Part H: The Human Cell Organelles – page 58

Human cells are Eukaryotic Bacterial cells are prokaryotic, i.e: no nucleus. Eukaryotic cells have a nucleus and are larger and more complex. They also have membrane-bound organelles which have unique functions.

Eukaryotic Cell

Prokaryotic Cell

Cells and Organelles

Nucleus Stores and replicates the genetic information (DNA) of the cell. DNA + protein = chromosomes. Chromosomes are visible during cell division but the rest of the time, appear as a complex mixture called chromatin.

Endomembrane System Consists of the nuclear envelope (membrane surrounding the nucleus), endoplasmic reticulum, Golgi apparatus and vesicles. Acts as the transportation and product-processing section of the cell. A system of membrane-bound compartments that are either continuous (joined together) or connected by the movement of vesicles.

Endoplasmic Reticulum Two types: Rough and Smooth Rough ER: has ribosomes, transports and processes proteins. Smooth ER: no ribosomes, makes phospholipids.

Ribosomes Made of protein and RNA. Two subunits – large and small. They assemble proteins....more on this in Genetics. Can be attached to the ER or free in the cytoplasm.

Ribosome

Golgi Bodies Looks similar to the ER; a folded network of membranes. It receives and produces vesicles so it’s part of the endomembrane system. Molecules are received and packaged for delivery to other cell components.

Lysosomes Also part of the endomembrane system. Arises from the Golgi body. Contains over 40 enzymes. Enzymes “clean up” the cell; digest particles, cells, viruses, bacteria and old organelles. These enzymes work best at pH 5. Since the cytosol is pH 7.2, even if a lysosome breaks, the enzymes are unlikely to destroy healthy cell components due to the pH difference.

Lysosome

Peroxisomes Arise from the ER as well. Contain enzymes that produce hydrogen peroxide which is toxic to the cell. Another enzyme (catalase) converts hydrogen peroxide to water. They detoxify alcohol, form bile acid and break down fats. Liver cells contain many peroxisomes.

Vesicles and Vacuoles Vesicles are formed by pinching off the cell and organelle membranes. Therefore, they can also fuse with cell and organelle membranes. Animal cells contain many small vesicles. Plant cells contain a single, large vacuole instead which contains water, ions, sugars, amino acids and macromolecules. It also serves to determine turgor pressure depending on the amount of water contained within in.

Chloroplast Contain chlorophyll which allow photosynthesis to take place in plants. A thick liquid called stroma surrounds discs called thylakoids which form stacks called grana. The thylakoids contain the chlorophyll. Contains some of its own DNA.

Mitochondria Have a two-membrane system – inner and outer. Folds of the inner membrane are called cristae. Fluid-filled inner space is called the matrix. Contains some of its own DNA. Site of aerobic respiration. More on this organelle in the next unit!

Cell Wall and Cytoskeleton Cells of plants, fungi and many protists have a cell wall for support and protection. All cells have an internal network of protein fibres called the cytoskeleton. This provides structure and support to the cell and keeps the cell membrane and organelles in place. Fibres act like tracks for the movement of vesicles and organelles.

Protein Fibres 1. Microtubles – thickest fibres in the shape of hollow tubes that maintain shape, facilitate movement (flagella and cilia) and assist in cell division. 2. Intermediate filaments – fibres of intermediate thickness, coiled into cables that maintain shape and anchor organelles. 3. Microfilaments – thinnest fibres consisting of two strands of actin wound together that maintain shape, aid in muscle contraction and assist in cell division.

Game Time!!

Name that organelle!!

What was it? Ribosome What does it do? Makes proteins!!

What is it? Mitochondria! What does it do? Site of respiration – energy!!

What is it? Lysosome! What does it do? Its enzymes clean up the cell.

What is it? Endoplasmic Reticulum! What does it do? Rough transports and processes proteins, smooth makes phospholipids.

What is it? Golgi Body! What does it do? Processes molecules for use in other parts of the cell.

Homework http://www.microscopy.fsu.edu/cells/animalcell.html http://www.cellsalive.com/cells/cell_model.htm Questions: page 63: #1-6, page 67: #13-18