CELL STRUCTURE & FUNCTION

CHAPTER 4 MISS COLABELLI

THE DISCOVERY OF CELLS

• All living things are made up of one or more cells• A cell is the smallest unit

that can carry out life processes

THE DISCOVERY OF CELLS

• Robert Hooke• English scientist that studied nature using a light

microscope• Looked at thin slices of cork from bark on a cork oak tree• Noted there were empty pores throughout the specimen

that resembled cells the monks would live in• Noticed other plant specimen had the same organization

of boxes

THE DISCOVERY OF CELLS

• Anton van Leeuwenhoek• First person to observe living cells• Made his own light microscope• Observed microorganisms such as algae

and protists

THE DISCOVERY OF CELLS

• The Cell Theory• A composition of understandings from different

scientists that all cells must go by1.All living things are composed of one or more cells2.Cells are the basic units of structure and function in

an organism3.Cells come only from the reproduction of pre-existing

cells

CELL DIVERSITY• Cell Size• Cells are limited by the relationship of their

outer surface area to its volume• As a cell grows, its volume increases much faster

than the surface area• Important to know because nutrients and wastes need

to move though the cell efficiently• A cell too large would take too long to diffuse these

materials and it can harm the cell• Most cells are better off being smaller and keeping their

surface area to volume ratio bigger

• Plasma Membrane• Cell’s outer boundary• Covers the cell’s surface and acts as a barrier

between inside and outside of the cell

• Cytoplasm• Area within the cell that contains the fluid,

cytoskeleton, and the organelles

• Nucleus• Membrane-bound area of the cell that contains

genetic information• Controls the function of the cell

TWO BASIC TYPES OF CELLSPROKARYOTE• Organisms that lack a

membrane-bound nucleus and membrane-bound organelles• General area of cell

where genetic information is located is called the nucleoid• Usually bacteria and

archaea

EUKARYOTE• Contain a

membrane-bound nucleus and organelles with membranes• Organelles carry out

functions for the cell• Usually plant and

animal cells

http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm

PLASMA MEMBRANE

• Membrane Lipids• Made of two layers of phospholipids

(phospholipid bilayer)

• Membrane Proteins• Specific proteins embedded in the lipid bilayer• These proteins help with transporting molecules

across the membrane and act as receptors • Send messages to the rest of the cell

INNER LIFE OF THE CELL

http://www.youtube.com/watch?v=B_zD3NxSsD8

NUCLEUS• Houses and protects the cell’s genetic information

• Contains instructions for the structure and function of the organism

• Before a cell divides, the DNA condenses to form chromosomes• Nuclear envelope

• Double membrane that surrounds the nucleus• Made of two phospholipid bilayers• Contains pores (holes) called nuclear pores for RNA and

other materials to enter and leave the nucleus

• Nucleolus• Dense area in the nucleus where DNA is concentrated• Where ribosomes are produced

MITOCHONDRIA• Organelles that transfer energy from organic

matter (foods) to ATP• ATP powers most of the cell’s chemical

reactions• Highly active organelles• Two layer of membrane• Outer membrane holds cytosol• Inner membrane has folds called cristae where

energy-harvesting chemical reactions take place

http://www.youtube.com/watch?v=Ju0HxI5GWTo

MITOCHONDRIA•Mitochondrial DNA• Have their own DNA and

reproduce on their own• Scientists think

mitochondria originated from prokaryotic cells and were incorporated into eukaryotic cells• Called the endosymbiotic

theoryhttp://www.sumanasinc.com/webcontent/animations/content/organelles.html

RIBOSOMES• Small, spherical organelles that are responsible for

synthesizing proteins• Do not have a membrane• Made of protein and RNA molecules• Synthesized in the nucleus• Made of two subunits • Some are free in the cytoplasm and some are

attached to another organelle called the endoplasmic reticulum

ENDOPLASMIC RETICULUM (ER)

• System of membranous tubes • Functions as a highway for molecules to

move throughout the cell• Two types of ER• Rough ER • Smooth ER

ROUGH ENDOPLASMIC RETICULUM• System of interconnected tubes covered with

ribosomes• Ribosomes make it look “rough”

• Area where some proteins are made

SMOOTH ENDOPLASMIC RETICULUM• Lacks ribosomes and looks smooth• Builds lipids like cholesterol and hormones

for the body• Helps detoxify drugs and poisons• Liver cells contain a high amount or smooth ER

cells • Long-term drug and alcohol users also increase

their smooth ER organelles in their cells

GOLGI APPARATUS

• System of flattened sacs• Sacs near the nucleus receive vesicles from

the ER that contain newly made proteins and lipids• Vesicles travels through the Golgi

• Golgi apparatus “stamps” the vesicles to where they need to travel to in the cell• Like address labels

VESICLES• Small sphere like sacs that are surrounded by a

single membrane• Lysosomes

• Vesicles that bud from the Golgi and contain enzymes that break down large molecules

• Also help break down cells when it is time for the cell to die

• Peroxisomes• Similar to lysosomes except contain different enzymes• Neutralize radicals and detoxify alcohol and drugs• Produce hydrogen peroxide as a product in their chemical

reactions

http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/microtubuletransport.swf

CYTOSKELETON

• Network of thin tubes and filaments that crisscross the cytosol• Give the cell its shape

• Like poles in a tent

• Internal tracks where items in the cell move around the cell• Three different types of tubes found in the

cytoskeleton• Microtubules• Microfilaments• Intermediate filaments

MICROTUBULES

• Hollow tubes made of protein called tubulin• Radiate outward from the center called centrosome

near the nucleus• Hold organelles in place• Maintain cell shape• Act as tracks to guide organelles and molecules as

they move within the cell

MICROFILAMENTS

• Smaller than microtubules• Long threads of bead like protein called actin• Contribute to cell movement• Crawling white blood cells• Muscle contraction

INTERMEDIATE FILAMENTS

• Rods that anchor the nucleus and organelles in place• Maintain internal shape of the nucleus• Make up most of the hair shaft

CILIA AND FLAGELLA

• Hair like structures that extend from the surface of the cell• Assist in movement• Cilia• Short and present in large numbers

• Flagella• Long extensions of the cell, usually one that

helps with the cell moving

CENTRIOLES

• Two short cylinders of microtubules at right angles to each other• Near the nuclear envelope• Occur only in animal cells• Organize microtubules of cytoskeleton during

cell division

PLANT CELLS• Most of the organelles and parts of the cell are in all

eukaryotic cells• Plants have three additional structures

• Cell wall• Central vacuole• Plastids

CELL WALL• Rigid layer that lies outside the cell’s plasma

membrane• This cell wall is composed of the

polysaccharide cellulose• Primary cell wall• On top of the plasma membrane• Can grow in one direction

• Secondary cell wall• Between the plasma membrane and the primary

cell wall• Does not grow

CENTRAL VACUOLE

• Reservoir that stores large amounts of water, enzymes, wastes, and other materials• Large, fluid filled organelle• May take up 90% of the cell’s volume• When there is a lot of water the

vacuole fills up • When there is little water the vacuole

deflates

PLASTIDS• Double membrane organelles and contain

their own DNA• Chloroplasts• Use light energy and water to make food and

oxygen• Used in photosynthesis

COMPARING CELLSPROKARYOTE• Lack a nucleus• No membrane-

bound organelles• Region called

nucleoid• Bacteria and

archaea

EUKARYOTE• Have a nucleus• Membrane-bound

organelles• Plant and animal cells

COMPARING CELLS

PLANT CELL• Cell wall• Large central vacuole• Contain plastids

ANIMAL CELL• No cell wall• No vacuole• Contain centrioles