Ch. 7 – Cell Structure Ch. 7 – Cell Structure and Functionand Function

Life is CellularLife is Cellular

Levels of OrganizationLevels of Organization

The levels of organization in a The levels of organization in a multicellular organism are individual multicellular organism are individual cells, tissue, organs, and organ systems.cells, tissue, organs, and organ systems.Cells are an organisms basic unitCells are an organisms basic unitTissues are a group of cells working Tissues are a group of cells working

together. Example – muscle tissuetogether. Example – muscle tissueOrgans are a group of tissues working Organs are a group of tissues working

together. Example – the heart.together. Example – the heart.Organ systems are a group of organs Organ systems are a group of organs

working together. Example – the digestive working together. Example – the digestive system.system.

The Discovery of the CellThe Discovery of the Cell

Discovery of cells was possible with Discovery of cells was possible with the invention of the microscope.the invention of the microscope.

In 1665 Robert Hooke was the first to In 1665 Robert Hooke was the first to use a microscope to look at cork use a microscope to look at cork cells.cells.

He called the boxes that he saw He called the boxes that he saw cells.cells.

At the same time, Anton van At the same time, Anton van Leeuwenhoek was the first to look at Leeuwenhoek was the first to look at animals in pond water. He called animals in pond water. He called these animals “animalcules”.these animals “animalcules”.

Soon, numerous observations made Soon, numerous observations made it clear that cells were the basic unit it clear that cells were the basic unit of life, and the cell theory was of life, and the cell theory was developed.developed.The cell theory states:The cell theory states:

All living things are composed of cells.All living things are composed of cells.Cells are the basic units of structure and Cells are the basic units of structure and

function in living things.function in living things.New cells are produced from existing cells.New cells are produced from existing cells.

Exploring the CellExploring the Cell

Electron microscopesElectron microscopesCapable of revealing detail as much as Capable of revealing detail as much as

1000 times smaller than those visible 1000 times smaller than those visible with a light microscope.with a light microscope.

Two types:Two types:Transmission electron microscopes – cells Transmission electron microscopes – cells

and tissues must be sliced thin in order to and tissues must be sliced thin in order to be examined.be examined.

Scanning electron microscopes – specimens Scanning electron microscopes – specimens do not have to cut into thin slices.do not have to cut into thin slices.

TEMTEM SEMSEM

TEM images SEM imagesTEM images SEM images

Scanning Probe MicroscopesScanning Probe MicroscopesPower that is so precise, that a single Power that is so precise, that a single

atom can be observed.atom can be observed.

Prokaryotes and EukaryotesProkaryotes and Eukaryotes

Prokaryotic cells – Do not have a Prokaryotic cells – Do not have a nucleus.nucleus.They are generally smaller than They are generally smaller than

eukaryotes.eukaryotes.Bacteria are an example of a Bacteria are an example of a

prokaryote.prokaryote.

Eukaryotic cells- contain a nucleus in Eukaryotic cells- contain a nucleus in which their genetic material is which their genetic material is separated from the rest of the cell.separated from the rest of the cell.Some eukaryotes are unicellular like Some eukaryotes are unicellular like

protists.protists.Most eukaryotes are multicellular, Most eukaryotes are multicellular,

plants, animals, fungi.plants, animals, fungi.

Topic: Eukaryotic Cell Topic: Eukaryotic Cell StructureStructure

Chapter 7 section 2Chapter 7 section 2

EQ: What are the functions of EQ: What are the functions of each cell organelle?each cell organelle?

Comparing the Cell to a Comparing the Cell to a FactoryFactory

In some ways, the eukaryotic cell is In some ways, the eukaryotic cell is like a factory, it has many parts and like a factory, it has many parts and functions.functions.

Cell OrganellesCell Organelles

Organelle – means little organs, Organelle – means little organs, these are the main structures of the these are the main structures of the cell.cell.

Cytoplasm – is the portion of the cell Cytoplasm – is the portion of the cell that is outside the nucleus. It is what that is outside the nucleus. It is what other organelles float in, and what is other organelles float in, and what is used to transport messages between used to transport messages between other organelles.other organelles.

Nucleus – this is the control center of Nucleus – this is the control center of the cell.the cell.

