Topic 3A: Cell Structures

tissues

a group of cells that work together to perform a particular function

organs

a group of different tissues working together to perform particular functions

systems

different organs with related functions that work together to perform body functions

protoplasm

cytoplasm + nucleus

fluid part in cytoplasm

cytosol

use of cytoplasm

1. containing organelles

2. where metabolic activities take place

use of nuclear pores

channels for chemical substances to pass in and out

nucleolus use

1. site of ribosome production

2. partly controls cell growth and division

mitochondria use

contains enzymes like ATPase needed in aerobic respiration

mitochondria eukaryotic traits

1. circular DNA

2. 70s ribosomes

3. double membrane

flattened membrane-bound sacs

cisternae

production + modification + packaging + transportation of proteins

1. mRNA is manufactured in the nucleus during transcription

2. ribosomes in the rough ER make polypeptides during translation

3. polypeptide chain synthesised at the lumen of the rough ER is transported within, where it is folded and processed

4. processed proteins are then packaged into transport vesicles from rough ER to Golgi apparatus

5. vesicles from rough ER fuses with the membrane of the Golgi apparatus cis face

6. proteins are released into cis face of the golgi apparatus

7. they are further modified moving along from cis face to trans face

8. modified proteins are packaged into secretory vesicles & sent to and fuse with cell membrane

9. secrete the finished protein product by exocytosis

prokaryotic cell wall component

peptidoglycan

use of pilus

attach to host cell and transfer genetic material during conjugation

plasmids

circular rings of double-stranded DNA that can be transferred between bacteria and replicate independantly

infolding of cell surface membrane of prokaryotic cells

allow cell wall formation / aerobic respiration / DNA replication

stains

• haematoxylin / methylene blue: nuclei

• acetocarmine: chromosomes in dividing nuclei

• iodine: starch-containing

• toluidine blue: DNA & RNA

• phloroglucinol: lignin

safe method to prepare and examine structure cell

1. use cotton bud to gently rub inside of cheeks

2. rub cotton bud in small circles in the centre of glass slide

3. place cotton bud in disinfectant immediately

4. add a few drops of methylene blue to sample

5. cover with cover slip

6. examine stained slide under low objective, then high power objective lens

Procedure for accurate determination of cell diameter

1. use light microscope to find cell under low power

2. focus & view under high power

3. calibrate eyepiece graticule with objective lens that will be used with stage micrometer

4. replace the stage micrometer with specimen slide without changing magnification

5. count number of eyepiece graticule units over the cell

6. convert eyepiece graticule units (epu) to micrometer (um) using calibration

7. measure diameter at different positions to obtain a mean value

calibration of eyepiece graticule

1. place stage micrometer on stage and rotate the eyepiece so that the eyepiece scale aligns with stage micrometer scale

2. count no. of divisions on eyepiece graticule between 2 clear points where the lines on both scales align perfectly

3. calculate length of one epu