Cell structure

what is ultrastructure?

detail within cells seeb using an electron microscope

what is eukaryotic cells?

cells that have a nucleus and have membrane-bound organelles

what are organelles?

structures within cells have specific functions and this provides a division of labour which allows the cell to function

what is the function of the nucleus?

controls the cells activities and contains genetic material to make proteins

what is the structure of the nucleus?

surrounded by a double membrane called the nuclear envelope and there are pores in the nuclear envelope called nuclear pores which allows substances to leave the nucleus

give an example of a substance that leaves the nuclues

mRNA

what is chromatin?

made from DNA and wrapped around histone proteins

what does chromatin condense to form?

chromosomes

what is the nucleolus?

contains RNA to make ribosomes

what does the RER consist of?

a series of membranes that are continuous with nuclear envelope with fluid cavities called cisternae

what is cisternae?

fluid cavities that form channels to transport substances from one area of a cell to another

what is the RER covered in?

ribosomes

what are ribosomes?

the site of protein synthesis

what is the difference between SER and RER?

SER is not covered with ribosomes

what does the SER do?

contains enzymes that are needed for synthesising and processing lipids

what is an example of a substance that the SER has to process?

cholesterol

where are ribosomes in a cell?

attached to the RER and free floating in the cytoplasm

what do ribosomes do in the RER?

makes proteins that are secreted outside the cell

what do free floating ribosomes do?

makes proteins that are used inside the cell

what does the golgi apparatus do?

makes lysomes

and it modifies processes and packages proteins into vesicles

what does the golgi apparatus consist of?

stack of membrane- band flattened sacs

what are vesicles?

bring materials to the Golgi apparatus and from the Golgi apparatus

what is the structure of the mitochondrion?

surrounded by a double membrane: inner and outer

and the membrane is highly folded into cristae

what is the inner part of the mitochondrion filled with?

matrix

what is matrix?

contains enzymes needed for aerobic respiration

what does aerobic respiration make?

ATP

what is the chloroplasts function?

site of photosynthesis

what is the structure of the chloroplasts?

thylakoids

what are thylakoids?

flattened membrane sacs

what do thylakoids form?

discs called grana

what is the inner part of the chloroplast called?

stroma

what are lysosomes formed by?

Golgi apparatus

what do lysomes contain?

hydrolytic enzymes

what do hydrolytic enzymes do?

engulf and digest old organelles, pathogen and foreign

what do lysomes do?

return digested components for the cell to re-use

what does the permeant vacuole do?

filled with water and solutes and then when its full it makes the cell turgid and stable by the tonoplast

what is the permeant vacuole surrounded by?

tonoplast (membrane)

what does the cellulose cell wall?

provides strength and support to cells and the whole plant

what does the plasma membrane contain?

lipids and protein

what does the plasma membrane do?

controls/regulates the transport of substances into and out the cell

what is the cytoskeleton made of?

3 types of fibres in the cytoskeleton

what are the 3 fibres found in the cytoskeleton?

microfilaments, intermediate filaments and microtubules

what are microfilaments made of?

actin protein

what do the microfilaments do?

responsible for changing shape of a cell which allows cell to move and contract

what do the intermediate filaments do?

provide mechanical strength and structure to the cell

anchors the nucleus and other organelles in place

what are microtubules made of?

tubulin protein

what do the microtubules do?

* form tracks which allows the movement of vesicles and organelles throughout the cells this involves master proteins
* form centrioles which are involved in the movement of chromosomes during cell division
* both flagella and cilia are made from microtubules formed by centrioles
* microtubules in flagella contract allowing the cell to propel forward
* cilia and flagella both have the same structural arrangement of microtubules

give examples of master proteins

kinsen and dynein

how are flagella and cilia formed?

made from of microtubules which is formed by the microtubules - this allows cilia to move which is responsible for moving substances along the cells surface

what is the 9 + 2 formation?

it is the structural arrangement of microtubules in the cilia and flagella

what is the process making and secreting a protein?

1. The gene coding for the protein is transcribed into messenger RNA (mRNA) inside the nucleus. This is called transcription.

2. The mRNA leaves the nucleus via a nuclear pore

3. The mRNA attaches to a ribosome on the RER and the protein is assembled (translation)

4. the protein then moves through the cisternae of the RER

5. the protein is pinched off into a vesicle from the RER and moves via microtubules and motor proteins to the Golgi apparatus

6. the vesicle fuses with the golgi apparatus and releases a protein inside

7. the golgi apparatus then modifies, processes and packages the protein into a secretory vesicle

8. the secretory vesicle is then pinched off from the Golgi apparatus

9. the secretory vesicle moves from the Golgi apparatus to the plasma membrane

10. the secretory vesicle fuses with the plasma membrane and the protein is released to the outside of the cell by exocytosis

what is an example of prokaryotic cell?

bacteria

what are the similarities between eukaryotic and prokaryotic cells?

plasma membrane

cytoplasm

DNA and RNA

ribosomes

both have these

why are prokaryotic cells different to eukaryotic?

