lecture 5 - Life and cellular functions Flashcards
describe lipid membranes
- define the boundaries between cells and their environment
- regulate the exchange of nutrients and other compounds with the environment
- complex structures made up of:
- phospholipids
- cholesterol
- membrane proteins (integral and peripheral)
- carbohydrates attached to the outside of the membrane
- attachment sites for the cytoskeleton (inside the membrane)
what diseases have bacteria been linked to?
obesity, type II diabetes, autism, kwashikor
what processes occur in the cytoplasm of bacterial cells?
-all metabolic reactions
- energy generation
- protein synthesis (ribosomes)
DNA replication
-synthesis of cell components
what are plasmids?
small circular DNA molecules
what are the two main types of cell membrane in bacteria? describe also
gram negative - small peptidoglycan layer -contains sophisticated outer membrane gram positive -large peptidoglycan layer
what is the peptidoglycan layer?
a rigid matrix that defines cell shape
what parts of bacterial cells are used for mobility and attachment?
flagella - nanomachines -work as mini motors - have a clutch protein pili
describe the nucleus
- contains DNA
- surrounded by double nuclear membrane
- membraned perforated by pores
- interior of nucleus contains DNA+protein = chromatin
- Nucleolus - structure in which ribosomes are assembled
describe the endoplasmic reticulum
- a membrane system continuous with the outer membrane of the nucleus
- many proteins are synthesised on the ribosomes in the ER
- some chemical modification begin inside the ER, then proteins are transported in the ER to the golgi body where modification can continue
describe ribosomes
- site of protein synthesis
- in all cells
- found free in cytoplasm and attached to ER, in mitochondria and chloroplasts.
describe mitochondria
- energy generating centres of the cell
- the site of respiration
- 2 membranes (outer =smooth, inner = folded into cristae)
- they function as semi-autonomous organisms with their own DNA and ribosomes for making some of their own proteins.
describe chloroplasts
- found only in plant cells
- contain the pigment chlorophyll
- the site where photosynthesis occurs
- contains 3 membrane systems (outer, inner and thylakoid)
- inner membrane surrounds the strome which contains soluble enzymes, ribosomes, DNA and thylakoids.
describe the Golgi apparatus
- the cell’s postal service
- packaging and distributing of i.e., proteins
what is the function of lysosomes?
the digestive compartment found only in animal cells
what are peroxisomes?
the cell’s detoxification centres
what are vacuoles? and where are the located?
in plant cells only
- storage and detoxification
what is the function of the cell wall?
plants and fungi only
- cell stability
what is the function of the cytoskeleton?
- essential for cell shape, cell support, cell movement
- dynamic set of three types of filaments
- key to the success of eukaryotic cell division
what are the three types of cytoskeleton filaments?
microtubules
- 25nm diameter, dynamic, used in eukaryotic flagella
microfilaments
-7 nm diameter, made of actin monomers, dynamic, key for cell division
intermediate filaments
- 8-12 nm in diameter, stable (support function), can be made of different monomers
explain the endosymbiont hypothesis
- suggests that mitochondria and chloroplasts came from prokaryotic cells that developed symbiotic relationships with another cell.
- bacteria are close living relative - i.e., there are bacteria that look extrememly similar to mitochondra - convoluted membrane structures
