Chapter 7-

Cell Structure & Function

I. Life is CellularA-The Discovery of the Cell• It was not until the _________ that

scientists began to use microscopes to observe organisms.

• In 1665 ____________used an early compound microscope to see tiny chambers in cork.He called these chambers cells after the tiny rooms in monasteries….we know these not to be empty now.

Mid-1500’sRobert Hooke

• About the same time in Holland________________used a single-lens microscope to look @ pond water,

Anton van Leeuwenhoek

• In 1838 Matthew Schleiden concluded plants were made of cells

• 1839 Theodore Schwann said all animals were made of cells

• 1855-Virchow said cells could only come from existing ones.

These 3 things compile_________________

– All living things composed of ___________– Cells are the basic units of

___________________of living things– New cells are produced from

______________________.

cellsStructure and function

Existing cells

B-Exploring the Cell

• Most microscopes use lens to magnify the image of a specimen with light or electrons

• _________________,which scans cells w/a laser beam can make 3-d images of cells

•Video technology make it possible to watch cell growth , division and development

Confocal light microscopy

• Light makes it difficult to visualize tiny structures because it scatters/______________________allow things like proteins to be visualized (things as much as 1000 x smaller can be visualized….TEMS allow you to see specimens cut into ultra thin slices

Electron microscopes

• With light microscopes stains need to often be used since most living cells are transparent-some stains are structure specific

• Some dyes show fluorescence dyes give off light of a ceratin color when viewed under specific wavelenghths

• May be able to track specific molecules

•W/ a ______________specimens do not have to be cut to see 3-D images….both must be placed into a vacuum so air molecules do not scatter electrons/TEM-shows details

•1990’s-____________________________have revolutionalized visualization of surfaces and atoms have been observed…can be used in ordinary air and can show DNA structure

SEMScanning probe microscopes

pollen

C .Prokaryotes and Eukaryotes

• Cells typically range from _________micrometers,but some bacteria are .2 and some amoeba are 1000 micrometers

• All cells have 2 things in common:»cell membrane-a barrier»@ some point they contain_______

5-50 micrometers DNA

2 broad categories:

– _____________________________-genetic material is NOT contained in a nucleus/generally less complicated than other cells/carry out all cell activities…present day members are ________________.

– Only organelles are ribosomes and they are NOT MEMBRANE BOUND

Prokaryotes bacteria

• _____________________________-contain a nucleus w/ genetic material,generally larger,much diversity

• HAVE all organelles/most membrane bound

• Include all organisms EXCEPT bacteria

Eukaryotes

Division of Labor

•A cell is made up of many parts with different functions that work together. Similarly, the parts of a computer work together to carry out different functions.•Working with a partner, answer the following questions.•1. What are some of the different parts of a computer? What are the functions of these computer parts?

•2. How do the functions of these computer parts correspond to the functions of certain cell parts?

Section 7-2

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Prokaryotes Eukaryotes

Cell membraneRibosomesCell wall

NucleusEndoplasmic reticulumGolgi apparatusLysosomesVacuolesMitochondriaCytoskeleton

Animal Cells Plant Cells

Lysosomes

Cell membraneRibosomesNucleusEndoplasmic reticulumGolgi apparatusVacuolesMitochondriaCytoskeleton

Cell Wall

Chloroplasts

Section 7-2

Venn Diagrams

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II. EUKARYOTIC CELL STRUCTURE

• Organelles

• 2 major parts of eukaryotic cells

Specialized structure that performs important functions within an eukaryotic cell. /”little organs”/

nucleus

cytoplasm

Cytoplasm is material inside membrane and outside nucleus

The Nucleus

• Contains nearly all the cell’s DNA• Codes for instructions to make proteins and

other molecules• Surrounded by nuclear envelope---has many

pores to allow material in and out• Contains chromatin—has DNA bound to

protein,usually spread throughout nucleus,but condenses during cell division to make CHROMOSOMES,containing genetic info

• Usually contain Nucleolus—assembly of ribosomes begin here.

