cells

description of a light microscope :

• small and inexpensive

• max magnification is x1500

• cannot see viruses, atoms or molecules because they are smaller than a wave of visible light

• maximum resolution is 0.2 um

description of a laser scanning confocal microscope :

• creates a 3D image

• cells are tagged with fluorescent dye

• the laser causes the dye to give off light

• light focused through a pinhole onto a detector

• computer will generate an image

• high resolution

description of a transmission electron microscope (TEM) :

• large

• electrons are smaller than photons so can see very small atoms

• produces a 2D image

• artificial colour

• maximum resolution is 0.0002 um

• magnification can be more than x1000000

• can see interior

description of a scanning electron microscope (SEM) :

• replicates the surface of cells

• specimen must be in a vacuum therefore no living organism

• 3D

• can see detailed structure of organelles

• maximum magnification is x500000

• can see small atoms

• maximum resolution is 0.002 um

• expensive

• preparing slides takes high level of skill

definition of resolution :

how well a microscope can distinguish between two separate points that are close together

magnification =

image size / object size

what is A?

ribosome

what is B?

rough endoplasmic reticulum

what is C?

nuclear envelope

what is D?

lysosome

what is E?

golgi apparatus

what is F?

cell membrane

what is G?

smooth endoplasmic reticulum

what is H?

nucleus

what is I?

nucleolus

what is J?

mitochondrion

what is a eukaryote?

any organism consisting of one or more cells that contain DNA in a membrane bound nucleus separate to the cytoplasm

• animals

• plants

• fungi

• protoctists

nucleus :

contains all the cells genetic material

chromatin :

made of DNA and proteins

nucleolus :

makes RNA which is made into ribosomes

nuclear envelope :

• dense, spherical structure

• surrounds nucleolus

• made of inner and outer membrane with fluid in between

• has nuclear pores to allow molecules to pass through

what is A?

cristae

what is B?

inner membrane coated in enzymes which catalyse reactions for aerobic respiration to produce ATP energy

what is C?

matrix

what is D?

outer membrane

mitochondrion :

energy generating organelle

why do mitochondria have their own DNA?

evolved from bacteria with a different genetic code

golgi apparatus - structure :

• stack of membrane bound flattened sacs

• single membrane has two layers

• membrane surrounds an area of fluid where complex molecules are stored and changed

golgi apparatus - function :

• receives proteins from the ER and modifies them

• packages modified proteins into vesicles to be transported

rough endoplasmic reticulum :

• made of cisternae

• studded with ribosomes

• transports proteins made on the attached ribosomes

• some will be secreted or placed on the cell membrane

smooth endoplasmic reticulum :

• same structure as rough but without ribosomes

• involved in making lipids

lysosomes :

• spherical sacs surrounded by a membrane

• specialised vesicles

• contain digestive enzymes which break down pathogens

ribosomes :

• site of protein synthesis

• acts as an assembly line for coded information from the nucleus

• used to make proteins from amino acids

centrioles :

• self replicating organelles made of nine bundles of microtubules

• help organise cell division

cilia and flagella :

• essential for locomotion of individual organisms

• move fluid or materials past an immobile cell

production of a protein :

• hormone instructions found in DNA in the nucleus

• nucleus copies instructions into mRNA

• mRNA leaves nucleus through nuclear pore

• attaches to a ribosome

• ribosome carries out protein synthesis

• assembled protein is pinched off in a vesicle

• golgi modifies and packages the protein

• excreted by exocytosis

function of the cytoskeleton :

• supports organelles

• strengthen and maintain shape of cell

• allow movement of materials

• cell movement with flagellas and cilia

structure of the cytoskeleton :

• microfilaments

• microtubules

• intermediate fibres

microfilaments :

small strands of actin that contract during cytokinesis helping new membranes form

microtubules :

tiny protein cylinders made of tubulin involved in cell movement

intermediate fibres :

provide mechanical strength to cells

what happens in the thylakoid membrane in chloroplasts?

it is the site of photosynthesis

structure of a vacuole :

membrane called tonoplast filled with a cell sap

function of a vacuole :

keeps cells turgid

structure of cell wall :

made of polysaccharide cellulose with plasmodesmata

function of the cell wall :

enable exchange and transport of materials and act as a carbohydrate store

dry mount sample preparation :

thinly cut solid specimen put on a slide

wet mount sample preparation :

specimens suspended in a liquid and cover slip placed at an angle

squash slides sample preparation :

wet mount but sample is squashed between two slides

smear slides sample preparation :

use an edge of a slide to smear a thin coating onto slide

why is staining necessary when preparing samples?

makes cell components more visible

definition of resolution :

ability to distinguish between two close together objects

actual size =

image size / magnification

definition of a prokaryote :

single celled organism that does not have a nucleus or membrane bound organelles

definition of eukaryote :

have membrane and complex organelles that are part of a multicellular organism performing a function

prokaryotes :

• smaller circular DNA

• no nucleus

• cell wall made of polysaccharide

• flagella made by protein flagellin in a helix

• small ribosomes

eukaryotes :

• larger

• linear DNA

• nucleus

• cellulose and chitin cell walls

• flagella made of microtubules

• larger ribosomes

what is a?

stroma

what is b?

thylakoid membrane

what is c?

grana