Chapter 3 Cell Structure Flashcards
1
Q
Prokaryote
A
- DNA is not enclosed within a nucleus
- Usually DNA is arranged as one circular chromosome
- They lack membrane- enclosed organelles
- Single celled organisms: Bacteria, Archaea
2
Q
Eukaryotes
A
- DNA is found in the nucleus: surrounded by a nuclear membrane
- DNA arranged as multiple chromosomes
- They have membrane-enclosed organelles
- Single celled or multicellular organisms
- Ex. Algae, Protozoa, Fungi, Plants, Animals
3
Q
Morphology (Shape ) of Bacteria
A
- Coccus (Pl. Cocci) = Spherical
- Bacillus (Pl. Bacilli) = Rod Shaped
- Vibrio = Curved
- Spirillum (Pl. Spirilla) = Spiral Shaped
- Spirochete = Corkscrew Shaped
4
Q
Bacterial Cell External Structures (Capsules and Slime Layers)
A
- Sticky, gelatinous layer external to the cell
- Composed of polysaccharide, protein or both
- If layer is organized and firmly attached to the cell wall = Known as a capsule
- If layer is unorganized and loosely attached to the cell wall = Known as a Slime Layer
- In some bacteria capsules play a role in virulence
- Protection against phagocytosis (Ex. Streptococcus pneumoniae. With Capsule = causes disease and without = no disease)
5
Q
Slime Layers
A
- Often allow bacteria to attach to surfaces
- Medical implants, water pipes, teeth
- Example: Streptococcus mutans
Makes polysaccharide slime from sucrose
Attaches to teeth, which can lead to cavities
6
Q
Flagella (Flagellum)
A
- Long protein appendages
- Used in motility
- Semi-rigid, helical turns like a propeller
- Bacterial cells have four typical arrangements of flagella:
1) Monotrichous = a single polar flagellum
2) Lophotrichous = Two or more flagella originating form opposite poles
3) Peritrichous = Flagella distributed all over the cell
7
Q
Flagellar Motility
A
- Flagella turn causing cell to move in one direction -“run”
- Periodically flagella reverse direction causing a random change in direction -“Tumble”
8
Q
Flagella allow chemotaxis
A
- Movement toward or away from a stimulant
- Toward a nutrient (attractant)
- Away from a toxin (repellent)
- Ex. E. coli will move toward glucose
- Flagellar protein can be used to distinguish among stains of species = E.coli
9
Q
Fimbriae and Pili General Info
A
- Short, hair-like appendages
- Hollow
10
Q
Fimbriae
A
- Allow the cell to adhere to surfaces
- Contribute to pathogenicity
- Example: Some stains of E.coli have fimbriae that allow them to attach to the intestinal wall
11
Q
Pili
A
- Allows attachment of two bacteria to each other
- Involved in transferor genetic material between bacteria
- Ex. E.coli’s sex pilus
12
Q
Bacteria Cell Wall
A
- Semi-rigid structure giving shape to the cell
- Major function is to prevent rupture of the cell - protects against environmental changes
- Useful in the identification of bacteria (Gram Stain)
13
Q
Bacteria Cell Wall Composed of the Complex macromolecule
A
- Peptidoglycan
- Which is a mesh-like structure composed of polysaccharide and amino acids
- Polysaccharide portion is composed of two alternating monosaccharides:
1) N-acetyl glucosamine (NAG)
2) N-acetyl muramic (NAM) - Peptide portion composed of short chains of amino acids
14
Q
A generalized View of Peptidoglycan
A
- Polysaccharide chains run parallel
- Peptide chains link polysaccharides together
- Forms a mesh-like net surrounding the cell
15
Q
The Gram Positive Cell Wall
A
- Made of thick layers of peptidoglycan outside of plasma membrane
1) Also contains teichoic acids
2) Wall teichoic acids: attached to the peptidoglycan
3) Lipoteichoic acids: attached to plasma membrane and extend through the peptidoglycan - Gram positive bacteria have only one membrane = cytoplasmic membrane
16
Q
The Gram Negative Cell Wall
A
- Thin peptidoglycan layer that is sandwiched between two membranes
- Outer membrane of lipids (phospholipids), proteins and lipopolysaccharides (LPS)
- Polysaccharide portion of LPS is composed of O-Sugars (Useful for distinguishing gram negative bacteria)
- Lipid portion of LPS is toxic
- Referred to as endotoxin
17
Q
What’s so Special About Peptidoglycan?
