Chapter 2 Cells

Comparing Cells Cells differ in size and shape depending on their function –Ex: nerve cell needs to communicate between places, so it is a long cell –Ex: a muscle cell can contract and change it’s shape Two cell types: Prokaryotic – lack membrane-bound internal structures Eukayrotic – contain membrane-bound internal structures

Cell Organization Cell wall –Tough, rigid outer coverings that protect the cell and give it shape –Made of cellulose –Only in plants, algae, fungi and most bacteria –“frame of a house” Cell Membrane –A protective layer around all cells –Inside the cell wall, if it is present –Allows food and gasses into the cell and waste products out of the cell –“the bouncer”

Cell Structures Cytoplasm –A gelatin-like substance inside the cell membrane –Medium for things to move about in the cell Cytoskeleton –Scaffolding-like structure in cytoplasm which helps cell keep its shape Organelles –Membrane bound structures inside eukaryotic cells that helps the cell perform life processes

Cell Structures Nucleus –Organelle that directs all cell activities –Contains instructions for everything a cell does (within the DNA) –“foreperson”

Cell Structures Chloroplasts –Organelles in plants and a few bacteria that help the organism make food –Photosynthesis occurs here Mitochondria –Organelles in all eukaryotes that release the energy from food and turn it into something the organism can use –“powerhouse”

Cell Structures Ribosomes –Organelles that make proteins –Produced in the nucleus Endoplasmic Reticulum (ER) –Series of folded membranes from the nucleus to the cell membrane –Moves materials around in a cell Two types of ER –Rough – ribosomes are attached –Smooth – no ribosomes attached Material movement and lipid processing

Cell Structures Golgi Bodies –Sort proteins and other cellular substances and package them into membrane-bound structures called vesicles –“post office” Vacuoles –Organelles that serve as temporary storage for materials Can be water, waste products, food, etc. –Vacuoles make up most of the volume of plant cells

Cell Structures Lysosomes –Organelles that contain digestive chemicals that help break down food molecules, cell wastes, and worn-out cell parts –“recycler”

From Cell to Organism Cell Tissues –Groups of similar cells working together on one job Ex: muscle tissue, nervous tissue Organ –Different types of tissues working together Ex: muscle, brain

From Cell to Organism Organ System –A group of organs working together on a particular function Ex: muscular system, nervous system Organism –All of organ systems working together to create a particular organism

Review Questions 1.Explain the important role of the nucleus in the life of a cell. 2.Compare and contrast the energy processing organelles. 3.Why are digestive enzymes in a cell enclosed in a membrane-bound organelle? 4.How are cells, tissues, organs and organ systems related? 5.How is the cell of a one-celled organism different from the cells in many-celled organisms? 6.What are some differences between plant and animal cell? 7.List 3 organelles and give their functions.

Early Microscopes Dutch reading glass maker put two lenses at ends of a tube (1500s) –Larger image Antonie van Leeuwenhoek (Dutch fabric merchant) –First simple microscope (p. 50 in book) –Could magnify up to 270 times

Modern Microscopes Use lenses to bend light A simple microscope has one lens while a compound microscope (what we have here) has mulitple lenses –Ex: one lens at 10x – 10 times bigger Two lenses at 10x – 100 times bigger Stereomicroscopes have two eyepieces, which create a three- dimensional image

Electron Microscopes Use a magnetic field inside a vacuum to bend electronic beams –Scanning Electron Microscope (SEM) bounce electrons off the sample to create a 3-D image –Transmission Electron Microscope (TEM) send electrons through a sample to see internally Either way, electons then end up on a screen to produce an image (kind of like older TVs)

Cell Theory 1665, Robert Hooke looked at cork under a microscope –Made of little boxes he named cells 1830s, Matthias Schleiden studied plant parts –Concluded all plants are made of cells

Cell Theory Theodor Schwann looked at animal cells –Concluded all animals are made up of cells Rudolf Virchow –Said that cells come from other cells that already exist

Cell Theory All organisms are made up of one or more cells The cell is the basic unit of organization in organisms All cells come from pre-existing cells

Review Questions 1.Explain why the invention of the microscope was important in the study of cells. 2.What is stated in the cell theory? 3.What is the difference between a simple microscope and a compound microscope? 4.What was Virchow’s contribution to the cell theory? 5.How do electron microscopes work? 6.Why would it be better to look at living cells rather than dead cells?

Cell Processes Passive Transport – the movement of substances through a cell membrane without the use of energy –Diffusion or Osmosis Active Transport – the movement of substances through the cell membrane using energy Endocytosis & Exocytosis – vesicles transport large materials into (endocytosis) and out of (exocytosis) the cell

Cell Processes Photosynthesis –The process plants and other organisms use to convert sunlight energy into chemical energy or sugars to be used as food Respiration –The process in which chemical reactions break down food molecules into simpler substances and release stored energy Fermentation –Cells that do not have enough oxygen for respiration use this process to release some of the stored energy in glucose molecules

Cell Processes Cell Division – process where one cell splits into two cells Mitosis – process in which the nucleus divides to form two identical nuclei –Four stages: Prophase, Metaphase, Anaphase, Telophase –Happens during growth of organism or during asexual reproduction Meiosis – process in which the nucleus divides to form cells with half the genetic material of the original –Eight Stages: Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II –Happens when an organism produces gametes (sex cells) for sexual reproduction

Review Questions 1.What is active transport? 2.What are the two main types of passive transport? 3.How do cells get large materials out? 4.What is photosynthesis? 5.What is respiration? 6.What is mitosis and when does it happen? 7.What is meiosis and when does it happen?