REVIEWER FOR EXAM IN Gen biology

• The cell was first discovered by the English scientist Robert Hooke in 1665, which can be found to be described in his book Micrographia (Small Drawings). Under a coarse compound microscope, he observed thin slices of bottle cork and discovered a multitude of tiny pores which he named as “cells”. This term originated from the Latin word cella, which means “a small room” like where monks lived in and cellulae, meaning the six-sided cell of a honeycomb. 
• Soon after Hooke did, Anton van Leeuwenhoek, a Dutch scientist, observed these cells using a microscope with improved lenses that can magnify objects almost 300-fold or 270x. Using this microscope, he saw motile objects and eventually named these “animalcules” which we know today as protozoa and other unicellular organisms like bacteria 
• In 1838, Matthias Jakob Schleiden, a German botanist, suggested that plants are made up of cells.  
• A year after, the German zoologist Theodor Schwann stated that along with plants, animals are also composed of cells
• In 1858, Rudolf Virchow, a German physician, concluded that cells come only from other cells
• These observations made by Schleiden, Schwann, and Virchow form the Cell Theory which is considered as one of the basic principles of biology. The theory has three important tenets:

  1. All living things are made up of one or more cells.

  2. Cells is the basic unit of life.

  3. All cells arise from pre-existing cells. 
• Cell wall - Thick outer layer made of cellulose and Helps in protecting the plasma  membrane Plays a vital role in supporting and protecting the cells
• Cell membrane - Double-layered, thin barrier surrounding the cell that Controls the entry and exit of certain substances
• Cytoplasm - Contains semi-fluid translucent substance known as cytosol that Protects the cell by keeping the cell organelles separate from each other Helps to keep the stability of the cell Site where many vital biochemical reactions take place
• Nucleus - Largest organelle Contains nearly all the cell’s genetic material that Control center of the cell Host for transcription, replication, and DNA
• Nuclear membrane -Bilayer membrane, separated by fluid, which contain nuclear pores Protects the nucleus Acts as a barrier between the nucleus and other organelles of the cell.
• Nucleolus -  Found inside the nucleus Produces the cell’s ribosomes
• Rough endoplasmic reticulum - has ribosomes on its outer surface that Transports proteins synthesized by ribosomes
• Smooth Endoplasmic Reticulum -does not have ribosomes on its

  Outer surface that Synthesizes lipids
• Golgi Apparatus/body - A stack of membrane-bound flattened sacs  Responsible for the modification of proteins received from the Endoplasmic Reticulum
• Lysosomes - embrane-bound spherical sacs Contain digestive enzymes used to break down materials Serves as the cell’s stomach
• Mitochondria -  Round double-membrane organelles  Inner membrane is folded inside to form cristae Responsible for Aerobic  Respiration producing adenosine triphosphate (ATP), the energy currency of the cell
• Chromosomes -  Made up of DNA and stored in the nucleus  Contain the instructions for traits and characteristics
• Chloroplast - Contain two fluid-separated membranes  Inner membrane is folded into a network of flattened sacs called thylakoids that are stacked into grana that is Responsible for photosynthesis
• Vesicles - Membrane-bound sacs Store and transports substances around the cell
• Vacuoles -  Essentially larger vesicles formed by the joining together of many vesicles . Function is  Storage vault of cells  Maintain turgor pressure in plant cells.
• Peroxisomes -  Organelles containing enzymes that produce hydrogen peroxide as a by- product  Break down fatty acids and detoxify alcohol in the liver  Convert the toxic hydrogen peroxide by- product into cell-friendly water.
• Ribosomes -  Small spherical organelles  Found on the RER, in the cytoplasm, in the mitochondria, and other places that  Translate genetic information in the form of mRNA into proteins
• The 3 basic parts of cell are the Dna, Cell membrane, and Cytoplasm.
• Bone cells (osteocytes) • Toughest body cells as they are bound together by calcium and phosphate
• Cartilage cells (chondrocytes) • Similar to bone cells but the surrounding material is loose and flexible; hence they are bendable • Present in external ears and in between large bones to ease movement
• Nerve cell Very long and have many branching at either ends • Specialized structures: a. Dendrites which receive electrical signal from another neuron b. Axons which transmit electrical signal to another neuron 
• Epithelial cells • Very simple cells that form covering layers of all the organs such as in skin, scalp, respiratory tract, buccal cavity surface, among others • Serve as barriers for pathogens, fluid loss, and mechanical injuries
• Muscle cells • Mostly long, large, and able to contract and relax allowing movements

  • Made up of a pair of special proteins known as

  actin and myosin which allow muscle contraction

  • Three types:

  a. Skeletal muscle cells are attached to long

  bones and assist in their movement.

  b. Cardiac muscle cells are responsible for

  heartbeats.

  c. Smooth muscle cells are present in stomach,

  intestine, and blood vessel walls. 
• Adipose cells • Fat cells; storage of fat • Seen in the soles, palms, and buttocks • Help reduce friction to the body
• Blood cells • Always motile and never stay in one place • Have limited lifespan • Never multiply to form new cells, but are formed from other cells

  Flow freely in the blood and never attached to one another • Three major types: 1. RBCs (erythrocytes) -Produced from bone marrow -  Contain hemoglobin to transport oxygen throughout the body 2. WBCs (leukocytes) - Fights pathogens and provide immunity 3. Platelets (thrombocytes) -  Helps in blood clotting to prevent excessive blood loss due to broken or damaged blood vessels 
• Sperm cells • Haploid cells which are only present in males after puberty • Have a flagellum (tail) which enables them to swim and move in the female uterus
• Oocytes • Haploid cells and present in adult female genital system after puberty until menopause
• Stem cells • Basic or parent cells which can differentiate into any cell
• 3 types of cell modification

  1. Basal
  2. Lateral
  3. Apical
• Cillia - hairlike structure
• Villi and microvilli - finger like structure
• Pseudopods - false feet
• Flagella - whiplike structure