Lecture 1. Properties of life The world of cell 30/10/2018

Transcription

1 Lecture 1 Properties of life The world of cell 30/10/2018 1

2 The Diversity of life Biology is the science of living things- The Science of Life The living worlds teems with a breath-taking variety of creatures. Creatures can be categorized into six groups, or kingdoms. 2

3 Properties of Life The living world is very diverse, but all living things share five basic properties 1- Cellular Organization All living things are composed of ONE or MORE CELLS. A cell is an organized unit that can live and reproduce by itself, Cells are the smallest units that can be alive. Some organisms are unicellular they are made of only 1 cell. Other organisms are multicellular. they are made of many cells that function together. 3

4 2- Metabolism and energy Human take in energy and materials by consuming food. Our bodies use the energy and raw materials to build and operate their parts in ways that keep us alive. Metabolism is all the chemical processes that build-up or break down materials and create waste. 4

5 3- Sensation and responding Living things sense and respond to changes in the environment. For instance, a tulip s petals close up when night falls, and you might put on a sweater or turn up the heat on a chilly afternoon. Organisms react to stimuli: Light Temperature Odor Sound Heat Water Pressure 5

6 4- Homeostasis Homeostasis is a state of chemical and physical stability inside the body that must be maintained in order for individual cells, and the whole body, to stay alive. Body cells are part of systems that maintain internal homeostasis. Example of homeostasis: 1. Controlling body temperature (thermal regulation) All mammals maintain a constant body temperature (37ºC). If your body is in a hot environment your body temperature is 37ºC If your body is in a cold environment your body temperature is still 37ºC 2. Controlling Glucose levels (Glucose homeostasis) The balance of insulin and glucagon to maintain blood. 6

7 5- Growth and Reproduction Living things reproduce and grow. Organisms can make more of their own kind, based on instructions in DNA, the genetic material. Only living things have DNA. Guided by the instructions in their DNA, most organisms develop through a series of life stages. Human reproduction 7

8 The Chemistry of Life All organism are chemical machines. Any substance in the universe that has the mass and occupies space is defined as matter. Matter is composed of extremely small particles called atoms. Atom is the smallest amount of an elements consists of proton, neutron and electrons Molecules: is a group of atom held together by chemical bonds. E.x. glucose Macromolecules: A macromolecule is a very large molecule, such as carbohydrate, commonly created by polymerization of smaller subunits (monomers). 8

9 Chemical composition of cells There are about 92 element occurring naturally in nature. From these 92 element, only about 25 elements are needed to build living organisms. Almost 99% of the mass of the human body is made up of six elements (essential elements): oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements (trace elements): potassium, sulfur, sodium, chlorine, and magnesium. 9

10 Chemical composition of cells Essential elements Trace elements Compounds Organic compounds Contain Carbon Carbohydrates Lipids Proteins Nucleic acid Inorganic compounds Do not contain carbon Water NaCl 10

11 Organic compounds The four major macromolecules essential forms of CELL are proteins, nucleic acids, carbohydrates, and lipid 1- proteins Proteins are macromolecules that carry many functions in the cell. The are produced by linking together of amino acid with covalent bond called Peptide bond. The sequence of amino acids is the primary structure of the protein. The chain of amino acids then folds into its final shape, exhibiting different level of complexity, from secondary to tertiary to quaternary structure. Example of protein in cells: enzyme, hormone, antibody, contractile protein, keratin, transport protein, collage..etc 11

12 2- Nucleic acids DNA (Deoxyribonucleic acid) DNA is the molecule that carries the genetic information in all cellular forms of life and some viruses. It belongs to a class of molecules called the nucleic acids, which are polynucleotides - that is, long chains of nucleotides. Each nucleotide consists of three components: a nitrogenous base: a five-carbon sugar molecule (deoxyribose in the case of DNA) a phosphate molecule 12

13 Primary Structure of DNA 13

14 Ribonucleic acid (RNA) RNA is typically single stranded and is made of ribonucleotides that are linked by phosphodiester bonds. A ribonucleotide in the RNA chain contains ribose (the pentose sugar), one of the four nitrogenous bases, and a phosphate group. 14

15 3- Carbohydrates Polymers called carbohydrates make up the structural frame work of cells and play critical role in energy storage. A carbohydrate with one unit of sugar is called a simple sugar or a monosaccharide. A disaccharide: is the sugar formed when two monosaccharides (simple sugars) are joined by glycosidic linkage. Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide C 6 H 12 O 6 glucose + C 6 H 12 O 6 fructose Condensation Hydrolysis C 12 H 22 O 11 sucrose + H2 O water 15

16 4- Lipids Lipids a diverse group of substance that contain carbon, hydrogen and oxygen. The proportion of oxygen is lower than that in carbohydrates. The main types of lipids are: a) Fats b) Oils c) Waxes (found in ear) d) Phospholipids e) steroids 16

17 Fats and oils Each molecule of fats or oils is made up of one glycerol combine with three fatty acids which may be the same or may be different. Three molecule of water are remove in this condensation reaction. + Condensation (- H 2 O) Hydrolysis (+ H 2 O) glycerol 3 fatty acids molecules Triglyceride + 3 water molecules Fat cells hold the triglyceride molecules until your body needs energy, such as between meals. 17

