2.1.1 cell structure

Question 1

what is the function of the plasma membrane

Answer 1

controls what enters and leaves the cells and has receptors for cell signalling and responding to chemicals.

Question 2

what is the cell wall

Answer 2

a rigid structure which surrounds plant cells. plant cell walls are made of cellulose.

Question 3

what is the function of a cell wall

Answer 3

supports the cell

Question 4

what is the nucleus

Answer 4

a large organelle surrounded by a nuclear envelope which has pores. it contains all the DNA . it contains a nucleolus.

Question 5

what is the function of a lysosome

Answer 5

it contains digestive enzymes to digest invading cells and break down worn-out components. these enzymes are separated from cytoplasm via a membrane

Question 6

what is a ribosome

Answer 6

a small organelle that floats freely or is attached to rough endoplasmic reticulum. made of proteins and RNA.

Question 7

what is the function of a ribosome

Answer 7

the site where proteins are made

Question 8

what is the rough endoplasmic reticulum

Answer 8

a system of membranes enclosing a fluid filled space. it is covered in ribosomes

Question 9

what is the function of the rough endoplasmic reticulum

Answer 9

it folds and processes proteins made at the ribosomes

Question 10

what is the smooth endoplasmic reticulum

Answer 10

a system of membranes enclosing a fluid filled space.

Question 11

what is the function of the smooth endoplasmic reticulum

Answer 11

synthesises and processes lipids

Question 12

what is a vesicle

Answer 12

a fluid filled sac in the cytoplasm that is surrounded by a membrane

Question 13

what is the function of a vesicle

Answer 13

transports substances in and out of the cell via the plasma membrane or between organelles.

Question 14

what is the Golgi apparatus

Answer 14

a group of fluid filled flattened sacs, vesicles are often found at the edges

Question 15

what is the function of the Golgi apparatus

Answer 15

packages and processes new lipids and proteins and makes lysosomes

Question 16

what is the function of mitochondria

Answer 16

the site of aerobic respiration where ATP is produced

Question 16

what is mitochondria

Answer 16

they are oval shaped and have a double membrane. the inner membrane is folded to create cristae. the inside is called the matrix which contains enzymes used in respiration

Question 17

what is a chloroplast

Answer 17

a small flattened structure found in plants. it is surrounded by a double membrane and has thylakoid membranes inside which are stacked up to form grana which are linked together by lamellae.

Question 18

what is the function of a chloroplast

Answer 18

the site where photosynthesis takes place.

Question 19

what is a centriole

Answer 19

small hollow cylinders made of microtubules found in animal cells

Question 20

what is the function of a centriole

Answer 20

involved in the separation of chromosomes in cell division

Question 21

what is cilia

Answer 21

small hair like structures found on the cell membrane of some animal cells. they have an outer membrane and a ring of 9 pairs of microtubules with 2 microtubules in the middle.

Question 22

what is the function of cilia

Answer 22

the microtubules allow them to move so they can move substances along the cell surface.

Question 23

what is the function of flagella

Answer 23

microtubules contract to move the flagellum. this propels the cell forward

Question 23

what is flagella

Answer 23

have 9 pairs of microtubules around the edge and 2 in the middle. are longer than cilia

Question 24

how are organelles involved in protein production

Answer 24

1. ribosomes synthesise proteins 2. proteins produces at ribosomes on the RER are processed and folded by the RER 3. they are transported to the Golgi apparatus 4. the Golgi apparatus processes and packages the proteins into vesicles to be transported round the cell.

Question 25

what is the cytoskeleton

Answer 25

a network of protein threads in the cytoplasm. in eukaryotic cells they are microfilaments and microtubules

Question 26

what are the functions of the cytoskeleton.

