Organelles

Question 1

Nucleus

Answer 1

• largest most prominent organelle
• usually spherical and about 10-20 micrometers in diameter

Functions:
- contains the organism’s genetic material (in the form of DNA- chromosomes)
- acts as the control centre of the cell
(Through controlling proteins synthesis)

Question 2

Mitochondria

Answer 2

• usually rod-shaped and around 1-10 micrometers long

Functions:
- site of aerobic respiration
- produce ATP as a product of respiration (used by cells as an immediate source of energy)
- cells with a chin level of metabolic activity that require a lot of ATP (muscle cells) have lots of large mitochondria

Question 3

Endoplasmic Reticulum

Answer 3

• a 3D system of membranes that spreads throughout the cytoplasm of a cell
• the membranes form a network of tubules and flattened sacs called cisternae
• it is continuous (attached to) the outer nucleus membrane

There are two types of ER:
- rough ER (RER)- synthesis & transport of proteins
- smooth ER (SER)- synthesis & transport of lipids and carbohydrates

Question 4

golgi apparatus

Answer 4

• A stack of membranes that form flattened sacs, called cisternae
• Collects, modifies and transports proteins (often adding non-protein components)
• Proteins, lipids and carbohydrates produced in the ER enter and are passed through the golgi apparatus
• The proteins are then ‘labelled’, to be sent to their correct destination
• The modified proteins are transported in golgi vesicles (which are regularly pinched off from the ends of the cisternae) to their destination

Question 5

ribosomes

Answer 5

• Small granules found in all cells
• Occur in large numbers (can be almost 25% of the dry mass of the cell)
• They may either be found in the cytoplasm or be attached to the rough ER
• They have 2 subunits - a large and small
• Made of ribosomal RNA and protein
• 2 types:
• 80S (found in Eukaryotic -cells)-larger
• 70S (found in Prokaryotic cells, mitochondria and chloroplasts) - smaller
• Function - the site of protein synthesis