Cell Biology Flashcards
What are the two types of cells?
Prokaryotes and eukaroytes
What are the significant characteristics of prokaryotes?
All processes in cytosol, no internal membranes, nucleus absent
What is DNA packaged in, in prokaryotes?
Nucleoid
What is DNA packaged in, in eurokartyotes?
Packaged and enclosed by a double membrane (nuclear envelope?
How does mRNA leave the nucleus?
Passes from the nucleoplasm to the cytoplasm via holes called nuclear pores
How is DNA packaged?
With histones forming a complex called chromatin
How is chromatin packaged?
Euchromatin and more dense heterochromatin
Where are most active genes found?
Euchromatin
Where are proteins made?
Ribosomes
Where are ribosomes made?
The nucleolus assembles ribosomes
Where are ribosomes found?
The rough endoplasmic reticulum
What is the basic pathway for secretion?
RER, Golgi, Secretion/plasma membrane
What carries the proteins to the golgi?
Vesicles
What does the golgi do?
It processes and sorts proteins, then sends them on the correct path within the cell
What carries the products from the golgi?
Constitutive vesicle
What are the functions of the RER?
Site of membrane synthesis
Modifies proteins
Quality control
Signals stress
What process releases the secretory vesicle cargo out of the cell?
Exocytosis
What do vesicle travel along?
A motor protein along the microtubules
Where do microtubules emanate from?
The centrosome
What can also travel along microtubules?
Organelles
How do motor proteins know which way they are going?
There is both a plus and negative end on each “track” and the motor recognises this
What are centrioles?
An array of microtubules
What is an interesting point about centrioles?
If removed from a cell, the cell still functions normally
What process causes the uptake of particles by the cell?
Endocytosis
Endocytosis of large particles is called?
Phagocytosis
Endocytosis of small particles is called?
Pinocytosis
What organelle degrades matter within the cell?
Endosomes and lyosomes
What allows lysosomes to degrade?
A low pH allowing the use of hydrolytic enzymes
What is it called when portions of the cell are walled off and digested?
Autophagy
Why does autophagy occur?
The cell needs energy as it is starving
How do proteasomes work?
“Junk” protein is tagged (with ubiquitin) and within the cytoplasm, the proteasome recognises this and breaks down the protein
What is lumen?
A membrane that compartmentalises the cell
What aids vesicle budding?
Molecular scaffold supports called clathhrin
How did mitchondria end up in eukaryotes?
An archaea engulfed a bacterium which had mitchondria
Functions of mitochondria
Producde most of the ATP supply
Enables cell growth
Present in all eukaryotic cells
Contain their own DNA
What are microfilaments?
Thinner than microtubules, generates contractile forces enabling cells to move, parts of cells to move, cells to contract
What are intermediate filaments?
middle thickness, strength, support, some in cytoplasm some support nuclear envelope
What is smooth ER?
Connected domain of the RER membrane with no ribosomes and involved in lipid, steroid production and detoxification
What are peroxisomes?
Break down some fatty acids, synthesis some specialised lipids, produces hydrogen peroxide but this is broken down by catalase
What is the difference between plant cells and animals cells?
Cell wall, chloroplasts, vacuole
In mitosis, what forms chromosomes?
Condensed chromatin
What is cell death called?
Apoptosis
What are totipotent cells?
A cell that can specialise into anything
What is a pluripotent cell?
A cell that has limited differentiation as it already be dervied from totipotent stem cells
How can cells communicate?
Through hormones
Local mediator
Neurotransmitter
Membrane-bound signal molecule
What are the two types of cilia?
Primary and motile cilium
How are microtubules aranged in primary cilium?
In 9 pairs
How are microtubules arranged in motile cilium?
9 microtubule pairs- with a radial spoke coming from the arm, outer and iner dynein arm
2 motile cilium
What does a motile cilium do that a primary cilium doesn’t?
Moves to the periphery of the cell to form cilia
Where can loose fibrocollagenous tissues be found?
Around epithelia cells and organs
Where can dense fibrocollagenous tissues be found?
Tendon, ligaments
Where can reticular fibrocollagenous tissues be found?
Liver, lymph nodes
What are the functions of fibroblasts?
Synthesize fibrous proteins
What are the functions of macrophages?
Phagocytse foreign bodies/organisms
What are the functions of mast cells?
Synthesize histamine and other mediators of inflammation
What are the functions of plasma cells?
Synthesize antibodies
What do eukaryotic and prokaryotic cells have in common?
Plasma membrane, cytoplasm, DNA, ribosomes
Describe the genetic material in eukaryotes
true nucleus bound by double membrane
Linear DNA
Organised into chromosomes
Large complex ribosomes
Describe the genetic material in prokaryotes
No nucleus, has a nucleoid, no physical boundary
Circular DNA
70S ribosomes
What are the structural components of bacteria?
Capsule, pili, flagellae, spores, cell wall, slime
Describe the bacterial capsule and its function
Loose polysaccharide structure
Protects cell from phagocytosis
Protects cell from dessication
Describe bacterial pili/frimbriae and its function
Appendage used for bacterial conjugation
Forms tube/bridge to enable transfer of plasmids
Highly antigenic
What is pili made out of?
Oliogomeric pilin proteins
Describe bacterial flagellae and its functions
Organs of locomotion, composed of flagellin protein, driven by rotary engine at anchor point on inner cell membrane
What are the 4 structures of flagellae?
Monotrichous- single stranded
Lophotrichous- multiple from one location
Amphitrichous- bacteria is sausage shape with multiple strands on each end
Peritrichous- strands everywhere
Describe bacterial spores and their function
Adapted for long-term survival allowing regrowth under suitable conditions
Hard, multi-layered coats making spore difficult to kill
Give some examples of common diseases caused by sporing bacteria
Botulism- clostridium botulinum
Tetanus- clostridium tetani
Describe bacterial slime and its function
Polysaccharide material
Secreted by some bacteria growing in biofilms
Protects against immune attack
Protecrs against eradication by antibiotics
What can all bacteria be split into?
Gram-postive and gram negative
What is the structure of a gram positive cell wall?
Peptidoglycan, cytoplasmic membrane, lipoteichoic acid, cytoplasm
What is the structure of a gram-negative cell wall?
Outer membrane, peptidoglycan layer, cytoplasmic membrane, lipopolysaccharide, cytoplasm
Describe the 4 steps of gram staining
Primary stain- all bacterial cells purple
Trapping agent
Decolourisation- alcohol/acetone
Counterstain- safranin- GN-pink GP-purple
Describe the peptidoglycan layer
Polymer of sugar and amino acid, forms mesh-like layer outside plasma membrane
Alternating residues of N-acetylglucosamine + N- acetylmuramic acid
Describe lipoteichoic acid
Complex of teichoic acid and lipids, provides cell rigidity, recognised by host immune cells
Describe lipopolysaccharide in Gram negative bacteria
Elicits potent immune and inflammatory host responses
Produces endotoxins
Describe outer membrane proteins
Lipoproteins and porins
Not endotoxins but do contribute to virulence
How does a bacteria reproduce?
Binary fission, genetic information distributed equally
Describe how the circular DNA in bacteria replicates
At the origin, two replication forks replicate in both directions until the whole sequence has finished. The termination point is then split
What are the 4 phases of bacterial growth?
Lag, log, stationary and death
What happens in the Lag phase of bacterial growth?
Represents the period of active growth
Bacteria prepare for reproduction
What happens in the log phase of bacterial growth?
Cells divide at maximum rate, uniform replication
What happens in the stationary phase of bacterial growth?
Cessation of growth, exhaustion of nutrients, accumulation of inhibitory end products, cell death=new cells
What happens in the death phase of bacterial growth?
Number of dying cells exceed new cells
What are the three types of bacterial recombination?
Conjugation
Transformation
Transduction
Describe conjugation in reference to bacteria?
One bacterium connects itself to another through pilus to transfer genes
Describe transformation in reference to bacteria?
Bacteria taking up DNA from their enviroment
Describe transduction in reference to bacteria?
Involves the exchanging of bacterial DNA through bacteriophages
How would you classify a bacteria?
Gram stain, cell shape, atmospheric preference, key enzymes, fastidiousness
What does the shape cocci refer to?
Spherical
What does the shape bacilli refer to?
Rod-shaped
What does the shape spiral refer to?
Helical rod
What are the structural components of viruses?
Nucleic acid, capsid, envelope, spikes
What forms of nucleic acid can viruses have?
ds DNA
ss DNA
ds RNA
ss RNA
What is a capsid in reference to a virus?
Protein coat/shell
Made of capsomeres-aggregated protomeres
What are the different shapes of capsids?
Rod-like, polyheral, complex
What is the viral envelope?
Amorphous structure surrounding some viruses, composed of lipid, protein and carbohydrates
What are the viral spikes?
Glycoprotein projections arising from the envelope
Highly antigenic. may have enzymatic, adsorption or haemagglutin activity
How to viruses replicate?
Uses host’s cellular machinery to replicate, produces progeny which leave host to infect other cells
What are the 6 steps in viral replication?
Adsorption, penetration, replication, assembly, maturation and release
Describe adsorption as a part of viral replication
Virus binds to host cell ,highly specific
Describe penetration as a part of viral replication
Virus injects its genome into host cell, occurs by fusion. binding and ingestion
Describe replication as a part of viral replication
Capsid digested by proteolytic enzymes, viral genome repliactes using the host’s cellular machinery
Describe assembly as a part of viral replication
Viral components and enzymes are produced and begin to assemble
Describe maturation as a part of viral replication
Virus fully develops
Describe release of naked viruses as a part of viral replication
Occurs at site of nucleic acid replication
Viral enzymes break down bacterial cell wall
RNA viruses released as they are produced
DNA viruses expelled from the host cell- in inclusion bodies
Describe release of enveloped viruses as a part of viral replication
Viruses migrate
Envelopes formed around nucleocapsids by budding of cell membrane
No inclusion bodies
What are protozoa?
Single celled eukaryotes
What are the classifications of protozoa?
Sporozoa-intracellular parasites
Flagellates- possess tail-like structure
Amoeba- use temporary cell-body projections
Ciliates- move by beating multiple hair-like structures
What are fungi?
Eukaryotic
Multinucleate
Describe the structure of fungi
Thick carbohydrate wall containing chitin and glucans
Grow as thread-like filaments (hyphae)
How do fungi reproduce?
Asexually by budding or binary fission
What are fungal infections called?
Mycoses
What are helminths?
All parasitic worms
What are the 3 important group of helminths?
Cestoda-tapeworms
Trematoda- flukes
Nematoda-roundworms
How are helminths transmitted?
Via intermediate host
Fecal-oral route
Active skin penetration
Injection
