Cell Structure

Question 1

Define a prokaryote

Answer 1

Single-celled organisms with a simple structure of just a single undivided internal area called the cytoplasm

Question 2

Define a Eukaryote

Answer 2

Eukaryotic cells make up multicellular organisms like animals, plants and fungi. They have a complictaed internal structure with many membrane bound compotents.

Question 3

Nucleus

Answer 3

• Contain coded genetic information in the form of DNA molecules
• DNA is contained within a double membrane called a nuclear envelope

Question 4

Nucleolus

Answer 4

• Area withing the nucleus which is responsible for producing ribosomes.
• Composed of proteins and RNA
• RNA is used to produce ribosomal RNA (rRNA) ehich combines with proteins to form thr ribosomes for protein sunthesis.

Question 5

Mitochondria

Answer 5

• Essential organelles in almost all eukarytotic cells
• Site of the final stages cellular respiration
• The energy stored in the bonds of complex, organic molecules is made avaliable for the cell to use through production of the molecule ATP
• The amount of mitochondria in a cell is generallt a reflection of the amount of energy it uses.
• Has a double membrane - The inner membrane is highly folded to form structures called cristae and the fluid interior is called the matrix
• The membrane which forms the cristae contains the enzymes used in aerobic respiration
• Mitochondria also contain a small amount of DNA called mitochondrial (mt)DNA meaning they can produce their own enzymes and reproduce themselves

Question 6

Vesicles and lysosomes

Answer 6

• Membranous sacs with storage and transport roles
• Single membrane with fluid inside
• Vesicles are used to transport materials inside the cell
• Lysosomes are specialised forms of vesicles that contian hydrolytic enzymes

Question 7

Outline how a student could prepare a temporary mount of tissue for a light microscope

Answer 7

1. Obtain a thin section of tissue by maceration
2. Place tissue smaple on the slide in a drop of water
3. Stain tissue on the slide to increase contrast and make structures visible
4. Add a coverslip wing a mounted needle at a 45 degree angle to avoid air bubbles

Question 8

Describe how light mircoscopes work

Answer 8

1. Lenses focus rays of light and magnify the view of a thin slice of specimen
2. Different structures absorb different amounts and wavelenghts of light.
3. Reflected light is trandmitted to the observer via the objective lens and eyepiece.

Question 9

Describe how a transmission electron microscope (TEM) works

Answer 9

1. Passes a high energy beam of electrons through a thin slice of specimen
2. More dense structures appear darker since they absorb more electrons
3. Focus image onto fluorescent screen or photographic plate using magnetic lenses

Question 10

Describe how a scanning electron microscope (SEM) works

Answer 10

1. Focus a beam of electrons onto a specimen’s surface using electromagnetic lenses
2. Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate