cell structure

Question 1

how would you prepare a slide to examine under a light microscope?

Answer 1

1. obtain a thin section of tissue - allows light to pass through
2. place a drop of water onto the tissue - prevents the cell from being damaged by dehydration
3. stain the tissue on a slide - makes the structures more visible
4. add a coverslip at a 45° angle - avoids trapping air bubbles

Question 2

what is the equation for magnification?

Answer 2

magnification = image size / actual size

Question 3

what is the definition of magnification?

Answer 3

the factor by which the image is larger than the actual specimen

Question 4

what is the definition of resolution?

Answer 4

smallest separation distance at which two separate structures can be distinguished from one another

Question 5

why do samples need to be stained for light microscopes?

Answer 5

coloured dye binds to the structures, and allows you to distinguish beetwween the different structures

Question 6

what is differential staining?

Answer 6

when a specimen is stained with multiple dyes to ensure the different tissues within the specimen show up

Question 7

what does methylene blue stain?

Answer 7

all-purpose stain (everything)

Question 8

what does acetic orcein stain?

Answer 8

binds to DNA, stains chromosomes dark red

Question 9

what does eosin stain?

Answer 9

cytoplasm

Question 10

what does sudan red stain?

Answer 10

lipids

Question 11

what is the magnification & resolution of a light microscope?

Answer 11

magnification : x2000
resolution : 200nm

Question 12

what is the magnification & resolution of a transmission electron microscope?

Answer 12

magnification : x500,000
resolution : 0.5nm

Question 13

what is the magnification and resolution of a scanning electron microscope?

Answer 13

magnification : x500,000
resolution : 3-10nm

Question 14

what is the structure of the nucleus?

Answer 14

• surrounded by a nuclear envelope (semipermeable double membrane)
• has nuclear pores which allows substances to enter & exit
• contains a nucleolus made of RNA & proteins, which synthesises ribsomes
• contains DNA coiled around chromatin into chromosomes

Question 15

what is the function of the nucleus?

Answer 15

controls cellular processes e.g. gene expression, mRNA transcription, mitosis, semiconservative replication

Question 16

what is the structure & function of the rough endoplasmic reticulum (RER)?

Answer 16

• has cisternae which is a network of tubules & flattened sacs, it extends from the cell membrane & connects to the nuclear envelope
• coated in ribosomes for protein synthesis & transport

Question 17

what is the structure & function of the smooth endoplasmic reticulum (SER)?

Answer 17

• has cisternae which is a network of tubules & flattened sacs, it extends from the cell membrane & connects to the nuclear envelope
• site of lipid synthesis

Question 18

what is the structure & function of the golgi?

Answer 18

• stack of membrane-bound, flattened sacs
• vesicles bud off via exocytosis, bringing molecules to and from the golgi
• modifies & packages proteins for export
• synthesisisees glycoproteins

Question 19

what is the structuure & function of ribosomes?

Answer 19

• formed of protein & rRNA
• site of protein synthesis

Question 20

what is the relationship between the organelles involved in the production & secretion of proteins?

Answer 20

the ribosomes that synthesise proteins are attached to the RER, the golgi’s membrane is aligned with the RER, and modifies the proteins for secretion

Question 21

what is the structure of mitochondria?

Answer 21

• surrounded by double membrane
• folded inner membrane forms cristae - the site of the electron transport chain
• fluid filled matrix - contains mitochndrial DNA, repiratory enzymes, lipids, & proteins

Question 22

what is the function of mitochondria?

Answer 22

site of aerobic respiration to produce ATP

Question 23

wat is the structure of a chloroplast?

Answer 23

• double membrane
• thylakoids which are flattened discs stacked to form grana - contain photosystems with chlorophyll
• intergranal lamellae - tubes attach thylakoids in adjacent grana
• stroma - fluid-filled matrix

Question 24

what is the function of chloroplasts?

Answer 24

site of photosynthesis to convert solar energy to chemical energy

Question 25

what is the structure & function of lysosomes?

Answer 25

- sac surrounded by a single membrane - embedded H+ pump to maintain acidic conditions - contains digestive hydrolase enzymes - glycoprotein coat to protect the cell interior - digests contents of phagosome - exocytosis of digestive enzymes

Question 26

what is the structure & function of a plant cell wall?

Answer 26

- composed of cellulose microfibrils for mechanical support - plasmodesmata forms part of the apoplast pathway to allow molecules to pass between cells

Question 27

what are bacterial cell walls composed of?

Answer 27

peptidoclycan

Question 28

what are fungi cell walls composed of?

Answer 28

chitin

Question 29

what is the structure & function of the plasma membrane?

Answer 29

- 'fluid mosaic' phospholipid bilayer with extrinsic & intrinsic proteins embedded - isolates cytoplasm from extracellular environment - selectively permeable to regulate the transport of substances - involved in cell signalling / cell recognition

Question 30

what is the structure & function of centrioles?

Answer 30

- spherical group of 9 microtubules arranged in triplets - located in centrosomes - migrate to opposite poles of the cell during prophase & spindle fibres form between them

Question 31

what is the structure & function of flagella?

Answer 31

- hollow helical tube made of the protein flagellin - rotates to propel the organism

Question 32

what is the structure & function of cilia?

Answer 32

- hairlike protusions on eukaryotic cells - move back and forth rhythmically to sweep foreign substances away, or enable the cell to move

Question 33

why is the cytoskeleton important?

Answer 33

- provides mechanical strength - aids transport within cells - enables cell movement

Question 34

what are the similarities between eukaryotic & prokaryotic cells?

Answer 34

both have: - cell membrane - cytoplasm - ribosomes

Question 35

compare the size of eukaryotic & prokaryotic cells?

Answer 35

prokaryotic cells are smaller

Question 36

compare the organelles in eukaryotic & prokaryotic cells?

Answer 36

- prokaryotic cells have no membrane-bound organelles & no nucleus - eukaryotic cells always have organelles & a nucleus

Question 37

compare the DNA in eukaryotic & prokaryotic cells?

Answer 37

- prokaryotic cells have circular DNA - eukaryotic cells have linear DNA

Question 38

compare the ribosomes in eukaryotic & prokaryotic cells?

Answer 38

- prokaryotic cells have 70S ribsosomes - eukaryotic cells have 80S ribosomes

Question 39

compare cell division in eukaryotic & prokaryotic cells?

Answer 39

- prokaryotic cells divide by binary fission, by asexual reproduction - eukaryotic cells divide by mitosis & meiosis, by either sexual or asexual reproduction

Question 40

compare the cell walls of eukaryotic & prokaryotic cells?

Answer 40

- prokaryotic cell walls are composed of peptidoglycan - eukaryotic cell walls are: absent in animals, cellulose in plants, and chitin in fungi

Question 41

what are the main features of a light microscope?

Answer 41

- Easy to use - Relatively cheap - Portable & able to be used in the field as well as in laboratories - Able to be used to study whole living specimens

Question 42

what are the main features of transmission electron microscopes?

Answer 42

- Very large - Very expensive - Need a great deal of training to use them - Able to study whole specimens - Specimens must be dead when studied - The metallic salt stains used for staining specimens may be hazardous to the user

Question 43

what are the main features of scanning electron microscopes?

Answer 43

- Very large - Very expensive - Need a great deal of training to use them - Able to study whole specimens - Specimens must be dead when studied - The metallic salt stains used for staining specimens may be hazardous to the user