CELL.docx

**CELL THEORY, CELL STRUCTURES AND ITS FUNCTIONS** **Cell Discovery Timeline** - **1590: Zacharias Janssen,** a Dutch eyeglass maker, invented the very first **[MICROSCOPE].** It is an instrument used to magnify small objects - **1665:** While looking at a piece of cork under the micr...

**CELL THEORY, CELL STRUCTURES AND ITS FUNCTIONS** **Cell Discovery Timeline** - **1590: Zacharias Janssen,** a Dutch eyeglass maker, invented the very first **[MICROSCOPE].** It is an instrument used to magnify small objects - **1665:** While looking at a piece of cork under the microscope, **Robert Hooke** saw box-shaped structures that he called **[CELL].** It is the basic unit of structure and function in living things. - **1674:** **Anton van Leeuwenhoek** (Father of Microbiology), while looking at pond water under the microscope observed what he called **"animalcules".** - **1838:** **Matthias Schleiden**, German a botanist stated that **[PLANTS]** are made up of cells. - **1839: Theodor Schwann**, a German physiologist, concluded that **[ANIMALS]** are made up of cells. - **1855: Rudolf Virchow** stated that cells come from pre-existing cells through **CELL DIVISION.** **CELL THEORY** 1\. All living things are made up of cells. 2\. Cells are the basic unit of structure and function in an organism. 3\. Cells come from pre-existing cells. "Omnis cellula e cellula" -- Rudolf Virchow 4\. Cells carry genetic material which is passed from cell to cell during cell division. 5\. All cells are basically the same in structure and chemical composition. 6\. Energy flow (biochemical processes) occurs within cells. **CELL STRUCTURES** **Organelles** - literally means "little organs" - specialized structures found within the cell which performs specific functions vital to cellular life. **1. Cell Membrane (BOTH)** - structure: a thin, double layer of protein and fat - separates the inner contents of the cell with its environment - regulates the passage of materials in and out of the cell **2. Cell Wall (Plant cell)** - structure: a rigid membrane surrounding plant cells made up mostly of cellulose - function: gives the cell protection, support, and structure **3. Nucleus (BOTH)** - a membrane-bound spherical body discovered by **Robert Brown in 1831** - function: stores the cell's DNA - controls and regulates cell activities - controls the synthesis of ribosomes and proteins **4. Nucleolus (BOTH)** - structure: a spherical body found inside the nucleus - function: produces and assembles ribosomes **5. Ribosome (BOTH)** - structure: a large complex of protein and RNA - function: site of protein synthesis **6. Mitochondrion (BOTH)** - structure: a double-membraned, rod-shaped organelle - has its own DNA - function: produces chemical energy needed to power the cell in the form of ATP (adenosine triphosphate) **7. Endoplasmic Reticulum (BOTH)** - structure: a series of interconnected membranous sacs and tubules **7.1 Rough ER** - structure: with ribosomes attached to its surface - function: modifies proteins synthesized by ribosomes - makes phospholipids for cellular membranes **7.2 Smooth ER** - structure: no attached ribosomes - function: production of carbohydrates, lipids, and steroids - detoxification of drugs and toxins - storage of calcium ions **8. Golgi Body (BOTH)** - structure: a series of flattened, sac-like membranes that resembles a stack of pancakes - function: sort, tag, package and distribute lipids and proteins **9. Lysosome (ANIMALS)** - Structure: spherical bodies containing digestive enzymes - Function: digests cellular nutrients - Breaks down worn-out or damaged organelles - Aids in apoptosis (programmed cell death) **10. Chloroplast (PLANTS)** - Structure: a long, disc-shaped organelle containing the pigment chlorophyll - Function: site of photosynthesis **11. Vacuole (PLANTS)** - Structure: a large space within the cell that is enclosed in a membrane and filled with fluid - Function: maintains water balance - Maintains cell shape - Stores nutrients and waste products **12. Cytoskeleton (BOTH)** - Structure: a network of protein filaments or fibers - Types: microfilaments, microtubules and intermediate filaments - Function: provide shape and structure - Movement - Involved spindle formation during cell division **MAJOR TYPE OF CELLS** **PROKARYOTIC vs EUKARYOTIC CELLS** **Prokaryotes** - **"pro"-**before + **"karyon"** -- kernel or nut - Simple, unicellular organisms that **do not have a nucleus** and membrane-bound organelles - Most of it's DNA is found in the cytoplasm concentrated in a region that is known as **nucleoid region.