StructuresandOrganelles Section 7.3

An internal skeleton supports the cell and enables movement.

The Cytoskeleton

Prior to 1970’s cytosol thought to be unorganized mix of organic molecules. Later found that cytosol was organized and protein fibers were identified.

Functions of The Cytoskeleton  Maintains cell shape  Allows organelles to move

Microtubules Hollow, protein cylinders Hollow, protein cylinders Maintain shape of cells Maintain shape of cells Tracks for vesicle and organelle movement Tracks for vesicle and organelle movement

Microfilaments Solid rods of protein (thinner than tubules) Solid rods of protein (thinner than tubules) Enable cell movement. Enable cell movement.

Flagella Flagella (L. flagello, whip)

Cilia Cilia (L. cilium, eyelash, hair) Short, usually numerous hair like projections that can move in an undulating fashion.

Flagella longer than cilia, usually fewer Flagella are whip-like projections Flagella move whip-like (e.g. Sperm cells), cilia move swimmer-like/oar- like Differences

No organelle or part works alone. The Cell as a Coordinated Unit

The Cell Builds a Diversity of Products Concept 6.4

Concept 6.4 Objectives Identify the role of the nucleus Describe how the function of ribosomes, the ER and the Golgi are related. Compare and contrast the functions of vacuoles and lysosomes. Summarize the path of cellular products through membranes.

Nuclear Envelope Double membrane Separates nucleoplasm from cytoplasm

The Nucleolus Dark-stained spherical body in nucleus where rRNA and proteins join to form ribosomal subunits.

protein Nuclear Pores (100 nm) ribosomal subunits

Ribosomes Cooridinate assembly of amino acids into polypeptide chains (i.e. protein synthesis).

Ribosomes Eukaryotic slightly larger than prokaryotic Composed of a large and a small subunit. Each subunit has its own mix of protein and rRNA.

Ribosomes

Endoplasmic Reticulum Main manufacturing and transport facility in the cell factory.

Rough ER is: Contiguous with the outer membrane of the nuclear envelope. Studded with ribosomes on the cytoplasm side.

Smooth ER Continuous with rough ER smooth No ribosomes (hence smooth)

Function of smooth ER 1.Synthetic processesPhospholipidsSteroids Fatty acids 2.Forms transport vesicles

Golgi Apparatus Delivery System Of the Cell Discovered in 1898 Named For Camillo Golgi

Golgi Apparatus Stack of 3-20 slightly curved saccules.

Golgi Apparatus Receives protein-filled vesicles that bud from the ER. Vesicles fuse with membrane of Golgi apparatus.

Golgi Apparatus Proteins modified as they pass through Move to outer face after modification. Vesicles form & move to different locations in cell

Vesicles Enzyme Storehouses

Lysosomes Intracellular digestion centers Produced by Golgi Membrane-enclosed vesicles Contains digestive enzymes (function best in acidic environment) Break down organelles

Vacuoles Large membranous sac Larger than vesicles Store substances Vacuoles in protozoans include digestive vacuoles and water- regulating contractile vacuoles.

Vacuoles In protozoans include digestive vacuoles and water-regulating contractile vacuoles.

Vacuoles Plant cell vacuoles (usually one or two) more prominent; water-filled and give support to cell. Plant vacuoles store water, sugars, salt, pigments, and toxic substances to protect plant from herbivores.

Chloroplasts & Mitochondra Energize Cells

Energy-related Organelles Mitochondria (Plants & animals) Chloroplasts (Plants)

General name for plant cell organelle Enclosed by a double membrane Contains a series of internal membranes and vesicles. Plastids

Chloroplasts “Packages” light energy from the sun (site for photosythesis). Double membraned organelle. Flattened sacs (thylakoids) piled into stacks of grana with a fluid-filled space around thylakoids called the stroma. Chlorophyll located with the thylakoid membrane.

Mitochondria “Unpacks” captured solar energy (cellular respiration). Double-membrane organelle ATP production occurs here. Found in all organisms except bacteria.