Chapter 2: The Cell

What is the cell theory?

1. A cell is the most basic unit of life

2. All organisms are composed of cells

3. All cells come from pre-existing cells

What are the shared characteristics of cells?

1. All cells are enclosed by a membrane

   • Regulates passage of materials between environment and inside of cell

2. All cells contain genetic material

T/F: Cells demonstrate a correlation between structure and function

T; “form fits function”

What are the two cells types of the body?

1. Somatic - “body cells”

   • All cells excluding gametes

2. Gametes - “sex cells”

   • Sperm

   • Oocyte

What pattern of inheritance does mitochondrial DNA follow?

Maternal inheritance; sperm does NOT donate cytoplasmic material

Which form of microscopy forms an internal image of a cell via the passage of electrons?

Transmission Electron Microscopy

Which form of microscopy utilizes a gold coating so that electrons bounce of the surface of specimen resulting in an image with surface detail?

Scanning Electron Microscopy

What are the membranous organelles of a cell?

• Golgi apparatus

• Lysosome

• Mitochondrion

• Nucleus

• Nucleolus

• Peroxisome

• Rough endoplasmic reticulum

• Secretory vesicles

• Smooth endoplasmic reticulum

What are the non-membranous organelles of a cell?

• Centriole

• Centrosome

• Cytoskeleton

• Microvilli

• Ribosomes

What is the main structural component of membranes?

Phospholipids

Which structure on a phospholipid is hydrophilic?

Head; polar due to O^- on phosphate group

Which structure on a phospholipid is hydrophobic?

Tail; lacks polarity

What are the roles of the plasma membrane?

• Cell-cell communication

• Structural support, adhesion

• Regulates exchange w/ extracellular fluid

• Physical barrier

• Senses extracellular stimuli

What are the components of a plasma membrane?

• Phospholipids

  • Form lipid bilayer

• Proteins

  • Allow passage of molecules through membrane

• Glycolipids

  • Cell-cell communication

• Sterols

  • Fluidity

What type of molecules can pass freely through the plasma membrane?

Small, uncharged molecules (i.e. O₂, CO₂, glycerol and alcohol)

What drives the passage of molecules through the plasma membrane?

Concentration gradient

What special channels allow for water to cross the plasma membrane?

Aquaporins

What is diffusion?

The net movement of solute molecules from areas of high concentration to areas of low concentration

What is osmosis?

The movement of water to establish equilibrium

Fick’s 1^st Law of Diffusion

J = DA(ΔC/ΔX)

What factors determine the rate of diffusion?

• Surface area (A)

  • Greater A, faster diffusion

• Diffusion coefficient (D)

• Difference in solute concentration (ΔC)

  • Greater ΔC, faster diffusion

• Diffusion distance; membrane thickness (ΔX)

  • Greater ΔX, slower diffusion

T/F: Temperature affects rate of diffusion.

F; temperature is relatively equal throughout the body

T/F: O₂ can diffuse quickly w/in the lungs.

T; the lungs have a large concentration difference and large surface area

What are the forms of passive transport?

• Simple diffusion

• Carrier-mediated diffusion

  • Shape-specific, used for larger molecules

• Channel-mediated diffusion

  • Diffusion of ions

• Osmosis

  • Diffusion of H₂O via aquaporins

T/F: Active transport requires energy to move solutes.

T; uses ATP to move solutes against the concentration gradient (i.e. Na⁺/K⁺ pumps)

What are some examples of active transport?

• Endocytosis

  • Pinocytosis (ECF and small molecules)

  • Phagocytosis (solid particles)

  • Receptor-mediated endocytosis

• Exocytosis

What does the cytoplasm include?

Everything inside of a cell, EXCEPT the nucleus

What are the characteristics of cytosol?

• Higher concentration of K⁺ ions and lower concentration of Na⁺ ions c/w ECF

• Negative intracellular charge

• High protein concentration

• Small carbohydrate concentration

• Large reserve of amino acids and lipids

What are the components of the cytoskeleton?

• Microfilaments

• Intermediate filaments

• Microtubules

What are the characteristics of microfilaments?

• Composed of actin

• Line inner edge of cell

• Smallest component

What are the characteristics of intermediate filaments?

• Anchor organelles

• Located throughout cell

• Transport materials

What are the characteristics of microtubules?

• Move organelles

• Cell movement

  • Cilia/flagella

• Essential for mitosis

  • Form centrioles

What is the role of microvilli?

• Increase surface area

• Churn ECF

• Microfilament support

What is the main role of ribosomes?

Protein synthesis using an RNA template

Which organelles have double-layered membranes?

• Mitochondrion

• Nucleus

What organelle is the site of ATP synthesis and oxidative phosphorylation?

Mitochondrion

Which organelle produces ribosomes?

Nucleolus

What is the role of the endoplasmic reticulum?

• Synthesis

• Storage

• Transport

• Detoxification

What is the role of the rough endoplasmic reticulum?

Stores and synthesizes proteins

What is the role of the smooth endoplasmic reticulum?

• Synthesizes lipids, steroids and carbohydrates

• Storage of Ca²⁺

• Detoxification

What is the role of the Golgi apparatus?

• Synthesis and packing of secretions

• Packaging of enzymes for use in cytosol

• Renewal and modification of cell membrane

What organelles make up the endomembrane system?

• Golgi apparatus

• Endoplasmic reticulum

• Lysosomes

• Peroxisomes

What is a lysosome?

Vesicle filled w/ digestive enzymes

What is a peroxisome?

Vesicle filled w/ “house-keeping” enzymes (i.e. oxidase, catalase)

What is the role of gap junctions?

Permit free diffusion of ions and small molecules b/w two cells

What is the role of hemidesmosomes?

Attach epithelial cells to extracellular structures

What is the role of a tight junction?

Prevent the diffusion of fluids and solutes between cells

What is the role of desmosomes?

Attach one cell to another cell