Chapter 3: Cell Structure and Function Flashcards
Common features of living organisms
- grow
- reproduce
- DNA genomes
- metabolism
- adaptable-homeostasis
Phospholipid by layer is ___________ (polar and nonpolar)
Amphipathic
The two layers in the phospholipid bilayer
Leaflets
What helps maintain the fluidity of membranes?
Hopanoids- Stiffening agents (bacteria)
Sterols- in eukaryotes, (esterol for fungi and cholesterol for animal cells)
Function of membrane proteins
- support
- signaling and communication
- export
- transport
- establish concentration gradients
Passive diffusion….
Facilitated diffusion…
Active transport…
Endocytosis and exocytosis…
- passive diffusion- gases like oxygen and carbon dioxide, lipids also dissolve in lipid bilayer
- facilitated diffusion- osmosis
- Active transport- cotransport (sodium potassium pump for ions)
- Exocytosis and Endocytosis-plasma membrane pinches to form a vesicle
How do you small uncharged molecules like O2 and CO2 get through the membrane?
By passive diffusion
Movement is not ATP dependent, high concentration to low concentration
* uses membrane bound carrier proteins
Facilitated diffusion
Channel that that the membrane can use to move water into the cell
Aquaporin
The ability of a solution surrounding a cell to cause the cell gain or lose water
Tonicity
When talking about plant cells, what is it called when the cell is in a hypertonic solution and a hypotonic solution?
Hyper- plasmalysis (lyse)
Hypo- turgid
Move substances against their concentration gradient also utilizes a carrier proteins
Helps to maintain ion gradients
Requires energy like ATP
Active transport
Uses ion gradients to cotransport more than one substance
uses an electrochemical gradient – generated by active transport – as an energy source to move molecules against their gradient, and thus does not directly require a chemical source of energy such as ATP.
Secondary active transport
Symporter- moves to substances in the same direction
Antiporter- moves to substances in opposite directions
Uniporter-moves one substance
Energy dependent transporter that chemically modifies the molecule as it is brought into the cell.
Ex: glucose can be phosphorylated
Group translocation
-can diffuse across the membrane and increase or decrease the hydrogen concentration within the cell
Membrane-permanent weak acids and bases
A- or BH+ is soluble in the bloodstream, uncharged HA or A is hydrophobic and can penetrate the cell membrane
How do prokaryotes protect the cell membrane?
Most common structural support is the cell wall
What are the functions of the cell wall?
- shape (protoplast)
- protection
- attachment (biofilms)
- pathogenicity (LPS, endotoxin in cell wall)
Bacterial cell envelopes…
Gram +, thick cell wall multiple layers of peptidoglycan (purple)
Gram -, thin layer of peptidoglycan in cell wall, with additional outer membrane (pink)
Mycobacterium, complex multilayer cell wall
Teichoic acid is unique to what kind of bacteria?
Gram-positive
*50%, negatively charged, helps pathogens attach to cells, key roles in antibiotic resistance, regulation of cell division
Describe the structure of the gram-positive cell wall
• composed primarily of peptidoglycan
- lipoteichoic acid links to plasma membrane
- wall teichoic acid links to peptidoglycan
*** very small periplasm
Propionibacteria acnes is what type of bacteria?
Gram-positive
Part of the normal flora in sebaceous glands
Describe the structure of Graham negative cell walls
-thin layer of peptidoglycan 10-20%
-larger periplasmic space (between plasma membrane and outer membrane, 20-40% of cell volume)
(many enzymes present like hydrolytic enzymes and transport proteins)
-much higher lipid content, much lower peptidoglycan content. Crystal violet can escape from the cell wall. Saffron stays (pink)
Where is the outer membrane found?
How is it attached to peptidoglycan?
Bilayer membrane found only in gram negative. External to cell wall. (Lipid proteins)
Attached by Braun’s lipoproteins
LPS is an endotoxin that makes what type of bacteria much more pathogenic?
Gram negative
What are porins? And what type of bacteria has them?
Span the outer membrane. Allow small molecules to penetrate the outer membrane, structure, defense against some antibiotics
Gram negative
What is the clinical significance of LPS (Lipopolysaccharide)?
- stability of outer membrane
- negative charge
- attachment
- permeability (porins)
- protection
- endotoxin (lipid A)
Bacterium that has a thick capsule, endotoxin LPS, and exotoxins
Secreted by upper respiratory tract secretions
Localized in trachea, bronchi
-toxin a inflammation (sticky exudate)
-three states (catarrhal, spasmodic, convalescent)
-DTaP vaccine
-Can cause secondary infections like pneumonia
Bordetella Pertussis or “whooping cough”
The three stages of pertussis disease
- catarrhal- kind of like the common cold
- spasmodic (paroxysmal)- severe cough, choking and gagging, fractured ribs
- convalescent- Cough subsides, but Lasting cough for months
Who developed the Gram stain?
