1. Cell Theory All organisms are composed of one or more cells.
Cells are the smallest living units of all living organisms.
Cells arise only by division of a previously existing cell.

2. Cell Characteristics Genetic material Cytoplasm fills cell interior –
single circular molecule of DNA in prokaryotes
double helix located in nucleus in eukaryotes – nuclear envelope (double membrane
Cytoplasm fills cell interior –
sugars, amino acids,
proteins - organelles
Plasma membrane encloses
the cell – phospholipid bilayer
Phospholipid
Membrane
proteins

3. Generalized Eukaryotic Cell

4. Cell Size
Most cells are relatively small because as size increases, volume increases much more rapidly.
longer diffusion time

5. Visualizing Cells
Resolution - minimum distance two points can be apart and still be distinguished as two separate points
Compound microscopes - magnify in stages using multiple lenses
Transmission electron microscope - electrons transmitted through specimen
Scanning electron microscope - electrons beamed onto surface of the specimen

6. Visualizing Cells

7. Prokaryotic Cells Simplest organisms
Cytoplasm is surrounded by plasma membrane and encased in a rigid cell wall composed of peptidoglycan.
no distinct interior compartments
gram-positive – thick single layer wall that retains a violet dye from Gram stain procedure
gram-negative – multilayered wall does not retain dye
Susceptibility of bacteria to antibiotics depends on cell wall structure.

8. Prokaryotic Cells Some use flagellum for locomotion
threadlike structures protruding from cell surface
Bacterial cell wall
Rotary
motor
Flagellin
Sheath

9. Eukaryotic Cells
Characterized by compartmentalization by an endomembrane system, and the presence of membrane-bound organelles.
Central vacuole – plants, storage
Vesicles (smaller)
Chromosomes - DNA and protein
Cytoskeleton (internal protein scaffolding)
Cell walls – plants and fungi

12. Nucleus Repository for genetic material Directs activities of the cell
Usually single, some cells several, RBC none
Nucleolus - region of intensive ribosomal RNA synthesis
Surface of nucleus bound by two phospholipid bilayer membranes
nuclear membrane
Nuclear pores – protein gatekeepers
Usually proteins going in and RNA going out

13. Nucleus

14. Chromosomes DNA of eukaryotes is divided into linear chromosomes.
exist as strands of chromatin, except during cell division
associated with packaging histones, packaging proteins
nucleosomes

15. Endomembrane System
Compartmentalizes cell, channeling passage of molecules through cell’s interior.
Endoplasmic reticulum
Rough ER - studded with ribosomes
Smooth ER - few ribosomes

16. Endoplasmic reticulum
Largest internal membrane
Composed of Lipid bilayer
Serves as system of channels from the nucleus
Functions in storage and secretion
Rough ER is “rough” because of associated ribosomes (sites of protein synthesis)
Smooth ER - lack associated ribosomes – contains embedded enzymes, catalyze synthesis of carbohydrate and lipid molecules

17. Endomembrane System Golgi apparatus collection of Golgi bodies
collect, package, and distribute molecules synthesized at one location in the cell and utilized at another location
Front - cis , Back – trans
Cisternae – stacked membrane folds

18. Cisternae cis face Proteins trans face Protein Ribosome
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cisternae
cis face
Proteins
trans face
Transport
vesicle
Golgi
apparatus
Protein
Vesicle
budding
from rough
endoplasmic
reticulum
Migrating
transport
vesicle
Fusion
of vesicle
with Golgi
apparatus
Ribosome

19. Endomembrane System Vesicles
Lysosomes - membrane-bound vesicles containing digestive enzymes – from Golgi
Microbodies - enzyme-bearing, membrane-enclosed vesicles.
Peroxisomes - contain enzymes that catalyze the removal of electrons and associated hydrogen atoms
Peroxisome – named for hydrogen peroxide produced as a by-product
Enzyme breaks down to water and oxygen

20. Cytoplasm Extracellular fluid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cytoplasm
Endoplasmic
reticulum
Phagocytosis
Food
vesicle
Golgi
apparatus
Lysosomes
Transport
vesicle
Old or damaged
organelle
Plasma
membrane
Digestion of
phagocytized
food particles
or cells
Breakdown
of old
organelle
Extracellular
fluid

21. Ribosomes
Ribosomes are RNA-protein complexes composed of two subunits that join and attach to messenger RNA.
site of protein synthesis
assembled in nucleoli

22. 1) Discovery of the cell
In 1965 Robert Hooke observed slices of cork from the bark of a tree under a simple magnifying glass. He noticed small boxes or compartments in the cork slice. The boxes were separated from each other by a wall or partition. He named each box as a Cell. The cells which Hooke observed were actually dead cells of plants.

23. Human cheek cells as seen under a microscope

24. Onion peel cells as seen under a microscope

25. Organelles With DNA Mitochondria Chloroplasts
bounded by exterior and interior membranes
interior partitioned by cristae
Chloroplasts
have enclosed internal compartments of stacked grana, containing thylakoids
found in photosynthetic organisms

26. Mitochondria A. "Powerhouse of the cell" - cellular metabolism
B. Structure- outer and inner membranes, cristae
C. Have their own DNA

27. Chloroplasts
Chloroplasts are larger and more complex than mitochondria
Grana – closed compartments of stacked membranes
Thylakoids – disc shaped structure – light capturing pigment
Stroma – fluid matrix

28. Cytoskeleton
Network of protein fibers supporting cell shape and anchoring organelles
Actin filaments
cell movement
Microtubules
Hollow tubes
Facilitate cell movement
Centrioles – barrel shaped
organelles occur in pairs –
help assemble animal cell’s microtubules
Intermediate filaments
Stable - don’t break down
Actin
Microtubules
Intermediate
filaments

29. Cytoskeleton

30. Plant Cells Central vacuole Cell wall
often found in the center of a plant, and serves as a storage facility for water and other materials
Cell wall
primary walls – laid down while cell is growing
middle lamella – glues cells together
secondary walls – inside the primary cell walls after growth

31. Plant Cell

32. Animal Cells Animal cells lack cell walls. form extracellular matrix
provides support, strength, and resilience