Cells & Tissues Chapter 3 – Part I Cell Organelles Wakefield 2014

Cells Robert Hooke discovered the cell in the late 1600’s The smallest part of any living organism Contains all parts necessary to survive in changing environments

Macromolecule Structure Cells Made primarily of H, O, C, & N Though it also needs trace elements Contains about 60% water Extracellular and Interstitial Main solid consists mainly of proteins Macromolecule Structure Carbohydrate – C, H, O Protein – C, H, O, N Lipid – C, H, O, P Nucleic Acids – C, H, O, N Water – H, O

Cells Cells are very diverse Vary in length 2 micrometers to more than 3 feet Structure defines in function which are also very diverse

Prokaryotic Cells vs. Eukaryotic Cells All cells have generalized features: Cytosol – semi-liquid fluid in which organelles are suspended – found in both pro & eukaryotic cells Organelles – small organs of cell – most found only eukaryotic cells Plasma Membrane – double layer of phospholipids which surrounds cell – found in both pro & eukaryotic cells Inclusions – Non-functioning parts of cell

NUCLEUS – CONTROL CENTER Located near the center of the cell Found in both plants & animals Found only in eukaryotic cells Contains the organism’s genetic material The cell (and organism’s) “blueprint” DNA – Deoxyribonucleic Acid Chromatin Genes Chromosomes

NUCLEOLUS – 1 OR MORE SMALL BODIES IN CENTRAL AREA OF NUCLEUS Located near the center of nucleus Found in both plants & animals Found only in eukaryotic cells Site for ribosome production which will migrate to cytoplasm

NUCLEAR ENVELOPE – (aka) NUCLEAR MEMBRANE Located surrounding the nucleus Found in both plants & animals Found only in eukaryotic cells Consists of a double-layer selectively permeable membrane with relatively large pores (nuclear pores) Serves to protect the nucleus and determines what enters & leaves nucleus

CHROMATIN– DNA (when it is not dividing) Located inside the nucleus Found in both plants & animals Found only in both prokaryotic and eukaryotic cells – just not within a membrane bound nucleus Consists of DNA (Genetic Material) Appears as loose bumpy granular material scattered throughout the nucleus

CHROMOSOME – DNA (when it is dividing) Located inside the nucleus Found in both plants & animals Found only in both prokaryotic & eukaryotic cells Consists of DNA (Genetic Material) Appears as shortened thick structures resembling X’s or curved lines – condensed chromatin material

CHROMASOME – CONDENSED CHROMATIN / DNA

PLASMA MEMBRANE – (aka) CELL MEMBRANE Surrounds the outside of the cell’s cytoplasm Found in both plants & animals Found only in eukaryotic cells & prokaryotic cells Consists of phospholipid bi-layer Functions to determine what enters and leaves the cell – is selectively permeable – selects which materials can pass across the membrane

PLASMA MEMBRANE – (aka) CELL MEMBRANE Specializations – Microvilli – tiny fingerlike projections that greatly increase the cell’s surface area Enhances cell’s absorption ability Small intestines

PLASMA MEMBRANE – (aka) CELL MEMBRANE Specializations – Membrane Junctions – varies structurally Tight Junctions Impermeable Bind cells together like a zipper Desmosomes Anchoring junctions which prevent cells from tearing apart (i.e. – skin to skin or skin to muscle)

PLASMA MEMBRANE – (aka) CELL MEMBRANE Specializations – Membrane Junctions – varies structurally Gap Junctions Connects adjacent cells with tubular connexons which look like hollow cylinders Found in the heart, embryonic cells Functions mainly in cell to cell communication

CYTOPLASM – Located outside the nucleus and inside the plasma membrane Found in both plants & animals Found only in prokaryotic & eukaryotic cells Consists of 3 major elements Cytosol Organelles inclusions

CYTOPLASM – 3 major elements of cytoplasm Cytosol – semitransparent fluid which suspends the organelles Organelles – “little organs” of cell where all cell functioning occurs Inclusions – non-functioning units of the cell such as lipid droplets,, melanin (color pigment), etc.

MITOCHONDRIA – (aka) POWERHOUSE OF CELL In the cell’s cytoplasm Found in both plants & animals Found only in eukaryotic cells only Consists of a double layer membrane surrounding “sausage-like” structures which can move and wriggle about Functions to carry out the reactions which use O2 to break down food into cellular energy (ATP) Found most in metabolically busy cells such as the liver & muscle cells

RIBOSOME – cell’s protein factories In the cell’s cytoplasm – tiny dark bilobed bodies of protein Ribosomal RNA – (rRNA) Some float free but most are attached to the Rough Endoplasmic Reticulum Found in both plants & animals Found in eukaryotic cells as well as prokaryotic cells Not membrane bound in prokaryotic cells Functions synthesize proteins for cell

ENDOPLASMIC RETICULUM – (aka) ER In the cell’s cytoplasm Found in both plants & animals Found only in eukaryotic cells ONLY A “network” of tubules or “cisterns” Accounts for about ½ of cell’s membranes Functions to carry substances (primarily proteins) from 1 part of cell to another part of cell 2 forms – Rough ER & Smooth ER

ROUGH ENDOPLASMIC RETICULUM – (aka) ROUGH ER Studded with ribosomes Site of protein synthesis Abundant in cells that export protein products Pancreas – insulin & other digestive fluids

SMOOTHENDOPLASMIC RETICULUM – (aka) SMOOTH ER Plays no actual role in protein synthesis – Communicates with the Rough ER & functions in lipid metabolism Detoxifies drugs & pesticides Abundant in: Liver Testes – to produce testosterone

GOLGI APPARATUS – (aka) GOLGI BODY Located in the cytoplasm of cell Found in both plant & animal cells Found in Eukaryotic cells only Functions to modify, package and transport proteins 2 types – Transport Vesicles – modifies & packages proteins Secretory Vesicles – transports proteins from Golgi Apparatus to plasma membrane

LYSOSOME – (aka) cell’s demolition sites Located in the cytoplasm of cell Found in both plant & animal cells Found in Eukaryotic cells only Functions to breakdown other materials Contain powerful “digestive” enzymes “digest worn-out or non-usable” cells or cell parts Exocytosis – transporting materials out of cell Abundant in white blood cells “digest” bacteria & other foreign substances

PEROXISOME – Located in the cytoplasm of cell Found in both plant & animal cells Found in Eukaryotic cells only Contains powerful oxidase enzymes that use molecular O2 to detoxify harmful substances Functions to disarm free radicals – highly reactive chemicals Look like small lysosomes Abundant in the liver & kidneys

CYTOSKELETON – Located in the cytoplasm of cell Found in both plant & animal cells Functions to provide form & structure to cells Found in Eukaryotic cells only

CYTOSKELETON – Consists of 3 types of protein filaments Intermediate filaments – help form desmosomes to provide internal guy wires to resist pulling forces Microfilaments – such as actin & myosin – involved in cell motility and changes in cell shape (muscle cells) Microtubules – determine the overall shape of the cell and the distribution of organelles Important during cell division

CENTRIOLES – Located in the cytoplasm of cell Found in both plant & animal cells Found in Eukaryotic cells only Rod-shaped bodies that lie at right angles to each other Made up of fine microtubules and form the mitotic spindle during cell division Some have cilia and/or flagella

Cilia & Flagella – Cilia - Microtubules used to move materials around outside of cell Usually many of these small projections surrounding the cell or at least the exterior surface of a cell Flagella – responsible for motility of the cell as a whole Usually only one or a few and are long whip-like structures