Hans Christan Gram
Members of genus ___________ have very complex cell envelopes.
Why are they difficult to stain?
Mycobacterium.
Difficult to stay in because of waxy coating but if they do stain, it will stain as gram-positive (membrane lipids- mycolic acid)
* waxy coating helps to prevent phagocytosis and engulfing, excludes many antibiotics, can escape host defenses*
-slow growing
Ex. Mycobacterium sap., Norcrdia, Legionella
Do mycobacterium have a cell wall?
No
How acid fast positive and negative cells stain?
Acid fast staining is used in what type of bacteria?
Acid fast positive- Hot pink
Acid fast negative- Blue or green
Used on mycobacteria
Mycobacterium tuberculosis
Transmitted through droplets Disease attacks lungs -latent and active TB Can cause severe cough maybe blood, chest pain can affect other parts of the body * granulomas à cessation
How is tuberculosis tested for?
Skin test: PPD injection
>15mm it is positive
Regular structured layers of proteins or glycoprotein that self assembles external to the cell, associated directly with peptidoglycan surface in gram positive, in gram negative it adheres to other membrane
-crystalline layer
S layer
- National protective layer commonly found in free living bacteria and in archaea
What are the functions of the S layer?
- protection (osmotic stress) pH stress
- maintain shape
- adhesion
- protects from host defenses
Do you all bacteria cells have a saw wall?
No
Mollicutes are bacteria without a true cell wall.
Have sterile like lipids in the membrane to help stabilize
- mycoplasma and chlamydia lack cell walls
Smallest known free living bacteria
With penicillin work against bacteria?
Mycoplasma
M. Pneunomiae causes walking pneumonia, atypical pneumonia
No, it does not have a cell wall
Caused by bacteria without a cell wall
Transmitted by direct sexual contact Most common STD in U.S.
Most are asymptomatic
Can cause pelvic inflammatory disease
Can cause ocular disease trachoma during childbirth
Chlamydia/ chlamydia trachomatis
How does the archaeal cell wall differ from bacterial cell wall?
- S layer is external to plasma membrane
- pseudomurein
What are two layers external to the cell wall in bacteria?
- capsules-polysaccharides, well organized firmly attached structure, not easily removed from the cell. Can evade phagocytosis, why not be recognized by the house, prevents dying
- slime layers-smaller, thinner, less organize and easy to remove. May help motility. Helps prevent dehydration.* aids an attachment (biofilms)
Describe the bacterial Cytoskeleton
- (FtsZ (Tubulin)
- MreB /MBl (actin) shape
- CreS (intermediate filaments) forms polymer along crescent shaped bacteria, curved
Polyhedral bodies that are packed with the enzyme RuBisCO, which is needed for CO2 fixation
Carboxysomes
Proteins and gas field, increases buoyancy
Gas vesicles
What are inclusion bodies used for?
Storage that can later be used by the cell
Ex. Glycogen, carbon, etc.
Can vary in size, number, and content
Short, thin, hair like protein appendages, used for attachment motility and DNA uptake
Made of pilin protein
Fimbriae
Longer, thicker, hollow, less numerous extension of cells
Pili
Membrane embedded extensions in the cytoplasm
Tips to create adhesion factors called holdfasts
Stalks
Thread like, locomotive appendage that extends from the plasma membrane in cell wall
Helical propellers made of flagellin proteins
Different species have varying numbers and arrangement of these
Flagella
Very number and arrangement of flagella…
Atrichous- Monotrichous- Amphitrichous- Lophotrichous- Petririchous-
Atrichous-none
Monotrichous- one
Amphitrichous- One or more from each pole
Lophotrichous- more than one extending from the same pole
Petririchous- flagella covered on all edges
Flagella and cilia are constructed of __________
Microtubules
Flagella-100-200 microns in length, move in Undulating fashion
Cilia-5-20 microns in length, more numerous,
both have a core of microtubules that is sheath by plasma membrane
Membraneous sac that contains hydrolytic enzymes. Most eukaryotic cells have these. To digest macromolecules lysosome enzymes are made by the rough ER. Then transferred to Golgi for processing, combined with food vacuoles to help digest “autophagy”
Lysosome
Metabolic compartment bound by single membrane, enzymes for oxidation of fatty acids may produce hydrogen peroxide. Abundant in liver cells helps with degradation of fat
Peroxisome
What supports the Endo symbiotic hypothesis
Mitochondria and chloroplasts similarities with bacteria
- same size
- double membrane
- free ribosomes
- Circular DNA
- can make their own proteins
- lack histone proteins
- can grow and reproduce independently via binary fission
Energy conservation organelle in some anaerobic protist
Has double membrane but does not have sister name, generally lacks DNA, ATP is generated by a fermentation process, not cellular respiration, products include CO2 hydrogen and acetate
Descended from common mitochondrial ancestor
Hydrogenosome
