3.2.1.1 Structure of eukaryotic cells

Question 1

what is the nucleus?

Answer 1

the largest organelle in a eukaryotic cell

Question 2

what is the purpose of the nucleus?

Answer 2

controls the cell’s activities and contains the organism’s hereditary material

Question 3

what is the nuclear envelope?

Answer 3

a double membrane that surrounds the nucleus

Question 4

what is the purpose of the nuclear enevelope?

Answer 4

it controls that entry and exit of materials in and out of the nucleus and contains the reactions taking place within it

Question 5

what is the purpose of nuclear pores?

Answer 5

allow the passage of large molecules out of the nucleus

Question 6

how many nuclear pores are in each nucleus?

Answer 6

typically 3000

Question 7

what is the nucleoplasm?

Answer 7

the granular, jelly-like material that makes up the bulk of the nucleus

Question 8

what are chromosomes?

Answer 8

consist of protein-bound, linear DNA

Question 9

what is the nucleolus?

Answer 9

a small spherical region within the nucleoplasm, there may be more than one nucleolus in a nucleus

Question 10

what is the purpose of the nucleolus?

Answer 10

manufactures ribosomal RNA and assembles the ribosomes

Question 11

what are the three functions of the nucleus?

Answer 11

• act as the control centre of the cell through the production of mRNA and tRNA and hence protein synthesis
• retain the genetic material of the cell in the form of DNA and chromosomes
• manufacture ribosomal RNA and ribosomes

Question 12

what is around the mitochondrion?

Answer 12

a double membrane which controls the entry and exit of material

Question 13

what are cristae?

Answer 13

extensions of the inner membrane of a mitochondrion

Question 14

what is the purpose of cristae?

Answer 14

they provide a large SA for the attachment of enzymes and other proteins involved in respiration

Question 15

what is the matrix?

Answer 15

it makes up the remainder of the mitochondrion

Question 16

what does the matrix consist of?

Answer 16

• protein, lipids, ribosomes and DNA that allows mitochondria to control the production of some of their own proteins
• many enzymes involved in respiration are found here

Question 17

what is the endoplasmic reticulum (ER)?

Answer 17

an elaborate, three-dimensional system of sheet-like membranes, spreading through the cytoplasm of the cells

Question 18

what is the ER continuous with?

Answer 18

the outer nuclear membrane

Question 19

what are cisternae?

Answer 19

a network of tubules and flattened sacs made up of the ER membranes

Question 20

what are the two types of endoplasmic reticulum?

Answer 20

• rough (RER)
• smooth (SER)

Question 21

what are the characteristics of RER?

Answer 21

ribosomes are present on the outer surfaces of the membranes

Question 22

what are the three functions of the RER?

Answer 22

• involved in the folding and processing of proteins
• provides a large SA for the synthesis of proteins and glycoproteins
• provides a pathway for the transport of proteins

Question 23

what are the characteristics of SER?

Answer 23

lacks ribosomes and is often more tubular in appearance

Question 24

what are the two functions of the SER?

Answer 24

• synthesise, store and transport lipids
• synthesise, store and transport carbohydrates

Question 25

what is the Golgi apparatus?

Answer 25

consists of a stack of flattened membranes that make up flattened sacs (cisternae) with small rounded hollow structures called vesicles

Question 26

what are the six functions of the Golgi apparatus?

Answer 26

- add carbohydrate to proteins to form glycoproteins - produce secretory enzymes, such as those secreted by the pancreas (digestive enzymes) - secrete carbohydrates, such as those used in making cell walls in plants - transport, modify and store lipids - form lysosomes - modifies, sorts and packages macromolecules for cell secretion (exocytosis) or for use within cells

Question 27

what are lysosomes?

Answer 27

spherical sacs containing digestive enzymes (lysozymes)

Question 28

what are lysosymes involved in?

Answer 28

the breakdown of invading cells / foreign material or worn down parts of the cell

Question 29

what are ribosomes?

Answer 29

small cytoplasmic granules found in all cells

Question 30

which ribosomes are found in eukaryotic cells?

Answer 30

larger - 80S

Question 31

which ribosomes are found in prokaryotic cells, mitochondria and chloroplasts?

Answer 31

smaller - 70S

Question 32

what is the structure of a ribosome?

Answer 32

contains two subunits, one large and one small

Question 33

what do the subunits in a ribosome contain?

Answer 33

ribosomal RNA and protein

Question 34

where are ribosomes made in a eukaryotic cell?

Answer 34

in the nucleolus

Question 35

where are the centrioles?

Answer 35

located at opposite poles of the cell

Question 36

what is the purpose of centrioles?

Answer 36

- important for accurate separation of chromosomes during cell division - create spindle fibres

Question 37

what are spindle fibres?

Answer 37

fibres that latch onto chromosomes to pull them apart

Question 38

the chloroplast is surrounded by a...

Answer 38

double envelope which is highly selective

Question 39

what is the stroma?

Answer 39

the fluid-filled matrix where the second stage of photosynethesis takes place

Question 40

what is found within the stroma?

Answer 40

- a number of other structures such as starch grains - all of the enzymes needed for the second stage of photosynthesis

Question 41

what are the grana?

Answer 41

stacks of disc-like structures made of thylakoid membranes

Question 42

what is found in the thylakoids?

Answer 42

chlorophyll

Question 43

what is the function of an intergranal lamella?

Answer 43

it connects the thylakoids of two different grana

Question 44

what are the adaptations of thylakoids?

Answer 44

they have a large SA for chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis

Question 45

what do chloroplasts contain in order to make proteins?

Answer 45

DNA and ribosomes

Question 46

what does the cell wall of plant cells contain?

Answer 46

- microfibrils of cellulose embedded in the matrix - a thin layer of middle lamella which cements adjacent cells

Question 47

what is the function of a cell wall?

Answer 47

to provide mechanical strength so that the cell does not burst under pressure

Question 48

what is the cell wall of a eukaryotic cell made of?

Answer 48

cellulose

Question 49

what is a permanent vacuole?

Answer 49

a large, fluid-filled sac bound by a single membrane

Question 50

what is the membrane of the permanent vacuole called?

Answer 50

the tonoplast

Question 51

what does the permanent vacuole contain?

Answer 51

a solution of mineral salts, sugars, amino acids and waste

Question 52

what is the function of the permanent vacuole?

Answer 52

- produces turgor pressure against the cell wall for support - stores water and various chemicals - may store insoluble wastes

Question 53

outline the role of organelles in the production, transport and release of proteins from eukaryotic cells

Answer 53

- DNA in nucleus codes for protein - ribosomes / RER produce proteins - mitochondria produce ATP for protein synthesis - Golgi apparatus modifies / packages - vesicles / RER transports - vesicles fuse with cell membrane