National 5 Biology Unit 2 Cell Biology Section

National 5 Biology Unit 2 – Cell Biology Section 7 Producing New Cells

We will be learning… • To describe the sequence of events in mitosis including the involvement of the chromatid, equator and spindle fibres • To state that a diploid cell contains 2 matching sets of chromosomes. • To state that a diploid cell divides in a process known as mitosis. • To explain why it is important that the chromosome complement of daughter cells in multi-cellular organisms is maintained. • To be able to analyse cell growth data • To state that mitosis provides new cells for growth and repair of damaged cells • To describe stem cells in animals as unspecialized cells which divide in order to make new cells. • To state that stem cells have the potential to become different types of cells. • To describe specialisation of cells which leads to a variety of cells, tissues and organs. • To describe the hierarchy of body systems as; cells tissues organs systems

Start Timer 2 Think, pair and share • Where do cells come from? 1 • When does the body need to produce new cells? • What would control cell division? 0

What is the Difference? MADE OF MANY CELLS MADE OF ONE CELL

Types of Organism Unicellular Multicellular Organisms with one cell Organisms made of many cells Amoeba Bacteria Yeast Paramecium Human Dog Mouse Oak tree

Cell Division • In a unicellular organism (Amoeba) cell division is a form of reproduction which produces two new individuals. • In a multicellular organism (human being or plant) cell division results in the growth of an organism. • Cell division is the means of increasing the number of cells in an organism. It is the nucleus that controls cell division. • In the video, you will see a paramecium dividing

Blood clotting Now write a short note on the role of cell division

Cell division in different organisms Unicellular Multicellular Reproduction Growth and Repair

Chromosomes Chromatids Centromere Condensed Chromosomes are made of DNA and are found in the nucleus. Human cells have 46 chromosomes- this is the chromosome complement

Chromosomes

Chromosomes are threadlike structures found in the nucleus. Chromosomes carry information necessary for the development of the cell and the survival of the organism. All body cells have a double set of chromosomes and are said to be diploid. One set of chromosomes come from the mother and the other set comes from the father.

Questions a)State the main events that occur during cell division. b)How does cell division in a plant differ from that in an animal? c)Which cell structure controls all cell activities including cell division? d) Draw a diagram to show genes on a pair of chromosomes:

Chromosome Complement • Every species has a definite and characteristic number of chromosomes present in each cell, this is called the chromosome complement. • Since chromosomes provide the genetic information for each species, it is essential that each new cell receives a full complement of chromosomes. • This ensures that animals and plants are provided with all the characteristics of their species.

Higher or Lower? Human body cells have 46 chromosomes but what about these organisms? 8 chromosomes (4 pairs) 54 chromosomes (27 pairs) 44 chromosomes (22 pairs) 54 chromosomes (27 pairs) 56 chromosomes (28 pairs) 94 chromosomes (47 pairs)

Mitosis • Mitosis is the process of cell division where the nucleus divides into two daughter nuclei. • Each nuclei has exactly the same number chromosomes as the original nucleus. of

Cell Cycle http: //www. cellsalive. com/mitosis. htm

What happens during Mitosis?

• • Cell Division: Animal Cell Nucleus divides Two daughter nuclei separate Cytoplasm pinches off Two daughter cells are formed.

Rat Skin Cell Mitosis

Cell Division: Plant cell • Nuclear division • Laying down of cell wall. • Two daughter cells formed

Stage 1 Chromosomes in the nucleus coil up, replicate and become visible on staining.

Stage 2 Centromer e Chromati d Chromosomes now consist of two identical Chromatids joined by a Centromere. Chromati d

Stage 3 Equator Chromosomes line up along the equator of the cell and spindle fibres form. Spindle fibres

North pole Stage 4 Spindle fibres pull identical chromatids towards opposite poles. South pole

Stage 5 Nuclear membranes reform. Cytoplasm divides. Separated chormatids now called chromosomes.

Stage 6 2 diploid daugheter cells which contain the same number of chromosomes as the original cell. They are identical to each other and the original cell.

Stages of Mitosis

1. Chromosomes become shorter and thicker (like a double thread). 2. Each single thread is called a chromatid. 3. The two chromatids are joined by a centromere. 4. Chromosomes line up at the equator. 5. Spindle fibres attach to the centromere of each chromosome. 6. The centromere splits and one chromatid moves to the “north” pole and the other to the “south” pole. 7. Finally a nuclear membrane forms around each group of chromatids (now called chromosomes). Nuclear division (mitosis) is complete forming 2 new daughter cells which are identical.

