Chapter 7 Biology

Cells What you will learn… 1. What is a cell? 2. Cell Theory 3. Cells Size 4. Two main cell categories: Prokaryotes and Eukaryotes 5. Prokaryote cell structures 6. Eukaryote cell structures: Plant and Animal

What is a cell? Cells are the basic units of life.

What is the Cell Theory? Collectively, the research of Schleiden, Schwann, and Virchow led to the formation of the Cell Theory: 1. All living things are made up of cells. 2. Cells are the basic units of structure and function in living things. 3. New cells are produced from existing cells.

Every cell must have… DNA Cytoplasm Cell Membrane Ribosomes

Cells are small! Cells are microscopic; they are visible only with light microscopes. Most of their size ranges from µm. They have to be able to carry materials from one side of the cell to the next in a short period of time. They must have a large enough surface area to be able to take in nutrients and oxygen and release waste quickly.

The surface-to-volume ratio must be large!

Two main categories of cells: Prokaryote: Cells that do not enclose their DNA in nuclei Eukaryote Cells that do enclose their DNA in nuclei

Prokaryotes small cells (about 1-10 µm) that do not have a nucleus and membrane-bound organelles Found in bacteria and archaebacteria

Prokaryotes Prokaryotic Cell Organelles: Nucleoid region – part of the prokaryotic cell where the DNA is found Cell membrane – innermost covering of the cell Cell wall – outside of cell membrane Capsule – outside of the cell wall, protective covering (not all bacteria have it)

Prokaryotes Flagella (sing. Flagellum) – long, whiplike structure that moves bacteria Pili – short, hair-like projection used to stick to other surfaces and for conjugation (exchange of genetic materials between bacteria) Cytoplasm – jelly-like fluid that dissolves substances and holds organelles Ribosomes – organelles that make proteins in the cytoplasm

Prokaryotes

Eukaryotes Protists, Fungi, Plants, and Animals Have nucleus and membrane-bound organelles Much larger and more complex than prokaryotic cells. Reproduce sexually and asexually

Eukaryotic organelles Nucleus Control center of cell; contains most of the cell’s DNA Nucleolus Location where ribosomes are synthesized Nuclear pore Allows RNA to move in and out of nucleus

Eukaryotic organelles Ribosomes Protein synthesis Rough ER Comprised of a network of tubes and flattened sacs; Continuous with plasma membrane and nuclear membrane Site of protein synthesis (consists of ribosomes) and used for transport

Eukaryotic organelles Smooth ER Synthesis of membrane lipids and detoxification of drugs Involved in transport. No ribosomes Golgi Apparatus Connected with rough ER; flattened disc-shaped sacs, stacked one on top of the other modification, storage, and packaging of proteins. “tags” proteins so they go to the correct destination.

Eukaryotic organelles Lysosomes (in animal cells and some protists) Digestion of nutrients, bacteria, and damaged organelles Vacuoles Large sac-like membrane that stores materials like water, salts, proteins, and carbohydrates. Large, single vacuole in plants; small, numerous vacuoles in animals.

Eukaryotic organelles Chloroplasts Conversion of light energy to chemical energy of sugars (site of photosynthesis) Bound by double membrane Mitochondria Conversion of chemical energy of food to chemical energy of ATP (site of cell respiration) “Power House” of cell Bound by double membrane

Mitochondria

Eukaryotic organelles Cytoskeleton Gives cells their shape and internal organization and helps in movement. Includes: Flagella- long, whip-like structure used for movement Cilia- short, hair-like structure used for movement Centrioles- type of microtubule only found in animal cells involved in cell division.

Eukaryotic organelles Cell membrane Regulates what goes in and out of the cell (we will study this more soon!) Cell wall Support, shape, and protect the cell. Found in plant cells only!