organs regulate CO₂?

lungs

Which organs regulate H⁺ and HCO₃?

kidneys

What causes protein denaturation?

• pH shifts

• Temperature extremes

• Chemicals

What happens during protein denaturation?

• Protein loses its shape

• Active site changes

• Function is reduced or lost

Can proteins recover from denaturation?

sometimes, but severe denaturation is irreversible

Which structure is NOT easily disrupted by denaturation?

primary structure (peptide bonds are strong covalent bonds)

How to find an “optimal” pH for a protein’s activity?

the pH at which the protein (or enzyme) shows its highest activity

Why would the body sometimes intentionally denature a protein?

to make them easier to break down, inactivate, or destroy

examples of intentional protein denaturation

• Digestive enzymes

• Lysosomes

• Immune defense

lysosome

a membrane-bound organelle that acts as the cell’s digestive and recycling center

function of lysosome

• Digest macromolecules

• Destroy pathogens

• Break down damaged organelles

• Recycle cellular parts

structure of lysosome

• Membrane-bound

• Filled with hydrolytic enzymes

internal environment of lysosome

very acidic

How do H+ ions get concentrated in a lysosome?

Active transport (ATP-driven proton pumps)

Three lysosomal pathways

phagocytosis, autophagy, and autolysis

Phagocytosis

• Eats large external particles

• Example: bacteria

Endocytosis

Eats small external material

Autophagy

• Eats self

• Removes damaged organelles

• Reduces inflammation

• Protects against disease

Autolysis

Self-destruction of a cell

What is the relationship between autophagy and inflammation?

Autophagy reduces inflammation by removing damaged proteins and organelles before they can trigger cellular stress and immune responses. When autophagy declines, cellular debris accumulates, leading to increased oxidative stress and chronic inflammation.

Why does lysosome function decline as we age?

• Accumulation of damaged material

• Increased oxidative stress

• Decline in proton pumping

• Reduced autophagy

• Changes in membrane integrity

What happens when lysosomes malfunction?

• Alzheimer’s

• Parkinson’s

• ALS

Amphipathic

hydrophobic + hydrophilic

Emulsification

a type of mechanical digestion where large fat globules are broken into many tiny droplets (doesn’t break chemical bonds, only change physical form)

How do amphipathic bile salts aid lipid digestion?

Amphipathic bile salts embed their hydrophobic regions into fat while their hydrophilic regions face water, breaking large fat globules into small droplets and preventing them from recombining. This emulsification increases surface area and allows lipase enzymes to digest lipids more efficiently.

What happens if lipases were lost?

• No fat digestion

• Poor absorption

• Greasy stool

• Vitamin deficiencies

major cellular functions (catabolism)

• Lysosome

• Mitochondria

• Peroxisome

major cellular functions (anabolism)

• Ribosome

• Rough ER

• Golgi

• Nucleus

major cellular functions (support)

• Cytoskeleton

• Cell membrane

major cellular functions (transport)

• Cell membrane

• Vesicles

• ER

• Golgi

energy balance equation

Energy in = Energy stored + Energy used + Energy lost as heat

metabolism at each level of organization

• Molecules → bonds

• Organelles → ATP

• Cells → work

• Organs → homeostasis

• Organism → metabolism