Eukaryotic and prokaryotic cell structure and function

Question 1

What is the cell theory ?

Answer 1

cells are the fundamental unit of structure, function and organisation in all living organisms

Question 2

unicellular organisms are …

Answer 2

composed of a single cell

Question 3

multicellular organisms are …

Answer 3

composed of many cells

Question 4

what is differentiation ?

Answer 4

the development process by which the structure of the cells of a multicellular organism specialise for a specific function

Question 5

what is a tissue ?

Answer 5

a group of cells that have a common origin and a similar structure that work together to form a single function

Question 6

what is an organ ?

Answer 6

a structure that has a specific function

Question 7

what is a system ?

Answer 7

a group of organs and tissues that perform a particular function

Question 8

nucleoid

Answer 8

the circular DNA molecule found in prokaryotic cells

Question 9

plasmid

Answer 9

circular DNA molecules in their cytoplasm
- usually contain a few genes including : genes conferring resistance to specific antibiotics

Question 10

What are 70s Ribosomes ?

Answer 10

these ribosomes are involved in protein synthesis but they are smaller than 80s ribosomes found in eukaryotic cells

Question 11

Cell wall

Answer 11

prevents cells bursting when in dilute solutions - made of peptidoglycan

Question 12

Pili and flagella

Answer 12

pili - help prokaryotic cells to attach to surfaces or each other
flagella - help the cells to move about

Question 13

what do bacterial cell walls contain ?

Answer 13

polymers of amino acids and sugars called peptidoglycan

Question 14

Gram positive bacteria have ..

Answer 14

thick walls made almost entirely of peptidoglycan

Question 15

what colour does the gram positive bacteria wall become ?

Answer 15

purple when stained by crystal violet

Question 16

Gram negative bacteria have ..

Answer 16

thin walls of peptidoglycan with an additional outer membrane

Question 17

why does the gram negative bacteria wall not become purple ?

Answer 17

the high lipid content of this outer membrane prevents the crystal violet stain getting to the cell wall

Question 18

The effects of antibiotics on these two types of bacteria ?

Answer 18

Gram negative bacteria - the outer membrane is relatively impermeable to antibiotics SO is resistant to many types of antibiotic, including penicillin
Gram positive bacteria - susceptible to penicillin

Question 19

Structure and function of nucleus

Answer 19

• surrounded by a double nuclear membrane that contains many pores

Structure: Nuclear pores
Function: allow movement of molecules between the cytoplasm and the nucleus

Structure: Nuclear envelope
Function: controls what enters and exists nucleus

Structure: Nucleolus
Function: site in the nucleus where the rRNA is created according to instructions in DNA

Structure: Chromatin( between nucleolus and nuclear envelope )
Function: makes up eukaryotic chromosomes

Question 20

Structure and function of 80s ribosomes

Answer 20

Structure: larger than 70s ribosomes
Function: synthesis protein

Question 21

Structure and function of rough endoplasmic reticulum

Answer 21

Structure: ribosomes attached to its outer surface
Function:
- develops the tertiary and quaternary shapes of proteins
- packages to vesicles, transports to the Golgi apparatus

Question 22

Structure and function of smooth endoplasmic reticulum

Answer 22

Structure: no ribosomes are attached to it
Function: synthesis lipids, phospholipids and steroids

Question 23

what is the function of the smooth endoplasmic reticulum in the cytoplasm of voluntary muscle fibres ?

Answer 23

site of storage of calcium ions - contraction of muscle fibres

Question 24

Structure and function of cell membrane

Answer 24

• double membrane surrounding organelle
• controls entry and exit of material

Structure: Cristae
Function: extensions of inner membrane - providing a large surface area for the attachment of enzymes and other proteins during respiration

Structure: Matrix
Function: interior of the mitochondria
- contains an aqueous solution of metabolites and enzymes

• site of aerobic respiration producing ATP for energy

Question 25

Structure and function of centrioles

Answer 25

Structure: microtubules
Function: forms a network of unbranched, hollow cylinders
- involved in moving organelles around in the cytoplasm - form centrioles

Question 26

Structure and function of lysosomes

Answer 26

Structure: small spherical vesicles bound by single membrane
- contain a concentrated mixture of hydrolytic enzymes
Function: breakdown of imported food vacuoles, old organelles and harmful bacteria

Question 27

Structure and function of Golgi apparatus

Answer 27

Structure: consists of flattened membranous sacs
Function: modifying and packaging polymers for secretion or for use within the cell

Question 28

Structure and function of Cell wall

Answer 28

Structure: made of polysaccharide - cellulose
Function: prevents the cell changing shape and bursting (lysis)

Question 29

Structure and function of chloroplasts

Answer 29

-biconvex in shape
- double membrane
- site of photosynthesis

Structure: Thylakoids
Function: system of branching membranes

Structure: Grana
- thylakoids arranged in flattened circular piles
Function: where chlorophylls and other pigments involved light capture are located

Structure: Stroma
Function: containing enzymes and small starch grains

Question 30

Structure and function of vacuole

Answer 30

Structure: contains cell sap - weak solution of sugars and salts
Function: maintains pressure in the cell - stop wilting

Question 31

Structure and function of tonoplast

Answer 31

Structure: membrane of the vacuole
Function: barrier between the fluid contents of the vacuole

Question 32

How do prokaryotic cells differ from eukaryotic cells ?

Answer 32

Prokaryotic cells:
- no membrane bound organelles
- no nucleus containing free-floating DNA
- DNA is circular and is not associated with proteins
- made of murein and peptidoglycan

Eukaryotic cells:
- membrane bound organelles
- nucleus
- DNA is linear and is associated with proteins
- made of cellulose and 70s ribosomes

Question 33

what is magnification ?

Answer 33

the extent to which an object has been enlarged by a microscope

Question 34

formula of magnification

Answer 34

size of image / size of specimen

Question 35

what is resolution ?

Answer 35

the ability to distinguish between points that are very close together

Question 36

what is the importance of staining specimens ?

Answer 36

provides contrast to distinguish between different structures in the sample

Question 37

what is a light microscope ?

Answer 37

A light microscope is a type of microscope that uses light to magnify the image of a specimen. It works by passing light through a specimen and focusing the light on an eyepiece or camera, which magnifies the image.

Question 38

advantages of light microscope

Answer 38

• Inexpensive to buy and operate.
• Relatively small
• Both living and dead specimens can be viewed

Question 39

disadvantages of light microscope

Answer 39

• Maximum magnification of 1500x
• Specimen may be disfigured during preparation to be viewed under the microscope
• The resolving power is 1 nm for biological specimens

Question 40

what is an electron microscope ?

Answer 40

The electron microscope uses a beam of electrons and their wave-like characteristics to magnify an object’s image, unlike the optical microscope that uses visible light to magnify images.

Question 41

advantages of electron microscope

Answer 41

• has a large depth of field, which allows more of a specimen to be in focus at one time.
• much higher resolution, so closely spaced specimens can be magnified at much higher levels.

Question 42

disadvantages of electron microscope

Answer 42

• expensive
• large
• must be housed in an area free of any possible electric, magnetic or vibration interference