Transcript Now for the rest of the cell. - Saint Demetrios Astoria School

A Tour of the Cell
Discovery of cells needed microscopes
• 1665
– Robert Hooke observes “boxes” in cork bark; he
calls them cells.
• 1674
– Anton van Leeuwenhoek observes single celled
organisms in well water
Three types of microscope images
(Figure 4.1)
Cell theory
1. Schwann and Schleiden (1839) - cells are the
elementary unit of all plants and animals
2. Virchow (1858)- cells come from preexisting
cells
3. Modern cell theory states that cells carry out
the biochemical processes of life.
4. Viruses do not fit into the cell theory and are
not considered living
Relative Sizes (Fig. 4.3)
Cells are small
• 1-100 µm (1µm = 0.001 mm)
• Cells must exchange materials with their
environment through their membrane.
• Cells need high surface area to volume ratio
in order to maximize this exchange.
As size increases, surface area to volume ratio
decreases
Length
SA = 6 * length2 V = Length3
SA/V
1
6
1
6
2
24
8
3
3
54
27
2
4
96
64
1.5
5
150
125
1.2
Two types of cells:
Prokaryotes and Eukaryotes
Prokaryotes are bacterial cells
• Archaea, Eubacteria
– Most primitive organisms
• No inner structure
• DNA floats in cytoplasm
• External structures
– Cell wall
– Flagella - move
– Pili – for attachment and transfer DNA
Bacteria Fig. 4.4
Eukaryotes
• All other kingdoms
– Animalia
– Plantae
– Fungi
– Protist kingdom(s)
Animal Cell (Fig. 4.5)
Plant Cell (Fig. 4.5)
External Eukaryote Structure
Cell membrane
• Isolates cell from outside environment
• Regulates movement of molecules in and out of
cell.
• Permeable to small molecules and non-polar
molecules; impermeable to polar molecules and
ions.
Three main components of cell membrane
• Phospholipid bi-layer: two layers of
phospholipids situated with hydrophilic ends
facing out ward and hydrophobic tails facing
inward
• Cholesterols – Four ringed lipids, regulates the
fluidity of membrane
• Proteins – Hydrophobic a.a within membrane
with hydrophilic a.a outside
Fluid Mosaic: molecules in membrane move freely
(Fig. 4.6)
Three Types of Membrane Proteins
• Transport proteins: allow specific molecules
to enter/exit cell
• Receptor proteins: bind to molecules ( i.e.
hormones, nutrients)
• Recognition proteins: cell specific proteins
that identify cell.
Flagellum and Cilia
•
•
•
•
Used for locomotion, moving particles
Made of protein filaments
Cilia – many “hairs”
Flagellum – Usually a single undulating “tail”
Flagellum and Cilia (Fig. 4.22)
Inside a Eukaryote
•
•
•
•
•
Cytoplasm
Organelles made of phospholipid bilayer
Nucleus containing chromosomes
Mitochondria – in most eukaryotes
Chloroplast – in plants and some protists
Cytoplasm
•
•
•
•
Viscous liquid
Dissolved molecules
Organelles
High concentration of proteins
Nucleus 4.8
• Contains chromosomes which stay inside nucleus
• Nucleolus - site of ribosome production
Ribosomes (Fig. 4.10)
• Small protein subunits (Large and small)
• Site of protein synthesis
Mitochondria (Fig. 4.20)
• Site of Kreb cycle and ATP production
• Inner folds increase surface area
Chloroplasts Fig. 4.19
• Contain chlorophyll (green pigment)
• Site of photosynthesis
Endoplasmic Reticulum
• Membrane extension of the nucleus
• Many folds = lots surface area
• Rough ER – contain ribosomes which make
proteins
• Smooth ER – makes phospholipids
• Makes new membrane
• Break down toxins
Endoplasmic Reticulum (Fig. 4.13)
Assembly of a protein
Golgi Complex (Fig. 4.15)
• Protein modification
• Protein storage
Vacuoles (Fig. 4.17)
• Membrane bound storage structures
• Contractile vacuoles regulate water content
Lysosomes (Fig 4.16)
• Membrane bound enzymes
• Digest food from extracellular fluid or
damaged organelles
Cytoskeleton provides structure and
support (Fig. 4.21)
• Interconnected proteins
• Can change arrangement and location within a cell
(Fig. 4.21)