A Look at Cells the smallest unit of

A Look at Cells -the smallest unit of life that can carry out all the functions of a living organism -not discovered until the invention of the microscope

UNICELLULAR Some living organisms are unicellular, only made of only 1 cell; they are the smallest of all living organisms Ex. Some bacteria Many protists

Some living organisms are made of many cells. MULTICELLULAR Ex. Plants, Animals, Fungi

Shape is related to Function Blood Cell-hemocyte; round to move through vessels Nerve-neuron; long to carry message to spinal cord Muscle-for contraction and relaxation

Robert Hooke-1665 • Gave the cell its name • Cork from an oak tree

Anton van Leeuwenhoek-1670 • First “real” microscope • Living organisms in pond water protists bacteria

Robert Brown— 1840 • discovered the nucleus of a cell • Observed the epidermal cells of orchids and the anthers of Tradescantia http: //2 bnthewild. com/plants/H 299. htm © Peter v. Sengbusch - Impressum http: //www. orchidworks. com/orchids/sept 98/carol 044. htm

3 men established The Cell Theory • M. Schleiden 1838, botanist, “all plants are made of cells” • T. Schwann 1839, zoologist, “all animals/organisms are made of cells” • R. Virchow 1855, physician, “all new cells come from other cells” (biogenesis)

The Cell Theory 1. Cells are the basic units of all life 2. All organisms are made of 1 or more cells 3. All cells come from other cells

Basic Cell Structures Cell Membrane-phospholipid and proteins Cytoplasm-everything inside the cell except the nucleus/DNA Cytoskeleton-system of fibers DNA-the genetic material Ribosomes-proteins are made on these

Cell Membrane Function: Homeostasis 1. Controls what enters and leaves 2. Boundary separating the cell from its environment *Figure 11 & 12, p. 60 -61

Cell Membrane Structure: 1. Thin layer of lipids embedded with proteins 2. Semipermeable (a. k. a. selectively permeable) 3. 2 phospholipid layers called a bilayer 4. Hydrophilic (H 2 O loving) head 5. Hydrophobic (H 2 O fearing) tail

Cell Membrane

Cytoplasm Function: 1. Contains or “suspends” structures called organelles inside the cell 2. Structure: 3. Jelly like base, consisting mainly of water and organic compounds called the cytosol 4. Other structures within the cytoplasm vary 5. Contains the cytoskeleton

Cytoplasm

Cytoskeleton • Function-provides support and a place to “anchor” other structures • Structure-composed of protein fibers; 3 types: • actin fibers – contract and expand to give the cell its shape • microtubules – “highway system”; transport information from nucleus to parts of the cell • intermediate fibers – framework for ribosomes/enzymes to be organized for metabolic pathways

Cytoplasm showing Cytoskeleton

DNA • All cells contain DNA at some point in their life cycle • Structure-complementary strands in a double helix • Function-carries the genetic code • Replicates itself to pass the genetic code on to its daughter cells

DNA

Ribosomes • Structure-spheres composed of RNA and protein • Function-site of protein synthesis • Free ribosomes make proteins that remain inside the cell • Attached ribosomes make proteins that become part of the cell or are exported from the cell

These are free ribosomes (in the cytosol). Other ribosomes are attached to the ER

Ribosomes

Ribosomes

Typical Animal Cell

Typical Plant Cell

Nucleus Found ONLY in eukaryotes!!! Function: 1. Control headquarters for the cell (brain)

Nucleus Structure: • Found in the cytoplasm • Contains the genetic materialchromosomes- made of DNA & proteins • Surrounded by a double membranenuclear envelope/membrane • Inside is a nucleolus that makes ribosomes

Nucleus

Nucleus

Overview of Organelles Eukaryotic cells contain a variety of organelles other than the nucleus. These include: • Endoplasmic reticulum (ER) – transport system of tubes • Golgi – stacked sacs that package and distribute materials through the cell Vesicles – membrane-bound sacs for transport of proteins Vacuoles – tiny membrane-bound storage container

