Arif Ullah - ITHS

Transcription

1 INTERNATIONAL TURKISH HOPE SCHOOL ACADEMIC YEAR CHITTAGONG SENIOR SECTION BIOLOGY HANDOUT CELLS CLASS 9 Name :... Date:... A cell is the basic structural and functional unit of Life. Usually all cells consist of a membrane, cytoplasm and a nucleus. 1. Cell membrane Also called plasma membrane. A thin, delicate layer made of layers of proteins and fats. Completely surrounds and holds in the constituents of the cell. High surface area of the cell provides for absorption of nutrients and the disposal of wastes. Differentially permeable, controlling the transport of materials in and out of the cell. Allows certain small substances like glucose, water and oxygen to enter the cell. Prevents larger molecules like protein and starch from leaving the cell. 2. Nucleus Most prominent structure of the cell Usually spherical in shape. Found near the center of the animal cell. Bound by two membranes forming the nuclear membrane. Isolates the genetic material from the rest of the cell. Nuclear pores are scattered over the surface of this envelope. Found within the nucleus is one or more small, spherical structures called nucleolus which is not bound by a membrane. Nucleoplasm is the cytoplasm-like material that fills up the nucleus. It contains chromatin, which is made up of DNA. Involved in cell division. Controls all cellular activity. Carries the instruction for protein synthesis. Houses the organism s genetic material (chromosomes). Nuclear pores act as channels, permitting certain molecules to enter or leave the nucleus. 3. Cytoplasm Jelly-like substance. Fills up the cell. Suspension of various organelles. Functions: It is here that metabolism takes place. Teacher in Charge: ARIF ULLAH Page 1

2 4. Organelles: All the tiny structures present within the cytoplasm. a) Mitochondria Rod-shaped organelles. Structures with inner folded membranes. Permanent structure in the cell. Power houses of the cell. Site for aerobic respiration which generates energy for all the cellular activities. Inner folds carry respiratory enzymes which help to control respiration and the release of energy from glucose molecules in the cell. Involved in chemical energy conversion during metabolic activities of the cell. b) Protoplasm (Cell Membrane + Nucleus + Cytoplasm) Combination of the living parts of the cell. Functions: Cells with protoplasm are regarded as living. c) Vacuoles Sacs filled with cell sap, a watery solution of sugars, salts and pigments. d) Endoplasmic Reticulum Endoplasmic reticulum is a maze of membranes which runs although the cytoplasm. It is found in all cells. It is described as rough when it has ribosomes attached to it and smooth when ribosomes are absent. They are assembly-lines for making fats and proteins out of smaller molecules in the cell. It provides shelter to the ribosomes. Protein synthesis occurs on the ribosomes in the endoplasmic reticulum. e) Ribosomes Tiny round objects. Often attached to the endoplasmic reticulum. Teacher in Charge: ARIF ULLAH Page 2

3 Parts of a plant cell: 1. Starch grains Insoluble carbohydrates. Occurs as very small grains. Food source plants. 2. Cell wall Rigid wall made up of a layer of cellulose. Provides support and shape to the individual plant cell. 3. Vacuole Large components. Known as the sap vacuole. Filled with a fluid called cell sap. Membrane that surrounds a vacuole is called a tonoplast. Plays a role in osmoregulation. Maintaining the shape of the cell. 4. Chloroplasts Collection of organelles known as plastids. Plastids that store chlorophyll are known as chloroplasts. Teacher in Charge: ARIF ULLAH Page 3

4 SIMILARITIES AND DIFFERENCES BETWEEN PLANT AND ANIMAL CELL Similarities: 1. Cell membrane 2. Cytoplasm 3. Nucleus Differences: Structures Plants Animals Cell wall Chloroplasts Sap vacuole Tonoplast Starch grain Rigid cell wall made of cellulose. It determines the size and shape of the cell. It also helps to support and strengthen the plant. Stores food as starch. Can be found in plastids. It contains chlorophyll to trap light energy for photosynthesis. Large and centrally located. It is usually filled with cell sap. This is the membrane that surrounds the sap vacuole, formed by a layer of cytoplasm. Found in green leaves. Actually it gives the leaves the characteristic green colour. TISSUES IN PLANTS a) Epidermal tissue 1.One layer of cells. 2.Maybe covered with a waxy cuticle. 3.The tissue is very thin. 1.Covers surface of plant. 2.Protects from physical damage and infection. 3.Reduces water loss by transpiration. Not present. Not present. Excess carbohydrate is stored as glycogen granules. Small in size. There may be some food vacuole or contractile vacuoles present. Not present. Not present. b) Meristamatic tissue: 1.Is made up of undifferentiated cells. 1.Undergoes cell division to produce new cells. Teacher in Charge: ARIF ULLAH Page 4