18 Phospholipid Phospholipids make up the plasma membrane and other membrane -surrounded organelles. It contains 2 fatty acid chains that are nonpolar. Head is polar and contain a Phosphate group and glycerol. Head Region It is Hydrophilic: Materials with a special affinity for water. Tail Region It is Hydrophobic Materials do not have affinity for water. 18

19 Steroids A steroid molecule has a complex ring structure Examples of steroids are cholesterol, testosterone, estrogen and progesterone. Steroid cholesterol testosterone estrogen and progesterone. Function Strengthens the cell membrane at high body temperature Male reproductive hormone female reproductive hormone 19

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21 A brief history Robert hooke first described cells in 1665: He examined a thin slice of non-living plant tissue called Cork. He observed a honeycomb of tiny, empty compartments. He called the compartments in the cork Cellulae (Latin, small room). The term has come down to us as Cells 21

22 Leewenhoek (1674) looked at blood, rainwater, scrapings from teeth through a simple microscope and observed living cells; called some 'animalcules' Leewenhoek Schleiden and Schwann (1838 & 1839) reported that cells are the structural units of plants and animals. 22

23 The Cell Theory states that: 1. All living things are composed of a cell or cells. 2. cell is the basic unit of structure and organization in organisms. 3. All cells arise by division from a preexisting cells. 23

24 Cell Diversity Cells show Enormous Diversity in: Size Shape Internal Organization 24

25 1- Cell Size Cells are very small and are seen only with microscope. The size of prokaryotic and eukaryotic cells vary. Bacterial cell are smallest cell ON EARTH, an ostrich egg is a big cell. In the human body, Female eggs are the largest cell. Nerve cells are longest cells Sperm cells are smallest cells 25

26 2- Cell shape Cells vary greatly in shape. These shape in human body may be: Squamous, Polygonal, Stellate, Cuboidal, Columnar, Spheroid to ovoid, Discoid, Fusiform, and Fibrous Squamous Cuboidal Columnar Polygonal Stellate Spheroid Discoid Fusiform (spindle-shaped) Fibrous 26

27 3- Internal organization Cells are classified by internal organization: 1-Prokaryotic cells Plasma membrane Cytoplasm No organelles No Nucleus 2-Eukaryotic cells Plasma membrane Nucleus Cytoplasm organelles 27

28 Prokaryotic cells First cell type on earth Cell type of Bacteria and Archaea 28

29 Characteristic of Prokaryotes Cells that lack a nucleus or membrane-bound organelles Single, circular chromosome Nucleoid = region of DNA concentration Cytoplasm is surrounded by cell membrane & cell wall Contain ribosomes in their cytoplasm to make proteins Bacteria have special structure such as flagella, Pili, and capsule.

30 Eukaryotic cells The three basic parts of a cell are the plasma membrane, cytoplasm and nucleus. 1. Plasma membrane The cells outer boundary, called plasma membrane (or the cell membrane), covers a cell`s surface and acts as a barrier between inside and outside of a cell. 30

31 2. Nucleus Brain of Cell (The control center of the cell) Bordered by a porous membrane - nuclear envelope. It contains most of the cell`s DNA and genetic material. It contains a small round nucleolus Nucleolus produces ribosomal RNA which makes ribosomes. 31

32 3. Cytoplasm Is the part of a cell that is enclosed within the cell-membrane. It is granular and many substances are dissolved or suspended in it (like ions, macromolecules, hormones and vitamins). In eukaryotic cells it contains organelles. Metabolic activities and protein synthesis occur in it. 32

33 The cytoplasm is composed of the cytosol + organelles. The cytosol is composed of a mixture of substances, especially proteins, dissolved in. Cytosol ph: Human cytosolic ph ranges between The cytosol components Water Ions Small molecules Macromolecules Cytoskeleton 33

34 Cell Water Water is the most abundant molecule in cells, accounting for 70% or more of total cell mass. There are few exceptions like bone. Total body water is about 50-60% of body weight in adults and 70% in children. The intracellular fluid makes up about 60 percent of the total water in the human body, and extracellular fluid makes up about 40% of the total water. Extracellular water includes plasma and interstitial water (the fluid in the tissue spaces between cells). 34

35 Main functions of cell water It therefore serves as a natural solvent for most macromolecules like proteins, carbohydrates and nucleic acids, and small molecules like mineral ions, salt, sugar, It forms saliva. It lubricates joints. Water flush waste product mainly in urine. It is needed by brain to make hormone and neurotransmitter. Helps deliver O2 and nutrient. Water regulate body temperature through sweating Moisten tissues such as in nose, mouth, and eye. Prevent constipation. 35

36 Cell Ions (electrolytes) Electrolytes are substances that dissociate in solution. These substances are located in the extracellular and intracellular fluid. Within the extracellular fluid, the major cation is sodium and the major anion is chloride. The major cation in the intracellular fluid is potassium. 36