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Unit 3. The Cell’s Processes Unit 3, Part 1. 3.1 Objectives. Describe the discovery of cells and the development of the cell theory. Relate the properties of the cell membrane to its structure. A History of the Cell.
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Unit 3 The Cell’s Processes Unit 3, Part 1
3.1 Objectives • Describe the discovery of cells and the development of the cell theory. • Relate the properties of the cell membrane to its structure.
A History of the Cell • 1665 - Robert Hooke, using a primitive microscope, sees empty cubicles in a slice of cork and calls them cells. • Scheiden stated that all plants are composed of cells. • Schwann concluded that all animals are composed of cells. • Virchow discovered that a cell can only come from other cells.
The Cell Theory • All organisms are composed of one or more cells. • The cell is the basic unit of structure and function in organisms. • All cells are produced from other cells. This is called biogenesis, which means life comes from other living organisms.
The Plasma (Cell) Membrane • Each cell, whether an entire organism or a small part of an organism, lives in a fluid environment. This means they are in constant contact with fluids and liquids, and that the environment changes constantly. • Cells must obtain materials from and release substances into their environment. They do this through a plasma membrane.
Properties of the Plasma Membrane • The outer boundary of an animal cell. Plant cells are surrounded by an additional cell wall that animals don’t have. • Selective permeability - allows specific items to enter while keeping others out. • Composed of a lipid bi-layer.
Passive Transport • Passive transport is the movement of particles without the use of energy. Three examples of this are diffusion, osmosis, and facilitated diffusion. • Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
Osmosis • Osmosis is the movement of water in and out of cells across a selectively permeable membrane from an area of high concentration to an area of low concentration. • Hypertonic - when the solute conc. is high and water is low. • Hypotonic - when the solute conc. is low and water is high. • Isotonic - when the solute conc. and the water conc. are equal.
The top picture shows a diagram of a hypertonic solution. In this case, water would move out of the cell. • The bottom photo shows a hypotonic solution. In this case, water would move into the cell.
Facilitated Diffusion • Facilitated diffusion is the use of transport proteins to aid the passage of particles across the plasma membrane. • Channel proteins are proteins that extend through the bi-layer membrane and allow some molecules to pass through. • Carrier proteins change the shape of the molecule which enables it to then pass through the membrane.
Active Transport • The use of transport proteins and energy to move molecules across a membrane from low to high concentration, against a concentration gradient. • Active transport is often referred to as a pump.
Endocytosis and Exocytosis • Endocytosis is the process by which the plasma membrane engulfs substances that cannot pass through the membrane. • Phagocytosis - engulfing solid pieces of material. • Pinocytosis - engulfing liquid particles. • Exocytosis is the process that cells use to remove substances. • These can be either active or passive transport.
The top picture shows endocytosis, while the bottom photo shows exocytosis.
Homeostasis • The biological balance of constant self-regulating adjustment to changing conditions. • For example, fish seek deep water in the heat of the day, and shallow during the night. • The body shivers when cold to produce heat. • The body sweats when the body is warm to maintain a constant body temperature.
The Structure of Cells • The smallest cells are bacteria, which are about half a micrometer in width. The largest are nerve cells, which can be up to 3 meters long. • Single-celled, or unicellular, organisms are composed of only one single cell. Some bacteria, amoeba, some yeasts, and algaes are unicellular. • Many-celled, or multicellular, organisms are composed of many cells, often having many specialized cells with different functions.
Organization of Life • Cells are the basic building blocks of life. There are many types of cells, such as blood cells, nerve cells, bone cells, etc. • Cells join to form tissues. Cardiac tissue is one example. • Tissues join to form organs. Organs are things like the heart, brain, liver, etc. • Organs join to form organ systems. Organ systems include the cardiovascular system, the respiratory system, the digestive system, etc.
Cells and Cell Parts Unit 3, Part 2
Organization Within Cells • Cells are filled with a substance called cytoplasm. • Remember, cyto- means cell and -plas means form. • The cytoplasm gives the cell shape and also gives cellular components a place to live to carry out their processes. • The sum of all cellular processes is called metabolism.
Cell Parts • There are two categories of cells to address before digging into all the different parts. The first is eukaryotes - cells that have a nucleus. The other is prokaryotes - cells that do not contain a nucleus. Bacteria are prokaryotes, while most animals and plants are eukaryotes.
Cell Parts You Should Know • Nucleus - the body that controls the activities of the cell in general including activities of the components of the cytoplasm. This is where DNA is located. • Cytoplasm - the thick fluid-like substance between the nucleus of the cell and the cell membrane that serves as a matrix in which other cellular components are found. • Chromatin - a thread-like substance composed of protein and DNA found in the nucleus. • Golgi apparatus - these bodies modify, store, and concentrate secretions of the cell. • Nucleolus - a small body inside the nucleus used to store RNA.
Lysosome - found only in animal cells and filled with digestive enzymes, these bodies break down substances in the cell to their basic parts. They also aid in the removal of waste products from the cell. • Endoplasmic reticulum (rough and smooth) - a complex system of membranes in the cell which controls the passage of materials within the cytoplasm. The membrane connects the cell membrane with the nuclear membrane. Rough ER has ribosomes attached to it, while smooth ER does not.
Mitochondria - these are sites of respiration in the cell, liberating and storing the available energy from simple sugars so energy will be available for the cell’s activities. These contain their own ribosomes and DNA and are capable of reproducing themselves. • Microtubule - tubules observed using electron microscopy that are important in cell division and wall formation. • Microfilament - protein structures that act alone or with microtubules to produce cellular movement.
Vacuole - a space within the cell generally used by the cell for the storage of food, water, or waste until it is used or eliminated. In plants it also increases the available surface area for access to the raw materials needed for photosynthesis. • Chloroplast - found only in the photosynthetic cells of plants, these are responsible for the conversion of light energy to chemical energy and for using that energy to synthesize other compounds in the cell. Chloroplasts contain their own ribosomes and DNA and are capable of reproducing themselves. • Ribosome - these bodies, found free in the cytoplasm or distributed along the endoplasmic reticulum, are responsible for the synthesis of proteins within the cell.
Cell membrane - a membrane made up of protein, carbohydrates, and lipids which controls what enters and/or leaves the cell and provides support and protection for the cell. • Cell wall - a semirigid, porous structure found around each plant cell. The cell wall is composed primarily of cellulose but also contains other materials.
Plant Cells: Have a cell wall Contain chloroplasts Contain chromoplasts (give the plants other colors like red and gold) Have larger vacuoles Square or brick-like shape Animal Cells: Contain lysosomes Have more mitochondria Have more ER Rounded shape Differences
