Revision Exercise Form 4 Biology

2. Does the rate of diffusion correspond with the molecular weight of the dye? The the density of the medium and the molecular weight of the dye will determine the rate of diffusion.

All mammalian cells are eukaryotic, and whilst the eukaryotic type of cell is not exclusive to mammals, mammalian cells differ from other eukaryotic cells because of the organelles that are or are not present. For instance some plant cells have chloroplasts which are not present in mammalian cells, but both plant cells and mammalian cells are eukaryotic in nature. The term eukaryotic refers to the cell having specific membrane bound organelles, which are not present in prokaryotic cells. The defining feature of a eukaryotic cell is usually its membrane bound nucleus (the exception being the red blood cell) [1].

1.Discuss the structure of the plasma membrane and explain the process of active and passive transport through the membrane.

B. The nature of plasma membrane. If the membrane is composed of lipid portion., only lipid soluble molecules can pass through while water molecules cannot.

According to Mattias Schleiden and Theodor Schwann the cell is the basic unit of life(Cell Theory- OI). Two common types of cells are the plant and animal cells. Although both kinds of cells share many similar, abundant structures, they also have varying descrepancies from cell to cell. Without a doubt, the nucleus is the most important organelle in the plant cell, even though, the lysosome is the most important structure in the animal cell.

Cytoplasm of eukaryotic cell is partitioned by organelle membranes. Organelles together form the endomembrane system.

The purpose of these experiments is to examine the driving force behind the movement of substances across a selective or semiperpeable plasma membrane. Experiment simulations examine substances that move passively through a semipermeable membrane, and those that require active transport. Those that move passively through the membrane will do so in these simulations by facilitated diffusion and filtration. The plasma membrane’s structure is composed in such a way that it can discriminate as to which substances can pass into the cell. This enables nutrients to enter the cell, while keeping unwanted substances out. Active

13. Understand the transportation of potassium and sodium across plasma membranes. (p. 10 bottom right, p. 20 bottom right, p. 21 diagram)

|(2 marks) | |c. |State two symptoms that may have led the veterinarian to suspect that George was suffering from a thyroid hormone |

Nucleus – The nucleus is the largest organelle in the cell. It acts as the control system for almost all the activities of the cell. It stores the cell 's hereditary material, or DNA

The cell’s nonmembranous organelles include the cytoskeleton, microvilli, centrioles, cilia, ribosomes, and proteasomes. Membranous organelles include the endoplasmic reticulum, the Golgi apparatus, lysosomes, peroxisomes, and mitochondria.

▪ Know the functions of the various organelles, e.g., glyoxysomes, peroxisomes, ribosomes, chloroplasts, mitochondria, rough and smooth ER, Golgi, etc.

In this lab, neutral red was used as a pH indicator. The color changes from yellow to red in a basic solution to an acidic solution. The neutral red dye was applied to Saccharomyces Cerevisiae. When the S. Cerevisiae cells come in contact with the neutral red dye, the dye gets to the cell by crossing the cell membrane. The cell membrane is the outer surface of the cell that functions as a barrier. The outside of the cell membrane is made of lipid and membrane proteins (Hardin, 2012). It is selectively permeable, which means only select ions and molecules can pass through it by transport. Membrane transport can be actively or passively moving a substance from side of the membrane to another (Hardin, 2012). Passive transport does not require energy to move molecules across the cell membrane. Diffusion is a form of passive transport that moves molecules across the membrane from an area of higher concentration to an area of lower concentration. Osmosis, diffusion, and facilitated diffusion are all examples of passive transport. Active transport requires energy to move molecules across the membrane from areas of lower concentration to higher concentration. It requires energy because it pushes sodium ions (Na+) and potassium ions (K+) (Hardin, 2012). When the dye entered the cell, it also showed its location. Sodium azide (Na+N3-) is a metabolic inhibitor that blocks the flow of electrons along

Cell membrane is a selective boundary composed of a unique phospholipid bi-layer structure consisting of lipids, proteins and carbohydrates. This structure regulates the import and export to maintain homeostasis condition inside the cell. (Knox et al., 2014) The plasma membrane is referred as a fluid mosaic which also has selective permeability. The permeability of the membrane can be varied depending on the external conditions. (Mitchel, 2015)

All cells contain membranes that are selectively permeable, allowing certain things to pass into and leave out of the cell. The process in which molecules of a substance move from an area of high concentration to areas of low concentration is called Diffusion. Whereas Osmosis is the process in which water crosses membranes from regions of high water concentration to areas with low water concentration. While molecules in diffusion move down a concentration gradient, molecules during osmosis both move down a concentration gradient as well as across it. Both diffusion, and osmosis are types of passive transport, which do not require help.