Biochemistry Lec 2 PDF

Biochemistry EBA1300 Dr. Rana Saeed PhD in Biochemistry Faculty of Science, Alexandria University  Lecture 2 Cell Biology  What is Cell Biology ? Cell biology: is the study of cell structure and function, growth, reproduction and genetics of the cell. Cell: is...

Biochemistry EBA1300 Dr. Rana Saeed PhD in Biochemistry Faculty of Science, Alexandria University  Lecture 2 Cell Biology  What is Cell Biology ? Cell biology: is the study of cell structure and function, growth, reproduction and genetics of the cell. Cell: is the smallest basic unit forming the living organism (the building block of an organism). Cell is a Latin word which means a small room.  Some organisms have only one cell (bacteria) , while others are composed of a huge numbers of cells (human).  Discovery of the cell Scientists contributed to the cell discovery Hans and Zacharias Jansen Robert Hooke Antony van Leeuwenhoek Robert Brown  Discovery of the cell Scientists contributed to the cell discovery Matthias Schleiden Theodor Schwann Rudolph Virchow  Hans and Zacharias Jansen Role Production 1595 of lenses (compound microscope)  Robert Hooke o The word cell was first used by Robert Hooke, a British biologist and early microscopist. o Hooke looked at thin slices of cork under a microscope. o The structure he saw looked like a honeycomb as it was made up of many tiny units. Oak tree Cork  Discovery of the cell Hooke’s drawing of cork is shown in this Figure, using Hooke’s microscope  Antony van Leeuwenhoek o During the 1670s, the Dutch Antony van Leeuwenhoek, used microscopes to observe many microbes and body cells. o Leeuwenhoek microscopes were able to magnify much more clearly than the compound microscopes of his day. o His microscope’s increased ability to magnify over 200 times is comparable to a other microscopes. o He discovered blood cells and was the first person to see living sperm cells.  Robert Brown He was a an English botanist 1833 discovered the nucleus in Orchid plant cell  Matthias Schleiden German botanist discovered that 1838 all plants are composed of tissues.  Theodor Schwann German zoologist discovered that all 1839 animal tissues are composed of cells. Started cell theory.  Rudolph Virchow A German doctor who 1858 completed cell theory.  Cell Theory o Later, biologists found cells everywhere. o Biologists suggested that all living things were made of cells, but the role of cells as the primary building block of life was not discovered until 1839 when two German scientists, Theodor Schwann, a zoologist, and Matthias Schleiden, a botanist, suggested that cells were the basic unit of all living things. o Later, in 1858, the German doctor Rudolf Virchow observed that cells divide to produce more cells. He proposed that all cells arise only from other cells.  Cell Theory The collective observations of all three scientists form the cell theory. The modern cell theory states that: All organisms are made up of one or more cells. All the life functions of an organism occur within cells. All cells come from preexisting cells. Prokaryotes vs. Eukaryotes  There are two main types of cells Prokaryotic cells Eukaryotic cells (have false nucleus) (have true nucleus) Prokaryotes Blue-green algae Eukaryotes  Organisms with prokaryotic cells are called prokaryotes (ex. Bacteria, blue green algae). Single-celled microorganisms (unicellular) known to be the earliest on earth. Prokaryotes These cells are smaller than eukaryotic cells and multiply in a faster rate. Nucleus not covered with membrane.  They are outermost covered with cell wall. Simpler and smaller than eukaryotes. Prokaryotes DNA is circular, without proteins. The DNA is directly attached to cytoplasm.  Organisms with Eukaryotic cells are called Eukaryotes. (ex. Plants, fungi, animals, human). More complex structure than prokaryotes. Eukaryotes Larger than prokaryotes. The nucleus is covered with nuclear membrane (true nucleus). What are the differences ?  Prokaryotes Eukaryotes Organisms with Organisms with prokaryotic cells Eukaryotic cells (ex. Bacteria, blue (ex. Plants, fungi, green algae) animals, human) Single-celled May be unicellular or microorganisms multicellular (unicellular) Smaller in size than Larger in size eukaryotes More simple structure More complex structure Multiply in a faster rate Multiply in a slower rate  Prokaryotes Eukaryotes Lack membrane Have membrane bound nucleus (The bound nucleus (The DNA is directly DNA is separated attached to from cytoplasm) cytoplasm) They are outermost Cell wall covers plant covered with cell wall cells and fungi , but the cover of animal cell is called cell membrane DNA is circular, DNA is linear, with without proteins proteins  Bacteria Bacteria are the smallest and simplest microorganisms. They are prokaryotes. There were firstly discovered by Antony van Leeuwenhoek. Reproduction in bacteria  Binary Fission Binary fission the simplest and most common type of reproduction in bacteria. It occurs during favorable conditions. Binary fission involves the division of a single cell, which results in the formation of two cells that are genetically identical. In binary fission, the cell elongates, replicates its DNA, and separates. Finally, a septum (or cross wall) is formed at between cells, dividing the parent cell into two daughter cells. Binary Fission  Endospores This type occurs during unfavorable conditions such as environmental stress. Bacterial cell is converted from normal vegetative form to spore. Therefore they are resistant to temperature, radiation and chemical disinfectants. Endospore is a resistant form for bacteria. Endospores are found in soil, water, high temperature areas. They survive and live for a long time until the environment becomes good. This form is a static (not moving) bacteria.  Endospores Sporulation = Process of endospore formation within a vegetative (parent) cell. Germination = return of an endospore to its vegetative form. Endospore formation (sporulation) and Germination Sexual Reproduction in Eukaryotes  Sexual Reproduction This is the way of reproduction of multicellular organisms. In this type of reproduction, male and female gametes (ova and sperms) are required. The union of male and female gametes produces the new individual. Somatic cells Two types of cells in multicellular organisms Germ Cells Germ cells (gametes) Somatic cells (of the body)  Germ Cells Haploid cells (one set Fertilization Embryo of chromosomes) N  One set of Germ cells chromosomes N (Haploid) Somatic Cells All other cells Two sets of chromosomes except germ cells 2N (Diploid) Haploid and Diploid Cells 23 chromosomes N 23 Pairs of chromosomes 2N 23 chromosomes N  Questions TRUE or FALSE? Binary fission occurs during favorable conditions ( ) Robert Hooke is the scientist who started cell theory ( ) Eukaryotes have more complex structure than prokaryotes ( ) In prokaryotes, the nucleus is covered with nuclear membrane ( ) Rudolph Virchow is the scientist who completed cell theory ( ) Animal cells have membrane bound nucleus, so called prokaryotes ( ) Gametes are somatic cells ( )