all cell structure

Nucleus structure

Largest organelle, surrounded by double membrane called nuclear envelope

Nucleus function

Contains genetic material, makes RNA and ribosomes, controls the cell's activities

Mitochondria structure

Surrounded by double membrane, inner membrane folded to form cristae. Contains DNA and ribosomes.

Mitochondria function

Site of aerobic respiration and produces ATP

Rough endoplasmic reticulum structure

Flattened membrane sacs called cisternae with ribosomes attached

Rough ER function

Site of protein synthesis and then transports proteins

Smooth ER structure

• Flattened membrane sacs called cisternae

• NO RIBOSOMES

Smooth ER function

Lipid and steroid synthesis

Golgi apparatus structure

Stack of membrane bound sacs

Golgi apparatus function

Modifies proteins (adding sugar or lipid molecules) and folding proteins into 3D shapes. Packages proteins into vesicles for transport.

what are vesicles

Membrane sacs used to transport materials

Chloroplast structure

Surrounded by a double membrane with a highly folded inner membrane embedded with chlorophyll. Also contain DNA and ribosomes

Inside of chloroplast structure

• Contains a matrix of stroma which has a system of membranes running through it.

• These are stacked in places to form grana (contain chlorophyll).

• Stroma contains circular DNA, ribosomes and starch grains.

Chloroplast function

Site of photosynthesis

Lysosome structure

Spherical sacs containing powerful digestive enzymes

Lysosome function

• contains lysins (very string digestive enzymes)

• Destroys worn out organelles

• digests the contents of vacuoles formed by phagocytosis

Vacuole structure

Bound by a single membrane called a tonoplast. Contains cell sap.

Components of cell sap

Mineral salts, pigments, organic acids and other substances.

Vacuole function

Stores waste products and cell sap. Changes in volume affect turgidity of the cell.

Ribosome structure

• Not membrane bound.

• Made of protein and RNA

Ribosome function

Protein synthesis

Centriole structure

Made of two bundles of protein. Each cylinder made up of nine fibres.

Centriole function

Form spindle fibres and are involved in formation cilia and flagella.

Cell wall structure

Made of cellulose and is fully permeable

Cell wall function

Provides mechanical support and protection. Prevents cell from bursting.

what are the 3 componants of the cytoskeleton?

• microfilaments

• microtubules

• intermediate fibres

cytoskeleton function

• hold organelles in place

• controls cell movement and movement of organelles within cells

microfilament function (and what it is formed from)

• formed from the protein actin

• Responsible for cell movement - cell contraction during cytokinesis

microtubules function (and what it is formed from)

• globular tubulin from a scaffold-like structure that determines the shape of a cell.

• act as tracks for movement for organelles e.g. vesicles

• spindle fibers are made from microtubules

what do intermediate fibres do?

• give mechanical strength

What are the 9 steps of exocytosis?

1. MRNA leaves the nucleus through a nuclear pore and attaches to a ribosome on the rough ER.

2. Protein is made on the ribosome attached to the rough ER.

3. Protein passes into the cisternae of the rough ER and is then packaged into a vesicle.

4. Vesicle moves to the Golgi apparatus using the cytoskeleton.

5. Vesicle fuses with the cis face of the Golgi apparatus .

6. The protein is modified in the Golgi apparatus.

7. The modified protein is packaged into a vesicle and leaves the Golgi apparatus via the trans face.

8. The vesicle to and fuses with the cell surface membrane.

9. the (secretary) vesicle then releases the protein outside the cell by exocytosis.

what size are ribosomes in animal cells?

80S

What is cell theory?

• all living organisms consist of cells

• cells are formed by division of pre-existing cells

• cells contain DNA that acts as instructions for growth

How long do temporary mounts last?

A few hours

How are permanent specimens prepared?