Organelles That Store , Clean-up and Support

• Vacuoles

• Sac like structures that store water ,salts ,proteins, and carbs

• Plants may have a single large water filled vacuole

• Contractile vacuoles control water in paramecium

• VESICLES-store and move between organelles and cell surface

• Lysosomes• Small organelles filled w/enzymes• May digest or break down lipids,carbs,and

proteins into small molecules that can be used by the rest of the cell

• Lysosomes remove “junk”,or used up organelles…-very important that this aspect / function occurs

• May be in some/ very few plants

Cell membrane

Endoplasmicreticulum

Microtubule

Microfilament

Ribosomes Michondrion

Section 7-2

Figure 7-7 Cytoskeleton

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Cytoskeleton

• Network of protein filaments that help cell maintain shape

• Also involved in movement• MICROFILAMENTS are threadlike structures made of

a protein-actin….make a major network and a tough framework///allows amoebas and such to move

• MICROTUBULES-hallow structures made of proteins called tubulins—important in holding a cell’s shape----form a mitotic spindle in cell division/which helps separate chromosomes

• CENTRIOLES are microtubules near nucleus in animals and help organize cell division

• Microtubules also help make projections like cilia or flagella

• Arranged in “9+2” pattern of microtubules

ORGANELLES THAT BUILD PROTEINS

• Ribosomes :• Proteins are assembled here• Made out of small particles of RNA and protein• Found throughout cytoplasm• Coded instructions from nucleus tell how to

make proteins• Cells active in protein synthesis have a lot of

ribosomes

ER

• Endoplasmic Reticulum

• ER-Site where lipid components of cell membrane are assembled ,along w/ proteins and other materials exported from cell(those proteins are made there)

• Rough ER is involved in protein synthesis,because ribosomes are on it-finishes twisting and folding

• Smooth ER involved in lipid metabolism and detoxifying poisons

• Newly made proteins leave ribosomes and insert on rough ER ,where they may be modified

• If cell makes a lot of protein ,there is much ER• Smooth ER may contain many specialized enzymes

GOLGI BODY:

• proteins from rough ER go here in this stack of membranes/get “address tags” to package and export to correct place-bundled in vesicles

• Golgi modifies ,sorts , packages proteins and other materials from ER for storage or release from cell

ORGANELLES THAT CAPTURE AND RELEASE ENERGY

• ==Mitochondria and Chloroplasts• Most all eukaryotic cells contain

mitochondria that convert chemical energy stored in food into compounds convenient for cell to use

• Mitochondria have an outer and inner membranes

• In humans,nearly all mitochondria comes from ovum(egg cell)

• Chloroplasts

• Capture energy from sunlight and convert into chemical energy in photosynthesis

• Contain 2 membranes and chlorophyll

Organelle DNA

• Organelle DNA• In chloroplasts and mitochondria• Small DNA molecules• Maybe descendants of early prokaryotes• ----Endosymbiotic theory says these

prokaryotic ancestors developed a symbiotic relationship w/ early eukaryotes and resided within---evolving into mitochondria

•  

• All cells have a _____________________________and some have a cell wall

Cell membrane

A. Cell Membrane• Regulates what enters and leaves the cell and also provides

_____________________________.• Almost all cell membranes are made of a double layered sheet

called a ___________________________-flexible,yet strong barrier

• Cell membranes usually have a protein molecule imbedded in the bilayer w/ carbohydrate molecules attached

• Called a _________________model• Some of the proteins form channels or pumps to move material

across the membranes• Some of the carbs act as ____________________tags

Protection and support

Phospholipid bilayer

Fluid mosaic

Chemical id tags

B. Cell Walls• In plants,algae,fungi, and many prokaryotes• Lie _______________the cell membrane• Usually porous enough to let water,O2,CO2 and

certain other substances to pass through easily• Main function is support and protection• Usually made of fibers of ____________________-

produced in cell and secreted to surface• Mostly _____________________-tough carb fibers/to

withstand gravity

outside

Carbohydrate and protein

cellulose

C.Diffusion Through Cell Boundaries

• Every cell is in a liquid environment

• Cell membrane regulates the movement of cell materials from one side to the other

1.Measuring concentration

– Cytoplasm is a solution of various substances in water

• _____________of a solution is the mass of solute in given volume of solution---ie. Mass/volume…..If you have 15 g salt in 3 mL water,what is the concentration?------_______….If you have 24 g salt in 2mL water you would have 12 g/mL salt….Which solution is more concentrated?______________

concentration5g/mL

12 g/mL

Diffusion-Passive Transport-needs no energy moves WITH concentration gradient

– In a solution the particles move constantly,spreading out randomly….tending to move where more concentrated to an area less concentrated…This is called __________________.

