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Transcript
CHAPTER 2 CELL STRUCTURE AND CELL ORGANISATION Diagram of a typical animal cell. Organelles are labelled as follows: 1. 2. 3. 4. 5. Nucleolus Nucleus Ribosome Vesicle Rough endoplasmic reticulum 6. Golgi apparatus (or "Golgi body") 7. Cytoskeleton 8. Smooth endoplasmic reticulum 9. Mitochondrion 10. Vacuole 11. Cytoplasm 12. Lysosome 13. Centriole Organelle chloroplast (plastid) Main function photosynthesis Structure doublemembrane compartment sorting and modification of proteins mitochondri energy production on vacuole storage, homeostasis nucleus DNA maintenance, Notes plants, protists has some genes all eukaryotes rough endoplasmic reticulum is covered with ribosomes, has folds that are flat sacs; smooth endoplasmic reticulum has folds that are tubular singlemembrane compartment all eukaryotes cis-face (convex) nearest to rough endoplasmic reticulum; trans-face (concave) farthest from rough endoplasmic reticulum doublemembrane compartment singlemembrane compartment doublemembrane most eukaryotes has some DNA translation and folding of new proteins (rough singleendoplasmi endoplasmic expression membrane c reticulum reticulum), of lipids (smooth compartment endoplasmic reticulum) Golgi apparatus Organisms eukaryotes all has bulk of genome Minor eukaryotic organelles and cell components Organelle Main function Structure Organisms centriole anchor for cytoskeleton Microtubule protein animals cilium movement in or of external medium Microtubule protein animals, protists, few plants lysosome breakdown of large molecules (e.g., proteins + polysaccharides) single-membrane compartment most eukaryotes myofibril muscular contraction bundled filaments animals nucleolus ribosome production protein-DNA-RNA most eukaryotes ribosome translation of RNA into proteins RNA-protein eukaryotes, prokaryotes vesicle material transport single-membrane compartment all eukaryotes • Chloroplasts are larger than mitochondria, and are surrounded by two specialized membranes. In plants and some other eukaryotes, chloroplasts are the sites of photosynthesis, a process in which atmospheric carbon dioxide is "fixed" into organic compounds, and oxygen is released into the atmosphere • Mitochondria are small, oval shaped organelles surrounded by two highly specialized membranes. Mitochondria are the sites of aerobic respiration, and are generally the major energy production center in eukaryotes • Cell Organisation 1. Organism can be categorised as unicellular or multicellular 2. Unicellular organism are organism with just one cell, for example Amoeba sp. and Paramecium sp. 3. Multicellular organisms are made up of more than one cell Amoeba proteus The Amoeba sp. Exhibits various living processes as follows: a) Feeding b) Locomotion c) Reproduction Feeding 1. Amoeba sp. feeds on bacteria and algae much smaller than itself. 2. When the amoeba sp comes in contact with its food, it puts its pseudopodia all around the food to enclose it in a drop of water, forming a food vacuole 3. The cytoplasm secrete enzymes into the food vacuole to digest the food. 4. The digested substances are absorbed into the cytoplasm while the undigested material are removed when the vacuole comes in contact with the plasma membrane and breaks Locomotion • The amoeba moves by putting out new pseudopodia in front withdrawing other behind. • Movement by means of pseudopodia is known as amoeboid movement • The shape of the amoeba changes as it move. Reproduction • The amoeba reproduce mainly by binary fission • Binary fission is a method of asexual reproduction which does not involve the fusion of gametes. • When food is abundant, the amoeba reproduces by binary fission. When the amoeba reaches a maximum size, the nucleus divides into two and the cytoplasm constrict, forming two new amoeba. • The amoeba does not reproduce sexually. Cell specialisation in multicellular organism • Being multicellular not only enables organisms to be larger, it also enables their to become specialised. • Each type of cell specialiseds in performing a particular function, for example the red blood cell in animal transports oxygen and the xylem vessel in plant transports water and mineral salt. This is known as division of labour. • The division of labour permits greater efficiency and enables multicellular organisms to exploit environments that are denied to unicellular organisms. Foe example, only multicellular organisms can adapt to life in terrestrial environment. • Multicellular organisms have a great potential for cell specialisation, leading to the development of tissues and organ Cell organisation in the formation of tissues, organ and systems in the multicellular organism • The study of cells is known as cytology Level of organisation Cell Tissue Organ Organ system meaning The smallest unit of life capable of carrying out all the function of living things. A group of cells of the same type that perform a specific function in an organism. Several type of tissue that carry out a particular function Several organ working together to perform a function cell Muscle cell White blood cell Sperm Red blood cell Nerve cell Function Able to contract and relax and are involve in movement Involves in defence of the body against diseases Fertilises the ovum Transport oxygen Receive and sends out nerve impulses Some of the human cell and their functions cell Function