Study guide ch. 4 A Flashcards
more cell stuff
What are the 5 distinguishing characteristics of prokaryotic cells?
- unicellular bacteria and archaea
- DNA not enclosed within a nuclear membrane, usually have singular chromosomes
- No histones (proteins) or membrane bound organelles
- Cell walls almost always contain peptidoglycan
- Usually divide via binary fission
What are the size ranges of prokaryotes?
- 0.2 to 2.0 micrometers in diameter
- 2.8 micrometers in length
Which arrangement of bacteria divide at random planes and form GRAPE-like clusters or board sheets?
Staphylococcus
Which arrangement of bacteria has two cocci?
diplococcus/diplobacilli
Which arrangement of bacteria have cocci in chains?
streptococcus
Which arrangement of bacteria is similar to the staphylococcus but divide in different angles?
Palisades
Which arrangement of bacteria have groups of 4 cocci?
Tetrads
TRUE OR FALSE: coccobacilli is NOT a cocci
TRUE
- true cocci have same measurements throughout, whereas coccobacilli does not
What is the glycocalyx and where is it usually found?
- It is a gelatinous polymer composed of polypeptide, polysaccharide, or both. Sticky material on cell surface
- found external to the cell wall
What is the slime layer and what is it used for?
- It is a type of glycocalyx that is loosely organized and attached
- used to protect bacteria cells from environmental threats
What is the capsule and why is it so important?
- It is a type of glycocalyx that is highly organized and tightly attached
- It is important because they prevent phagocytosis and dehydration and allow for substrate attachment
Which of these is NOT a function of the glycocalyx?
- Attachment: formation of biofilms
- Inhibit killing by white blood cells by phagocytosis, contributing to pathogenicity
- maintain shape of bacterium
- Protect cells from dehydration and nutrient loss
Maintain shape of bacterium
When a bacterium moves in one direction for a period of time it is called a _______. When is it used by bacteria?
- Run
- Used when its flagella rotate counterclockwise and bundle together
When a bacterium has abrupt random changes in direction it is called a _______. When is it used by bacteria?
- Tumble
- Caused by a reversal of flagellar rotation
What is taxis?
Phototaxis?
Chemotaxis?
Attractants?
Repellents?
- The movement of bacterium towards or away from a particular stimulus
- movement of bacterium if the stimulus is light
- movement of bacterium if the stimulus is chemical
- movement of bacterium if it is a positive chemostatic stimulus
- movement of bacterium if it is a negative chemostatic stimulus
What are pilli and which bacteria have it?
- They are rigid tubular structures made of pilin protein responsible for conjugation
- only found in gram-negative cells
Cell wall of bacteria is found surrounding the _________ and is made up of _____,______, and_____.
- surrounding the plasma membrane
- peptidoglycan, alternating NAG and NAM which form the carbohydrate backbone, and polypeptide links
Name the 4 functions of the cell wall
- To prevent rupture of bacterial cells
- maintain the shape of the bacterium
- serve as a point of anchorage for flagella
- produce symptoms of disease in some species
What is the composition of the gram positive cell wall?
Thick peptidoglycan, teichoic acids, lipoteichoic acid, 1 periplasmic space
What is the composition of the gram negative cell wall
Thin peptidoglycan, outer membrane, 2 periplasmic spaces
What are the functions of teichoic and lipoteichoic acid?
- function in cell wall maintenance and enlargement during cell division
- move cations across the cell envelope
- stimulate a specific immune response
TRUE OR FALSE:
Gram negative bacteria has teichoic and lipoteichoic acid
FALSE
Gram positive bacteria has it
What do cell walls of acid-fast bacteria consist of?
- Large amounts of mycolic acid within their cell walls (fatty waxes)
What does the outer membrane of the gram-negative cell wall provide a barrier to?
- Heavy metals
- Bile salts
- Digestive enzymes
- Certain dyes
Transmembrane channels found in the outer membranes of bacteria are known as…
Porin proteins
Proteins that permit passage of specific molecules are called __________
Specific channel proteins
What genus of bacteria do not have any cell walls but have sterols in its plasma membrane?
mycoplasma
How does mycolic acid help bacteria evade our immune system?
It contains a waxy hydrophobic barrier that prevents our immune cells from easily recognizing and engulfing it
Which enzyme breaks down the cell walls of gram positive bacteria and where is it found?
- Lysozyme
- in the rough ER
What part of the cell does penicillin interfere with?
Outer membrane of gram negative bacteria
What molecules make up the plasma membrane of prokaryotes?
Proteins and phospholipids (polar head and hydrophobic tail)
Explain the structure of the plasma membrane
- Viscuous like olive oil, as the proteins move freely for various functions while phospholipids rotate and move laterally. Also self sealing
What are the functions of the plasma membrane?
- It is selectively permeable, allowing passage of some molecules, but not others
- Contains enzymes for ATP production
- some membranes have photosynthetic pigments on foldings called chromatopheres
What substances can destroy plasma membranes?
- Certain alcohols
- quatenary ammonium compounds
- antibiotics such as polymyxins
Explain simple diffusion.
What molecules can enter the cell via simple diffusion?
- When lipid soluble substances move from an area of high concentration to low concentration through a gradient
- oxygen, carbon dioxide, and nonpolar organnic molecules
What is facilitated diffusion and what molecule uses this to enter cells?
- Diffusion with the help of a carrier protein to transport molecules across the membrane
- Glucose
What is osmosis?
The movement of water molecules from an area of high water concentration to low water concentration
What would happen if a bacterium was placed in an isotonic solution?
the bacteria would remain normal due to the balance of water and solute
What would happen if a bacterium was placed in a hypertonic solution?
It would crenate due to the solute being more abundant than water, causing the water to be drawn out of the bacteria
What would happen if a bacterium was placed in a hypotonic solution?
the bacteria would swell and lyse, due to excess water
What is plasmolysis?
(think solutes and water)
The shrinking of a cell due to water loss in a hypertonic solution
Explain active transport
The movement of substances against the concentration gradient across a membrane depending on a carrier protein