– ____________________= concentration of a solute is the same throughout a system

– does not require energy because random movement

• if equilibrium is reached,particles keep moving across the membrane,still balancing concentration

isotonic

DIFFUSION

Cellmembrane

Higher Concentrationof Water

Lower Concentrationof Water

Water molecules

Sugar molecules

Section 7-3

Figure 7-17 Osmosis

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D. Osmosis

– Some molecules are too large or too strongly charged to make it across the lipid bilayer----thus impermeable to it

– Most membranes are selectively permeable– _____________________is the diffusion of water

across a selectively permeable membrane– water moves easily and will move to balance the

concentration of a solute,water moving from area of higher to lesser conc. For the WATER

– ____________________-same strength of a solute on both sides of a cell membrane

osmosis isotonic

– more concentrated side of solute is ____________________

– less concentrated side is____________________– Osmosis exerts a pressure known as

____________________________on the hypertonic side of a membrane….This could results in a cell bursting

– Bursting not so much a problem in larger organisms….tend to be in isotonic environments

• Osmotic pressure may not allow a plant or bacterial cell to burst , but could weaken the cell wall

hypertonic hypotonicOsmotic pressure

• Many cells have water channel proteins-aquaporins-allowing water to pass as they are lipid soluble

E.Facilitated Diffusion

» Some molecules,like glucose ,diffuse quickly across due to ________________________

» These allow only certain molecules to pass

» Since it is diffusion it does not require energy and still goes from area of higher to lower concentration

» Use channel proteins» Channel proteins provide a tunnel for the

substrate to pass across the membrane. Carrier proteins actually bind the substrate then change shape and deposit the substrate on the other side of the membrane

VESICULAR TRANSPORT_Endocytosis and

Exocytosis• Transports larger molecules and even clumps of

matter• ________________________is the process of

taking material inward by enfolding,or pockets• In endocytosis ,the pocket breaks loose from the

cell membrane and forms a vacuole…large molecules,food and even whole cells can be taken in this way

endocytosis

2 examples of endocytosis are

– ___________________-extensions of cytoplasm surround a particle and package it in a food vacuole,then the cell engulfs it ---This is how amoebas eat-----is a form of active transport

• _______________-Cells use this to take up liquids in the environment—tiny pockets filled w/ liquid form along the cell membrane and pinch off to form vacuoles

phagocytosispinocytosis

– ___________________________--releases large amounts from the cell by pinching off or a contractile vacuole as in paramecium---also active transport

exocytosis

Molecule tobe carried Low

Concentration

CellMembrane

HighConcentration

Moleculebeing carried

LowConcentration

CellMembrane

HighConcentration

Energy Energy

Section 7-3

Figure7-20 Active Transport

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A. Unicellular Organisms--Single-celled Organisms that do

all a living thing would----They dominate life on earth in

terms of numbers

IV. The Diversity of Cellular Life

B. Multicellular organisms

• Multicellular organisms– Made up of many cells– Depend on communication and cooperation between

specialized cells

---_______________-cells throughout organism can develop in

different ways to perform different tasks

Cell specialization

– 3 Types of cell junctions– 1) gap junctions-hallow tubes carry out

chemical communication-eg.heart tissue– 2)desmosomes-protein filaments create

elasticity between skin cells– 3)Tight junctions- adhere closely and are

more impermeable

• 1. Specialized animal cells– eg. Red blood cells equipped to carry

oxygen ;cells specialized to produce proteins produced in pancreas(have many ribosomes and rough ER);muscle cells have actin and myosin cytoskeleton elements for contraction

• 2. Specialized Plant cells• ______________________-are tiny openings on

underside of leaves and exchange gases• _____________________-regulate gaseous

exchanges in stomata,changing shape due to plant’s internal conditions

•  

stomata Guard cells

C. Levels of Organization

– 1. individual cells– 2. _____________________-group of similar cells w/

particular function– 3. ______________-group of tissues working

together– 4. ______________-group of organs working

together for particular function•  

tissueorgan Organ system

Muscle cell Smooth muscle tissue Stomach Digestive system

Section 7- 4

Levels of Organization

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