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Danyal Education Cell Structure and Organisation Notes 2 l.l e Cell Structure and Function 1 The cell structure of plants was first discovered by Robert Hooke in 1665. 2 He examined fine slices of cork with a primitive microscope. 3 He observed that the cork was actually made up of many small compartments like bricks and separated by partitions (Figure ,,, .:'':','.',.,.,..,.'.....'.,'..,..... :::,,aa.:t t.tr.t.trt What You Will Learn 1,,1 Cell Str,ucture and Function 1.2 These compartments were named cells and the partitions were called cell walls. 5 Robert Hooke's discovery showed that all organisms are made up of one or more cells. 6 Hence, the cell is the basic unit or building block for all living organisms. '::t' :. Specialised Cells,Tissues and Organs Figure 1.1 Cork cells Structure of Animal Cells and Plant Gells 1 2 Cells are the basic units of life. The function of cells is to carry out life processes such as respiration, excretion, growth and division. ny a ti. Da r I 4 l E du ca tio n Cell ,, Structure and ,,::,:, Organisation 1.1 ). 3 4 5 6 7 8 Cells exist in various shapes and sizes. Generally, a cell is made up of a plasma membrane which encloses protoplasm. Protoplasm is made up of cytoplasm and a nucleus. The cytoplasm contains many organelles. Organelles are specialised structures which are surrounded by their own membranes and perform specific functions. Organelles that are found in animal cells include the nucleus, rough and smooth endoplasmic reticulum, mitochondria, Golgi apparatus, ribosomes and vacuoles. 1 Plant cells have chloroplasts in addition to all the organelles in animal cells. 10 Structure of an animal cell (a) A cheek cell is an example of an animal cell, (b) Animal cells do not have regular shapes. (c) Each animal cell is enclosed by a plasma membrane. (d) Each cell has protoplasm which consists of the cytoplasm and a nucleus. IIE IJJ F g 11 Structure of a plant cell (J (a) The epidermal cells of an onion or cells of hydrilla leaf are examples of plant cells. a (b)Each cell is enclosed by a plasma membrane which is protected by a cell wall. (c) Plant cells have a fixed shape because they have cell walls. (d) Each cell has a nucleus and cytoplasm. (e) Plant cells have chloroplasts which contain chlorophyll.These are present in the cells of hydrilla leaves but not in the epidermal cells of onions. (f) A mature plant cell has a large vacuole which contains cell sap. 12 Figure 1.2 shows the structure of an animal cell and a plant cell as seen through an electron n 9 tio microscope. plasma nucleus membrane nucleus l E du rough endoplasmic reticulum ca ribosome cytoplasm reticulum mitochondria lysosome cell centriole lr-----;a rc ::cell ny a (a) Animal vacuole cytoplasm (b) ptant ceil Da Figure 1.2 Structure of an animal cell and a plant cell 2 CONCEPT FOCUS The cytoplasm is a jelly-like liquid surrounding the nucleus. lt is where metabolic activities take place. The cytoplasm together with the nucleus constitutes protoplasm. I q EXPERIMENT E Obiective Prepare and study a slide of animal cells (human cheek cells) E* Apparatus and materials Light microscope, glass slide, cover slip, long needle, toothpick, methylene blue, filter paper UI I Procedure The inside of the cheek is scraped with a toothpick. 2 The cheek extract is placed on the slide. A drop of water is dripped on it (Figure t.3(a)). 4 5 n water With the help of a long needle, a cover slip is gently lowered onto the specimen (Figure 1.3(b)).There should be no air bubbles trapped under the cover slip. uc at io 3 A drop of methylene blue solution is placed at one end of the cover slip and a strip of filter paper is placed at the other end.The filter paper will draw the solution across the specimen and colour it.This technique is called the irrigation technique (Figure t.3(c)). The slide is then observed under the light microscope using the lowpowered lens, followed by the high-powered lens. Ed Observation t cytoplasm \- , T distilled 1 C) slide (a) long needle slip (b) methyle blue (c) Figure 1.3 Preparing slide of human cheek cells plasma membrane