Bio 277 : Unit 1 Homeostasis, proteins, cells and metabolism)

Unit 1 Objectives

1. What is Homeostasis?

The maintenance of a stable internal environment despite external changes.

What are the components of a homeostasis loop?

• Controlled Variable: What is regulated (e.g., body temp)

• Sensor: Detects changes (e.g., receptors)

• Integrating Center: Processes input (e.g., brain)

• Effector: Carries out response (e.g., sweat glands)

What does a typical human cell contain?

• Plasma Membrane: Controls entry/exit

• Nucleus: Stores DNA

• Ribosomes: Make proteins

• Rough ER: Protein synthesis

• Smooth ER: Lipid synthesis

• Golgi: Packages proteins

• Mitochondria: Make ATP

• Lysosomes: Break down waste

• Peroxisomes: Detoxify

• Cytoskeleton: Support and transport

What are the 3 main types of cell junctions?

• Tight Junctions: Seal cells (e.g., intestines)

• Desmosomes: Anchor cells (e.g., skin)

• Gap Junctions: Communicate (e.g., heart)

What are the 4 major macromolecules?

• Carbohydrates: Energy & structure

• Lipids: Energy storage, membranes

• Proteins: Enzymes, structure

• Nucleic Acids: DNA/RNA, genetic info

What is an Ion?

An atom/molecule with a charge due to loss or gain of electrons.

Types of Chemical Bonds?

• Covalent: Share electrons (e.g., H₂O)

• Ionic: Transfer electrons (e.g., NaCl)

• Hydrogen: Weak bonds (e.g., DNA strands)

• Van der Waals: Weak attractions (e.g., lipids)

What is pH?

• pH = –log[H⁺]

• ↓ pH = ↑ H⁺ = acidic

• ↑ pH = ↓ H⁺ = basic

What are the 3 fluid compartments?

• Intracellular Fluid (ICF): Inside cells

• Interstitial Fluid (IF): Between cells

• Plasma: Blood fluid
  Exchange via diffusion/osmosis/transport.

What is the Central Dogma?

DNA → RNA → Protein
DNA is transcribed to mRNA, then translated into protein.

Protein Structure Levels?

• Primary: Amino acid sequence

• Secondary: Helices/sheets (H-bonds)

• Tertiary: 3D shape (various bonds)

• Quaternary: Multiple subunits

How does protein shape relate to function?

Shape and charge determine binding and activity (e.g., enzymes, antibodies).

What is the Law of Mass Action?

In reversible reactions, direction depends on concentrations of reactants/products.

What is the difference between anabolism and catabolism?

• Anabolism: Builds molecules, uses energy

• Catabolism: Breaks down molecules, releases energy

Give examples of anabolic/catabolic reactions

• Carbs: Glycogenesis / Glycolysis

• Lipids: Lipogenesis / Beta-oxidation

• Proteins: Protein synthesis / Proteolysis

What’s the difference between oxidative & substrate-level phosphorylation?

• Oxidative: ETC + O₂, lots of ATP

• Substrate-level: Direct phosphate transfer, little ATP

What are the steps of ATP production?

• Glycolysis → 2 ATP

• Krebs Cycle → e⁻ carriers

• ETC + O₂ → 28+ ATP

What do diffusion, facilitated diffusion, and osmosis have in common?

All are passive transport; no ATP needed.
Diffusion: Small molecules
Facilitated: With proteins
Osmosis: Water

Graph: Simple vs. Facilitated Diffusion Rate

• Simple: Linear

• Facilitated: Levels off at saturation

What is transporter saturation?

Point where all transporters are full—max rate is reached.

What is active transport?

Moves substances against gradient:

• Primary: Uses ATP directly

• Secondary: Uses gradient from primary

What are normal ion gradients across a membrane?

• High inside: K⁺, proteins⁻

• High outside: Na⁺, Ca²⁺

What are ion channels & gating types?

Pores for ions; gates open via:

• Voltage change

• Ligand binding

• Mechanical force

What is transcytosis?

Vesicle-mediated transport across cells.
Examples:

• Antibodies in infants

• Insulin across capillaries