cell structure

Question 1

what are the advantages of having membranous organelles?

Answer 1

1. allows compartmentalisation of specific reactions to provide specific conditions for enzymatic reactions to occur
2. regulation of cell’s contents
3. increase membrane surface area for embedding enzymes and proteins
4. increases efficiency of enzymatic reactions
5. maintain characteristic differences for incompatible processes to occur simultaneously

Question 2

what organelles have double membranes?

Answer 2

nucleus, chloroplast, mitochondrion

Question 3

what 5 organelles are part of the endomembrane system?

Answer 3

rough endoplasmic reticulum, smooth endoplasmic reticulum, golgi apparatus, lysosomes, vesicles

Question 4

what is the function of the nucleus?

Answer 4

the nucleus encloses genetic material and protects DNA from the metabolically active cytoplasm

Question 5

what is the function of the rER?

Answer 5

the rER contains ribosomes which is the site of protein synthesis. polypeptide chains synthesised by ribosomes are folded in the ER lumen

Question 6

what is the function of the sER?

Answer 6

the sER synthesises lipids, detoxifies drugs and poisons, stores calcium ions and metabolises carbohydrates

Question 7

what are ER cisternae? (singular: cisterna)

Answer 7

the extensive network of hollow, membranous tubules, sacs or sheets in the ER

the extensive network of cisternae increases membrane surface area for synthesis

Question 8

what is the function of the golgi apparatus?

Answer 8

the golgi apparatus is the site of modification and packaging ofER products

Question 9

what are GA cisternae? (singular: cisterna)

Answer 9

flattened, membrane bound sacs

Question 10

what modifications can the golgi apparatus carry out?

Answer 10

glycosylation (adding sugar groups) and trimming (removing excess monomers)

Question 11

what is the function of lysosomes?

Answer 11

digestion of materials taken into cells, autophagy of worn-out organelles and autolysis

Question 12

why is it necessary for lysosomes to be membranous?

Answer 12

lysosome contents are acidic in nature and contain hydrolytic enzymes. segregation is necessary to provide optimal pH for hydrolytic reactions and to protect cellular contents from hydrolysis

Question 13

what is the difference in structure for vacuoles between in animal cells and that of plant cells?

Answer 13

animal cells: small, mobile vacuoles
plant cells: one large central vacuoles surrounded by a single membrane called the tonoplast

Question 14

what is the difference in function for vacuoles in animal cells and plant cells

Answer 14

animal cells: house and transport substances
plant cells: store organic compounds, dispose toxic substances, pigmentation, plant protection, cell growth & elongation

Question 15

what are cristae?

Answer 15

the highly convoluted inner membrane of mitochondria which increases the surface area for attachment of enzyme systems

Question 16

what is the function of mitochondria?

Answer 16

mitochondria are the site of cellular respiration, generating ATP for cellular activities

Question 17

what is the name of the compartment enclosed by the inner membrane of the mitochondria?

Answer 17

the mitochondrial matrix

Question 18

what is the function of chloroplasts?

Answer 18

chloroplasts are the sites of photosynthesis and convert solar energy to chemical energy by absorbing sunlight

Question 19

what is the name of the double membrane surrounding the chloroplast?

Answer 19

the chloroplast envelope

Question 20

what is the stroma?

Answer 20

the semi-fluid compartment enclosed by the inner membrane of the chloroplast envelope. the stroma contains circular DNA which enables the synthesis of chloroplast proteins

Question 21

what are thylakoids?

Answer 21

thylakoids are the 3rd set of membranes within the stroma. thylakoids enclose the thylakoid lumen. the thylakoid lumen and thylakoid form a flattened sac called the thylakoid discs

Question 22

what is a granum? (singular: grana)

Answer 22

thylakoid discs stack up to form granum

Question 23

what is the function of ribosomes?

Answer 23

ribosomes are the site of protein synthesis

Question 24

what are the 4 cellular locations ribosomes can be found in?

Answer 24

eukaryotic cells: attached to the rER and free in the cytosol.
prokaryotic cells: in the mitochondrial matrix and in the chloroplast stroma

Question 25

what is the cytoskeleton?

Answer 25

an intricate 3D array of interconnected filaments and tubules

Question 26

what are the functions of the cytoskeleton?

Answer 26

1. provide mechanical support
2. allow for anchorage + direct movements of organelles and molecules
3. provide cell motility

Question 27

are centrioles found in plant cells?

Answer 27

NO. they are only found in animal cells

Question 28

describe the shape of centrioles.

Answer 28

centrioles are found in pairs are right angles to each other. each member of the pair consists of 9 triplets of microtubules arranged in a ring

Question 29

what is the cell wall made up of?

Answer 29

cellulose

Question 30

what are the functions of the cell wall?

Answer 30

1. protect the cell from mechanical injury and invasion
2. withstand hydrostatic pressure exerted by uptake of water (because of cellulose high tensile strength)

Question 31

what is the name of the region between adjacent plant cells?

Answer 31

the middle lamella

Question 32

how does the golgi apparatus modify and package ER products?

Answer 32

1. membranes of transport vesicles fuse with the cis face membrane and deposit their contents into the golgi cisternal space
2. at the trans face, membranes bud off to form secretory vesicles, which contain materials to be transported to the extracellular matrix
3. membranes can also bud off from the trans face to form lysosomes
4. some golgi vesicles also bud off from the trans face to transport substances to other organelles in the cell
5. between the golgi sacs, golgi vesicles are responsible for transferring materials between the parts of the golgi