Vertebrate Physiology - Ch 2

Categories of biological molecules

1) Carbohydrates: sugars

2) Lipids: fats

3) Amino acids: proteins

4) Nucleic acids: DNA and RNA

How is differential gene expression accomplished?

• Regulation of individual genes with promoters and transcription factors

• Regulation of transcription factors in different tissues and at different stages

Protein transport

1) Synthesized in rough endoplasmic reticulum

2) In ER → modified, folded, and packaged into vesicles

3) Vesicles fuse with golgi apparatus

4) In golgi → modified further and packaged into vesicles

5) Vesicles sorted to various locations in cell

6) Certain stimuli cause release of proteins

Function of peroxisomes

Aid cell in detoxifying oxygen radicals

Function of centrosomes

Microtubule organizing centers

Function of microtubules

Attach centromer to chromosomes during anaphase

Vaults

Hollow structures capable of docking with nuclear pores

→ Transport mRNA from nucleus to cytoplasm

Exocytosis

Primary mechaism for secretion into extracellular fluid

Pinocytosis

*Not selective

*Cell drinking

→ Takes in macromolecules

1) Particle attaches to receptors on outside of cell

2) Proteins pull membrane inward

3) Vesicle forms and breaks off

Phagocytosis

*Cell eating

→ Takes in bacteria or whole cells

1) Ligand on particle binds with receptor

2) Membrane evaginates out and surrounds particle

3) Vesicle forms and breaks off

Receptor mediated endocytosis

*Selective

→ Takes in specific large molecules

1) Ligand binds to receptor

2) Proteins pull membrane inward

3) Vesicle forms and breaks off

Proteosomes

Large, tunnel-shaped structures made of proteins

→ Break down internal proteins

Cristae

Folded inner membrane of mitochondria

→ Folding implies surface where lots of exchange happens

Glycolysis

• Takes place in cytosol

• Anaerobic

• Glucose → 2 pyruvate, 2 ATP, 2 NADH

• Purpose: generate pyruvate to feed citric acid cycle

Citric acid cycle

• Occurs in mitchondrial matrix

• Aerobic

• 2 pyruvate → 2 acetyl CoA, 2 NADH

  • Acetyl CoA → 2 ATP, 6 NADH, 2 FADH2

Electron transport chain

• Occurs in inner mitochondrial membrane

• Aerobic

• Protons pumped into intermembrane space produce gradient

• ATP synthase allows H+ to cross membrane and generates ATP

• Glucose → 30 ATP

Anaerobic respiration

• Glycolysis still occurs: glucose → 2 pyruvate, 2 ATP, 2 NADH

• 2 pyruvate → 2 lactate

  • Pyruvate acts as electron acceptor → NADH oxidized to NAD+

• Glucose → 2 ATP

Three componenets of cytoskeleton

1) Microtubules

2) Microfilaments

3) Intermediate filaments

Function of microtubules in cytoskeleton

• Maintain cell shape

• Position organelles

• Coordinate complex cell movements

Function of microfilaments in cytoskeleton

• Contractions

  • Actin/myosin interactions

• Cell locomotion

Function of intermediate filaments in cytoskeleton

• Maintain structure and resist mechanical stress

Adhering junctions (desmosomes)

Achor together two closely adjacent cells

Tight junctions

Joins cells in epithelial sheets (permeable)

Prevents materials from passing between cells

Gap junctions

Link adjecent cells by connexons

→ Movement of ions through gap junctions transmits electrical activity

→ Enables synchronized muscule contractions