1. Prokaryotic Cells Eukaryotic Cells domains Bacteria & Archaea 1-10 μm
DNA located in nucleoid
region
cell wall
capsule
pili
flagella
domain Eukarya (protists,
fungi, plants, & animals) μm
DNA located in nucleus
organelles
plasma membrane
cytosol/cytoplasm
ribosomes
chromosomes

2. Limits on Cell Size
as a cell increases in size, its volume grows proportionally more than its surface area
cells need a surface area large enough to accommodate its volume
if the surface area : volume ratio is too great, the rate of chemical exchange with the environment may be too slow to meet the cell’s needs

3. Generalized Animal Cell

4. Generalized Plant Cell

5. Nucleus contains most of the cell’s genes
directs protein synthesis by synthesizing mRNA
surrounded by a porous double membrane called the nuclear envelope
DNA is organized into chromosomes (made up of chromatin)
nucleolus – sythesizes rRNA (ribosomal subunits)

6. Ribosomes made of rRNA and protein carry out protein synthesis
free ribosomes make proteins that function within cytosol
bound ribosomes make proteins destined for insertion into membranes, for packaging within organelles, or for secretion

7. Endomembrane System
consists of membranes related through direct physical continuity or by vesicles
includes:
nuclear envelope
endoplasmic reticulum
Golgi apparatus
lysosomes
vacuoles & vesicles
plasma membrane

8. Endoplasmic Reticulum
continuous with nuclear envelope
rough ER
has ribosomes attached to surface
makes secretory proteins
makes membrane
smooth ER
lacks ribosomes
synthesizes lipids
metabolizes carbohydrates
detoxifies drugs/poisons
stores calcium ions

9. Golgi apparatus consists of flattened membranous sacs two poles:
cis = receiving end
trans = shipping end
modifies products of ER, stores them, “tags” them, & sends them to other destinations
manufactures macromolecules (ex: polysaccharides)

10. Lysosome contains hydrolytic enzymes
fuse with vesicles or vacuoles to…
digest macromolecules
recycle organic material (ex: old organelles)
break down food
destroy invaders

11. Vacuoles
similar to lysosomes because they carry out hydrolysis in plant & fungal cells
food vacuoles store & break down food
contractile vacuoles pump excess water out of cell
central vacuole of plant cells stores organic compounds & ions, acts as a disposal site for waste, contains pigments, and may contain poisons for defense against predators

12. Mitochondrion site of cellular respiration
enclosed by 2 membranes: outer is smooth & inner is convoluted (cristae)
between membranes is intermembrane space
interior is called the matrix
contains its own DNA & ribosomes
number in cell is related to cell’s level of metabolic activity

13. Chloroplast site of photosynthesis contains chlorophyll
found in leaf cells & cells of other green organs
enclosed by 2 membranes with a narrow intermembrane space
interior fluid is called the stroma
stroma contains stacks of membranous sacs called thylakoids (a stack of thylakoids is called a granum)
contains its own DNA & ribosomes

14. Peroxisome bound by a single layer of phospholipids
contains enzymes that catalyze oxidation reactions producing hydrogen peroxide (H2O2) as a by-product
additional enzymes break down the H2O2 which is toxic to the cell

15. Cytoskeleton network of fibers extending throughout cytoplasm
provides mechanical support to the cell
maintains the shape of the cell
anchors organelles
involved in cell movement (cilia & flagella)
may also be involved in the regulation of biochemical activities

16. Components of the Cytoskeleton
microtubules
shape & support the cell
serve as tracks for the movement of organelles
separate chromosomes during cell division
“9+2” arrangement and dynein arms cause cilia & flagella to beat
grow out from centrosome (which includes a pair of centrioles in animal cells)
continued

17. microfilaments (actin filaments)
built from molecules of actin
helps cell bear tension (pulling forces)
play a role in cell motility
works with myosin to cause muscle cell contraction in animals & cytoplasmic streaming in plant cells
intermediate filaments
helps cell bear tension
reinforces shape of cell
helps anchor organelles
make up nuclear lamina (lining on nuclear side of nuclear envelope)

18. Cell Wall protects & maintains shape of plant cell
prevents excessive uptake of water
composed primarily of cellulose in plants & chitin in fungi
perforated by channels called plasmodesmata that connect adjacent cells

19. Extracellular Matrix
consists primarily of glycoproteins (carbohydrate attachments to membrane proteins)
most abundant glycoprotein is collagen

20. Intercellular Junctions
Plant Cells
plasmodesmata = cytoplasmic channels between adjacent plant cells
Animal Cells
tight junctions = bind cells tightly together to prevent fluid from leaking into surrounding tissues
desmosomes = anchoring junctions (fasten cells together)
gap junctions = cytoplasmic channels between adjacent animal cells