lecture 5 - Life and cellular functions

Question 1

describe lipid membranes

Answer 1

• 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)

Question 2

what diseases have bacteria been linked to?

Answer 2

obesity, type II diabetes, autism, kwashikor

Question 3

what processes occur in the cytoplasm of bacterial cells?

Answer 3

-all metabolic reactions
- energy generation
- protein synthesis (ribosomes)
DNA replication
-synthesis of cell components

Question 4

what are plasmids?

Answer 4

small circular DNA molecules

Question 5

what are the two main types of cell membrane in bacteria? describe also

Answer 5

gram negative 
- small peptidoglycan layer
-contains sophisticated outer membrane
gram positive
-large peptidoglycan layer

Question 6

what is the peptidoglycan layer?

Answer 6

a rigid matrix that defines cell shape

Question 7

what parts of bacterial cells are used for mobility and attachment?

Answer 7

flagella 
- nanomachines
-work as mini motors
- have a clutch protein
pili

Question 8

describe the nucleus

Answer 8

• 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

Question 9

describe the endoplasmic reticulum

Answer 9

• 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

Question 10

describe ribosomes

Answer 10

• site of protein synthesis
• in all cells
• found free in cytoplasm and attached to ER, in mitochondria and chloroplasts.

Question 11

describe mitochondria

Answer 11

• 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.

Question 12

describe chloroplasts

Answer 12

• 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.

Question 13

describe the Golgi apparatus

Answer 13

• the cell’s postal service

- packaging and distributing of i.e., proteins

Question 14

what is the function of lysosomes?

Answer 14

the digestive compartment found only in animal cells

Question 15

what are peroxisomes?

Answer 15

the cell’s detoxification centres

Question 16

what are vacuoles? and where are the located?

Answer 16

in plant cells only

- storage and detoxification

Question 17

what is the function of the cell wall?

Answer 17

plants and fungi only

- cell stability

Question 18

what is the function of the cytoskeleton?

Answer 18

• essential for cell shape, cell support, cell movement
• dynamic set of three types of filaments
• key to the success of eukaryotic cell division

Question 19

what are the three types of cytoskeleton filaments?

Answer 19

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

Question 20

explain the endosymbiont hypothesis

Answer 20

• 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