ure 1.4 Human cheek cells ny al Conclusion The human cheek cells are not regular in size or shape. Each human cheek cell contains a nucleus, cytoplasm and plasma membrane. M ENrr,.iilE Da f5,,..e,xu,ent Objective Prepare and study a slide of plant cells (epidermal cells of onion and cells of hydrilla) Apparatus and materials Light microscope, glass slide, cover slip, razor blade, long needle, dropper, forceps, filter paper, iodine solution, big onion, hydrilla plant, distilled water 3 Procedure 1 A leaf from a bulb of an'onion is peeled off (Figure 1.5(a)). E 4 E UJ a, -(J "V An epidermal layer from the leaf is peeled with a razor blade. drop of distilled The epidermal layer is then placed on the glass slide that alreadv has a droo of water on it (Fioure r.itOtt (a) A cover slip is placed at an angle over the water droplet on the slide and gently lowered to cover the specimen without trapping any air bubbles (Figure t.5(c)). (b) , long >--Qi needle ---4\( 5 The slide is observed under a microscope starting with the low-powered lens, followed by the high-powered lens. )G. 6 A drop of iodine solution is added to one end of the cover slip and allowed to seep beneath the cover slip. cover slip -t-? I A strip of filter paper is placed at the other end of the cover slip to absorb any excess iodine and water (Figure 1.5(d)). 8 The slide is observed under the microscope again, first on low magnification, then on high magnification. 9 The structure of the onion cell is drawn. Observation cytoplasm nucleus cell wall membrane Figure 1.6 Epi dermal cells of Figure chloroplast cell wall plasma membrane cytoplasm nucleus vacuole vacuole onion Figure 1.7 Cells of hydrilla leaf Conelusion Plant cells have a regular shape. All plant cells contain a nucleus, cell wall, 4 Da ny al plasma membrane, cytoplasm and a big vacuole. Epidermal cells of the onion do not contain chloroplasts while the cells of hydrilla leaves contain ch Ioroplasts. (d) 1.5 Preparing slide of onion cells Ed uc 10 The experiment is repeated using a hydrilla leaf (c) filter paper solution at io 7 water leaf n 2 3 epidermal layer epidermis of onion Functions of Cellular Components Cellular component N o Structure Function(sl Plasma membrane . Thin, semi-permeable membrane r Cell wall . Thick layer outside the plasma o Maintains the shape of the plant o cells Provides support for plant body . Acts as a medium for metabolic N o membrane R o Made up of cellulose and fully G Controls the movement of substances in and out of the cell *l E G UI o- permeable A N . Cytoplasm L . L E Jelly-like substance that contains water and mineral salts Contains organelles S . . Small particle consisting of RNA (ribonucleic acid) Exists freely in the cytoplasm or on the surface of the rough endoplasmic reticulum Ribosome o Rough and smooth endoplasmic reticulum A N . Ed R G . E t L endoplasmic reticulum . o Controls and regulates all the activities of the cell Contains the hereditary factors (genes) responsible for the traits of the animal or plant o Synthesis of protein o Transport system for protein and lipids within the cell Rough endoplasmic reticulum transports the protein synthesised by the ribosomes to other parts of the cell Smooth endoplasmic reticulum stimulates the synthesis of lipids and cholesterol and transports them within the cell . . rough endoplasmic reticulum o ny Mitochondrion A system of membrane-enclosed tubules closely packed together and continuous with the nuclear membrane Rough endoplasmic reticulum has ribosomes while the smooth endoplasmic reticulum does not have ribosomes al E s Spherical with a double membrane Contains nucleolus, chromosomes, nucleoplasm and nuclear membrane reactions Supplies the substances required by the organelles at Nucleus . uc t o ion E outer membrane inner membrane membrane Outer membrane is smooth and regulal the inner membrane is folded to form cristae . o Known as the 'power-house' of the cell Releases energy as it is the site for aerobic respiration I Da crista o Rod-shaped with a double I tr Function{s} Structure Cellular component . Golgi apparatus Vacuolar region surrounded by complex meshwork of