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

what is differentiation ?

Answer 2

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

Question 3

what is a tissue ?

Answer 3

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

Question 4

what is an organ ?

Answer 4

a structure that has a specific function

Question 5

what is a system ?

Answer 5

a group of organs and tissues that perform a particular function

Question 6

nucleoid

Answer 6

the circular DNA molecule found in prokaryotic cells

Question 7

plasmid

Answer 7

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

Question 8

What are 70s Ribosomes ?

Answer 8

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

Question 9

Cell wall

Answer 9

prevents cells bursting when in dilute solutions - made of peptidoglycan

Question 10

Pili and flagella

Answer 10

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

Question 11

what do bacterial cell walls contain ?

Answer 11

polymers of amino acids and sugars called peptidoglycan

Question 12

Gram positive bacteria have ..

Answer 12

thick walls made almost entirely of peptidoglycan

Question 13

what colour does the gram positive bacteria wall become ?

Answer 13

purple when stained by crystal violet

Question 14

Gram negative bacteria have ..

Answer 14

thin walls of peptidoglycan with an additional outer membrane

Question 15

why does the gram negative bacteria wall not become purple ?

Answer 15

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

Question 16

The effects of antibiotics on these two types of bacteria ?

Answer 16

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 17

Structure and function of nucleus

Answer 17

• surrounded by a double nuclear membrane that contains many pores

Question 18

what is the function of nuclear pores ?

Answer 18

Function: allow movement of molecules between the cytoplasm and the nucleus

Question 19

what is the function of the nuclear envelope ?

Answer 19

Function: controls what enters and exists nucleus

Question 20

what is the function of the nucleolus ?

Answer 20

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

Question 21

what is the structure and function of chromatin ?

Answer 21

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

Question 22

Structure and function of 80s ribosomes

Answer 22

Structure: larger than 70s ribosomes
Function: synthesis protein

Question 23

Structure and function of rough endoplasmic reticulum

Answer 23

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 24

Structure and function of smooth endoplasmic reticulum

Answer 24

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

Question 25

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

Answer 25

site of storage of calcium ions - contraction of muscle fibres

Question 26

Structure and function of cell membrane

Answer 26

- 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 27

Structure and function of centrioles

Answer 27

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

Question 28

Structure and function of lysosomes

Answer 28

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 29

Structure and function of Golgi apparatus

Answer 29

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

Question 30

Structure and function of Cell wall

Answer 30

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

Question 31

Structure and function of chloroplasts

Answer 31

-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 32

Structure and function of vacuole

Answer 32

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

Question 33

Structure and function of tonoplast

Answer 33

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

Question 34

How do prokaryotic cells differ from eukaryotic cells ?

Answer 34

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 35

what is magnification ?

Answer 35

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

Question 36

formula of magnification

Answer 36

size of image / size of specimen

Question 37

what is resolution ?

Answer 37

the ability to distinguish between points that are very close together

Question 38

what is the importance of staining specimens ?

Answer 38

provides contrast to distinguish between different structures in the sample

Question 39

what is a light microscope ?

Answer 39

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 40

advantages of light microscope

Answer 40

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

Question 41

disadvantages of light microscope

Answer 41

- 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 42

what is an electron microscope ?

Answer 42

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 43

advantages of electron microscope

Answer 43

- 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 44

disadvantages of electron microscope

Answer 44

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

Question 45

what is the structure of gram positive bacteria ?

Answer 45

thick layer of peptidoglycan no outer membrane

Question 46

what is the structure of gram negative bacteria ?

Answer 46

thin layer of peptidoglycan outer membrane contains lipopolysaccharides

Question 47

what does the function of outer membrane in gram negative bacteria ?

Answer 47

provides additional protection and barrier against certain antibiotics

Question 48

what happens to gram positive bacteria when stained ?

Answer 48

The thick peptidoglycan layer retains the crystal violet stain. The bacteria appear purple under the microscope.

Question 49

what happens to gram negative bacteria when stained ?

Answer 49

The thin peptidoglycan layer does not retain the crystal violet stain after the decolorization step. The bacteria lose the crystal violet and instead take up the counterstain (safranin or fuchsine), appearing pink under the microscope.

Question 50

how does gram positive bacteria react with antibiotics ?

Answer 50

effective because these antibiotics target the peptidoglycan layer, disrupting cell wall synthesis. Since Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, these antibiotics can easily reach their target.

Question 50

how does gram negative bacteria react with antibiotics ?

Answer 50

more resistant due to the presence of outer membrane, which acts as a barrier to antibiotic molecules