cells and microscopes

Question 1

what are the components of the cytoskeleton

Answer 1

• microfillaments
• microtubules
• intermediate fibres

Question 2

what are microfillaments

Answer 2

• made from protein called actin

- responsible for cell movment and cell contraction during cytokinesis

Question 3

what are mictrotubules

Answer 3

• made from a globular protein called tubulin
• polymerise to form tubes
• act as tracks for movement of organelles

Question 4

what are intermediate fibres

Answer 4

• give mechanical strength to cells

- help maintain their integrity

Question 5

what is the structure of the nucleus

Answer 5

• nuclear envelope: double membrane which compartmentalises the nucleus and prevents damage
• Nuclear pores: allows molecules to enter and leave
• chromatin : contains genetic code
• nucleolus: makes ribosomes composed of RNA

Question 6

what is the function of the nucleus

Answer 6

1) Controls all the activity of the cell.
2) Where the Genetic Code (DNA) of the cell is stored, replicated,
and copied into RNA (transcribed).
3) The Nucleus is attached to the Rough ER so the mRNA can easily
get to ribosomes

Question 7

what is the structure of the rough endoplasmic reticulum

Answer 7

System of hollow tubes and
membrane bound sacs which form sheets
called cisternae. 
attached to the nucleus and
covered with ribosomes.
• Consists of an interconnected system of
flattened sacs.

Question 8

what is the function of the rough endoplasmic reticulum

Answer 8

Site of protein synthesis

Question 9

what is the function of the smooth endoplasmic reticulum

Answer 9

similar to RER but lacks ribosomes -is a system of
interconnected tubules.

SER: responsible for carbohydrate & lipid synthesis, and storage.

Question 10

what is the structure of ribosomes

Answer 10

A 2 subunit organelle.
• Made from RNA and protein.
• Not membrane bound.
• Very small organelles: about 22nm in diameter.
• Found free floating in the cytoplasm or attached
to the Rough ER

Question 11

what is the fucntion of ribosomes

Answer 11

These are where protein is made.

• They assemble amino acids into proteins in chains using mRNA.

Question 12

what is the structure of mitochondria

Answer 12

Oval shaped.
• Surrounded by two membranes (double membrane).
• The inner membrane forms finger-like structure
called cristae which increases the surface area.
• The solution inside is called a matrix which contains
enzymes for respiration.
• Mitochondrial DNA – Small amounts of DNA, enable
mitochondrion to reproduce and create enzymes.

Question 13

what is the function of mitochondria

Answer 13

Site of aerobic respiration.
• As a result of respiration, they produce ATP (energy
carrier in cells).

Question 14

what is the structure of golgi body

Answer 14

Stack of flattened, membrane bound sacs
(cisternae).
These are continuously formed from the ER at one
end and budding off as Golgi vesicles at the other

Question 15

what is the function of the golgi body

Answer 15

• Allows internal transport.
• Receives proteins from the RER
• Modifies and processes molecules (such as new lipids
and proteins) and packages them into vesicles.
• These may be secretory vesicles (if the proteins need
to leave the cell) or lysosomes (which stay in the cell).
• Makes lysosomes
• Lipid synthesis

Question 16

what are lysosomes

Answer 16

They are spherical sacs surrounded by a
single membrane.
• They contain powerful hydrolytic
digestive enzymes known as lysozymes.
• Their role is to break down worn out
components of the cell or digest
invading cells.

Question 17

what is the structure of the centrioles

Answer 17

A component of the cytoskeleton,
composed of many microtubules.
• Small hollow cylinders that occur in
pairs next to the nucleus in animal cells
only.
• Each centriole contains a ring of 9
microtubules.

Question 18

what is the function of centrioles

Answer 18

Makes a copy of itself during cell division
and then helps to form the spindle in
cell division.

Question 19

what is the structure of cilia

Answer 19

• ‘Hair like’ extensions that protrude from some
animal cell types.
• In cross section they have an outer membrane
and a ring of nine pairs of protein
microtubules inside with two microtubules in
the middle.
• Known as a 9 +2 arrangement.
• Arrangement allows movement.

Question 20

what is the function of cilia

Answer 20

sensory function (e.g. nose), beat
creating a current to move
fluid/mucous/objects
For locomotion

Question 21

what is the structure of flagella

Answer 21

Similar to flagella but longer.
• They stick out from the cell surface and are
surrounded by the plasma membrane.
• Like cilia they have a 9 +2 arrangement.
• Function:
• (Whip-like) enables a cells mobility.
• The microtubules contract to make the flagellum
move.
• Propel cells forward e.g. sperm cells

Question 22

what is the structure and function of chloroplasts

Answer 22

• Double membrane which encloses the
stroma.
• Stroma contains: Starch grains, lipid
stores, DNA, RNA, ribosomes.
• Series of membrane-bound flattened
sacs called thylakoids in the stroma.
Thylakoids stacked together are called
grana.
• Grana are linked together by lamellae.
• The grana contain chlorophyll
Function
• Photosynthetic reactions

Question 23

what are plasma membranes

Answer 23

Structure
• The membrane found on the surface of animal cells and inside the
cell wall of plant and prokaryotic cells.
• A phospholipid bilayer.
• Composed of proteins and lipds.
Function
• Regulates the movement of substances into and out of the cell.
• Contains receptor molecules which allow it to respond to
chemical like hormones

Question 24

what is the function and structure of cell wall

Answer 24

Structure:
• Made of cellulose microfibrils– complex carbohydrate
• Cell wall is fully permeable to substances
• Thin layer called the middle lamella which marks the
boundary between adjacent cell walls and ‘cements’
adjacent cells together.
Function:
• Gives the plant mechanical strength
• Gives the plant cell support and it’s shape
• Contents of plant cell can ‘push’ against the cell wall
(turgid cell). This gives the cell (and the whole plant)
good support.

Question 25

explain how the process of protein production

Answer 25

1.) proteins are synthesisied on the ribosomes bound ot the RER
2.) then they pass into its cisternae and are packaged into transport vesicles
3.) vesiciles move towards to the golgi body via cytoskeleton
4.) the vesicles fuse with the cis face of the golgi body and proteins enter
5.) these proteins are structurally modified before leavin the golgi body
the vesicles fuse with the cell surface membrane releasing their contents by exocytosis.

Question 26

what are the 2 types of electron microscopes

Answer 26

• transmission electron mictroscope

- scanning electron microscope

Question 27

describe the snanning microscope

Answer 27

• a beam of electrons is sent across the surface of a specimen
• and the refelcted electrons are collected
• resolving power is 3-10n,
• 3 dimensional images are produced (3D)

Question 28

describe the transmission microscope

Answer 28

• a beam of electrons is transmitted through a specimen an focused to produe an image
• best resolution of 0.5nm

Question 29

define resolution

Answer 29

• Resolution is how well a microscope distinguishes between two points that are close together.

Question 30

define magnification

Answer 30

• how many times larger the image is than the actual size of the object being viewed