In this topic of IBDP Biology, we will learn about the second part of membranes.
Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus, and plasma membrane.
- vesicle is made by pinching off a piece of membrane
- fluidity of membrane allows this
- vesicles can be used to transport material around inside cells
- When it comes to IBDP Biology, proteins are transported in vesicles
- from the rough endoplasmic reticulum to the Golgi apparatus
- from the Golgi apparatus to the plasma membrane
- formation of vesicle from plasma membrane allows material to be taken in
- endocytosis/pinocytosis/phagocytosis is absorption of material using a vesicle
- fusion of vesicle with plasma membrane allows material to be secreted / passed out
- exocytosis is secretion of material using a vesicle
Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis
- In endocytosis part of the plasma membrane is pulled inwards. A droplet of fluid becomes enclosed when a vesicle is pinched off. Vesicles can then move through the cytoplasm carrying its contents.
- In exocytosis vesicles fuse with the plasma membrane. The contents of the vesicles are then expelled. The membrane flattens out again.
The stages in the cell cycle, including interphase (G1, S, G2, mitosis and cytokinesis)
- G1- period of growth, DNA transcription and protein synthesis
- S - period during which all DNA in nucleus is replicated
- G2 - Period in which cell prepares for division
- mitosis - process by which nucleus divides to form 2 genetically identical nuclei
- cytokinesis - process of dividing cytoplasm to form two cells
State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue
If you look at the IBDP Biology curriculum, tumors are formed when cell division goes wrong and is no longer controlled. This can happen in any organ or tissue.
State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts
Interphase is an active period in the life of a cell during which many metabolic reactions occur such as protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplast.
Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase)
- Prophase: The spindle microtubules are extended from each pole to the equator.
- Metaphase: Chromatids move to the equator and the spindle microtubules from each pole attach to each centromere on opposite sides.
- Anaphase: spindle microtubules pull sister chromatids apart making the centromeres to split. This brings the sister chromatids apart, splitting them into chromosomes. Each identical chromosome is pulled to opposite poles.
- Telophase: Spindle microtubules break down, while chromosomes uncoil and therefore are no longer individually visible. The nuclear membrane now reforms. The cell then is divided by cytokinesis to form two daughter cells with identical genetic nuclei.
Explain how mitosis produces two genetically identical nuclei
- During prophase, chromosomes become visible under a light microscope as they super coil and therefore they get shorter and becomes more bulky.
- The nuclear envelope disintegrates and the spindle microtubules grow, moves towards each pole, towards the equator.
- Referring to the IBDP Biology specification, At metaphase the chromatids move to the equator.
- The sister chromatids are two DNA identical molecules as they were replicated during DNA replication.
- These sister chromatids are then separated in anaphase as the spindle microtubules attaches to the centromere, it pulls the sister chromatids to opposite poles.
- Now that sister chromatids are separated, they are known as chromosomes.
- This means that each pole has the same chromosomes.
- Finally the microtubules break down, the chromosomes uncoil and the nuclear membrane reforms.
- The cell then divides into two daughter cells with genetically identical nuclei.
That's the end of this topic.
