Introduction to CellsIntroduction to Cells

Cells are the basic units of organisms

Cells can only be observed under microscope

Basic types of cells:

Animal Cell

Plant Cell Bacterial Cell

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Cell Structure and Cell Structure and FunctionFunction

Cells are a collection of living matter enclosed by a barrier that separates the cell from its surroundings

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Every Cell Contains:Every Cell Contains:• Membrane – thin layer of material that

serves as a covering or lining• Structure containing the cells genetic

material

Number of Cells

• Organisms may be:

• Unicellular – composed of one cell

• Multicellular- composed of many cells that may organize

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Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles

Eukaryotes include most other cells & have a nucleus and membrane-bound organelles

Cells May be Prokaryotic or Eukaryotic

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Prokaryotes•Genetic material is not contained in the nucleus

•Less complicated than eukaryotic cells

•Bacteria are examples of prokaryotes

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Eukaryotic Cell• Larger and more

complex than prokaryotes

• Plants, Animals, Fungi are eukaryotes

Contain 3 basic cell structures:

• Nucleus – contain genetic info

• Cell Membrane• Cytoplasm with

organelles

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NucleusNucleus• Nucleus – a large membrane-enclosed

structure that contains the cell’s genetic material in the form of DNA– Controls many of the cells activities

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Cell TheoryCell Theory• All living things are composed of cells.• Cells are the basic units of structure and

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

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Basic Structure of a Eukaryotic Cell

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Two Main Types of Eukaryotic Cells

Plant Cell

Animal Cell

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Plant Cell

Plant Cell

Nuclearenvelope

Ribosome(attached)

Ribosome(free)

Smooth endoplasmicreticulum

Nucleus

Rough endoplasmic reticulum

Nucleolus

Golgi apparatus

Mitochondrion

Cell wall

CellMembrane

Chloroplast

Vacuole

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Animal Cell

Centrioles

Nucleolus

Nucleus

Nuclearenvelope

Rough endoplasmic reticulum

Golgi apparatus

Smooth endoplasmicreticulum

Mitochondrion

CellMembrane

Ribosome(free)

Ribosome(attached)

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Organelles – “little Organelles – “little organs”organs”

Very small size

Can only be observed under a microscope

Have specific functions

Found throughout cytoplasm

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Nucleus• “The Control Center”• Contains nearly all the

cell’s DNA with the codes for the cells proteins and other molecules

• Surrounded by the nuclear envelope– Full of nuclear pores

• Chromatin – DNA and proteins spread throughout the nucleus

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Nucleus• Chromosomes –

condensed form of chromatin– Passes on from

one generation to the next

• Nucleolus – place where ribosomes are assembled

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Ribosomes• “Protein Factories”• Small particles of RNA and protein• Located in the cytoplasm• Organelle where proteins are

assembled• Ribosomes get codes for proteins from

nucleus

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Endoplasmic Reticulum• “Highway System

of the cell”• Internal

membrane system

• Transports- – Proteins– Other

macromolecules Two types:SmoothRough

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Smooth & Rough Endoplasmic Reticulum

Smooth ER lacks ribosomes & makes proteins USED In the cell

Rough ER has ribosomes on its surface & makes proteins to EXPORT

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Golgi Apparatus• “The Shippers of

the cell”• Closely stacked

membranes, resembles stacks of pancakes

• Modifies, sorts, and packages proteins from the ER for storage or secretion

• Sends proteins to their final destination

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Lysosomes• “Clean-up Crews”• Small organelles filled with enzymes• Breaks down lipids, carbohydrates, and proteins into

smaller molecules that can be reused by the cell• Also breaks down old organelles

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Mitochondria• Nickname: “The

Powerhouse”• Function: Energy formation• Breaks down food to make

ATP• ATP: is the major fuel for all

cell activities that require energy

• Two membranes – outer and inner

• Inherit mitochondria from mother

• Contains its own DNA

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Vacuole• Saclike structure• Stores materials

– Water, salts, proteins, carbohydrates

• Plants have a large central vacuole

• Single-celled organisms use a contractile vacuole to maintain homeostasis

Cell or Plasma Cell or Plasma MembraneMembrane

– Living layer– Controls the

movement of materials into and out of the cell

– Selectively permeable

Cell membrane

Cytoplasm of a CellCytoplasm of a Cell

Cytoplasm

Jelly-like substance enclosed by cell

membraneProvides a medium

for chemical reactions to take

place

Cytoskeleton

• Supporting framework of the cell

• Cytoskeleton = cell skeleton

• Many components• Microtubules /

microfilaments made of proteins.