5 c) Vascular tissue 1.Made of vascular bundle of xylem, phloem and cambium. 1.Transports water and mineral salts in plants. 2.Transports food. 3.Provides support. 4.New tissue growth in the cambium. d) Photosynthetic tissue 1.Contains cells with chloroplasts. Functions: 1.Cells with chlorophyll. 2.Absorption of sunlight. 3.Carrying out photosynthesis. TISSUES IN ANIMALS (More important for Human Biology) a) Bone (connective tissue) Bone is alive. It consists of living cells which are supplied with food and oxygen by blood vessels. The cells are arranged in rings around the blood vessels. Bone is mostly made of mineral substances (such as calcium, phosphate with small amounts of magnesium salts) which make it very hard. Bone also contains collagen which gives it elasticity. Collagen is a type of protein. The hardest bone is called compact bone is on the outside. Underneath this is a layer of spongy bone which has spaces in it and stops the bone from becoming too heavy. In the center is the bone marrow which is very soft and has a good supply of blood. Red blood cells, white blood cells and platelets are made here. 1. Provides protection and support. 2. Allows movement to occur. 3. Joins body structure together. b) Muscle tissue i) Voluntary (striated muscle) e.g. all muscles attached to bones are striated. 1. Striated muscles are striped. 2. Striated muscle contains striated cytoplasm which is not divided into cells. 3. They are isolated from each other. 1. The striated muscles are under conscious control. 2. They help to carry out locomotion. Teacher in Charge: ARIF ULLAH Page 5

6 ii) Involuntary (smooth muscles) e.g. the walls of the alimentary canal and bladder. 1. Smooth muscles are isolated from each other. 2. Smooth muscles are elongated. 3. They contain non-striated cytoplasm. Functions: 1. Smooth muscles are involuntary muscles and carry out involuntary actions i.e. actions which are not controlled by the will. 2. The elongated cell can shorten its length and so contribute to muscle contraction. 3. Help in breathing and peristalsis. iii) Cardiac muscle (found only in the heart). 1. Adjacent cells in cardiac muscle are linked by bridges between cells. 2. They contain striated cytoplasm. 1. Cardiac muscle makes up the walls of the atria and ventricles. 2. It controls the movement of the heart. c) Blood (connective tissue) 1.The liquid part of blood is called plasma. 2.Floating in the plasma are mostly red blood cells and a much smaller number of white blood cells. 3.There are also small fragments formed from special cells in the bone marrow, called platelets. 1.Red blood cells carry oxygen. 2.Glucose, amino acids, salts, hormones, blood proteins and antibodies are substances which are essential for the body and are found in plasma. 3.White blood cells fight infection. 4.Platelets help blood to clot. 5.Blood acts as a transport. 6.Blood helps in regulation of body temperature. d) Nervous tissue 1. Is made up of nerve cells and neurons 1. Conducts nerve impulses throughout the body. e) Epithelial tissue i) Squamous surface for e.g. the cells lining the cheek are squamous. 1.It is made up of sheets of cells. Teacher in Charge: ARIF ULLAH Page 6

7 2.It is smooth and does not contain any hair. 1.Covers internal and external surfaces of the body. 2.Serves as a protective lining. ii) Ciliated muscle 1.Contains tiny hair-like projections called cilia. Functions: 1. The cilia helps to sweep dust particles up the bronchi and trachea into the pharynx. 2. The cilia are always moving and bacteria or dust particles get trapped in them in the mucus. 3. Cilia in the nose also waft the mucus into the oesophagus where it is swallowed. 4. Some epithelial cells are specialized to secrete substances e.g. mucus in the lining of the nose. These are gland cells. Gland cells may clump together in large groups forming the glands of the body. Specialization of cells: The changing of the shape and size (adaptation) of a cell for performing a particular function is known as Specialisation or Differentiation of cells. [After MITOSIS, one of the cells retains the ability to divide further and the other cell adapts for a particular task.] In Plants 1. Root hair cell: It has long hairs to increase surface area of the cell. It has a large number of mitochondria to provide energy for active up take. 2. Xylem vessels: It transports water and minerals to the plant. The xylem cells are dead and are made of long hollow tubes running throughout the root, stem, and leaves. It has thick cell walls. 3. Phloem cells: They transport sugar and amino acids to the body from the place they were made (the leaf). The phloem cells are long cells joined together. The cell wall where 2 phloem cells join together has holes which allows the cytoplasm of both cells to communicate passing down the dissolved food. 4. Guard cell (stomata): Allows O 2 and CO 2 to pass in and out the leaf. They can change their shape thus can open and close their holes. In Animals 5. Red blood cells: It transports oxygen from the lungs to tissues. It has no nucleus, t has hemoglobin which absorbs oxygen, its shape gives it a high surface area and it is small to fit in capillaries. 6. Nerve cells: they conduct electrical impulses which travel to & from the brain. They are very long and their chemical reactions cause impulses to travel through their fibers. They also have a layer of fat for insulation. 7. White blood cells: These occur in large amounts in the blood stream. They get rid of bacteria and viruses. They are able to change shape and can penetrate the blood vassals to enter tissues. They also contain enzymes that kill microorganisms in their cytoplasm. 8. Ciliated cell: These have cilia (hairs) which can move mucus away from the lungs by a wavy motion. Teacher in Charge: ARIF ULLAH Page 7