The nucleus contains nearly all of the The nucleus contains nearly all of the cell’s DNA and with it the coded cell’s DNA and with it the coded instructions for making proteins and instructions for making proteins and other important molecules.other important molecules.The nucleus is surrounded by a nuclear The nucleus is surrounded by a nuclear

envelope. It is dotted with thousands of envelope. It is dotted with thousands of pores that allow material to move in and pores that allow material to move in and out.out.

The granular material in the nucleus is The granular material in the nucleus is called called chromatin.chromatin.

Chromatin consists of DNA bound to a Chromatin consists of DNA bound to a protein, and will condense to form protein, and will condense to form chromosomes.chromosomes.

The nucleus also contains a The nucleus also contains a nucleolus,nucleolus, which is where ribosomes are made.which is where ribosomes are made.

RibosomesRibosomesRibosomes – make and assemble Ribosomes – make and assemble

proteins.proteins.They get their instructions from the They get their instructions from the

nucleus, and are found either free nucleus, and are found either free floating in the cytoplasm or on top of floating in the cytoplasm or on top of the endoplasmic reticulum.the endoplasmic reticulum.

Endoplasmic reticulum – is the site Endoplasmic reticulum – is the site where lipid components of the cell where lipid components of the cell membrane are assembled, along with membrane are assembled, along with proteins and other materials that are proteins and other materials that are exported from the cell.exported from the cell.

Endoplasmic reticulum with ribosomes Endoplasmic reticulum with ribosomes on it is called rough ER. If it has no on it is called rough ER. If it has no ribosomes it is called smooth ER.ribosomes it is called smooth ER.

They are also involved in the They are also involved in the detoxification of drugs in the body.detoxification of drugs in the body.

Golgi apparatus or golgi body – the Golgi apparatus or golgi body – the function is to modify, sort, and function is to modify, sort, and package proteins and other material package proteins and other material from the endoplasmic reticulum for from the endoplasmic reticulum for storage in the cell or secretion storage in the cell or secretion outside the cell.outside the cell.

The golgi apparatus is kind of like the The golgi apparatus is kind of like the UPS of the cell.UPS of the cell.

Lysosomes – are small organelles Lysosomes – are small organelles filled with enzymes.filled with enzymes.

They break down lipids, They break down lipids, carbohydrates, and proteins that can carbohydrates, and proteins that can be used by the cells.be used by the cells.

They also break down dying They also break down dying organelles in the cell.organelles in the cell.

Vacuoles – store materials like water, Vacuoles – store materials like water, salts, proteins, and carbohydrates.salts, proteins, and carbohydrates.

Plants have huge vacuoles to store Plants have huge vacuoles to store water.water.

Mitochondria – are organelles that Mitochondria – are organelles that convert the chemical energy stored convert the chemical energy stored in food into compounds that are in food into compounds that are more convenient for the cell to use. more convenient for the cell to use. In other words they make ATP, or In other words they make ATP, or energy.energy.

They have two membranes and their They have two membranes and their own DNA.own DNA.

Chloroplasts – are only found in Chloroplasts – are only found in plants, and their job is to convert plants, and their job is to convert energy from sunlight into food during energy from sunlight into food during photosynthesis.photosynthesis.

They contain the pigment chlorophyll They contain the pigment chlorophyll which makes a plant green.which makes a plant green.

Cytoskeleton – A network of protein Cytoskeleton – A network of protein filaments that helps the cell to filaments that helps the cell to maintain its shape. The cytoskeleton maintain its shape. The cytoskeleton is also involved in movement.is also involved in movement.

The cytoskeleton is made up of The cytoskeleton is made up of microfilaments and microtubules.microfilaments and microtubules.

Cell BoundariesCell Boundaries

Chapter 7, section 3Chapter 7, section 3

Cell MembraneCell Membrane

The cell membrane regulates what The cell membrane regulates what enters and leaves the cell and also enters and leaves the cell and also provides protection and supportprovides protection and support

The cell membrane is made up of a The cell membrane is made up of a phospholipid bilayer.phospholipid bilayer.Meaning that the cell membrane has Meaning that the cell membrane has

two layers.two layers.

Cell WallsCell Walls

Cell walls are present in plants, algae, Cell walls are present in plants, algae, and fungi.and fungi.

Cell walls lie outside of the cell Cell walls lie outside of the cell membrane.membrane.

The main function of the cell wall is to The main function of the cell wall is to provide support and protection for the provide support and protection for the cell.cell.

