cell structure & function professor andrea garrison biology 11 illustrations ©2010 pearson...

CELL STRUCTURE & FUNCTION

Professor Andrea GarrisonBiology 11

Illustrations ©2010 Pearson Education, Inc.

Cell Theory

• Cells :– Most basic unit of living system– Arise by cell division from existing cell– Make up all living organisms

• All living things composed of one or more cells & cell products

Cell Structure and Function 2

Basic cell structure

NucleusContains genetic material; controls cell activities

Cell membraneSeparates cell from environment and regulates passage in/out of cell

Cytoplasm 80% water, organelles


How tiny are cells, anyway?


How tiny are cells, anyway?

Very, very tiny


Resolution of lenses


µm

µm

µm

Electron Microscope

• Used to see things smaller than 0.1 mm (= 100 μm)

• Uses beam of electrons to “see” structures

• Scanning EM used to study surface of object

• Transmission EM used to internal structure


Light microscope SEM TEM


Categories of Cells

• Based on how they feed– Autotrophs vs. Heterotrophs

• Based on cell structure– Prokaryotes vs. Eukaryotes


Categories of Cells

Autotrophs make their own food

Heterotrophs eat another organism


Categories of Cells

Prokaryotes lack organelles

Eukaryotes have organelles


• Organelles– Internal membrane-bound structures

• For example, nucleus & chloroplasts


• Organelles– Internal membrane-bound structures

• For example, nucleus & chloroplasts

– Perform specific functions• Nucleus contains DNA, transcribes genetic code into

messages that control cell activities• Chloroplasts site of photosynthesis


Prokaryote--no organelles


Eukaryote--organelles


Eukaryotic Cell Structure

• Variety of organelles present• Cell structure related to cell function

– Not all organelles present in all cells– Abundance of organelles differs between cells


Plant vs. Animal Cells

• Plant cells • Animal cells



• Plant cells– Cell wall

• Animal cells– None



• Plant cells– Cell wall– Chloroplasts for P/S

• Animal cells– None– None



• Plant cells– Cell wall– Chloroplasts for P/S– Central vacuole

• Animal cells– None– None– None



• Plant cells– Cell wall– Chloroplasts for P/S– Central vacuole– None

• Animal cells– None– None– None– Lysosomes



• Plant cells– Cell wall– Chloroplasts for P/S– Central vacuole– None– None

• Animal cells– None– None– None– Lysosomes– Centrioles to assist with

cell division


Nucleus

Functions: • Holds genetic

material (DNA)• Controls cell

activities


Nucleus

Nuclear Envelope:• 2-layered membrane• Pores allow chemical

communicationInside Nucleus:• Chromatin =

DNA + protein• Nucleolus

– makes ribosomal RNA (rRNA)


Nucleus

Ribosomes:• Made of rRNA• Not organelles• Present in cytoplasm

& on membrane outside nucleus

• Function in makingproteins


Nucleus

Inside nucleus:• DNA messenger RNAOutside nucleus:• Ribosomes use mRNA

to make proteinsto be used in cell functions


Ribosomes


Endomembrane System

• Membrane made around nucleus


Endomembrane System

• Membrane made around nucleus• Membrane moves from nucleus to outer

plasma membrane– Moves through various organelles on the way– Different function with each new organelle


Endomembrane System


Organelles of Endomembrane System


Organelles of Endomembrane System: Nuclear Envelope

• Membrane made around the nucleus

• Moves into Endoplasmic Reticulum


Organelles of Endomembrane System: Endoplasmic Reticulum

Rough ER:• Has ribosomes• Surface area • Makes proteins



Rough ER:• Has ribosomes• Surface area • Makes proteins

Smooth ER:• No ribosomes, has enzymes• Surface area• Makes lipids• Breaks down drugs, etc.