• specimen is dehydrated 

• fixed in wax

• thinly sliced

Dry mount preparation

• solid specimens can be viewed as a whole

• or cut into very thin slices (sectioning)

• placed on slide and covered with a coverslip

Wet mount preparation

• specimens suspended in liquid

• coverslip placed at an angle to avoid bubbles

• eg, aquatic life, living organisms

Squash slide preparation

• wet mount prepared and coverslip pressed on

• sample is squashed between two slides

Smear slide preparation

• edge of slide used to smear a sample along another 

• coverslip then placed on top 

• eg. blood slide

Why use a stain?

Provides contrast - different components within a cell take up stains to different degrees

What is the magnification equation?

Magnification = Image size ÷ actual size (IAM)

What do positively charged dyes stain?

Cell components 

What do negatively charged dyes stain?

Stain outside of the cells - the background

Why use a differential stain?

• provides contrast

• only some organelles take up stain

Gram stain technique 

Separates bacteria into two groups:

• gram positive 

• gram negative

Definition of magnification

the number of times larger an image is compared with the real size of the object (this does not increase the detail)

Definition of resolution

the ability to distinguish between two separate points

What are the two types of electron microscopes?

1. Transmission electron microscope 

2. Scanning electron microscope 

Transmission electron microscope

• beam of electrons passes through the sample

• electrons are detected by a sensor

• imaged is 2D

• magnification x500 000

• resolution = 0.5nm

Scanning electron microscope 

• scans the surfaces of the sample

• electrons are reflected

• sensor detects electrons and an image is created

• produces a 3D image

• magnification x500 000

• resolution = 3-10nm 

Light microscope

• specimen can be viewed whilst still alive

• can be stained to add contrast

• color can be seen

• light is shone through specimen then passes through two lenses

• lenses magnify the image

• maximum magnification = x1500

• maximum resolution = 200nm

Disadvantages of electron microscopes

• only produce black and white images 

• specimen must be in a vacuum - must not be living 

• specimen must be dehydrated

• very expensive 

• very large

Artifact definition

a visible structural detail caused by processing the specimen and is not a feature of the specimen eg. air bubbles trapped under a slide when using a light microscope

Eyepiece graticule

• small ruler that is inserted into the eyepiece of a microscope

• scale is arbitrary

• the eyepiece graticule remains constant at all magnifications

• must be calibrated using a stage micrometer

Stage micrometer

• used to calibrate eyepiece graticule 

• it is 1cm long and is divided into 100 division 

• 1 division = 100 micrometers 

what 2 lenses does a compound light microscope have?

• eyepiece lens

• objective lens

Functions of the cytoskeleton

• Establishes cell shape

• Provide mechanical strength

• Locomotion

• Chromosome separation in mitosis and meiosis

• Movement of organelles within a cell

Composition of the cell cytoskeleton

• Microtubules

• Microfilaments

• Intermediate fibres

Microtubules

• 25nm in diameter.

• Globular tubulin proteins polymerise to form tubes.

• Involved in transport of organelles.

• Make up the spindle fibres during cell division. 

Microfillaments

• 7nm in diameter.

• Contractile fibres formed from the protein actin.

• Responsible for cell movement and cell contraction during cytokinesis. 

Intermediate fibres

• 8-10nm in diameter.

• Give mechanical strength to cells and help maintain their integrity.

Undulipodia and cilia

• Hair like extensions that stick out from the surface of cells.

• Made of 9 pairs of microtubules in a circle w/ two more in the middle (9+2 arrangement)

Function of undulipodia and cilia

• Move liquid past the surface of the cell.

• For single cells this enables them to swim.

• For anchored cells this moves liquid over the surface of the cell. 

Flagella

• Only present in bacterial cells.

• Made of a spiral of flagellin protein attached by a hook to a protein disc than can rotate. 

Advantage of being a eukaryote: division of labour

• Organelles allow for division of labour.

• Each organelle is specialised to carry out a specific role.

What type of organelles do they contain?

They contain only non-membrane bound organelles.

How do they store their genetic information?

As a single looped chromosome in cytoplasm

Size compared to eukaryotic

Much smaller (1-10 micrometers vs 10-100)

Multi or uni-cellular?

Typically uni-cellular

How do they divide?

Binary fission