Upload
matthew-hodges
View
228
Download
5
Embed Size (px)
Citation preview
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)•10-100 μm•DNA located in nucleus•organelles
•plasma membrane•cytosol/cytoplasm•ribosomes•chromosomes
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
Generalized Animal Cell
Generalized Plant Cell
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)
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
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
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
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)
Lysosome• contains hydrolytic
enzymes• fuse with vesicles or
vacuoles to…• digest macromolecules• recycle organic material
(ex: old organelles)• break down food• destroy invaders
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
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
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
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
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
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
• 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)
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
Extracellular Matrix• consists primarily of glycoproteins (carbohydrate
attachments to membrane proteins)• most abundant glycoprotein is collagen
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