Cell Structure

Nucleus, Organelles, and Cytoplasm The nucleus is an internal compartment that houses the cell’s DNA Organelles are other internal structures that carry out specific functions in the cell Cytoplasm is everything inside the cell membrane but outside the nucleus

Cilia are short, hair-like structures that protrude from cell surfaces Flagella and cilia can propel cells or they can move substances across a cell’s surface Cilia in lungs sweep mucus and debris away and in your ears they conduct sound vibrations Flagella and Cilia

Cytoskeleton The cytoskeleton is a web of protein fibers It holds the cell together and keeps cell membranes from collapsing Anchored to cell membrane It links one region to another Anchors nucleus and organelles to fixed locations 3 different kinds—microfilaments, microtubules, and intermediate filaments

Microfilaments Long and slender, made of actin Network beneath cell’s surface that is anchored to the membrane proteins Determines the shape of the cell

Microtubules Hollow tubes of tubulin Within the cytoskeleton, microtubules act as the highway for transportation of information from the nucleus out RNA/protein complexes are transported along the “tracks” of microtubules by motor proteins

Cell Membrane Cell membranes are made up of phospholipids, which are a phosphate group and two fatty acids Phospholipids are made up of a polar “head” and two nonpolar “tails” Phospholipids form a phospholipid bilayer

Cell Membrane Cell membranes have selective permeability The lipid bilayer allows lipids and substances that dissolve in lipids to pass through Membrane proteins are also part of the membrane—some are for transport

Cell Membrane There are several types of membrane proteins, including: – Marker proteins – Transport proteins – Enzymes – Receptor proteins Proteins move, because phospholipids are constantly in motion

Nucleus Houses most of the DNA, which controls the cell’s functions Surrounded by a double membrane, called the nuclear envelope or nuclear membrane The nuclear envelope is made of two lipid bilayers Why do you think that there are 2?

Nucleus Nuclear pores are small channels through the nuclear envelope What are the pores for? The nucleolus is an area of the nucleus where ribosomes are partially assembled Eukaryotic DNA is tightly wound around proteins, and appears as a dark mass under magnification most of the time

Ribosomes Made up of dozens of proteins and RNA Cells make proteins on ribosomes Some are suspended in the cytosol. These are “free” ribosomes. “Free” ribosomes make proteins that remain in the cell. Proteins that leave the cell are made on ribosomes on the surface of the endoplasmic reticulum

Endoplasmic Reticulum An extensive system of internal membranes that move proteins and other substances through the cell The membrane of ER is a lipid bilayer with embedded proteins

Rough Endoplasmic Reticulum The Rough ER has ribosomes attached – It helps transport proteins made on the attached ribosomes – The proteins enter the ER and a small, membrane-bound sac, or vesicle, pinches off – Proteins made on ribosomes on the rough ER stay separate from proteins made on free ribosomes

Smooth Endoplasmic Reticulum The Smooth Endoplasmic Reticulum lacks ribosomes, so it appears smooth under an electron microscope The smooth ER makes lipids and breaks down toxic substances

Golgi Apparatus A flattened, membrane- bound sac that serves as the packaging and distribution center of the cell Enzymes in the Golgi Apparatus modify proteins from the ER

Lysosomes Lysosomes are small, spherical organelles th at contain the cell’s digestive enzymes

Mitochondria Organelle that uses organic compounds to make ATP, the primary energy source of cells Cells with high energy requirements, like muscle cells, may contain hundreds or thousands or mitochondria

Mitochondria The mitochondria has two membranes – The outer membrane is smooth – The inner membrane is greatly folded, so that it has a lot of surface area – The two membranes form two compartments

Mitochondria The mitochondria also contain DNA and ribosomes, because they make some of their own proteins Most mitochondrial proteins are made in the cytosol

Organelles Only Found in Plants Plants have 3 unique organelles – Cell wall – Chloroplasts – Central vacuole

Cell Wall Plants’ cell membranes are surrounded by cell walls Plant cell walls are made of proteins and carbohydrates, including cellulose Helps support and protect the cells Connects cells to one another

Chloroplasts Chloroplasts are organelles that use light to make carbohydrates from CO 2 and H 2 O Found in algae as well as plants Surrounded by 2 membranes Contain their own DNA

Central Vacuole The central vacuole stores water It may contain ions, nutrients, and wastes It makes the cell rigid, when it is full Enables plants to stand upright

Let’s Review We use microscopes to look at cells that are too small to see with the naked eye The Cell Theory What is a cell? What do all cells share? Prokaryotes vs. Eukaryotes Nucleus, Organelles, and Cytoplasm, oh my! What separates plants from other eukaryotes?

The Cell CytoplasmRibosomes3. ER & Golgi apparatus 4.5. Support/ structure 6. Power Plants 1.2. contains Function as