* they smaller
* no nucleus
* no membrane bound organelles
* smaller ribosomes
* dna not associate with histone proteins
* cell wall
* less developed cytoskeleton and no centrioles
* have plasmids
* protective waxy capsule surrounding the cell wall
* different flagella structure
* small hairs - pili

what size are ribosomes in prokaryotic and eukaryotic?

70s in prokaryotic

80s in eukaryotic

how does DNA exist in a prokaryotic cell compared to eukaryotic?

prokaryotic exists as a loop free-floating in the cytoplasm

eukaryotic exits as linear

what is the cell wall made of in prokaryotic cells?

peptidoglycan not cellulose (in plants)

what do plasmids do?

give extra properties

what does pili allow?

bacteria to adhere to host cells or each other

what do prokaryotic cells divide by?

binary fission

what is magnification?

how many times larger an image is compared with size of an object

what is resolution?

the ability to distinguish between two separate points and therefore how much detail can be seen

what is a light microscope?

use visible light (400 to 700nm)

have two lenses to magnify images:

eyepiece - what you look through

objective - above the specimen

what magnification is the eyepiece lens in a light microscope?

10 x

what is the total magnification of a light microscope?

magnifying power of eyepiece lens x magnifying power of objective lens

what is the maximum magnification of a light microscope?

x 1500

what is the maximum resolution?

200 nm

what microscope is used to view living organisms?

light microscope

what can’t light microscopes be used for?

observe any objects smaller than 200nm

how do TEM microscope work?

a beam of electrons pass through the specimen which are absorbed by the specimen

what image does an TEM produce?

2D black and white image

what is the magnification of TEM?

more than x 500 000

can be more than x 1 000 000

what is the maximum resolution of TEM?

0.2nm

what are the two different electron microscopes?

TEM - Transmissor electron microscope

SEM - scanning electron microscope

how do SEM work?

a beam of electrons is used but they do not pass through the specimen. the electrons is sent across a specimen causing electrons already on the specimen to bounce off and are focused onto a screen

what image does a SEM produce?

produces 3D black and white which can be falsely coloured and show the cell surface of a specimen

what is the maximum magnification of a SEM?

less than x 500 000

what is the maximum resolution of SEM?

0\.2nm

how does a laser scanning confocal microscope work?

using a laser light to scan living cells

what image does a laser scanning confocal microscope produce?

a coloured 3D image which focuses on structure at different depths of the specimen

how are images in laser scanning confocal microscope coloured?

using fluorescent tags

what is the maximum resolution of a laser scanning confocal microscope?

200nm

what are the two main ways of preparing a slide?

dry mount and wet mount

when do we usually use a dry mount?

hairs, part of insects, pollen and parts of flowers etc

how do you prepare a dry mount?

* using tweezers place a thin slice of your specimen and place in the middle of the slide
* place a coverslip on top

when do we usually use a wet mount?

living samples e.g tiny aquatic organisms

how do you prepare a wet mount?

* pipette a small top of water onto the slide (or immersion oil) onto the middle of your glass slide
* using tweezers place your specimen on top of the water drop
* put the cover slip on starting upright next to the water droplet and then slowly lower it avoiding air bubbles

how do you add a stain?

add a drop of stain to one edge of the cover slip

place a piece of blotting paper on the opposite edge to draw the stain under the coverslip

use blotting paper to remove excess stain

why do we use stains?

* provides contrast
* identify/see organelles

what is differential staining?

some stains will bind to specific organelles

what are the 4 types of stain?

eosin

acetic orcein

methylene blue

iodine

what does eosin stain?

cytoplasm pink

what does acetic orcein stain?

chromosomes red/purple

what does methylene blue stain?

DNA and RNA blue

what does iodine stain?

plant cell walls orange/brown

what is needed for a good biological drawing?

* include a title
* include magnification
* use a smooth sharp pencil for drawings and labels
* draw smooth continuous lines
* no shading or sketching
* label lines drawn parallel to the top of the page
* label lines do not have cross or arrowheads
* use as much paper as possible (white and unlined)
* draw clearly identified structures
* ensure proportions are correct

what is the magnification equation?

image size/actual size

what is an eyepiece graticule?

fitted onto the eyepiece of a microscope

it is transparent with a ruler etched onto it

what is an eyepiece graticule used for?

measure the size of specimens

as you increase magnification of the specimens the length of the eyepiece graticule remains constant

what must be done to the eyepiece graticule at different magnifications?

calibrated