1 Paramecium Human Cheek Cells OF THE Onion

1 Paramecium Human Cheek Cells. OF THE Onion Cells OVERVIEW CELL Biology 20

Before we could see cells. . 2 There had to be the microscope! Early lens makers (often physicists) allowed for the study of microbiology

The first people to see cells. . . 3 Robert Hooke - He was looking at cork and noted that he saw a “great many boxes” (1665). Anton van Leeuwenhock – observed living cells in pond water. He called these “animalcules”.

The first people to see cells. . . 4 Theodore Schwannobserved that the tissues of animals had cells (1839) Mattais Schleiden– observed that plants contained cells (1845) Rudolf Virchow – every living thing is made up of cells (1850)

The Cell Theory 5 1. 2. 3. Every living organism is made of one or more cells. The cell is the basic unit of structure and function. It is the smallest unit that can perform life functions. All cells arise from pre-existing cells.

Question for you. . . 6 Why is the Cell Theory called a Theory and not a Fact?

Main Points 7 All organisms are made up of cells. They can be: • • Unicellular (1 cell) OR multicellular (many cells) In unicellular organisms all life functions are carried out by a single cell. In multicellular organisms, cells specialise to perform specific functions – division of labour.

Cells as seen with a microscope 8 Living protoplasm surrounded by surface membrane (& non-living cell wall in plants). The living material between the nucleus and the cell surface membrane is known as cytoplasm. Cytoplasm contains variety of cell organelles.

Two main types of cells 9

Prokaryotic Cells 10 Very simple cells, probably first to inhabit the earth. Do not contain a membrane bound nucleus. Their nucleus material (DNA) lies free in a region known as nucleoid. Example: Bacteria. DNA of bacteria is circular.

Eukaryotic Cells 11 More advanced cells. Possess true nucleus and nucleus material are found inside the nucleus surrounded by the two membranes, i. e nucleus envelope. Example: plant cell, animal cell.

Eukaryotic Cells 12 4 main parts: • • cell membrane - outer boundary cytoplasm - jelly-like fluid interior nucleus - the "control center”, contains the cell's DNA (chromosomes) organelles - "little organs" that carry out cell functions

13 Organelles in Animal & Plant Cells Animal Cell Plant Cell

Diagram Cell Part Function Mitochondria Energy center or "powerhouse" of the cell. Turns food into useable energy Ribosomes Make protein Golgi Apparatus Processes, packages and secretes proteins. Like a factory. Lysosome Contains digestive enzymes, breaks things down Endoplasmic Reticulum Transport, "intracellular highway". Ribosomes are positioned along the rough ER, protein made by the ribosomes enter the ER for transport. Smooth ER - no ribosomes Rough ER - ribosomes 14

Diagram 15 Cell Part Function Nucleolus Located inside the nucleus, makes ribosomes Vacuole Stores water or other substances, plant cells contain a large central vacuole. Chloroplast Uses sunlight to create food, photosynthesis (only found in plant cells) Cell Wall Provides additional support (plant and bacteria cells) Microtubules Part of the cytoskeleton, function in support Also make up cilia and flagella (cell movement)

16 Differences in Animal & Plant Cells Found only in Animal Cells Lysosomes Found Only in Plant Cells Cell Wall Chloroplasts Chromoplasts/Amylopla sts

17 Prokaryotic versus Eukaryotic Cells Prokaryotic cell Eukaryotic cell Nucleus material are not enclosed by nuclear membrane Nucleus material are enclosed by nuclear membrane Contains few organelles Contains many organelles No membrane bounded organelles such as; chloroplast and mitochondria Has membrane bounded organelles DNA is circular and lies free in cytoplasm DNA is linear and enclosed in nucleus No mitosis or meiosis, divide by binary fission Mitosis and meiosis occur It contains 70 s ribosome (smaller) It contains 80 s ribosome (larger) Mainly unicellular Mainly multi-cellular