Chapter 7: Cell structure

Microscopes Magnification – increase of an object’s apparent size Total magnification – mag. of eyepiece x mag. of objective lens Ex: (10X) x (4X) = 40X Resolution (resolving power) – the distance needed to distinguish 2 points as separate Three types of microscopes: compound light, transmission electron, scanning electron

A.Base B.Pillar C.Arm D.Stage E.Slide F.Cover slip G.Stage clip H.Light source I.Low power objective lens J.High power objective lens K.Body tube L.Ocular (eyepiece) M.Coarse adjustment knob N.Fine adjustment knob O.Nosepiece P.Diaphragm

Compound light microscope: Specimen is enlarged as light passes through set of glass lenses Magnification – up to 2000X Resolving power – up to 200nm Can be used to view living specimens

Transmission electron microscope: Electrons passing through a specimen are brought into focus by a set of magnetic lenses Image is projected onto a fluorescent screen or photographic film; flat image Magnification – up to 200,000X Resolving power – 0.2nm Cannot be used to view living specimens

Scanning electron microscope: A narrow beam of electrons is scanned over the surface of the specimen, which is coated with a thin layer of metal Metal gives off secondary electrons, which are collected to produce a picture of the specimen on the screen Magnification – up to 100,000X Resolving power – 10 nm Cannot view living specimen; 3D image

Microscope images:

The Cellular Level of Organization Living things are made of cells. Living things may be unicellular or multicellular. Cell have different shapes & sizes based on jobs. Organelles – a structure that carries out specific activities inside the cell

First cells observed in 17 th century by Anton van Leeuwenhoek Term “cell” coined by Robert Hooke - observing cork cells, reminded him of cells (rooms) in a monastery. Observations by Matthias Schleiden, Theodor Schwann, and Rudolf Vichow contributed to the development of the cell theory.

The cell theory states: 1.All organisms are composed of one or more cells. 2.Cells are the basic unit of structure and function in organisms. 3.All cells come only from other cells.

Sizes of living things

Eukaryotic cells Have a nucleus that controls all cell activities. Contain many cell organelles that perform specific jobs. Organisms in the following kingdoms are eukaryotic: Protists, Fungus, Plants, and Animals

Plasma (cell) membrane – A Nucleus* Nuclear membrane – B Nuclear Pore – C Nucleolus – D Chromatin – E Cytoplasm* Cytosol – F Mitochondria – G Golgi apparatus – H Centriole – I Cytoskeleton* Microtubules – J Microfilaments – N Vacuole – K Lysosome – L Ribosome – O Endoplasmic reticulum* Rough ER – Q Smooth ER - P

Plasma (cell) membrane – A Cell wall – B Cytoplasm* Cytosol – C Vacuole – D Chloroplast – F Golgi apparatus – I Ribosome – J Endoplasmic reticulum* Rough ER – K Smooth ER – T Mitochondria Cytoskeleton* Microtubules – M Microfilaments – N Lysosome – O Nucleus* Nuclear membrane – R Nuclear pores – S Nucleolus (not shown) Chromatin (not shown)

Cell membrane (plasma membrane): Cell’s outer boundary Regulates what materials enter & leave cell

Cell wall: –Found in plant cells in addition to the plasma membrane. Cytoplasm – area between the nucleus and the plasma membrane –Contains all cell organelles and cytosol Cytosol - The fluid in-between the organelles

Structure of the Nucleus Nucleus: stores genetic information and controls cell activities Nucleus contains the following: Chromatin Nucleolus Nuclear envelope (nuclear membrane) Nuclear pores

Chromatin: DNA and protein Will coil to form chromosomes just before cell division Nucleolus: Darkened region in nucleus Makes ribosomes Nuclear membrane: surrounds the nucleus Nuclear pores: openings in nuclear membrane to allow proteins into the nucleus and rRNA out of the nucleus

Nucleus and nuclear membrane

Ribosomes Location where proteins are made Where ribosomes can be found: –alone in the cytoplasm –attached to the endoplasmic reticulum ER with ribosomes is called rough ER

Ribosomes on ER

Endoplasmic reticulum System of channels – helps transport materials around the cell. Rough ER - has ribosomes; site of protein synthesis Smooth ER - lacks ribosomes; packages proteins and sends them to the golgi apparatus

The endoplasmic reticulum

Golgi apparatus Often compared to stack of plates. Modifies, sorts, and packages proteins for distribution.

The Golgi apparatus

Vacuoles Stores substances in cell Much larger in plants than in animals – plants make own food and need to store it for times when they cannot make food Plant vacuoles are typically filled with fluid to give the cell added support

Lysosomes Produced by the Golgi apparatus. Contain enzymes. Involved in digestion (even digesting worn-out cell parts). When cells bring in food at plasma membrane, small vacuoles they are stored in fuse to lysosome and contents are digested

Chloroplasts – use solar energy to make sugars – photosynthesis; found in plants Mitochondria – break down sugars to produce energy (ATP) – cellular respiration; found in plants & animals

Chloroplast structure

Mitochondrion structure

Cytoskeleton Made up of microfilaments & microtubules Maintain cell shape Helps cell move Helps cell organize its parts Constantly changing

Centrioles Only in animal cells Roles in cell: Help with cell division Help with formation of cilia and flagella.

Cilia and flagella Cilia - small and numerous Flagella - large and single Involved in cell movement.

Plant vs. animal cells PlantAnimal Cell wallYesNo Plasma membrane Yes ChloroplastsYesNo CentriolesNoYes Vacuoles1 large central one Several small ones

Organisms can be any of the following: Unicellular organisms Multicellular Colonial Unicellular organisms Entire organism is 1 cell No specialization – 1 cell does all jobs for the organism Ex: some bacteria, protists and fungi Paramecium E.Coli bacteria

Multicellular organisms Organism is composed of more than 1 cell Cells are specialized – have distinct jobs; are dependent upon one another Ex: All plants & animals, most fungi & some protists LilyGiraffe MushroomUlva

Colonial organisms Cells live as a connected group, but do not depend on one another for survival Ex: Some bacteria, protists Volvox Slime molds Bacteria

Levels of cellular organization (in multicellular organisms): Cells  tissues  organs  organ systems Tissue – distinct group of cells that have similar structures and functions Ex. in plant: vascular tissue – helps carry nutrients to various parts of plant Ex. in animal: muscle tissue – helps in movement Cardiac muscle Vascular tissue

Organs – a collection of tissues that carry out a specific function in the body Ex. in plants: leaf (made of vascular tissue and other tissues that work together to trap sunlight and produce sugar) Ex. in animals: heart (made of muscle, nerve, and other tissues that work together to pump blood) LeafHeart

Organ systems – made up of various organs that carry out a major body function Ex. in plants – shoot system (consists of stems, leaves, and the vascular tissue that connects them) Ex. in animals – circulatory system (made up of the heart, blood vessels, and blood) Circulatory system Shoot system

Prokaryotes vs. eukaryotes ProkaryotesEukaryotes OrganismsBacteriaProtists, Fungus, Plants, & Animals NucleusNoYes Cell wall/membraneYes RibosomesYes Other organellesNoYes CytosolYes

ProkaryotesEukaryotes Cilia or flagella Yes DNASingle loop In cytoplasm In nucleus Cell specialization NoIf multicelled