Cells, Membranes, Tissues and Skin

Transcription

1 Session Objectives. What you will cover Basic cell organelles Plasma membrane structure Basic function of membrane proteins Tissues Skin Cells, Membranes, Tissues and Skin Your objectives are List the functions of the nucleus and mitochondria Identify the components of the plasma membrane and give their functions Describe the different functions of transmembrane proteins. Suggested Reading: Tortora, Ch ; Marieb Ch.

2 Cells, Membranes Tissues and Skin A basic principle of biology is that of cell theory. This consists of three ideas. The first is that all living things are made of one or more cells. The second is that a cell is the basic unit structure of all organisms, like bricks are the basic unit structure of a brick wall. The third idea is that all cells arise from pre-existing cells. Task. Here are some examples of typical cells. Use the list below to complete the names of the cells in the boxes provided. cell Epithelial cells Neuron [brain] Adipose Sperm Smooth muscle cell Oocyte Blood cells Bone Cells As you will observe, the cells appear different. What are the differences that you can observe? It may help you to select examples as illustrations of your answers. Differences:

3 Cell Structure Our cells are the products of millions of years of evolution. You have just labeled diagrams showing we have many different types of specialised cells in our in bodies. Despite these differences, they have common internal structures. These internal structures carry out the essential functions of the cell. There are three main functions. Some structures are for synthesis [making or repairing bits of the cell], transport [moving stuff around the cell] or producing energy for the cell. These internal structures are called organelles. Task. The nucleus contains DNA. What is DNA used for? What information does DNA contain? What are mitochondria used for? Explain why a skeletal muscle cell would have many more mitochondria than an epithelial cell.

4 Membranes. Here is a diagram of a typical cell [plasma] membrane. Outside the cell you find extracellular fluid. Inside the cell is the cytoplasm. Task Use the diagram, and a suitable textbook to help you to complete the following passage. The missing words are given underneath. Surrounding the cell and some of the organelles are membranes. These are physical boundaries. Membranes have a typical structure, which is known as a. These membranes are allowing cells to change shape e.g. red blood cells have to squeeze through capillaries. If the red blood cell plasma membrane was rigid this would not happen. There are two main components to cell membranes. These are proteins and phospholipids. The have a characteristic shape. They have heads and tails. The heads are water loving or and project into the cytoplasm and extracellular fluid. The tails are and point away from any sources of water. These phospholipids form a. Think of this as similar to a soap bubble. The molecules float in this phospholipid sea. These molecules can be classed by their position in the membrane double layers. Integral proteins are those that are in the membrane. Peripheral proteins can be found associated with integral proteins either on the outside or inside of the membrane. Integral proteins can be intracellular, extracellular or [meaning they pass through the phospholipid layers]. Hydrophobic Protein fluid mosaic flexible Phospholipids Hydrophilic bilayer embedded Transmembrane

5 Membrane Proteins The membrane proteins can be classed by their functions. Match the number of the membrane protein with the correct letter of the correct function. 6 Membrane Protein Channel Receptor Linker/Anchor Enzyme Cell Identity Marker Transporter Function A Catalyse reactions inside or outside of the cell [depending on location in membranes]. B Characterise cells as self or foreign. Some are the basis of the ABO blood grouping system. C Transport specific materials across the membrane. Usually this will involve the protein changing shape and use of ATP. D Allow movement of chemicals through water filled pores; usually are specific for particular ions e.g. sodium or calcium E Attach to the cytoskeleton or can bind two cells together. F Recognise and bind ligands. This may cause the protein to alter shape, and effect a cellular change. ANSWERS. 6

6 Tissues There are four main tissue types epithelial, muscle, connective and nervous tissue. Task Why does the body need so many different tissue types? What are the functions of each of the tissue types? Epithelial Muscle Connective Nervous 6

7 Skin This is the largest organ in the body. Task Label the parts identified on the cross-section diagram of the skin.... Number Structure Suggested further reading/note preparation. Functions of nucleus & mitochondria; Membrane structure and function Membrane proteins as receptors for ligands Tissues know the differences between the tissue types & give examples Skin structure and function of layers, gland and nerves 7