Chapter 7 Explain the cell theory. Name the basic cell structures. Describe prokaryotes and eukaryotes.

What is the Cell Theory? Widely accepted explanation of the relationship between cells and living things. The cell theory states the following: All living things are composed of cells. Cells are the basic unit of structure and function in living things. All cells are produced from other cells.

Robert Hooke “Cells are the basic unit of structure and function in living things” In 1665, Hooke looked at a thin slice of cork through one of the first light microscopes. Hooke described the cork as being made of thousands of tiny chambers. Hooke called these chambers “cells” because they reminded him of the monastery’s tiny rooms which were called cells.

All living things are composed of cells

Rudolf Virchow “New cells are produced from existing cells” Studied cell reproduction

Cell Types Prokaryotes Organisms who’s cells LACK nuclei. REMEMBER: Pro has no nucleus Eukaryotes Organisms whose cells have nuclei (more advanced) REMEMBER: Eu do have a nucleus

Cell Structures and functions

Cell membrane Function – controls what enters and exits the cell; also provides protection and support for the cell. Structure – phospholipid bilayer (two layers of phospholipids with carbohydrate chains and protein channels). Selectively permeable barrier. Found in all cells Similar to the gates of a gated community, or a fence

Cell wall Structure – rigid structure made up mostly of cellulose fibers Function – to provide support and protection for the cell. Found only in plant, bacteria, and fungi cells Similar to gates of a gated community/fence

Nucleus Structure – has a nucleolus (where the making of proteins begins), chromatin (grainy mixture of DNA and protein), chromosomes (condensed chromatin) and nuclear envelope Function – controls most cell processes and contains the hereditary material DNA Found in eukaryotic cells, plant and animal cells Similar to the boss, city hall, library

Cytoplasm Structure – clear, thick, jellylike material inside the cell. Contains cytoskeleton fibers (microtubules and microfilaments) Function – supports, protects, and helps transport organelles inside the cell Found in all cells Similar to the interstates, highways, roads, and the support beams in buildings

Ribosomes Structure – small bodies free or attached to ER and made of protein and rRNA Function – synthesizes (assembles or makes) proteins Found in all cells Similar to a construction site

Endoplasmic Reticulum Structure – network of tubes or membranes; connected to nuclear envelope and cell membrane (rough has ribosomes/smooth doesn’t) Function – carries materials through cell and aids in making proteins, parts of the cell membrane. Found in all eukaryotic cells Similar to a factory

Golgi Apparatus Structure – stacks of flattened sacs Function – package and export proteins, modify proteins (attaches carbohydrates and lipids to proteins) made by the cells in the ER. Found in all eukaryotic cells Similar to a shipping company (UPS/Post Office)

Vacuoles Structure – fluid-filled sacs (the largest organelle in a plant cell) Function - store food, water, and waste Found in eukaryotic cells; plant cells have one large vacuole and animal cells have multiple small vacuoles. Similar to storage company or water tower

Chloroplasts Structure – green, oval containing chlorophyll; double membrane with inner membrane modified into sacs Function – uses solar energy to make food (glucose) and release oxygen. Found in plants and algae Similar to solar energy panels

Mitochondria Structure – peanut shaped, double membrane (outer is smooth and inner is folded) Function – breaks down glucose (food) molecules to release energy Found in all eukaryotic cells Similar to MLGW or other similar power company

Nuclear envelope Structure – flexible, selectively permeable, double membrane Function – controls movement of materials in/out of nucleus Found in all eukaryotic cells Similar to a gate/door

Lysosome Structure – small, round organelle with a single membrane Function – digests old cell parts; breaks down larger molecules into smaller molecules Found mostly in animal cells and only occasionally in plant cells Similar to a garbage/recycling company

Centrioles Structure - a cylinder of microtubule pairs; found in pairs near the nucleus Function – separates chromosome pairs during cell division Found only in animal cells

Transportation through the Cell Membrane Active transport moves substance against the concentration gradient (from low concentration to high concentration) Passive transport moves substances with the concentration gradient (from high concentration to low)

The Cell Membrane What are the main functions of the cell membrane? It regulates what enters and leaves the cell and provides protection and support What does it mean that a cell membrane has a “lipid bilayer”? It is composed of two “bi” layers of lipid molecules with protein molecules that help certain substances to enter or exit the cell. It also has carbohydrates that behave as identity markers (name tags).

What does it mean when a membrane is selectively permeable? The membrane will allow only certain materials to pass across the membrane.

Diffusion Diffusion is the movement of molecules from an area of high concentration (where there are many) to an area of low concentration (where there are few). This is a type of Passive transport since it does not require the input of additional energy.

Osmosis Osmosis is the diffusion of water molecules through a permeable membrane from an area of high concentration to an area of low concentration. Because it is the diffusion of water, it is also a type of passive transport.

Facilitated Diffusion During facilitated diffusion, the protein channels in the cell membrane help (facilitate) certain molecules like glucose (which can not simply diffuse) to pass through those protein channels into or out of the cell. Again, this is a type of diffusion, so it is also a type of passive transport (the movement of molecules is from areas of high concentration to low concentration)

Equilibrium When is equilibrium reached in a solution? – When the concentration of the solute is the same on both sides of the cell membrane or throughout a solution

Endocytosis Endocytosis is the process of taking material into the cell by enfolding of the cell membrane around large molecules, clumps of food, or even whole cells. This is a type of active transport because it requires the input of additional energy and the substance is moving against the concentration gradient (from an area of low concentration to high concentration).

Exocytosis During exocytosis, the membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell. Because this type of transport requires the cell to use energy and the substance is moving against the concentration gradient, exocytosis is a type of active transport.