vesicles budding off at its end . a I IIt . lrt Golgi apparatus secretory vesicle cells o r . Disc-shaped organelle with . a double membrane Consist of an orderly arrangement of grana within the stroma Each granum contains chlorophyll stroma granum tonoplast CONCEPT FOCUS Carries out photosynthesis Cavities filled with cell sap surrounded by a semi-permeable membrane called the tonoplast Contains water, sugar and dissolved minerals Maintains turgidity of cells in plants al Ed uc Vacuole nucleus Controls the secretory activity of o Formation of lysosomes Chloroplast cytoplasm be secreted at (J o modifies them to form specific secretions such as enzymes and hormones Packs the secretions formed Into secretory vesicles and transports them to the plasma membrane to ion c < Receives protein and lipids from endoplasmic reticulum and Animal cell Difierences Plant cell No fixed shape Shape Fixed shape Organelles are subcellular structures found in the cytoplasm, each with a specific functional role in the cell. Comparison Between the Structure of an Animal Gell and a Plant Gell ny Plant cell Similarilles Da Both have a plasma membrane, cytoplasm, a nucleus, mitochondria, Golgi apparatus and endoplasmic reticulum 6 Does not have a cell wall Cell wall Does not have ch loro p lasts Usually has numerous small Vacuole vacuoles Contains glycogen g ra nu les Granules Has a cellulose cell wall Has chloroplasts which contain chlorophyll Usually has a large vacuole Contains starch g ranules Understanding key ideas Tick 1 (/) 1 if the statement is true. The cell is the basic unit of life for all organisms. 2 Plant cells have a plasma membrane, 2 The nucleus consists of chromosomes and a nucleolus. Organelles that are found in the cytoplasm of a cell include the nucleus, vacuole, endoplasmic reticulum, mitochondria and Golgi apparatus. 5 The vacuole of a plant cell is enclosed by the tonoplast. 6 Human cheek cells and epidermal cells of onions do not have chloroplasts. 7 Epidermal cells of onions have small vacuoles. T tf tl State the components of cells which carry out the following functions. (a) Contains a pigment which absorbs energy from sunlight for photosynthesis (b) Site for generating energy (c) Controls the movement of substances going in and out of the cell (d)An organelle which contains the hereditary factors called genes (e) Helps to keep the cell turgid (f) Has ribosomes on it to synthesise protein (g) Provides support and shape to the cell (h) Receives organic molecules and packages them to form specific secretions ny Give three differences between human cheek cells and the epidermal cells of an onion. 3 Suggest why sperm cells have a high density of mitochondria while the human cheek cells have only a few mitochondria. Da 2 UJ a o! (J Each multicellular organism is organised as follows: cell ) tissue organ system ) ) organ ) organism Cell 1 Cells are the basic units of life in all organisms. 2 The structural features of cells are related to their functions. 3 Ed Main concepts and facts 3 4 Cells undergo differentiation to acquire special structures and become specialised cells with specific functions. The following describe the various types of cells with their specific functions. (a) Root hair cells (i) The functions of the roots are to anchor the plant to the soil and to absorb water from the soil. Root hairs are outgrowths of the epidermal cells. (iii) They help to increase the surface area and thus increase the absorption of water and mineral salts. (ii) al B 1 [] t The organisation of cells allows every part of multicellular organism to perform various fu nctions efficiently. uc at io 4 n cell. nucleus and cytoplasm. 