** **Eukaryotes** - **"eu"**-good, well or true + **"karyon"** -- kernel or nut - Organisms whose **cell has a nucleus** enclosed by a membrane - Other organelles are also bound by membranes **CELL TYPES AND CELL MODIFICATIONS** atom \> molecules \> cell \> tissue \> organ \> organ systems **Four Main Types of Cells** **1. Epithelial Tissue** - is commonly seen outside the body as coverings or as linings of organs and cavities. Epithelial tissues are characterized by closely-joined cells with tight junctions - contributes to numerous body functions, including supporting organs and cells, transporting nutrients and wastes, defending against pathogens, storing fat, and repairing damaged tissues. These tissues are composed of the following: **BLOOD** ---made up of plasma; erythrocytes that carry oxygen (RBC), leukocytes for defense (WBC), and platelets for blood clotting. **CONNECTIVE TISSUE PROPER (CTP)---**made up of loose connective tissue that is found in the skin and fibrous connective tissue that is made up of collagenous fibers found in tendons and ligaments. **CARTILAGE** ---characterized by collagenous fibers embedded in chondroitin sulfate. Chondrocytes are the cells that secrete collagen and chondroitin sulfate. Cartilage functions as cushion between bones. **BONE** ---mineralized connective tissue made by bone-forming cells called osteoblasts which deposit collagen **3. Muscle Tissue** - are composed of long cells called muscle fibers that allow the body to move voluntary or involuntary. Movement of muscles is a response to signals coming from nerve cells. In vertebrates, these muscles can be categorized into the following: **skeletal**---striated; voluntary movements **cardiac**---striated with intercalated disk for synchronized heart contraction; involuntary **smooth**---not striated; involuntary **4. Nerve Tissue** - are composed of nerve cells called neurons and glial cells that function as support cells. - These neurons sense stimuli and transmit electrical signals throughout the animal body. Neurons connect to other neurons to send signals. - The dendrite is the part of the neuron that receives impulses from other neurons while the axon is the part where the impulse is transmitted to other neurons. **CELL SPECIALIZATION-** also known **as cell differentiation**- it is the process by which generic cells **change to different types of cells** to be able to perform special or specific functions. **Specialized cells in Animals** **1. Red blood Cell** - **Function:** Carry O2 throughout the body - **Adaptation:** No nucleus - Biconcave shape - Contains hemoglobin **2. White blood Cell** - **Function:** Plays an important role in the immune system - **Adaptation**: irregular shape - Can produce antibodies and antitoxin **3. Sperm Cell** - **Function:** fertilize an egg cell to make a baby - **Adaptation**: long tail to swim - Numerous mitochondria - With chemical on the head for egg cell entry **4. Egg Cell** - **Function:** carries genetic material - **Adaptation:** large and bulky - A chemical change in the membrane prevents fertilization of more than one sperm **5. Nerve cell or neuron** - Function: carry nerve impulses through the body - Adaptation: long, thin axon - Branching dendrites - Myelinated **6. Muscle cell** - Facilitate movement - Elongated and elastic - Numerous mitochondria **Specialized Cells in Plants** **1. Guard Cell** - **Function:** Regulates rate of transpiration - **Adaptation:** Cell wall has varying thickness **2. Root hair cell** - **Function:** absorbs water and minerals from the soil - **Adaptation:** long and thin with large surface area **3. Photosynthetic cells** - **Function:** produces food through the process of photosynthesis - **Adaptation:** contains numerous chloroplasts **4. Xylem vessel** - **Function:** transport water and minerals from the roots to other parts of the plant - Adaptation: has lignin - No protoplasm - Cells form a continuous tube **CELL MODIFICATION** - Adaptations or changes acquire by the cell after cell division that aids the cell in various beneficial ways. **1. CILIA** - Hair-like organelles extending from the cell surface - Types of cilia: - Non-motile or primary cilia (sensory) - Motile (movement) **2. FLAGELLA** - Long, whip-like, tail-like structures made of protein filaments - Aids in movement  **3. VILLI or MICROVILLI** - Small, slender, vascular, finger-like projections - Increases surface absorption **4. PSEUDOPODS** - "false feet" - Temporary extensive of the cytoplasm - Movement and ingestion (phagocytosis)