Chapter 7 Cytology-study of cells

Cell Theory Rudolf Virchow proposed idea #3 -that animal and plants cells were produced only by the division of existing cells. 1. All living things are composed of cells. 2. Cells are the smallest working units of living things. 3. All cells come from preexisting cells by cell division.

Important Cell Scientists Robert Hooke – credited with the discovery and naming of cells. Anton Van Leeuwenhoek – credited with being the inventor of the microscope and identifying “animalcules” or little pond organisms.

Important Cell Scientists Matthias Schleiden – Cell Theory: concluded cells make up every part of a plant Theodor Schwann - Cell Theory: discovered animals were also made entirely of cells Rudolf Virchow – Cell Theory: cells come only from existing cells

Tiny structures within the cell that have a function. Organelles Tiny structures within the cell that have a function.

Cell Wall Structure Rigid layer that surrounds the cell membrane of some cells. Function Supports and protects cell.

Cell Membrane Structure Function Fluid semi-permeable layer made mainly of phospholipids and proteins. Function Regulates what enters and leaves the cell. Offers some support and protection

Nucleus Structure Double membrane surrounding the chromosomes (DNA) and the nucleolus. Function Store the genetic information (DNA). Called the "Control Center" of the cell

Nucleolus Structure Dark, dense area enclosed in the nuclear membrane. Function Production of ribosomes and RNA.

Ribosomes Structure Tiny spheres made of RNA and protein. 2 types: (1) Free Ribosomes – floating freely in cytoplasm. (2) Bound Ribosomes – attached to ER Function Make Proteins – “The Protein-making Factory” Free ribosomes make proteins that will remain in the cell. Bound ribosomes make proteins that will leave the cell.

Mitochondria singular is Mitochondrion “The Powerhouse of the Cell” Structure Large structures that are surrounded by a double membrane. Contains folded membrane inside called cristae. Contains own DNA and ribosomes. Function Site of cellular respiration (energy production). Energy in food is converted into energy for use by the cell (ATP).

Chloroplasts Structure Surrounded by a double membrane, containing stacked thylakoid membranes. Contains own DNA. Function Site for photosynthesis. Light energy is converted into chemical energy of food.

Rough Endoplasmic Reticulum (Rough ER) Structure A network of interconnected membranes forming channels within the cell. Covered with bound ribosomes. Function Transportation System for proteins to exit the cell. Production of proteins by attached ribosomes.

Smooth Endoplasmic Reticulum Structure A network of interconnected membranes forming channels within the cell. Function Transportation System. Synthesis of lipids. Breaks down toxins. Regulation of Calcium levels.

Golgi apparatus Structure Stacks of membranous sacs. Function Involved in the secretion, packaging, and modifying of proteins.

Lysosome Structure Function A small, membrane bound organelle filled with digestive enzymes. Function Digestion of proteins, old organelles, food, dead cells, and other materials.

Vacuoles/Vesicles Structure Function Membrane surrounded "bags“ Small in animal cells. Large in plant cells. Function Storage of food, water, and other materials.

Cytosol and Cytoplasm Structure Functions Cytosol is a jelly-like substance that fills the cytoplasm, which is the region between the nuclear membrane and the cell membrane. Functions Cytosol gives internal support to cell. Cytosol contains many molecules such as enzymes/catalysts needed by cell for metabolism.

Cytoplasm & Cytosol

Cytoskeleton Structure Microfilaments and microtubules forming a network throughout the cytoplasm. Function Help support & suspend organelles. Maintain cell shape. Allow movement within cell – can serve as tracks that molecules can move along.

Cytoskeleton

Centrioles Structure Small, cylindrical parts of the cytoskeleton. Function Aid in Cell Division

All Cells Contain Cell Membrane Cytosol DNA Ribosomes

Prokaryotes Cells without a membrane-bound nucleus

Eukaryotes Cells with a membrane-bound nucleus.

Similarities 1. They both have DNA as their genetic material. 2. They both have cell membranes. 3. They both have ribosomes 4. They have similar basic metabolism or cell activities . 5. They both are amazingly diverse in the kinds and forms of cells there are.