Organelles of Endomembrane System: Transport Vesicles

• Flattened sacs pinched off ER or other organelles

• Transport– to Golgi apparatus– to other areas of cell– to outside of cell


Organelles of Endomembrane System: Golgi Apparatus

• Flattened sacs pinched off Rough ER

• Receives proteins from rough ER via transport vesicles

• Modifies proteins• Packages proteins for

transport


Organelles of Endomembrane System: Golgi Apparatus


Organelles of Endomembrane System: Lysosomes

• Sac pinched off from Golgi membrane

• Contains digestive enzymes

• Intracellular digestion– Food vacuoles to digest

food– Damaged organelles– Cell destruction after

death


Organelles of Endomembrane System: Lysosomes


Organelles of Endomembrane System: Vacuoles

• Sacs pinched off from internal membrane or plasma membrane

• Variety of types with different functions– Contractile vacuoles in Protista – Central vacuole in plants



Contractile vacuole• Absorbs excess

water in cytoplasm

• Contracts to expel excess water



Central vacuole• Storage

– Water– Nutrients– Wastes – Toxins – Pigments


Other Organelles & Structures Not Associated with Endomembrane

System


Organelles associated with energy

• Chloroplasts and mitochondria– Provide cellular energy– Contain their own DNA

• Feature not found in other organelles• Encodes some of their proteins• Still require nuclear DNA for full function• Considered evidence that these organelles evolved

form free-living prokaryotes


Organelles associated with energyChloroplasts• Found in

photosynthetic cells – plants and

some protistans

• Site of P/S


Chloroplasts

• Grana– Surface area

to trap light– Contains

chlorophyll

• Stroma– fluid– Site of sugar

production


Organelles associated with energyMitochondria• Found in all

eukaryotes• Site of ATP

production


Mitochondrion

• Cristae– Surface area

for ATP production

• Matrix– Fluid– Site of sugar

breakdown


Non-membrane bound structures

• Found in prokaryotes or eukaryotes• May or may not be found in all cells


Non-membrane bound structuresCytoskeleton• Network of fibers

– Microtubules• Associated with

cell movement

– Intermediate filaments

– Microfilaments

• Function– Support – Movement


Non-membrane bound structuresCytoskeleton• Support

– Maintains cell shape– Holds organelles in

place


Non-membrane bound structuresCytoskeleton• Movement

– Network of fibers constantly dissolving and reforming in new arrangements

• Allows cell to change shapes

• Pulls chromosomes apart during cell division


Non-membrane bound structuresFlagella & Cilia• Hair-like structures

that aid in movement• Core of microtubules

creates beating motion

• Move cells through liquid

• Create currents past non-moving cells


Non-membrane bound structuresFlagella• Long whipping “tails”• Usually 1-3 per cell• Propel cell forward• Found in many

protists• Found in human

sperm


Non-membrane bound structuresCilia• Short hair-like

structures• Usually many on cell

surface• Beat in synchrony• Found in many

protists• Found in human

tissues


Non-membrane bound structures


Non-membrane bound structuresCell Wall• Found in variety of

cells– Bacteria– Protistans– Plants– Fungus

• Protective structure outside plasma membrane

• Porous to water, salts

Cell Structure and Function

Cell wall

68

Cell Junctions


• Connections between cells– Proteins tie cells together

69

Cell Junctions


• Types– Tight junctions

• Seal cells together so molecules cannot slip between cells

– i.e., cells lining intestine

– Adhering junctions (desmosomes)• Strengthen attachment so cells won’t tear apart

– i.e., skin

– Gap junctions• Channels allow movement of molecules between cell

– i.e., heart muscle

70

Cell Junctions


• http://www.biology.arizona.edu/cell_bio/problem_sets/membranes/junctions.html

71

http://www.biology.arizona.edu/cell_bio/problem_sets/membranes/junctions.html

http://www.biology.arizona.edu/cell_bio/problem_sets/membranes/junctions.html

cell structure & function professor andrea garrison biology 11 illustrations ©2010 pearson...

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