• Move organelles w/in the cell.

Cytoskeleton Continued• Microtubules / Microfilaments make up

– Cilia – Flagella

•Used in cellular locomotion

Different kinds of animal Different kinds of animal cellscells

white blood cell

red blood cell

cheek cells

sperm

nerve cell

muscle cell

Amoeba

Paramecium

• Now let’s talk about structures only found in PLANT Cells!!

Section 7-2

Figure 7-5 Plant and Animal Cells

Go to Section:

Plant Cell

Cell Membrane

Vacuole

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Chloroplast• Organelles that

capture energy from sunlight and convert it into chemical energy– Photosynthesis

• Two membranes• Contains

pigment chlorophyll

Eukaryotic Cell Organelles and Function

Cell Wall– Function: provides

support and protection to the cell membrane

– Found outside the cell membrane in plant cells

Different kinds of plant Different kinds of plant cellscells

Onion Epidermal Cells

Root Hair Cell

root hair

Guard Cells

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Similarities between Similarities between plant cells and animal plant cells and animal

cellscellsBoth have a cell membrane surrounding the cytoplasm

Both have a nucleus

Both contain mitochondria

Differences between Differences between plant cells and animal plant cells and animal

cellscells Animal cells Plant

cells

Relatively smaller in size

Irregular shape

No cell wall

Relatively larger in size

Regular shape

Cell wall present

Differences between Plant Differences between Plant Cells and Animal CellsCells and Animal Cells

Animal cells Plant cells

Vacuole small or absent Large central vacuole

Glycogen as food storage starch as food storage

Nucleus at the center Nucleus near cell wall

Endosymbiont Hypothesis• Lynn Margulis U-Mass.

• Found that mitochondria / chloroplasts did not fit the roles of organelles.

• They had unusual properties.

3 properties of Mito / Cplasts

• Contain own DNA• Both surrounded by 2 membranes

– Most organelles only surrounded by one membrane.

• Both reproduce separately from the rest of the cell

Margulis’s Model• Both Mitochondria / Chloroplasts had ancestors that

were free-living organisms.• These formed endosymbiotic relationships with

other cells.• Over time offsprings of these organisms lost their

independence becoming organelles of larger cells.

Further Evidence• Studies of DNA in chloroplasts show that they are

much like the DNA prokaryotic cells.• Mitochondria / chloroplasts contain their own

ribosomes and make many of their own proteins.• These ribosomes are smaller / chemically different

from those in eukaryotic cells.• More closely resemble ribosomes in prokaryotic

cells.

Levels of organizationLevels of organization

•Cells are grouped together and work as a whole to perform special functions

• Known as “Cell Specialization”

TissueTissue•A group of similar cells to perform a particular function–Animals : epithelial tissue, muscular tissue

–Plants : vascular tissue, mesophyll

OrganOrgan•Different tissues group

together to carry out specialized functions–Heart : consists of muscles, nervous tissue and blood vessels

–Leaf : consists of epidermis, mesophyll and vascular tissue

The Structures of a Leaf (Plant Organ)

Chloroplast

Palisade Mesophyll Cell

Spongy Mesophyll Cell

Air Space

Stoma

The Structures of a Heart (Animal Organ)

Organ SystemOrgan System• Several organs and tissues work together

to carry out a particular set of functions in a co-ordinated way

– Human : digestive, respiratory, excretory, circulatory and reproductive systems

– Plant : root and shoot systems

Human Body SystemsHuman Body SystemsExamples of systems :Digestive SystemRespiratory SystemCirculatory SystemNervous SystemReproductive System

Examples of a Human Body System

Examples of a Human Body System

The Respiratory System

Levels of Levels of OrganizationOrganization

CELLS (muscle cells,nerve cells) TISSUES (muscle, epithelium) ORGANS (heart, lungs, stomach) SYSTEMS (circulatory system) ORGANISM (human)

It’s You!