3 ln general, organisms are divided into unicellular organisms with single cells and multicellular organisms with more than one n A Specialised Cells, Tissues and Organs 1.2 I n, hair 0 Figure 1.8 A root hair 7 .uE a. o (ii) The red blood cells contain haemoglobin. This combines readily with oxygen to form oxyhaemoglobin. (iii) Red blood cells are flat and biconcave in shape to increase the surface area for gas exchange. (iv) Red blood cells do not have a nucleus and can fold easily.This allows them to squeeze through the blood capillaries. n E (c) Red blood cells (i) The function of the red blood cells is to transport oxygen all around the body. (b)Xylem vessels (i) The functions of the xylem vessels are to conduct water and mineral salts from the roots to the leaves and to provide support to the plant. (ii) Xylem vessels are non-living, i.e. they do not contain protoplasm and so are hollow. (iii) The vessels are placed end to end to form a continuous tube for passage of water and mineral salts. (iv) The vessels are thickened with lignin to provide strength and support to the pe. ca tio Plant. Figure 1.10 Red blood cells Tissue Figure 1.9 Xylem vessels Trpe ol animal tissue 2 al . Epithelium lining of skin (ii) Epithelium lining of blood capillary (b) Nervous tissue ny (i) Da Examples: sensory neurone, motor neurone, intermediate neurone cell body 8 work together to perform a specific function. axon terminal There are four main types of animal tissues: epithelial tissue, nervous tissue, muscle tissue and connective tissue. Characteristic{s}, and f unction{s} o (a) Epithelial tissue A tissue is defined as a group of similar cells that Ed u 1 . Consists of epithelial cells arranged in a continuous layer Covers the body surface (exterior) or lines the cavities within the body o Protects the underlying cells from mechanical inlury Acts to absorb food and water by diffusion . . Consists of nerve cells called neurones Sends and receives impulses to coordinate the activities . of the body Found in the brain and spinal cord Type of animal tissue Characteristic{s} and lunction{s} o (c) Muscle tissue cardiac o Consists of muscle cells which can contract to perform work and cause body movement Three types of muscle tissue: smooth muscle, skeletal muscle and cardiac muscle ET ffi,::::"- t ut EffiJ (ii) Smooth muscle in the walls of ileum G Cardiac muscle of the heart () or stomach Connective tissue o @em Ar \/ o @o s@'B OGB \\v/ (i) Blood . . Consists of elastic and non-elastic fibres Joins together body structures, as well as protects, holds and supports the cells in the body Can store and transport materials al Ed uc at io (dl n (i) (iii) Cartilage (iv) Bone o /1 m (ii) Adipose tissue CONCEPT FOCUS / Da ny Tissues are made up of the same type of cells which carry out a special function. Some types of tissues contain several types of cells, but the whole tissue performs one function. Connective tissue, for example, connects different parts of an organ or organs together.This kind of tissue is called complex tissue. q 3 Examples of plant tissues are epidermal tissue, meristematic tissue and vascular tissue 'Charaaeristic(s}' and lunction{s} Type'of plant tissue ' Iil r (a) Epidermal tissue stoma iII & : '. , . Examples: epidermis of leaves, stems and roots ! Consists of one layer of cells o Covers the entire surface of the plant 'l o Protects underlying tissues from physical damage and -T G . infection Reduces water loss Epidermal cells of leaf differentiate to become guard cells while those at the root become root hair cells . '. (b) Meristematic tissue nucleus Consists of undifferentiated cells which are able to divide Occurs at the tip of roots and shoots (apical meristem) and in the cambium of stems and roots (lateral meristem) Examples: apical meristem of root and shoot, cambium in the stem . Vascular tissue o xylem vessels phloem Examples: xylem, phloem Each organ in an animal is formed from the four main types of animal tissues. All these tissues work together to perform a specific 10 Da fu nction. 4 . i' . al Examples of organs in animals are the heart, stomach, skin, kidneys and lungs. ny 3 I A group of different tissues that work together to perform a specific function is called an o rga n. 2 Consists of xylem tissues and phloem tissues Transports water and mineral salts from roots to the stems and leaves by xylem tissues Transports dissolved nutrients such as sugars from the leaves to the roots and stems by phloem tissues Xylem tissues also provide support to the plants 7 0rgan 1 : Ed uc at (c) ion (J For example, the heart is an organ made up of epithelial tissue, muscle tissue, nervous tissue and connective tissue to pump blood to all parts of the body. 5 Examples of organs in plants are leaves, stems, roots and flowers. 