8 9. Muscle cells: These cam contract to move the body (they don t relax but they return to their original shape by the influence of other cells) they contain a lot of mitochondria to provide the energy needed. Teacher in Charge: ARIF ULLAH Page 8

9 ORGANS Types of organs Function Animals Alimentary canal To digest food. Nose, trachea, lungs Gaseous exchange. Heart, blood vessels. Transport oxygen and dissolved substances. Plants Leaf Photosynthesis Transpiration Flower Reproduction. ORGAN SYSTEMS Organ system Integumentary system(skin) Respiratory system Circulatory system Muscular system Skeletal system Lymphatic system Digestive system Excretory system Nervous system Immune system Endocrine system Reproductive system Function Waterproof barrier. Regulate temperature. Takes in oxygen Releases carbon dioxide. Regulates body temperature. Transports food, wastes, and gases to and from cells. Movements of parts of the body. Muscles found in internal organs serve to move substances in the organs. Supports body. Protects internal organs. Filters bacteria. Takes in and breaks down food. Absorbs nutrients. Undigested food is eliminated. Removes wastes from the body (includes lung and skin). Controls and co-ordinates body movement. Transmits information from the brain. Defends against infection. Secretes hormones. Produces response in the body. Produce sex cells. Protects and nourishes young during development. Teacher in Charge: ARIF ULLAH Page 9

10 Teacher in Charge: ARIF ULLAH Page 10

11 PLANT CELL ANIMAL CELL Teacher in Charge: ARIF ULLAH Page 11

12 Preparing a slide/ Mounting of a cell: 1. Plant Cell: i. Take an onion. ii. Peel the inner membrane from the flesh of an onion cell. iii. Place the membrane on a glass slide. iv. Drop few drops of iodine solution. v. Carefully place a cover slip. vi. Transfer the slide to a microscope and observe. *The cover slip prevents the lens from coming in contact with the specimen. It also prevents the entry of dust, the cover slip should be lowered carefully, so that no air bubbles are trapped, using a sharp needle. *Chloroplast are absent in an onion cell as they do not photosynthesize. STAINS: They allow the organelles to be vivid while observing under a microscope. The organelles like nucleus, chloroplast, and cell membrane become clear as they absorb the stain. *Iodine is one of the more commonly available stains and is used to identify starch in a variety of samples. It will stain carbohydrates in plants and animal specimens brown or blue-black. Glycogen will show as red. *Methylene Blue is an alkaline stain useful in identifying acidic cell nuclei and DNA in animal, bacteria or blood samples. It s also useful in aquariums to prevent the spread of fungal infections in fish. *Eosin Y is an acidic stain which stains pink for alkaline cells (cytoplasm, for example). It colors red for blood cells, cytoplasm and cell membranes. Eosin's most important medical uses are in blood and bone-marrow testing. *Gram's Stain is one of the most frequently used processes in identifying bacteria used daily in hospitals. It is a primary test that quickly and cost effectively divides bacteria into one of two types: Gram positive or Gram negative. 2. Animal Cell: i. Take some liver cells or using a cotton bud gently scrape the inner surface of your cheeks. ii. Rub the glass slide using the cotton bud. iii. Drop some methylene blue on the glass slide iv. Gently lower a cover slip. v. Transfer the slide to a microscope and observe. Organizations of cells: Cells Tissues Organs System Organisms. Cells-It is a structural and functional unit of life. Tissues-They are a group of similar cells with a particular function. Organs-Organs are a group of tissues with a particular function. System-A group of organs with a particular function. E.g. digestive system. Organism-Many organ systems make up an organism. Teacher in Charge: ARIF ULLAH Page 12