cell structure

Question 1

what are light microscopes used to observe

Answer 1

larger structure such as entire cells, nuclei, mitrochondria and chloroplasts

Question 2

advantages of light microscopes

Answer 2

• small and relatively cheap
• specimen preparation can be straightforward
• colour images
• allow the observation of living specimens

Question 3

maximum resolution of a light microscope

Answer 3

0.2 micrometers

Question 4

limitations of electron microscopes

Answer 4

• large and expensive
• specimen preparation is a highly complex process
• specimens must be viewed in a vacuum (live specimens can’t be observed)
• images are black and white

Question 5

two types of electron microscopes

Answer 5

• trasmission electron microscopes
• scanning electron microscopes

Question 6

How do TEM’s work

Answer 6

• use electromagnets to transmit a beam of electrons through a specimen.
• denser parts of the speciment absorb more electrons meaning they appear darker

Question 7

what are TEM images like

Answer 7

• high resolution
• two dimensional
• allow the internal structures within cells and within organelles to be seen

Question 8

how do scanning electron microscopes work

Answer 8

• pass a beam of electrons across the surface of a specimen
• then detect the rate at which the electrons bounce back

Question 9

SEMs images

Answer 9

• three dimensional
• show the surface of specimens
• lower maximum resolution

Question 10

what is chromatin - where is it found

Answer 10

the nucleus of a cell contains chromatin which is the genetic material of the cell

Question 11

what are nuclear pores

Answer 11

important channels for allowing mRNA and ribosomes to travel out of the nucleus
allow enzymes and signalling molecules to travel in

Question 12

site of ribosome production

Answer 12

nucleolus

Question 13

mitochondria structure + function

Answer 13

• surrounded by a double membrane with the inner membrane folded to form cristae
• the matrix formed by the cristae contains enzymes needed for aerobic respiration. producing ATP

Question 14

chloroplasts structure and function

Answer 14

• found in plant cells
• surrounded by a double membrane
• membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
• grana are held together by lamellae

Question 15

structure and function of ribosomes

Answer 15

• made up of two subunits
• found in all cells
• found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells
• site of translation (protein synthesis)

Question 16

what size ribosomes are found in eukaryotic and prokaryotic cells

Answer 16

80S - eukaryotic
70S- prokaryotic

Question 17

what is grana

Answer 17

within the chloroplasts and contains chlorophyll

Question 18

what is always present in a prokaryotic cell

Answer 18

cell wall
cell surface membrane
cytoplasm
circular DNA
ribosomes

Question 19

what is sometimes present in a prokaryotic cell

Answer 19

• flagellum
• capsule
• infolding of cell surface membrane
• plasmid
• pili

Question 20

what does the flagella connect to

Answer 20

hook connects to the basal section in the cell mebrane

Question 21

what is the purpose of plasmids

Answer 21

small circular loops of DNA
contain genes that are passed between prokaryots

Question 22

what is the purpose of capsules

Answer 22

surround the prokaryote (e.g. bacteria) to help protect bacteria from drying out and from attack by cells of the immune system of the host organisms

Question 23

what is the purpose of flagellum

Answer 23

hair like structure that rotates - enabling prokaryote to move

Question 24

what is the cell wall made of in prokaryotes

Answer 24

peptidoglycan

Question 25

what is the role of pilli

Answer 25

to transfer DNA

Question 26

what is the cytoskeleton

Answer 26

a network of fibres necessary for the shape and stability of the cell. organelles are hekd in place by the cytoskeleton and it controls the cell and organelle movement

Question 27

what **3 things** is the cytoskeleton made of and their roles

Answer 27

microfilaments - made of actin, responsible for cell movement and cell contraction during cytokinesis microtubules - globular tubulin proteins polymerise to form scaffold across the cell to determine cell shape, they act as tracks for the movement of organelles around the cell and the spindle fibres intermediate fibres - provide mechanical strength and help maintain integrity

Question 28

8 steps protein synthesis and excretion

Answer 28

- mRNA copy of the genes is made in the nucleus - mRNA leaces the nucleus through a nuclear pore - mRNA attaches to a ribosome (attached to endoplasmic reticulum). Ribosome reads each codon and tRNA brings the correct amino acids - protein are pinched off in vesicles and travel towards golgi - vescile fuses with golgi which processes and packages proteins ready for release - proteins are pinched off in vesicles and move towards cell surface membrane - vesicle fuses with membrane and proteins are released

Question 29

4 functions of the cytoskeleton

Answer 29

- mechanical strength - maintains shape of the cell - movement of vesicles - formations of microtubules (which form the spindle fibres used to move chromatids in mitosis + meiosis

Question 30

3 functions of tubulin

Answer 30

- movement of mRNA from nucleus to ribosome - movement of polypeptides through the rER - movement of vesicles from golgi apparatus to cell surface membrane