Medical Microbiology Lec 1: Introduction to Microbiology PDF

Medical Microbiology Lec:1 Introduction to Microbiology  MSc: Zaineb Aziz Al-abbassi  Introduction  Every living organism falls into one of two groups: eukaryotes or prokaryotes. Cellular structure determines which group an organism belongs to. In this lecture, we will expl...

Medical Microbiology Lec:1 Introduction to Microbiology  MSc: Zaineb Aziz Al-abbassi  Introduction  Every living organism falls into one of two groups: eukaryotes or prokaryotes. Cellular structure determines which group an organism belongs to. In this lecture, we will explain in detail what prokaryotes and eukaryotes are and outline the differences between the two. Prokaryote definition  Prokaryotes are unicellular organisms that lack membrane-bound structures, the most noteworthy of which is the nucleus. Prokaryotic cells tend to be small, simple cells, measuring around 0.1-5 μm in diameter.  Prokaryotic cell features Nucleoid: A central region of the cell that contains its DNA. Ribosome: Ribosomes are responsible for protein synthesis. Cell wall: The cell wall provides structure and protection from the outside environment. Most bacteria have a rigid cell wall made from carbohydrates and proteins called peptidoglycans. Cell membrane: Every prokaryote has a cell membrane, also known as the plasma membrane, that separates the cell from the outside environment.  Prokaryotic cell features Capsule: Some bacteria have a layer of carbohydrates that surrounds the cell wall called the capsule. The capsule helps the bacterium attach to surfaces. Fimbriae: Fimbriae are thin, hair-like structures that help with cellular attachment. Pili: Pili are rod-shaped structures involved in multiple roles, including attachment and DNA transfer. Flagella: Flagella are thin, tail-like structures that assist in movement. Examples of prokaryotes  Bacteria  Viruses  mycoplasma Eukaryote definition  Eukaryotes are organisms whose cells have a nucleus and other organelles enclosed by a plasma membrane. Organelles are internal structures responsible for a variety of functions, such as energy production and protein synthesis.  Eukaryotic cells are large (around 10-100 μm) and complex. While most eukaryotes are multicellular organisms, there are some single-cell eukaryotes. Eukaryote cell Eukaryotic cell features Nucleus: The nucleus stores the genetic information in chromatin form. Nucleolus: Found inside of the nucleus, the nucleolus is the part of eukaryotic cells where ribosomal RNA is produced. Plasma membrane: The plasma membrane is a phospholipid bilayer that surrounds the entire cell and encompasses the organelles within. Cytoskeleton or cell wall: The cytoskeleton or cell wall provides structure, allows for cell movement, and plays a role in cell division. Eukaryotic cell features Ribosomes: Ribosomes are responsible for protein synthesis. Mitochondria: Mitochondria, also known as the powerhouses of the cell, are responsible for energy production. Cytoplasm: The cytoplasm is the region of the cell between the nuclear envelope and plasma membrane.  Eukaryotic cell features Cytosol: Cytosol is a gel-like substance within the cell that contains the organelles. Endoplasmic reticulum: The endoplasmic reticulum is an organelle dedicated to protein maturation and transportation. Vesicles and vacuoles: Vesicles and vacuoles are membrane- bound sacs involved in transportation and storage. Examples of eukaryotes  Animals  Plants  fungi  algae  protozoans Main differences between prokaryotic and eukaryotic cell Main similarity between prokaryotic and eukaryotic cell All cells, whether prokaryotic or eukaryotic, share these four features: 1. DNA 2. Plasma membrane 3. Cytoplasm 4. Ribosomes Cytosol is the liquid matrix found inside cells. It occurs in both eukaryotic (plant and animal) and prokaryotic (bacteria) cells. In eukaryotic cells, it includes the liquid enclosed within the cell membrane, but not the cell nucleus, organelles (e.g., chloroplasts, mitochondria, vacuoles), or fluid contained within organelles. In contrast, all of the liquid within a prokaryotic cell is cytoplasm, since prokaryotic cells lack organelles or a nucleus. The cytosol is also known as groundplasm, intracellular fluid (ICF), or cytoplasmic matrix.  The cytosol is a component of the cytoplasm. The cytoplasm includes the cytosol, all the organelles, and the liquid contents inside the organelles. The cytoplasm does not include the nucleus. The main component of cytosol is water. It also contains dissolved ions, small molecules, and proteins. Cytosol and cytoplasm are related, but the two terms are not usually interchangeable. The cytosol is a component of cytoplasm. The cytoplasm encompasses all of the material in the cell membrane, including the organelles, but excluding the nucleus. So, the liquid within mitochondria, chloroplasts, and vacuoles is part of the cytoplasm, but is not a component of the cytosol. In prokaryotic cells, the cytoplasm and the cytosol are the same.  Cytosol and cytoplasm are related, but the two terms are not usually interchangeable. The cytosol is a component of cytoplasm. The cytoplasm encompasses all of the material in the cell membrane, including the organelles, but excluding the nucleus. So, the liquid within mitochondria, chloroplasts, and vacuoles is part of the cytoplasm, but is not a component of the cytosol. In prokaryotic cells, the cytoplasm and the cytosol are the same. Cytosol Composition The cytosol consists of a variety of ions, small molecules, and macromolecules in water, however, this fluid is not a homogeneous solution. About 70% of the cytosol is water. In humans, its pH ranges between 7.0 and 7.4. The pH is higher when the cell is growing. Ions dissolved in the cytosol include K+, Na+, Cl-, Mg2+, Ca2+, and bicarbonate. It also contains amino acids, proteins, and molecules. Cytosol Functions The cytosol serves several functions within a cell. 1. It is involved in signal transduction between the cell membrane and the nucleus and organelles. 2. It transports metabolites from their production site to other parts of the cell. It is important for cytokinesis, when the cell divides in mitosis. 3. The cytosol plays a role in eukaryote metabolism. A. In animals, this includes glycolysis, gluconeogenesis, protein biosynthesis, and the pentose phosphate pathway. B. However, in plants, fatty acid synthesis occurs within chloroplasts, which are not part of the cytoplasm. C. Nearly all of a prokaryote's metabolism occurs in the cytosol.