Cytology Part 1 PDF - Biology Past Paper

## BIOLOGY ### SEEK YOUR DREAM AND YOU WILL REACH IT ### CYTOLOGY - Part 1 **I. MOHAMMED WALID ELCANAI** * The science that studies the cell. **Definition of cell:** * Unit of composition and function in living organisms * The smallest unit of a living organism * The cell is linked to the d...

## BIOLOGY ### SEEK YOUR DREAM AND YOU WILL REACH IT ### CYTOLOGY - Part 1 **I. MOHAMMED WALID ELCANAI** * The science that studies the cell. **Definition of cell:** * Unit of composition and function in living organisms * The smallest unit of a living organism * The cell is linked to the discovery of the microscope which invented by (Antony Levinhock 1591). >> Levinhock improved microscope was able to see things that no man had ever seen before. >> He saw yeast, bacteria, blood cells and tiny animals swimming about a drop of water. * Cell Is basic building blocks of all organisms. * All living organisms are made of one cell (like bacteria) or many cells (like a human). * Cells vary in size. * Cells cannot be seen with naked eye, scientists use microscopes to study the cell. **Definition of microscope** * A microscope is an instrument that magnifies an object. * Most photographs of cells are taken with a microscope and these images can also be called micrographs. **Cell Theory:** * Botanist Matthias Schleiden * Zoologist Theodor Schwann * Were studying tissues and proposed the unified cell theory, which states that: * All living things are composed of one or more cells. * The cell is the basic unit of life. * New cells arise from existing cells. **Basic structures of the cell:** 1. Plasma (Cell) membrane: an outer covering that separates the cells interior from its surrounding environment. 2. Cytoplasm: it is jelly-like material. 3. DNA: the genetic material of the cell. 4. Ribosome: which synthesize proteins. **Main Types of the Cells:** **1. Prokaryotic:** * Simple cell * Like Bacteria & Archea (mostly unicellular organisms). * They lack nucleus & membranous organelles. * The DNA is found in the central part of the cell which is called Nucleoid. * All have cytoplasm & ribosomes (Small ribosome (70s) scattered in cytoplasm) * All have cell membrane. * Most prokaryotic have cell wall made up of peptidoglycan. **The cell wall is important for:** 1. Extra layer for protection 2. Help the cell maintain its shape. 3. Prevent dehydration. * Some have capsule made up of polysaccharide * The capsule act as: * Enable the cell to attach to the surfaces in its environment. * Some prokaryotic have flagella for locomotion. * Some prokaryotes have pili used for exchange genetic material (plasmid) during a type reproduction called Conjugation. **2. Eukaryotic:** * Complexed cell. * Like: animals, plants, fungi & protists * Have true nucleus & membranous organelles * Have several rod-shaped chromosomes * All have cytoplasm and large ribosome (80s) attached to endoplasmic reticulum. * All have cell membrane. * Plant cells have cell wall made up of cellulose. * Some have flagella for locomotion. | **Eukaryotic** | **Prokaryotic** | |---|---| | True nucleus | No true nucleus | | Have membranous bounded organelles such as mitochondria & endoplasmic reticulum | No membranous organelles | | Large ribosome (80s) attached to endoplasmic reticulum | Small ribosome (70s) scattered in cytoplasm | | Cell wall if present made up of cellulose | Cell wall containing peptidoglycans | | If present flagella (9+2) arrangement of microtubules | If present flagella are made of a single microtubule | | Cells are large (10-100mm) | Cells are small (0.3 - 5mm)|