Cell Structure

1
Chapter 4

• Cell Structure Function

2
Cells

• All living things are made up of cells
• Cell the smallest unit that can carry on all
  processes of life.

3
Discovery of cells

• Microscope observations led to the discovery of
  the basic characteristics common to all living
  things
• Cells first discovered in the 1600s using crude
  microscopes
• Observations made in the 1800s with the use of
  more powerful microscopes led to the formation of
  the cell theory!

4
Cell Theory

• 3 parts
• All living organisms are composed of 1 or more
  cells.
• Cells are basic units of structure and function
  in an organism.
• Cells only come from the reproduction of existing
  cells.

5
Cell Theory

• Led to developments in cell biology
• Able to clarify definition of life
• All living things share characteristics
• Consist of organized parts
• Obtain energy from surroundings
• Perform chemical reactions
• Change with time
• Respond to environment
• Reproduce
• Maintain homeostasis

6
Cell Diversity

• Cells vary in
• shape
• size
• organization
• A cells shape reflects its functions
• The function influences the physical features

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Cell Diversity

• Shape
• Reflects different functions of cells
• Cells are shaped to perform most efficiently!
• A) extensions allow to send and receive nerve
  impulses
• B) platelike allow to cover protect surface of
  body

8
Cell Diversity

• Size
• Some large enough to be seen by unaided eye
• Ex giraffe nerve cell (from spinal cord to foot)
  2 m.
• Human egg cell .
• Most cells 10-50 um
• Size is limited by relationship between outer
  surface area volume.
• Small cells have greater surface area to volume
  ratio than large cells
• Small cells function more efficiently than large
  cells.

9
Cell Diversity

• Size Contd
• As cell grows
• Volume inc much faster than Surface Area (S.A).
• Important because cell needs and wastes must pass
  through its surface
• If a cell became very large
• The volume would increase much larger than S.A.
• This S.A. would NOT allow materials to enter or
  exit cell quick enough for the cell needs
• SoCells are microscopic!

10
Cell Diversity
11
Cell Parts

• Plasma Membrane
• Also called Cell Membrane
• Cells outer boundary
• Covers cell surface
• Acts as barrier between inside and outside of
  cell
• All materials enter/exit through it
• Cytoplasm
• Within plasma membrane
• Includes fluid, cytoskeleton all organelles
  except nucleus
• Cytosol- includes molecules small particles but
  NOT membrane bound organelles
• 20 made up of proteins
• Control Center
• All cells have DNA (coded information)
• Some cells DNA floats freely inside
• Other cells have nucleus membrane bound
  organelle that controls the cells function

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2 Types of Cells

• Prokaryotes
• Lack membrane bound nucleus
• Lack membrane bound organelles
• Genetic information stored as DNA
• Concentrated in nucleoid
• Eukaryotes
• Have nucleus
• Have membrane bound organelles
• Have organelles intracellular bodies that
  perform specific functions
• Similar to our organ organization
• Heart, pancreas, liver all perform functions to
  enable life

13
Cell Organelles Features

• Plasma membrane
• (aka Cell membrane)
• Functions
• allows only certain molecules to enter or exit
  cell
• Separates inside from outside
• Allows to excrete wastes
• Allows interaction with environment

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The Nucleus

• Controls most functions of eukaryotic cells (the
  brain)
• Filled with liquid nucleoplasm (similar to
  cytoplasm)
• Houses protects genetic info (DNA)
• Contains chromosomes
• Nuclear envelope double membrane that surrounds
  the nucleus
• Nuclear pore allows RNA other material to
  enter/exit through the nuclear envelope
• Nucleolus denser area where DNA is concentrated
  ribosome parts are made

15
Mitochondria

• Aka the powerhouse of the cell
• Function
• Transfer energy from organic molecules to ATP
• ATP powers most chemical reactions
• Highly active cells (ex muscle cells) have 100s
  of mitochondria
• Have inner outer membrane (like nucleus)
• Have own DNA
• Scientists believe that mitochondria originated
  from prokaryotic cells that were incorporated
  with ancient eukaryotic cells.

