Cells

Question 1

Nucleus

Answer 1

Information centre of eukaryotic cell
- DNA is stored, replicated and copied into mRNA

Question 2

Nuclear pores

Answer 2

Gaps in the nuclear envelope that allow substances to move in and out of the nucleus

Question 3

Nuclear envelope

Answer 3

Double membrane that separates the contents of the nucleus form the cytoplasm

Question 4

Nucleolus

Answer 4

Part of the nucleus that produces ribosomes

Question 5

Cell surface membrane

Answer 5

Phospholipid bilayer that contains cholesterol and proteins
• it is a fluid layer that surrounds the cell and enables it to communicate with other cells (cell signalling)
• detect and respond to changes in the environment
• physical barrier - controls what enters and exits the cell

Question 6

Extracellular matrix

Answer 6

The material in between cells that holds tissues together
- usually made of scaffolding proteins such as collagen
- important for cell signalling

Question 7

Rough endoplasmic reticulum (RER)

Answer 7

Site where proteins are made, folded and moved to Golgi body

Question 8

Smooth Endoplasmic reticulum

Answer 8

• lipid and steroid synthesis
• drug detoxification

Question 9

Ribosomes

Answer 9

Make new proteins from mRNA through translation (protein synthesis)
- found as free ribosomes in cytoplasm and attached to rough ER

Question 10

Golgi body

Answer 10

Modifies, packages and directs newly made proteins to where they are needed

Question 11

Cytoplasm

Answer 11

Site of chemical reactions
- viscous aqueous fluid containing water, proteins and other inorganic molecules and organelles

Question 12

Mitochondria

Answer 12

Supply chemical energy to the rest of the cell
- they are surrounded by a double membrane

Question 13

Microfilaments

Answer 13

Made from repeating actin subunits
- responsible for cell movement and changes in shape, making muscle contractions possible
- thinnest component of the cytoskeleton

Question 14

Vacuole

Answer 14

Internal, surrounded by a membrane, which cells use for storing food and waste

Question 15

Microtubules

Answer 15

Small, tubular assemblies of protein
- Help maintain cell’s internal structure and move organelles and cytoplasm using molecular motors
- part of cytoskeleton

Question 16

Centrioles

Answer 16

A pair of organelles that organise microtubules into spindles on which chromosomes are separated when cells divide

Question 17

Lysosomes

Answer 17

Membrane bound organelles that digest other organelles (e.g. Bacteria)
- contain hydrolysis enzymes (lysozymes)

Question 18

Light microscope

Answer 18

• illuminates the specimen with light
• beam is focused using the eyepiece and objective lense
• specimen can be live
• section view of specimen
• relatively cheap
• coloured dyes required

Question 19

Transmission electron microscope (TEM)

Answer 19

• uses electron beam
• max magnification: x1,000,000
• max resolution: 0.1nm
• specimen must be dead
• expensive
• heavy metal stains required
• 2D

Question 20

Scanning electron microscope (SEM)

Answer 20

• uses electron gun and electromagnetic lenses
• max magnification: x500,000
• max resolution: 1nm
• 3D

Question 21

Prokaryotes

Answer 21

Capsule- slippery layer outside cell wall of some bacteria
• protects the cell and prevents desiccation

Cell wall- made of peptidoglycan
• protects and supports each cell

Ribosomes 70s- protein synthesis occurs here

Nucleoid- irregularly shaped region that holds nuclear material without a nuclear membrane
• genetic information found

Plasmid- small loops of DNA
• carry genes beneficial for the survival of the organism

Question 22

Protein trafficking

Answer 22

1. Transcription- mRNA is made in the nucleus. DNA can’t fit through the nuclear pore so mRNA is made (smaller, length of one gene)
2. mRNA leaves the nucleus through a nuclear pore
3. Translation- mRNA is made into a polypeptide on the ribosomes on the rough ER then enters the RER
4. Polypeptide moves through the RER. As it moves, it if folded and gains it’s 3D shape
5. The end of the RER buds off with the folded polypeptide inside (becomes vesicle)
6. The vesicle travels to the Golgi body and the membrane fuses with it. The folded polypeptide is now inside the Golgi body
7. Modification- the polypeptide is modified as it moves through the Golgi body

8a. If protein is an intracellular protein then it buds off the Golgi and remains in the cell e.g. RNA polymerase

8b. If the protein is an extracellular protein then it binds off the Golgi body and leaves the cell in exocytosis
e.g. secretory enzymes like amylase or hormones