Cells Flashcards
What is the function of histones?
Helps support and protect DNA
Heterochromatin vs Euchromatin
Densely packed vs not densely packed
What is the function of the nucleolus?
Contains DNA -> rRna- makes ribosomes essential in the process of protein synth
What does DNA code for?
Codes for protein synthesis in cytoplasm. Isolates chr from the rest of cytoplasm protects DNA
What is achieved by presence of nuclear pores?
DNA code for prot synth taken from safety of nucleus to cytoplasm where it takes place
What is found on the outer membr of nuclear env?
Encrusted w ribosomes and is site of orig for RER
What carries gen code from DNA and how does it pass thru nuclear pores?
mRNA- passes thru nuclear pores to cytoplasm
What is the function of the RER?
Provides scaffolding for ribosomes to make prot and ER operates as distr network for proteins
What facilitates the transp of mRNA?
ER is joined with nuclear env fac transp of mRNA which carries gen code from nucl to ribosomes
What is the function of SER?
Synth of lipids e/g phospholipids
What are the 2 poss locations of ribosomes?
Free in cytoplasm/ attached outer surf of ER
What does each ribosome have?
Each one has a large and small sub-unit made of protein and rRNA
What is the G.A?
Series of curved flattened sacs (cisternae)
What do the vesicles in Golgi body do?
Vesicles containing newly synth proteins pinch off from RER and coalesce with forming convex edge of syst- usually edge closest to nucleus
How may proteins be mod in G. body?
May have carb added to form glycoprot
Lipids may be added to form lipoprot
May have prosthetic group/ cofactors added
Dif pp joined together to form protein w quaternary str
They can be labelled packaged or sorted
What happens to vesicle once prot is modified?
Vesicles cont final protein are pinched ff from maturing concave face (usually side furthest away from nucleus)
What is the function of the final vesicles?
Transp protein either within cell/ fuse with cell surf membr to release contents outside the cell
What are lysosomes?
Tiny vesicles, formed by GA
What do lysosomes contain and what do these do?
Hydrolytic enzymes fuse with other vesicles in cell that cont something to be destroyed/ digested e.g cell debris
Why do lysosomes have an important role in phagocytes>
They digest engulfed bacteria enclosed in a phagosome
How are mitochondria enclosed?
In double membr
How is mitochond inner membr folded?
Folded to form cristae that extend into matrix of mit
What do cristae do?
Increase sa which increases no. enzymes that can be embedded within the membr
What is the function of the mitochondria?
Site of ATP synth during aerobic resp
How are the cristae dif in more active cells>
More of them and they are more deeply folded
What are microtubules?
Hollow cylinder fibres formed from tubulin that form cytoskeleton
What is function of spindle fibres?
imp in movement of chr during mitosis and meiosis and are formed of microtubules
What is the function of the centrioles?
Inv in assmbley of spindle fibres during cell div formed of microtubules and also important constit of cilia and flagella
What do animal cells not have that plant cells do?
Lysosomes and Centrioles
What is the plant cell wall made up of?
Made up of polysacc cellulose which is laid down as microfibrils- consists of many cel mol cross linked to each other
Describe the primary c.w
Many microfibrils orientated in dif and random dir
Rel loose arrangement of microfib allows c.w to expand as cell grows
Descr sec cell wall
When cell reaches full size, add layers of cel can be dep to form sec c.w
In sec cw each layer of microfib or in same dir
However, add layers or in dif dir to other layers
What is the middle lamella?
Cell walls of adj cells linked by middle lamella- largely made up of polysacc pectin
How does calcium pectin work?
Forms a gel/cement that acts as an adhesive and holds neighbouring cells together
What are plasmodesmata?
Strands of cytoplasm that ext between neighbouring plant cells
What is the function of plasmodesmata?
Prov gap in cw of adj cells that enable dif kinds of mol to pass thru
What are chloroplasts surrounded by?
Surr by double membr/env which encloses stroma
What is found within stroma? What is found within these?
Thylakoids- arranged in stacks called grana
Contain chlorophyll
What is function of chloroplasts?
Site of phs- located in palisade cell of leaves
What is cell wall of fungal cells made of?
Made of glycoprotein chitin
What acts as storage in fungal cells?
Glycogen
What do fungal cells have in common w animal cells?
SER,RER, nucl, vac, gly, granules and mitochondria
What do all viruses have in common?
They all have a protein coat (caspid) that surrounds nucleic acid- DNA/ RNA
How are bacteriophage proteins formed?
Inside host cells viral DNA codes for prod of new proteins for new protein coats
DNA itself replicates to make copies then packaged within protein coats, forming new viruses
Bact cells destroyed and ruptures and many new viruses released to cont cycle
Descr the structure of HIV:
RNA core and typical protein coat and lipid bilayer containing glycoprotein
What do HIV viruses deliver?
Deliver RNA to host cell together with enzyme reverse transcriptase
What is the function of reverse transcriptase?
Catalyses synth of DNA from RNA
How does DNA make new viruses in HIV?
Synth new protein coats and viral RNA
Why are retroviruses known as retroviruses?
Viral RNA used as template to make DNA. This is reverse of normal transcr. process where DNA is used to make mRNA as protein synth
In humans what does HIV invade?
Invades a type of lymphocyte called helper T cells
What happens as more T cells destroyed?
Immune syst crit compr- AIDS
Why are viruses not true cells?
NO cytoplasm or organelles assoc w it
Viruses inert unless they gain access to a living cell
What are the sim in HIV and Bact?
Both v. small and non-cellular
Contains genetic material within a protein coat
What are the dif between HIV and Bact?
Dif shape and phages have tail fibres attached to a base plate- Tail fibres imp in attaching virus to bact plates
In HIV protein coat/ head is within a phospholipid bilayer (no lipid bilayer in phages)
Glycoprotein present in HIV, not phages
Bacteriophages normally cont DNA vs HIV: RNA
HIV cont reverse transcriptase (norm not in phages)
