Chapter 3 Key Terms 1 CiliaOrganelles CentriolesRibosome CelluloseLysosome NucleusVacuole Protein SynthesisMitochondrion AutolysisCentrosome ChromatinLamella LeucoplastChloroplast

ANATOMY & PHYSIOLOGY CHAPTER 3: CELL STRUCTURE 2

History of the Cell Theory  Cells were first observed near the middle of the 17 th century when the microscope was invented  Robert Hooke was the first to describe cells in 1665  Viewed cork cells under a microscope and called them cellulae (Latin for “small rooms”)  This is where we get the term cell 3

History of the Cell Theory  A few years later, Anton von Leeuwenhoek was the first to observe living cells  Viewed tiny organisms swimming around in what he thought was pure water  Called these organisms “animalcules”  It was not until 150 years later before cells became known as the building blocks of biological organization 4

History of the Cell Theory  1838 – Matthias Schleiden stated that all plants are composed of individual units called cells  1839 – Theodor Schwann stated that all animals are composed of individual units called cells 1. Cells are the basic units of organization in all organisms 2. All organisms are composed of 1 or more cells in which all life processes occur 3. Cells arise from preexisting cells through cell division 5

Cells  Eukaryotic cells: organelles are membrane bound  Prokaryotic cells: organelles are not bound by membrane  Basic composition of cells  Protoplasm  Cell membrane  Organelles  Protoplasm is an aqueous colloidal solution of carbs, proteins, lipids, nucleic acids, and inorganic salts surrounded by a cell membrane 6

Cells  Nucleoplasm  Protoplasm inside the nucleus  Cytoplasm  Protoplasm outside the nucleus  Most cells are too small to be seen by the unaided eye and are measured in microns (micrometers)  General characteristics can be seen using light microscopes  Electron microscopes are needed to study details of cells 7

Cell Membrane  Cell Membrane  Surrounds the cell  Often called the plasma membrane or the plasmalemma  Cell membrane is composed of a double phospholipid layer  Phospholipid heads are hydrophilic  Fatty acid tails are hydrophobic  This arrangement allows for easy passage of water molecules through cell membrane via osmosis 8

Cell Membrane  Proteins embedded in the phospholipid bilayer  Functions:  Transport channel for small dissolved ions  Enzymes for active transport of materials across concentration gradient – needs ATP to function  Receptor site for hormones to enter the cell  Cell identity markers  Cell adhesion to hold cells together  Structural supports attaching to cytoskeleton structures 9

Cell Membrane  Sodium-Potassium pump  Found in cell membranes like muscle and nerve cell membranes  Pumps sodium and potassium ions across cell membranes against the concentration gradient  Fluid Mosaic Model 10

Cells  Protoplasm outside the nucleus is called ________________?  Cytoplasm  Made up mostly of water  Contains vacuoles  Area within the cytoplasm surrounded by vacuolar membrane  Usually filled with a watery mixture, but can also contain stored food (food vacuole) and waste products of the cell (waste vacuole) 11

Nucleus  Surrounded by nuclear membrane (nuclear envelope)  Composed of 2 membranes  Inner membrane and outer membrane  Is the control center of the cell  Contains pores that allow transport of materials that from nucleoplasm that need access to cytoplasm  Nuclear membrane is same structure as cell membrane (fluid mosaic model) 12

Nucleus  Nucleoplasm contains DNA and RNA  Chromatin  Genetic material of cell  46 chromosomes/cell (except egg and sperm cells)  22 pairs of autosomes  1 pair of sex chromosomes  Fine, long threads = chromatin  Short, thick threads = chromosomes 13

Nucleus  Contains a nucleolus  Spherical particle in nucleoplasm that does not have membrane  Composed mostly of DNA, RNA, and proteins  Is the site of ribosomal synthesis and is involved in protein synthesis 14

Mitochondrion  Considered the powerhouse of the cell  Converts food (chemical energy) into ATP  Composed of two membranes  Cristae  Inner folds where cellular respiration occurs  Contains enzymes needed to burn glucose and generate ATP  Known as cellular respiration 15

Lysosome  Small bodies in cytoplasm that contain enzymes to break down cellular components 1. Aid food vacuoles in breaking down stored food 2. Maintenance and repair of cellular components 3. Autolysis  In old and weak cells, the lysosome will expel enzymes that destroy the cell 16

Endoplasmic Reticulum  Complex system of membranes that forms a collection of membrane-bound cavities  When these cavities are channel or sac-like, they are called cisternae  Attached to the outer nuclear membrane and connects to the cell membrane  Used to transport materials made by the cell 17

Rough ER  Also known as granular ER  Called rough because it has ribosomes attached to it  A site for protein synthesis because of the ribosomes  Cavities provide transport of these proteins 18

Smooth ER  Also called agranular ER  Attached to granular ER  Does not have attached ribosomes  Functions:  Synthesis of sex hormones  Manufacture and transportation of carbs and lipids  Accumulation of Ca ions 19

Golgi Apparatus  Also called Golgi Body/Golgi Complex  The point within the cell where compounds to be secreted by the cell are collected/concentrated 20

Ribosomes  Distributed throughout the cytoplasm and attached to granular ER  Not surrounded by a membrane  Composed of protein and RNA  Provides the support and enzymatic activity to link amino acids to form proteins (protein synthesis) 21

Protein Synthesis  Messenger RNA (mRNA) copies the code from DNA by transcription  Transcription occurs with assistance from RNA polymerase  Transfer RNA (tRNA) reads the code and collects amino acids from cytoplasm to place, in sequence, on the mRNA  This is called translation  Anticodon contains the 3 nitrogenous bases  Ribosome connects amino acids to create a polypeptide chain 22

Centrosome  Found only in animal cells  Aids in cell division  Centrosome contains 2 centrioles near the nuclear membrane  During cell division, centrioles move to opposite sides of cell and form spindle fibers that pull on chromosomes  Spindle fibers are made of protein called tubulin 23

Cilia and Flagella  Located on the surface of the cell  Flagella are usually longer than cilia and usually present alone or in pairs  Anatomically they are the same, but they perform different functions because of length 24

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