Differences Prokaryotic cells are smaller and eukaryotic cells are larger. Eukaryotes have membrane-bound organelles, while prokaryotes do not. The DNA of prokaryotes floats freely around the cell; the DNA of eukaryotes is held within its nucleus. Eukaryotes have more organelles, which are also more complex than those of prokaryotes. Prokaryotic cells are found in kingdoms of bacteria. Eukaryotic cells are found in kingdoms of plants, animals, fungi, and protists.

Eukaryotic – defined nucleus Prokaryotic – genetic material spread out in thread-like filaments throughout the cell

Comparison Feature Animal Cell Plant Cell Centrioles Present None Cell Wall Chloroplast Vacuole Small Large Cell Size

Animal Cell

Plant Cell

Organelles work together The main job of the cell is to produce proteins and other molecules that will help the cell function. Some of those proteins remain in the cell, but some are shipped to other cells.

Processes Ribosomes are made in nucleolus. They exit the nucleus through nuclear pores, which are openings in the nuclear membrane. Some ribosomes float in cytosol - they are free ribosomes and will produce proteins that will remain in the cell. Some ribosomes attach to the ER. They are bound ribosomes, and will produce proteins that will leave the cell.

Processes Once proteins are produced, they will be transported through the rough ER. A piece of the ER membrane will pinch off containing the protein products. This is called a vesicle. The vesicle will travel to the Golgi apparatus, where it will fuse with the membrane of the Golgi. Once the vesicle fuses, the contents of the vesicle are modified and packaged so they are ready to leave the cell.

Processes After packaging, a piece of the Golgi membrane (vesicle) pinches off containing the modified products. The vesicle travels to the cell membrane and fuses with the cell membrane. Once the vesicle fuses, the contents of the vesicle are released outside the cell, where they can be transported to their destination.

Cell Membrane

Structure Phospholipid Bilayer Membrane Proteins Carbohydrates Hydrophilic (Water-Loving) Heads Hydrophobic (Water-Fearing) Tails Membrane Proteins For transport through membrane Carbohydrates Attached carbohydrates can hold cells together Viruses and chemical messages can attach to carbs too.

Movement of Molecules Passive Transport Active Transport No energy required Molecules move from high to low concentration. Active Transport Energy required Molecules move from low to high concentration.

Passive Transport Follows diffusion, which is the natural tendency of molecules to move from high to low concentration. Diffusion occurs freely for substances that are small, hydrophobic, and uncharged.

Passive Transport Diffusion requires proteins for molecules that are large, hydrophilic, or charged (ions). This is called facilitated diffusion. Water is polar (hydrophilic) and requires a protein channel to move across the membrane. Osmosis describes the facilitated diffusion of water through a semi-permeable membrane such as the cell membrane.

Osmosis Rule: Water moves via osmosis from hypotonic to hypertonic solutions. Hypertonic A solution that has more solute than another. Isotonic A solution that has the same amount of solute as another. Hypotonic A solution that has less solute than another.

Diffusion of dye in water

OSMOSIS IN RED BLOOD CELLS

Plant Cell OSMOSIS

Practice What is the solute? What is the solvent? If water can move through the bag, but salt cannot, which way will the water move? 90% Saltwater 98% Saltwater

Practice What is the solute? What is the solvent? If water can move through the bag, but salt cannot, which way will the water move? 4% Saltwater 2% Saltwater

Practice What is the solute? What is the solvent? If water can move through the bag, but sugar cannot, which way will the water move? 15% Sugarwater

Active Transport Cell Membrane Pumps Proteins in membrane that move molecules against concentration gradient. Movement of ions can result in the formation of electrochemical gradient. Electrochemical gradient can be used to do work or to transmit nerve impulses.

Active Transport Endocytosis – a condition of moving into the cell Movement of molecules into the cell through a vesicle or vacuole, created by the cell membrane. Phagocytosis – movement of large molecules such as food; “cell eating”. Pinocytosis – movement of small molecules such as water; “cell drinking”. Exocytosis- a condition of moving out of the cell; “exiting” Movement of molecules out of the cell through a vesicle that fuses with the cell membrane.