Answer 26

1. support organelles and keep them in place 2. strengthen cell to maintain shape 3. movement of materials inside cells 4. movement of cell itself

Question 27

why is the cytoskeleton said to be dynamic

Answer 27

it changes in response to the environment to carry out its functions

Question 28

what is the difference in size between Eukaryotic and prokaryotic cells

Answer 28

eukaryotic cells are larger (10-100 micrometres). prokaryotic cells are less the 2 micrometres

Question 29

how is DNA different in eukaryotic and prokaryotic cells.

Answer 29

eukaryotic cells have linear DNA enclosed in a nucleus and prokaryotic cells have circular DNA called plasmids which are free in the cytoplasm

Question 30

how is the cell wall different in eukaryotic and prokaryotic cells

Answer 30

it is made of chitin (fungi) or cellulose (plants) in eukaryotic cells. in prokaryotic cells it is a different polysaccharide.

Question 31

which type of cell does not contain membrane bound organelles

Answer 31

prokaryotic cells

Question 32

how is the arrangement of the flagella different in eukaryotic and prokaryotic cells

Answer 32

in eukaryotic cells it is in the 9+2 arrangement of microtubules and in prokaryotic cells it is arranged as a helix

Question 33

which type of cell has larger ribosomes

Answer 33

eukaryotic cells (80s rather than 70s)

Question 34

define magnification

Answer 34

how much bigger the image is than the actual specimen

Question 35

define resolution

Answer 35

how well it can distinguish between two objects close together

Question 36

what is the equation for magnification

Answer 36

magnification = image size/object size

Question 37

what is the resolution and magnification of a light microscope

Answer 37

resolution: 0.2 micrometres magnification: x1500

Question 38

how does a laser scanning confocal microscope work

Answer 38

1. laser beams scan the specimen which is tagged by a fluorescent dye. the laser causes the dye to give off light. 2. the light is focused through a pinhole to a detector hooked up to a computer that generates an image (3D) 3. they produce a clearer image than a normal light microscope as out of focus light is blocked

Question 39

why do we use a laser scanning confocal microscope

Answer 39

it can be used to look at objects at different depths in thick specimens

Question 40

what are the two types of electron microscope

Answer 40

scanning and transmission

Question 41

how does a scanning electron microscope work

Answer 41

a beam of electrons is scanned across the surface of the specimen. this knocks electrons off the specimen which are collected in a cathode ray tube to form an image, the images produced are 3D

Question 42

what is the resolution and magnification of a scanning electron microscope

Answer 42

resolution: 0.002 micrometres magnification: less than x 500 000

Question 43

how does a transmission electron microscope work

Answer 43

a focused beam of electrons is passed through the specimen. denser parts of the specimen absorb more electrons making them look darker in the image. specimen must me thin and image is 2D

Question 44

what is the resolution and magnification of a transmission electron microscope

Answer 44

resolution: 0.0002 micrometres magnification: can be more than x1 000 000

Question 45

why do we stain specimen

Answer 45

increases the contrast and allows transparent components to be picked up in the image

Question 46

how do we stain for light microscopes

Answer 46

we use a dye. different parts of the specimen absorb different amounts of dye so it increases contrast. we can use different dyes at the same time.

Question 47

how do we stain for electron microscopes

Answer 47

specimen dipped in heavy metal like lead, metal ions spread the electrons increasing contrast.

Question 48

how do we prepare a microscope slide

Answer 48

1. take thin slice of specimen 2. use tweezers to place on the slide 3. on a wet mount we add a drop of water on the slide before placing specimen. 4. gently add the cover slip at a tilt to prevent air bubbles.

Question 49

how do we use a microscope

Answer 49

1. clip slide in place 2. select lowest powered objective lens 3. use coarse adjustment knob to bring the stage up until image is roughly in focus 4. use fine adjustment knob to get a clear image 5. increase magnification by moving up an objective lens and refocusing.

Question 50

how do we calibrate an eyepiece graticule

Answer 50

Line up the zero of the eyepiece graticule and the zero of the stage micrometer. Make sure the scales are parallel. Look at the scales and see where they are in line again. see how many micrometres each division of the eyepiece graticule is. we use magnification x number of divisions of stage micrometer.