CellsThe Smallest Unit of Life

Organization• All cells have DNA, ribosomes, a plasma

membrane, and cytoplasm

• Cells make up tissues, tissues make up organs, and organs make up organ systems

Can We See Cells Without A Microscope?

• They are not doing much metabolically

• They are mostly nutrient warehouses

Surface To Volume Ratio• Surface area is squared but volume is cubed

• Growing volume increases faster than surface area

• The cell has to be small enough to transport materials through the cell from the plasma

membrane

• If growth increases four times, then the volume increases 64 units, (4X4x4) ,but the surface area only increases 16 units, (4X4)

• The cell membrane would have to service 4X as much cytoplasm

• Cells Respond To Stimuli

• Receptor molecules detect stimuli and activate to trigger necessary changes

Cells Maintain Homeostasis

Cells Grow And Reproduce

Cells Pass On Their Traits

Prokaryotes• Archaebacteria and Eubacteria

• Most metabolically diverse forms of life on Earth

• They are alike in outward appearance and size

Prokaryotic Cell Structure• Prokaryotic cells DNA is located in the

nucleoid

• They have a circular chromosome and plasmids with only a few genes

Prokaryotic Cell Structure• Cell walls are permeable to dissolved substances crossing to and from the cell

membrane

• Many have a thick, jellylike capsule for attachment

Archaebacteria• Are adapted to extreme environments

• Are more closely related to Eukaryotic cells

• 2 main shapes: Coccus –, Bacillus – rod ( but can be triangular and square)

Methanogens• Anaerobic bacteria that helps break down

peat in the swamp and vegetation in cow’s intestines

• Produce methane with its distinctive odor

Halophiles

• Salt loving bacteria

Thermophiles• Heat loving bacteria

Eubacteria• 3 shapes : Cocci - round, Bacilli – rod,

Spirilla - spiral

Eubacteria

Eukaryotic Cells• All cells synthesize, store, break down, and transport diverse substances but Eukaryotic

cells compartmentalize those operations

Eukaryotic Cells• Have a nucleus and membrane bound

organelles

• Organelles interact to keep the cell functioning properly

Plasma Membrane• Plasma membrane encloses/sustains

microenvironment for cell activities

• Separates cell activities that might be incompatible

Plasma Membrane• Controls the types and amounts of

substances entering and leaving

• Phospholipid bilayer – polar heads and non polar tails with proteins attached and

embedded

• Fluid mosaic model

Cytoplasm• Semifluid substances between the plasma

membrane an nucleus

• Contains structural components for cell tasks

Nucleus• Double nuclear membrane with pores

• Outer membrane merges with ER and controls movement to and from the

cytoplasm

• Inner membrane has fibrous proteins that anchor the DNA and helps keep them organized and makes copying easier

Nucleus• The grainy substances are chromatin which

is a collection of DNA and proteins

• A chromosome is a double stranded DNA molecule and its associated proteins whether it is dispersed or condensed

Nucleolus• Dense proteins/ copies of genes coding for

rRNA

• 1 large and 1 small subunit join after they move out of the pores into the cytoplasm to

make an intact ribosome during protein synthesis

Ribosomes• Site of protein synthesis

Endoplasmic Reticulum• Demo – folding

• A flattened, folded channel where proteins are modified and lipids are assembled and

sent to and fuse with the Golgi Bodies/Apparatus

Endoplasmic Reticulum• Rough E.R. – contain fixed ribosomes and are

sites for translation

• Smooth E.R. - no ribosomes – makes lipid that become part of the cell membrane –takes part in fatty acid breakdown and

degrades some toxins

Golgi Bodies• Membrane channels fold back on themselves

like a stack of pancakes

• Removes some protein, adds sugars chains to proteins and lipids, packages them in vesicles

to be sent where needed

Lysosomes• Contain diverse enzymes that can digest

almost all biological molecules

• The enzymes are activated when they fuse with another vesicle and digest it

• It is how tadpole lose their tail

Mitochondrion• Site of Aerobic Respiration, produces ATP

• Double membrane, inner highly folded

• Has own DNA and can divide on their own

Chloroplasts

• Site of Photosynthesis

• A double membrane encloses a semifluid interior called the stroma

Chloroplasts• In the stroma, a 3rd membrane folds to resemble a stack of flattened disks called

grana(pl)

• Chlorophyll and other pigments are located in the thylakoid membrane

Central Vacuoles• Can take up to 50-90% of a plant cells

interior

• Fluid filled – stores A.A. ,sugars, ions, toxic waste

• Expands during growth

• Responsible for turgor pressure

Cell Wall• Physical protection and support for plants,

give plant cells shape

• Porous – allows water and solutes to move into and out of plasma membrane

Cytoskeleton

• System of protein filaments that extend between the nucleus and plasma membrane

• It reinforces, organizes, and transports materials throughout the cell

• High concentration to low concentration

• No energy required

Passive Transport

Active Transport• Going from a high concentration to a low

concentration…against the gradient

• Requires energy…ATP

• Acknowledgements• https://health.howstuffworks.com/medicine/modern-technology/can-use-microbes-to-

fight-disease.htm• https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwjF1LjZv9vcAhVK3FM

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• http://www.assignmentpoint.com/science/biology/types-of-cells-in-human-body-and-functions.html

• http://phytophactor.fieldofscience.com/2012/01/new-semester-new-course-unprepared.html

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