1. Organelles within the cell
Cell membrane
Description: A double layer of phospholipids embedded with protein molecules, glycoproteins and some short carbohydrate chains.
Function: encloses cell contents regulates the movement of materials into and out of the cell, helps to maintain shape and communicates with neighbouring cells.
From Unit 3 Biology Notes Page 12

2. Organelles within the cell
Nucleus
Description: surrounded by a double membrane. The nucleus is usually large compared to other organelles. Contains chromosomes and nucleolus.
Function: information in the chromosomes controls the production of proteins in the cell. These proteins in turn control cellular functions.
From Unit 3 Biology Notes Page 12

3. Organelles within the cell
Nuclear membrane
Description: a double membrane containing many pores, which separates the nucleoplasm from the rest of the cell.
Function: regulates the movement of material between the cytoplasm and nucleus.
From Unit 3 Biology Notes Page 12

4. Organelles within the cell
Nucleolus
Description: a granular structure in the nucleus, made of protein and nucleic acid.
Function: site of manufacture of ribosomal RNA.
From Unit 3 Biology Notes Page 12

5. Organelles within the cell
Mitochondria
Description: sacs made up of two membranes. The inner membrane is folded to create cristae which increase the surface area. The cristae enclose the fluid filled matrix.
Function: the site of aerobic respiration, they are responsible for most of the cell’s energy production. They are most abundant in cells with high energy needs; eg muscle cells and cells of the kidney tubule.
From Unit 3 Biology Notes Page 12

6. Organelles within the cell
Ribosomes
Description: small speherical bodies and composed of RNA and protein.
Function: the site of protein synthesis.
From Unit 3 Biology Notes Page 12

7. Organelles within the cell
Smooth Endoplasmic Reticulum
Description: a network of membranes creating channels in the cytoplasm, from the nucleus to the cell membrane.
Function: the site of lipid synthesis and transport of many materials throughout the cell. Abundant in cells which produce steroid hormones.
From Unit 3 Biology Notes Page 12

8. Organelles within the cell
Rough endoplasmic reticulum
Description: a network of membranes creating channels in the cytoplasm. Rough ER is studded with ribosomes.
Function: transport and folding of proteins produced by ribosomes, synthesis of glycoproteins. Parts of the ER pinch off to become vesicles for the transport of proteins to the membrane or to other organelles including Golgi bodies.
From Unit 3 Biology Notes Page 13

9. Organelles within the cell
Golgi complex
Description: stacks of flattened membrane sacs
Function: packages proteins and glycoproteins into vesicles for secretion from the cell or to be sent to other organelles; modifies some proteins/ glycoproteins. Synthesises cellulose in plant cells. Abundant in cells which export cell products.
From Unit 3 Biology Notes Page 11

10. Organelles within the cell
Lysosome
Description: a membrane sack containing many digestive enzymes
Function: contain enzymes which digest ingested materials and wastes. Important in programmed cell death.
From Unit 3 Biology Notes Page 11

11. Organelles within the cell
Vacuole
Description: a membrane bound sac containing fluid, sugars and ions. Appear as clear areas when seen through a microscope.
Function: important in turgor in plant cells: the pressure of fluid in the large vacuole helps maintain cell shape. Also storage of sugars, ions and food.
From Unit 3 Biology Notes Page 11

12. Organelles within the cell
Chloroplast
Description: surrounded by a double membrane contains stacks of membrane (grana) embedded in less dense membrane and fluid (stroma).
Function: the site of photosynthesis. Grana (or thylakoid membranes) contain chlorophyll, the pigment which traps light energy. Abundant in leaf cells.
From Unit 3 Biology Notes Page 11

13. Organelles within the cell
Centriole
Description: a pair of cylindical structures made up of several smaller tubes.
Function: the spindle forms between centrioles during cell division.
From Unit 3 Biology Notes Page 11

14. Organelles within the cell
Flagella or cillia
Description: made of membrane material and microtubules, they protrude from the cell. Prokaryotic flagella lack membrane material.
Function: provides a means of movement of the cell or of the fluid surrounding the cell.
From Unit 3 Biology Notes Page 11

15. Organelles within the cell
Cell wall (not really an organelle – outside the cell)
Description: a layer of cellulose (in plants) secreted by the cell and completely surrounding the cell membrane. Other chemicals make up the cell walls of bacteria and fungi.
Function: provides structural support and defines the shape of cells.
From Unit 3 Biology Notes Page 11

16. Protein pathways
Proteins can be tracked by labelling them with fluorescent dyes and radioactive atoms.
All proteins are made in the ribosomes (ribosomes consist of RNA and proteins)
Ribosomes are either free-floating or attached to the endoplasmic reticulum (called rough ER)
What does smooth ER do?
The site of phospholipid and cholesterol synthesis.

17. Protein pathways
Vesicles transport unfinished proteins from the ribosomes to Golgi apparatus.
Within the Golgi apparatus the proteins combine with carbohydrate groups to form glycoproteins and glycolipids.
Vesicles then transport from the Golgi apparatus to other parts of the cell or to the plasma membrane for release by exocytosis.

18. Protein pathways What are lysosomes?
Lysosomes are vesicles containing powerful digestive enzymes that can break down all major macromolecules.
They are the cleaners and recyclers of the cell.