A
- Completely different from anything found in animal cells
- Many antibiotics have been discovered that act against peptidoglycan
- Example: Penicillin - inhibits production of peptidoglycan
- Also degraded by one of our own natural defences: Lysozyme (Found in tears, saliva, mucous)
18
Q
The Cytoplasmic Membrane
A
- Composed of phospholipid bilayer
- Serves as a semi-permeable barrier
- Selectively allows inflow and outflow of materials
- Exists in a semi-fluid state
19
Q
Antimicrobial Agents
A
- Alcohols disrupt the membrane
- Can be used as a disinfectant
20
Q
Internal Components Cytoplasm
A
- The substance inside the plasma membrane
- Is about 80% water
- Contains most of the ‘stuff’ needed for life
1) Sugars, amino acids, nucleotides etc.
2) Enzymes
3) Some functional structures
21
Q
The Nucleoid
A
- Contains the bacterial chromosome (DNA)
- All genetic information required for cell’s structures and functions
- Not surrounded by a nuclear membrane
- May also contain plasmids:
Smaller double stranded DNA molecules
Contain non-essential genes (Genes for antibiotic resistance)
22
Q
Ribosomes
A
- Site of protein synthesis (translation)
- Made of protein and ribosomal RNA (rRNA)
- Two parts:
30S subunit
50S subunit
Together form the complete 70S ribosome
23
Q
Ribosomes of Bacteria differ from Eukaryotic Ribosomes
A
- Eukaryotes have 80S ribosomes
- Several antibiotics target bacterial ribosomes
- Ex. Streptomycin, Erythromycin
- Prevent the bacteria from making new proteins
24
Q
Storage Granules (Inclusion Bodies)
A
- Usually deposits or granules of nutrients, stored for later use
- Examples: Sulfur granules, polysaccharides (glycogen), Lipid inclusions, enzymes, magnetite
- Variety of inclusion bodies occur in different bacterial species - can serve as a basis for identification
25
Endospores
- Formed only by Gram positive bacteria
- Special resting structure - allows bacteria to enter dormant state
- Extremely durable: Resists heat, desiccation, chemicals, radiation, etc. (Some can survive in boiling water)
- Remains dormant until good growth conditions occur - can form a new population
26
Sporulation
1) Cell replicates its DNA
2) Septum forms, dividing the cell into unequal compartments
3) Larger compartment engulfs the smaller
4) Peptidoglycan and other protective material forms around the forespore (Spore Coat)
5) Finished spore is freed from the mother cell as the mother cell dies
27
Eukaryotic Cell Structure
- Includes microorganisms: Algae, fungi, protozoa
- Higher organisms: Plants and animals
- Larger and more complex than prokaryotes
- Genetic material is housed in a nucleus
- Membrane bound organelles
28
Cytoplasmic Membrane (Eukaryotic)
- Same basic structure as in prokaryotic cells
- Contains phospholipids, proteins, and sterols
- Sterols make membrane relatively rigid compared to bacteria
29
Cell Wall (Eukaryotic)
- Not all eukaryotes have cell wall - allows endocytosis
- Simple structure compared to bacteria
- Made of:
Cellulose (algae, plants)
Chitin (fungi)
30
Cytoplasm (Eukaryotic)
- Substance inside the plasma membrane, but outside the nuclear membrane
- Cytoplasm has complex internal structure - cytoskeleton
- Protein filaments on the inside of the plasma membrane
- Provides support and shape
- Transports substances through the cell
31
Ribosomes (Eukaryotic)
Larger and heavier than bacterial ribosomes = 80S
32
Membrane Bound Organelles (Eukaryotic)
- Structures with specialized functions
- Not present in bacteria
- Examples:
1) Nucleus: compartment holding genetic material
2) Mitochondria: site of energy production
3) Chloroplasts: site of photosynthesis in algae and plant cells
33
Appendages External to the Cell
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Flagellum and Cilia
- Long flexible projections that contain protein and cytoplasm
- Move in a whip-like fashion
- Can be used for:
Motility
Sweeping material past stationary cells
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