B.2.2 HL Flashcards
State the adaptations of mitochondria for the formation of ATP.
The mitochondria is an organelle which is responsible for the production of energy in the cell. Because of this, it needs a series of adaptations such as a double membrane with small volume of intermembrane space. They also have a large surface area filled with cristae and a compartment of enzymes and substances of the Krebs cycle in the matrix.
State the adaptations of chloroplasts for photosynthesis.
Chloroplasts are essential for photosynthesis which allows plants to covert sunlit into nutrients and gases they need. Some of the adaptations they need for this include a large surface area of thylakoids which provides more photosystems. These thylakoids have small volume inside for high concentration of protons and compartmentalization of calvin cycle enzymes and chloroplast in the stroma.
Describe the composition of the nucleus.
The nucleus has many different components such as:
- Nucleoplasm: semi fluid matrix
- Chromatin: how the DNA is found within the nucleus. Less condensed form of the cells DNA which organises into chromosomes during prophase of mitosis or meiosis
- Nucleoli: organelles that synthesize ribosomes
What are the functional benefits of the double membrane of the nucleus?
The nucleus’s double membrane, has nuclear pores which create a selective passageway through which molecules are able to travel between the nucleus and cytoplasm. They are big and if in the cell membrane it is considered damaged. The nucleus dissembles and reforms every time cells divide in cell division. During prophase it becomes vesicles which travel to the edge of the cell.
What are the structure and function of free ribosomes in the RER?
Ribosomes are made from dozens of proteins arranged on a scaffold of ribosomal RNA and are composed of two subunits that come together to form a functioning structure. Ribosomes have binding sites to which mRNA and tRNA bind during translation. The large subunit has 3 binding sites for tRNA and the small subunit has a binding site for the mRNA. Ribosomes catalyst the synthesis of polypeptides and in eukaryote cells they can be free (floating and produce proteins that are to be used inside the cell) or bound (attach to the RER and put into a vesicle and transported to the membrane or outside). The ribosomes synthesize polypeptides and release them in to the inside of the RER. From the RER the polypeptide can be transported elsewhere in the cell by a vesicle that buds off from the RER. The typical destination of a vesicle from the RER is the Golgi apparatus.
What are the structure and function of the Golgi apparatus?
The Golgi forms part of the endomembrane system. It is made of flattened membrane enclosed sacs which are called cisternae. The Golgi has two sides:
- Cis face: entry face, facing the nucleus. convex
- Trans face: exit face, transport side. Concave. Sorts, concentrates and packs proteins into vesicles
It is where polypeptides are modified into their functional state either by adding a carbohydrate to make a glycoprotein or by combining with other polypeptides to form the quarternary structure of a protein. There are two models of polypeptides moving through the Golgi:
- Vesicle transport model
- Cisternal maturation model
What are the structure and function of the vesicles?
The vesicles are part of the endomembrane system. The fluid membrane allows for constant formation of vesicles. A vesicle forms when the membrane bulges and pinches off. Clathrin is a protein that plays a major role in formation of vesicles. It creates a coat that helps the phospholipids create a rounded shape as the vesicle is forming. Once the vesicle is formed the clathrin coat is removed from the vesicles. Then, formed vesicles are moved through the cell by motor proteins along the cytoskeleton track. There are different types of vesicles which carry out different functions such as:
- Transport vesicles: transport lipids and proteins inside the cell
- Secretory vesicles: transport lipids and proteins from inside the cell to the plasma membrane
- Endocytic vesicles: formed by an invagination of the plasma membrane around an extracellular substance during endocytosis.
Vesicle fusion happens when vesicles fuse with another organelle or with part of the cell membrane, this happens by adding phospholipids to the target area.