Cell walls are made up cellulose, Cell walls are made up cellulose, which is what your paper is made of.which is what your paper is made of.

Diffusion Through Cell Diffusion Through Cell BoundariesBoundaries

Diffusion – when materials pass from Diffusion – when materials pass from an area of high concentration to an an area of high concentration to an area of low concentration, until the area of low concentration, until the system has reached equilibrium.system has reached equilibrium.

Because diffusion depends upon Because diffusion depends upon random particle movements, random particle movements, substances diffuse across substances diffuse across membranes with-out requiring the membranes with-out requiring the cell to use energy.cell to use energy.

OsmosisOsmosis

Osmosis – is the diffusion of water Osmosis – is the diffusion of water through a selectively permeable through a selectively permeable membrane, or semipermeable membrane, or semipermeable membranes.membranes.Selective permeability means that some Selective permeability means that some

but not all substances can pass through but not all substances can pass through the cell membrane, some require energy the cell membrane, some require energy to get through the membrane. Osmosis to get through the membrane. Osmosis and diffusion do not require energy.and diffusion do not require energy.

How osmosis works-How osmosis works-Some solutions are isotonic meaning Some solutions are isotonic meaning

that they have equal parts.that they have equal parts.Some are hypertonic meaning they have Some are hypertonic meaning they have

more solute than solvent.more solute than solvent.Some are hypotonic meaning they have Some are hypotonic meaning they have

more solvent than solute.more solvent than solute.REMEMBER OSMOSIS IS WATER MOVING REMEMBER OSMOSIS IS WATER MOVING

FROM AN AREA OF HIGH CONCENTRATION FROM AN AREA OF HIGH CONCENTRATION TO AN AREA OF LOW CONCENTRATION.TO AN AREA OF LOW CONCENTRATION.

Facilitated DiffusionFacilitated Diffusion

Facilitated diffusion – is the Facilitated diffusion – is the movement of specific molecules movement of specific molecules across cell membranes through across cell membranes through protein channels. Like sugar. protein channels. Like sugar. Requires no energy.Requires no energy.

Active TransportActive Transport

Sometimes cells need to move Sometimes cells need to move substances from areas of low substances from areas of low concentration to areas of high concentration to areas of high concentration.concentration.

How cells do this is through active How cells do this is through active transport. This requires energy.transport. This requires energy.

Sometimes the transport of larger Sometimes the transport of larger materials involves changes in the materials involves changes in the shape of the cell membrane.shape of the cell membrane.

Types of active transport –Types of active transport – Endocytosis – is the process of taking material Endocytosis – is the process of taking material

into the cell by means of infoldings, or pockets, into the cell by means of infoldings, or pockets, of the cell membrane. Two types of of the cell membrane. Two types of endocytosis are:endocytosis are:

Phagocytosis – extensions of cytoplasm surround a Phagocytosis – extensions of cytoplasm surround a particle and package it within a food vacuole. The particle and package it within a food vacuole. The cell then engulfs it. cell then engulfs it.

Pinocytosis – process by which a cell takes in liquid Pinocytosis – process by which a cell takes in liquid from the surrounding environment.from the surrounding environment.

Exocytosis – the forcing of material out of a Exocytosis – the forcing of material out of a cell.cell.

The Diversity of Cellular The Diversity of Cellular LifeLife

Unicellular OrganismsUnicellular Organisms

A single celled organism is also A single celled organism is also called a unicellular organismcalled a unicellular organism

In terms of numbers, Unicellular In terms of numbers, Unicellular organisms dominate life on earth.organisms dominate life on earth.

Example - yeastExample - yeast

Multicellular OrganismsMulticellular Organisms

Some organisms (like yourself) are Some organisms (like yourself) are made up of many cells.made up of many cells.

Cells throughout a multicellular Cells throughout a multicellular organism can develop in different organism can develop in different ways to perform different tasks. This ways to perform different tasks. This is called is called cell specialization.cell specialization.

Animal and plant cells are specialized Animal and plant cells are specialized in many ways.in many ways.

They can transport oxygen, make They can transport oxygen, make proteins, store food, and digest food.proteins, store food, and digest food.

They also help organisms to moveThey also help organisms to movePlant cells help it to make food, and Plant cells help it to make food, and

get rid of oxygen.get rid of oxygen.