Parenchyma cell For support and storage Xylem vessel element Transports water and mineral salt Sieve tube element Transports organic product of photosynthesis Companion cell Regulates the metabolic activity of sieve tube element Epidermal cell For protection and covering of other cells beneath Some of the human cell and their functions • The study of tissues is known as histology • In human and animal, there are four basic types of tissuesc Tissue Function Example Epithelial tissue Forms thin sheets that line Ciliated cells that line and cover body structure; the respiratory tract the function depends on its location in an organ Connective tissue Holds the body together Bone, cartilage, blood, tendon, ligament Muscular tissue Contract to produce Skeletal muscles, movement smooth muscle, cardiac muscle Nervous tissue Conduct nerve impulses Densely packed nerve cells Humans and animal tissues • There are three major plant tissues; epidermis, ground tissue and vascular tissue Tissue Epidermis Function Covers and protects underlying tissues from drying out and form mechanical abrasions Ground tissue Chief functions are to store food and to provide support Vascular tissue Distribute water, mineral salts and photosynthetic products throughout the plant Plant tissues Example Epidermis of leaves, cork layer of stems and roots Parenchyma at the cortex and pith Xylem, phloem • Organ consists of several types of tissues and it is specialised to perform a specific function • Example of human organ include heart, stomach, kidney, liver and blood vessels • Organ system consists of a group of organs which carryout major function such as respiratory, nutrition and other • There are 12 organ system in human. Circulatory system Function; Transport material such as nutrient, gases, metabolic waste and heat around the body Organs and structure; hear, blood vessels Function; provides a means for gaseous exchange, that is oxygen Organs and structure; hear, blood vessels Function; Breaks down complex food into simple substance for easy absorption by body cells Organs and structure; mouth, oesophagus, stomach, intestine, rectum and anus Excretory system Function; Discard toxic waste product Organs and structure; Liver, kidney, urinary bladder Intergumentary System Function; • Physically separates the body from the external environment • Protects the body against mechanical injuries, microbial infection and dehydration Organs and structure; Skin Skeletal System Function; Provides bodily support and protection to soft internal organs Organs and structure; skull, rib cage, humerus, backbone, ulna, radius, femur, fibula and tibia Muscular System Function; help in movement of the body Organs and structure; all muscle.. Lymphatic System Function; • Defend the body against infection • Return excess tissue fluid to the blood Organs and structure; all muscle.. Endocrine System Function; produces hormone that control the bodily activities Organs and structure; Pituitary gland, adrenal gland, thyroid gland, pancreas, testes and ovaries. Female reproductive system Cell organisation Plant tissue • Meristematic tissue consist of small cells which have thin walls, large nuclei, dense cytoplasm and no vacuoles. • Apical meristems are located at the tips of roots and the bud of shoots. The tissues undergo mitotic cell division to increase the number of cell division to increase the number of cell for plant growth. • Lateral meristems or cambium are found in the peripheral areas of stem and roots. They are responsible for secondary growth which adds girth to the plants. Permanent tissues • Permanent tissues consist of more mature cells that are either undergoing differentiation or have already undergone differentiation. • There are three types of permanent tissues a) Epidermal tissues • forms a layer to cover the entire surface of the plants and protects the surface of plants • Protect the underlying tissues from physical damage infection • Reduce water loss b) Ground tissues • Provide support and strengthens the plants c) Vascular tissues • Transport water and food • Provide support The importance of maintaining an optimal internal environment in cells 1. The self-regulation of the internal environment of organisms have or cells is called homeostasis 2. Multicellular organisms have a series or organ and systems that functional in homeostasis 3. For a multicellular organisms to function efficiently, other factors in the internal environment also have to be maintained within narrow limits. Examples of these factors include the volume of water, temperature, acidity and concentration of salts. 4. Homeostasis is essential for the maintenance of health and its breakdown will inevitably result in disease Appreciating the uniqueness of the cell 1. Each cell is unique and its organelles are specialised to perform specific roles to carry out the cell mechanisms 2. With the division of labour among the different types of cells, it ensures the efficient and smooth functioning of the life processes in the body and the survival of the organism. 3. The function of intracellular organelles such as mitochondria, lysosomes and the endoplasmic reticulum also depend on the integrity of their cell membrane (explain the function of each organelles) 4. Generally, any damage to the cell parts or organelles can effect the cell’s activities and this could be detrimental to the cell as it could lead to cell death.