Lab 3: Cellular Structure and Function

What is the basic unit of life?

The simplest form of life is the cell!

All living things are either: • unicellular (only one cell)

• multicellular (many cells make one organism)

We never think about it, but we are made of probably trillions of cells!

Inner Life of a Cell

3 minute version

8 minute version

Review from Lab 2

Last week we mentioned a few key terms:

• Plasma membrane – a double membrane, outer barrier of a cell, it controls what goes in or out

• Cytosol – liquid-like substance that fills the cytoplasm

• Organelles – term for membrane-bound structures in cell

We also mentioned one common organelle:

• Nucleus – membrane-enclosed storage area and processing center for genetic information (e.g.: DNA)

The 2 main types of cells

All living cells can be split into two groups: • Prokaryotic (“Pro”= before, “karyon” = kernel) • Eukaryotic (“Eu” = true) One main difference between the two is

whether or not they have a nucleus!

Prokaryotic vs. Eukaryotic Cells

PROKARYOTIC EUKARYOTIC Genetic information is found in…

Nucleoid region

Nucleus

Does it have membrane-bound organelles?

NO

YES

Ribosomes? Chromosomes?

YES YES

Which cells are Prokaryotic? Which are Eukaryotic?

PROKARYOTIC • Bacteria • Archae

EUKARYOTIC • Animal cells • Plant cells • Fungi • Protists (like Euglena)

Parts of the eukaryotic cell Nucleus

Nucleolus: area of concentrated chromatin, RNA and proteins. Produces ribosome components.

Nuclear envelope: encloses nucleus in double membrane with nuclear pores and is attached to Endoplasmic Reticulum.

Nuclear Envelope and ER attached

Parts of the eukaryotic cell

Endoplasmic Reticulum (ER) Channels and canals that create and modify proteins and lipids. It also makes vesicles for transport.

– Rough ER – Smooth ER

Ribosome: “Protein factory,” seen both bound to Rough ER and free in the cytosol.

Types of Endoplasmic Reticulum

Rough ER • Attached to nuclear

envelope • Ribosomes attached • Makes proteins

Smooth ER • Makes lipids: oils,

phospholipids, and steroids (hormones)

• Detoxification – Helps flush out drugs and poisons.

Parts of the eukaryotic cell

Mitochondrion:“power plants” that carry out cellular respiration and produce ATP (energy).

Parts of the eukaryotic cell

Golgi apparatus: • The “Post Office” • Processing center that

accepts lipids and proteins from ER.

• Modifies, re-packages and distributes lipids/proteins in vesicles cannibalized from its own membrane.

Parts of the eukaryotic cell

Vacuoles and vesicles: storage containers

Lysosomes: “Recycling centers,” vesicle containing hydrolytic enzymes that break down proteins, nucleic acids, lipids, and carbohydrates. Release their enzymes by fusing with vesicles /organelles.

Parts of the eukaryotic cell

Cytoskeleton: Maintain cell shape and can act like “highways” to assist internal movement of cell parts.

– Microtubules – Intermediate Filaments – Actin Filaments

Cilia and Flagella: On surface of the cell, help the cell move in its environment

Animal vs. Plant Cells

Since both are eukaryotic = both have organelles

But some organelles and cell structures are specific to animals or plants:

• Cell wall (plant) • Chloroplast (plant) • Centrioles (animal) • Size of vacuole

Animal Cells

Centrioles: A pair are found in the centrosome of animal cells and made of microtubules. However its function is unknown.

Plant Cells

Cell wall: rigid outer layer that maintains shape of the plant cell and protects from damage. Made of cellulose.

Large central vacuole: used for storage & to breakdown waste molecules Chloroplast: turns sunlight to sugar molecules for energy (photosynthesis).

Diffusion

The movement of molecules from high to low concentration until

reaching equilibrium.

See Figure 3.6 on page 29

Equilibrium: state in which molecules are moving back & forth in equal amounts & speed.

Net change = 0

Osmosis

The same concept of diffusion!

However it specifically means diffusion of

water across the plasma membrane.

Tonicity

• Compare the relative concentration of solute (particles) and solvent (water) outside of the cell to inside of the cell.

• A solution is either: – Isotonic: Conc. outside & inside are the same – Hypertonic: Less water (more solute) outside cell – Hypotonic: More water outside the cell

Tonicity

Experimental Procedure: Diffusion across Plasma Membrane

• Dialysis bag: semi-permeable membrane

• Benedict’s reagent: detects reducing sugars (monosaccharide/disaccharides). If it is heated and a red/yellow precipitate forms then glucose is present.

• Iodine: detects starch & turns dark (blue/black)

Experimental Procedure: Diffusion across Plasma Membrane

Iodine

Blue: Starch Red: Glucose