• Lysosomes – contain digestive enzymes, “suicide sacs” Mitochondria – function in the 2 nd part of cell respiration, taking the energy from small carbon compounds and storing it in ATP; have their own DNA “powerhouse of cell” Centrioles –a region for microtubule assembly once thought to function in cell division (animal cells only); part of the centrosome • Chloroplasts – type of plastid containing chlorophyll; functions in photosynthesis (plant cells and a few protists only) ; have their own DNA • Central vacuole (plant cells only) – large central structure for storing water and its solutes

Organelles—A Closer Look Nucleolus Location Within the nucleus Structure knot of chromatin Function Produces ribosomes

Endoplasmic Reticulum Rough Structure: Network of membranes near nucleus Contains ribosomes on surface Function: Transports proteins that were made by the attached ribosomes through the cell to the golgi.

Endoplasmic Reticulum Smooth Structure: Network of folded membranes throughout cell Contains no ribosomes on surface Function: Makes lipids and breaks down toxic substances.

Endoplasmic Reticulum

Golgi Apparatus Location In the cytoplasm Structure Closely stacked, flattened membrane sacs Function n Stores, packages, and transports products inside for use outside n Vesicles (a bit of the golgi pinches for transport of stored materials).

Lysosome (not found in plants) Structure. Saclike Contains digestive enzymes Function. Digests food particles Digests old organelles

Mitochondria (found in all eukaryotic cells) Structure. Oval Inside is a complex matrix of folded membranes to increase surface area. Function. Changes energy stored in food into a more useful form Energy storing molecule called adenosine triphosphate (ATP is formed)

Centrioles Location Animal cells only Structure 9 sets of 3 protein fibers. Function Aid in the division of chromosomes in mitosis.

Microtubules Location Throughout the cell’s structure Structure thick filaments made of protein Function • gives structure and shape to cells • Anchors organelles

Microfilaments Location throughout the cell structure Structure hollow, thin protein tubes Function allow for elasticity and movement within cells.

Vesicles Location inside or outside of the plasma/cell membrane Structure bits of membrane from the plasma membrane or the golgi apparatus Function Vesicles fuse with the cell membrane may be used to release or transport chemicals in or out of the cells. Exocytosis out of the cell Endocytosis into the cell

Vacuole Location cytoplasm Structure sac of fluid surrounded by a membrane Plants: Large in size Animals: small in size Function Sites of storage of water, ions and some nutrients. Plants: allows plants to maintain turgor pressure, holds water to prevent wilting. In plants, this is referred to as the Large Central Vacuole— animal cells do not have these, only small ones.

Chloroplast. Location Plant cells and some protists Structure Double phospholipid bilayer. Inner layer – Stacks = grana – Non stacked area = stroma Function • Capturing radiant energy and converting it to chemical energy. • Chlorophyll is the green pigment that traps the energy from the sun

Cell Wall Location surrounding Plant cells Structure contains polysaccharide cellulose Function • Provides structure and support for plant cells

Vesicles, Golgi, and ER are all involved in protein production in the cell. They are all found in both plant and animal cells. Mitochondria are found in both plant and animal cells. They are involved in cellular respiration

Centrioles are found only in animal cells. They were thought to be involved in cell division. Lysosomes contain digestive enzymes for breaking down toxins and worn out organelles, invading cells, or “food” for phages

Chloroplasts are found only in plant cells. They take in light energy and store it in carbohydrates during photosynthesis. Note the cell wall and central vacuole in this diagram of a plant cell. They are also found only in plant cells.

Flagella and Cilia Location outside of cells Structure • Cillia: short hair-like • Flagella long whip-like Function Locomotion = movement • Cilia: tiny, flutters of movement. • Flagella: one big wave motion will cause a large amount of movement

Some Cell Web Sites for Further Study • http: //sun. menloschool. org/~cweaver/cells/ • http: //www. enchantedlearning. com/subjects/biology/cells/ • http: //web. jjay. cuny. edu/~acarpi/NSC/13 -cells. htm • http: //www. borg. com/~lubehawk/cell. htm • http: //www. rkm. com. au/CELL/ • http: //www. rkm. com. au/BACTERIA/bacterial-cell. html • http: //www. emc. maricopa. edu/faculty/farabee/BIOB K/Bio. Book. CELL 2. html#Golgi%20 Apparatus%20 and% 20 Dictyosomes