6 The leaf of a plant is made up of epidermal tissue, vascular tissue and mesophyll tissue to ca rry out photosYnthesis. Certain organs perform more than one function. For example, the liver can convert excess glucose to glycogen as well as secrete bile. CONCEPT FOCUS An organ, such as the stomach or liver, is a structure made up of different types of tissues working together to perform a function. For example, the stomach is made up of four types of tissues - glandular tissue, muscle tissue, connective tissue and nervous tissue. 0rgan System 1 2 Several organs which work together to carry out a specific function form an organ system. The human body has different systems, each performing a specific function in the body (Figure 1.11). I 4 mouth salivary glandsoesophagus VESSEI heart liver caecum rectum anus @," E J stomach pancreas ileum \,'1 multicellular organrsm A \\ E )) EI r organ w I o ion system Figure 1.12 An organism (b) Digestive system (Breaks down food into simple substances so that they can be absorbed by the cells) CHECK A 1 ny al Figure 1.11 Different types of systems in the human body 3 Each system consists of a few organs made up of various tissues. 4 For example, the digestive system consists of the mouth, oesophagus, stomach, ileum, duodenum and large intestine. 5 if the statement is true. Cell specialisation allows cells to form tissues. 2 Tissues are organised into functional units called organs. 3 The stomach, small intestine, liver and pancreas work together as parts of the digestive system which is required for the intake, digestion and absorption of food. Ed nerves (c) Nervous system (Conducts impulses around the body and coordinates activities in the body) (/) uc spinal cord / Understanding key ideas Tick brain 1,.2 at (a) Blood circulatory system (Transports food substances and oxygen around the body) All the organ systems work together to form an organism (Figure 1.12). Da E 6 A flowering plant has two main systems: a root system and a shoot system. 7 The shoot system consists of the stem, leaves, buds, flowers and fruit while the root system consists of the tap roots and lateral roots. 4 Root hair cells are long and narrow to increase the surface area for the absorption of water and mineral salts. B 1 Main concepts and facts tf Red blood cells contain which enables them to transport oxygen from the lungs to the tissues. 2 A root hair is an example of 3 The stomach is an example of an organ because do not have 4 a nucleus and can fold easily. 5 Xylem vessels are adapted to conduct water and mineral salts from roots to leaves because 11 6 Fill in the blanks in the concept map with the words given to show the levels of organisation in animals. Word list F Organs Cartilage Muscle E. Kidney Brain Tissues Organism Reproductive Homo sapien Liver Systems Bone Excretory Endocrine Cells uc such as such as form Ed such as form t Da ny al such as 12 '' ion () I at ul g I CELL STRUCTURE AND ORGANISATION Function Nucleus Controls all cell activities Endoplasmic reticulum- Transports proteins, lipids and glycerol Mitochondria Produce energy II I I Cof Si apparatus I Ribosome Chloroplasts t Cell Plasma membrane Non- kp:l:lle, t o Controls secretory activity of the cell Synthesise protein Carry out photosynthesis Contain cell sap Vacuoles - Cytoplasm Cell wall Controls flow of materials in and out of cell Medium for chemical processes Gives shape, support and protection to cell Ed u tlu*99 Plant cells lt q Unicellular Types of organisms Multicellular Cell specialisation Cell organisation I ny al Cells with specific structu res and functions (Root hair cells, xylem vessels, red blood cells) l'issues Organs Nervous Muscle Connective I'IN Stomach Brain Heart tlll Nervous Circulatory Digestive system system system Da Systems Epithelial Plants Animals Epidermal Vascular Meristematic Stem ' Root ' Transport system Root system r Bone Leaf I Skeletal system Foodmaking system E o. ion Structure r ca t Organelles ::irllil IJ