Cell Structure Organelles

Recall the Characteristics of Life All Living things share the following: –Cells –Organization –Energy use –Homeostasis –Growth/Development –Reproduction

Organization 2 levels: Molecular and Cellular Molecular: –Macromolecules are organized into structures called organelles. Organelles working together make up a cell. –4 macromolecules: proteins, carbohydrates, lipids, and nucleic acids Cellular: a multi-celled organism has cells grouped as a tissue, tissues into organs, etc.

Cells Cell Theory: –All living things are made of one or more cells. –Cells are the basic unit of life. The organelles in a cell can perform all of the functions for life. –Cells come from the reproduction of existing cells.

How is a single, tiny little cell able to do so much? Each organelle in the cell performs a specific function. –Organelles: small structures that carry out specific functions in a cell. Remember, all cells have –A cell membrane –DNA (genetic information) –Cytoplasm (contains the organelles) Only eukaryotic cells have a nucleus and other membrane-bound organelles.

Cell Membrane The cell membrane is the boundary between the inside of the cell and the external environment. Cells must acquire nutrients and get rid of wastes. The membrane controls traffic of substances into/out of the cell. Analogy: security guard or border control

Cell membrane vs. Cell Wall The cell membrane is mostly made of lipids (phospholipids) with some proteins as well. All cells have cell membranes, but only some cells (plant/bacteria) have cell walls. –The wall is rigid and helps support and protect the cell. –The cell wall is mainly made of cellulose, a complex carbohydrate.

Phospholipid bilayer

Cell Membrane “Quiz”: What cell is this?

Cell Wall Cell membrane

Cell Wall “Quiz”: What cells are these? These cells have a cell membrane, it’s just not visible next to the thicker cell wall.

The cytoplasm contains the organelles of a cell The cytoplasm is the region of the cell between the membrane and the nucleus. It consists of a gelatin-like fluid which “bathes” the organelles. –It is a solution with dissolved salts, minerals, etc. Region where most of the cell’s activities are carried out.

cytoplasm

Organelles provide compartments for specialized activities to occur Mitochondria (or mitochondrion) –Transfers energy from organic compounds (food) to ATP (a molecule that provides energy for the cell to do “work”). –Analogy: Power Plant- converts energy to a usable form. –Think of ATP as a cell’s “energy bank” –Structure: surrounded by 2 membranes; a smooth outer membrane and a folded inner membrane. The folds allow for a lot of space for chemical reactions to occur.

Mitochondrion “Membrane-bound” = found only in eukaryotes (plant and animal cells)

Ribosomes DNA contains the instructions that control growth and development of an organism. However, it is only like the blueprints for a new house. A contractor is needed to build the house according to the plans in the blueprint. Growth and development depends on the production of proteins. –Ribosomes make (synthesize) proteins Analogy: Construction workers.

Ribosomes

More on Ribosomes Structure: made up of proteins and RNA. –They are not membrane-bound so they are found in both prokayotic and eukaryotic cells. (i.e.: ALL cells) Some are attached to the endoplasmic reticulum; others float freely in the cytoplasm.

“Dots”

Endoplasmic Reticulum It’s an “intracellular highway”; molecules move from one part of the cell to another through the ER. Rough ER: studded with ribosomes; plays a role in protein synthesis. (connects to nuclear membrane) Smooth ER: synthesizes lipids, breaks down toxic substances. Structure: membranous tubules and sacs Analogy: factory; conveyor belts, machines, etc.

Endoplasmic Reticulum

Golgi Apparatus Works closely with the ER. It processes, packages, and helps release substances made by the cell (ex: proteins). –A protein made by a ribosome on the ER will be transported to the golgi where it is processed and given a “shipping label” before being secreted (released) from the cell. Analogy: shipping department, Post Office Structure: flattened membranous sacs- like pancakes.

Golgi Apparatus

Lysosomes Contain enzymes (a special type of protein) that digest (break down) molecules, old organelles, viruses, and bacteria. Analogy: garbage/waste disposal. Structure: spherical, single membrane –Note: rare in plant cells

Lysosomes

Cytoskeleton Provides support for the cell, may allow for movement of the cell or within the cell. Analogy: frame of a car/house. Made of microfilaments and microtubules; strands of protein. Not surrounded by membrane.

Cytoskeleton

Nucleus Besides the cytoplasm the nucleus is the other major region of a cell. Stores hereditary (genetic) information-DNA. It also synthesizes RNA. Analogy: county office that stores the original building blueprints. “Brain”, stores info and sends out messages. Inside the nucleus is an area called the nucleolus which is where ribosomes are made. Structure: surrounded by a double membrane = nuclear envelope. Membrane has pores that allow molecules to pass through.

Nucleus 4 = nucleolus 3 = nuclear membrane (with pores) 5 = chromatin (DNA)

Nucleus Nuclear membrane

Cilia and Flagella Both are extensions of the cell membrane; cylindrical in shape. Made of microtubules. They can be used to propel a single cell, or to move fluid or materials past cells. Cilia = short extensions, many per cell Flagella = long extensions, one or few per cell.

Flagella

Cilia _______________

Plant and Animal Cells have many organelles in common Plant Animal

Plant cells and Animal cells have some key differences A cell wall Vacuole : stores salts, minerals, nutrients, water, etc., may sequester harmful substances. Plays an important structural role for the plant Large compartment, surrounded by a membrane Analogy: Warehouse

Chloroplasts –A type of plastid –transfer energy from the sun to make organic compounds (food) –surrounded by double-membrane, contain chlorophyll (green pigment). –Analogy: solar panels

Chloroplast

Plant cell organelles