The stages of mitosis 30 of 32 © Boardworks Ltd 2007

Questions a)Describe the process of mitosis in a cell including the terms chromatid; centromere and spindle fibre in your answer. b)Why is it important that the chromosome complement of daughter cells in a multicellular organism is maintained?

Stem Cells • Involved in growth and repair of organisms • Stem cells are found in all multicellular animals • Stem cells are undifferentiated i. e they have no specific structure or function. • Produce specialised cells in animals. • Have the ability to become any type of cells.

Stem cells • They have the ability to renew themselves through mitotic division. • They are found throughout the organism. • There are two main types of mammalian stem cells • 1. embryonic stem cells 2. Adult stem cells

Stem cells 34 of 7 © Boardworks Ltd 2014

Types of Stem Cells • Embryonic stem cells • - derived from embryos that develop from eggs fertilised in a laboratory. • • Adult stem cells Found in body along side other differentiated cells Examples - bone marrow - blood vessels - skin - liver - heart • They are body’s built-in repair kits • Replace cells damaged by disease, injury and every day wear and tear

Embryonic Stem Cells • In an embryo many types of cells and tissues are forming. • e. g. Heart, lungs, skin, blood. • Each new cells develops from a stem cell. • The cells become differentiated i. e. they now have a particular structure and function.

Adult Stem Cells • In adult tissue there are stem cells present also. They are found throughout the body. • In adults these cells act as a repair system i. e. this allows the replenishment of cells such as, blood, skin or intestinal tissues which are in constant need of replacement. • Used to replace any damaged tissue.

Can develop into any cell [as in embryo] Can develop into some cells

Source of stem cell Medical Use Marrow in bones Treating leukaemia, a type of cancer caused by abnormal blood cells. Skin Growing new layers of skin that can be used to treat burn victims. Heart muscle Repairing damaged heart muscle after a heart attack (still being tested at the moment) Bladder Building a new bladder in the laboratory for a patient whose bladder has been damaged by injury or disease.

Complete the following table • Unlimited supply • Can differentiate into any cell • Doesn’t mean that embryos are destroyed • Embryos have to be destroyed – ethical issue e. g. pro-life campaign • Limited supply • Can only differentiate into

Types of Cells cheek cells Palisade Mesophyll Sperm Cell Nerve cells Blood cells Stoma

Complete the table in notes Nerve cell Red Blood cell Sperm cell Root Hair cell Plant cell Guard cell (stomata)

Nerve Cell Structure Made up of a cell body and long tail called an axon. They have many projections that allow them to communicate with other neurons Function Cells that receive and transmit signals as electrical impulses

Red Blood Cell Structure Bi-concave shape for maximum surface area. Contains haemoglobin which binds oxygen. No nucleus or ribosomes present Function Transport oxygen to all cells in the body.

Sperm Cell Structure Made up of a head that contains genetic information, a midpiece and a tail for movement. Contain many mitochondria for energy Function To pass on genetic information required to produce a new organism

Root Hair Cell Structure Long root hair to increase surface area Function Collects water and mineral nutrients present in soil to transport this to the rest of the plant

Plant Cell Structure Cell wall, chloroplasts, nucleus, cell membrane, vacuole etc Function Basic unit of life for plants – contains chloroplasts for photosynthesis.

Guard Cell Structure Stomata pore lies between two guard cells Function Helps regulate the rate of transpiration by opening and closing the stomata

Levels of Organisation in Animals have levels of organisation in their bodies that allows them to function efficiently.

Types of Tissue Skin Tissue Bone Tissue Plant Transport Tissue

Specialised Cells Specialised cells that perform specific functions group together to form tissues e. g. muscle cells group together to form muscle tissue. Tissues work together to form organs with specific functions e. g. the heart contains muscle and nervous tissue. The cells in organs are specialised for their function e. g. the muscle cells in the heart are able to contract in a regular pattern. This allows the heart to beat and pump blood round the body. Organs work together forming a system. The heart is part o the circulatory system, which also includes the blood vessels.

Cell Basic biological unit of all known living organisms Tissue Groups of distinct types of specialised cells of which plants and animals are made Organ Collection of tissues with similar function

Brain Types of Organs Leaf eye

A collection of systems working together is called an organism