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Ribosomes

• Small spherical organelles made up of protein
  RNA
• Function
• Build proteins
• Ribosome assembly begins in nucleolus is
  completed in cytosol
• Some float free in cytosol
• Others attached to Rough Endoplasmic Reticulum

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Endoplasmic Reticulum (ER)

• A system of tubes sacs
• Function
• Intracellular pathway that allows molecules to
  move from one part of the cell to another in
  vesicles
• 2 Types
• 1. Rough ER
• 2. Smooth ER

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Endoplasmic Reticulum

• Rough ER
• Covered with ribosomes
• Produces phospholipids proteins (ex digestive
  enzymes)
• Most abundant in cells that produce large amounts
  of protein (ex digestive glands, antibody
  producing cells)
• Smooth ER
• Lacks ribosomes
• Produces lipids (ex cholesterol or steroids)
• Not abundant in cells
• Most common in heart, gonads, liver

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Golgi Apparatus

• Function
• Receives vesicles from ER that contain newly made
  lipids or proteins
• Vesicle is modified as it goes
• Proteins get address labels that direct it to
  other parts of the cell.
• Or add carbohydrate labels to proteins
• Or alter lipids

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Vesicles

• Small spherical sacs with one membrane that
  migrate to the plasma membrane release contents
  outside the cell
• Many types of vesicles

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Vesicles

• A) Lysosomes
• Bud from golgi apparatus contain digestive
  enzymes.
• Ex in liver, lysosomes break down glycogen to
  release glucose into the bloodstream
• Also responsible for autolysis breaking down
  cells when time for cell to die
• Maintains cell health by destroying cells that
  are no longer functioning

22
Vesicles

• B) Peroxisomes
• Similar to lysosomes but contain different
  enzymes arent produced by the golgi apparatus.
• Function neutralize toxins free radicals found
  in liver kidney
• Named for H2O2 produced from breaking down
  alcohol
• Also break down fatty acids for mitochondria to
  use

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Protein Synthesis

• Step 1 Proteins assembled by ribosomes on the
  rough ER
• 2 Vesicles transport proteins to the Golgi
  apparatus
• 3 Golgi modifies proteins and packages them
  in new vesicles
• 4 Vesicles release proteins that have
  destinations outside the cell
• 5 Vesicles containing enzymes remain inside
  the cell

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Cytoskeleton

• Thin tubes filaments that crisscrosses the
  cytosol
• Similar to tent poles supporting the tent
• Function
• Support Transport
• 3 components
• Microtubules
• Microfilaments
• Intermediate Filaments

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Cytoskeleton 3 components
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Cilia Flagella

• Hairlike structures that extend from surface of
  the cell
• Function
• Assist in movement
• Cilia short many present
• Ex inner ear cilia help detect sound
• Flagella long few present
• Ex human sperm cells

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Centrioles

• Occur in animal cells
• Plants lack centrioles
• Function
• Organize microtubules during cell division
• Centrioles are a component of the centrosome

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Plant Cells

• Contain organelles parts common to eukaryotic
  cells
• Also have 3 addition structures
• Cell Wall
• Large central vacuole
• Plastids
• Why?
• different lifestyle than animal cells
• Make own food
• Perform photosynthesis

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Cell Wall

• Rigid layer outside plasma membrane
• Contains cellulose (a carbohydrate)
• Forms stiff box around each cells
• Pores in cell wall allow water, ions some
  molecules to enter/exit cell
• There are primary secondary cell walls.
• All plants have primary. Some have secondary.
• Ex wood desks tabletops

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Central Vacuole

• Function
• Store large amounts of water, enzymes, wastes,
  other materials
• Can make up 90 of cells volume!
• When a plant is watered, the vacuole fills, cells
  expand, and the plant stands up straight.
• Other vacuoles store toxins pigments

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Plastids

• Organelles similar to mitochondria (have double
  membrane own DNA)
• Several types
• Chloroplasts
• Chromoplasts
• Other plastids
• All arose from protoplastids

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Plastids

• Chloroplasts use energy to make carbohydrates
  from CO2 H2O
• Contain thylakoids flattened sacs that contain
  chlorophyll
• Chlorophyll molecules that absorb light
  captures light energy
• Have own DNA
• Scientists believe that chloroplasts originated
  from prokaryotic cells that were incorporated
  with ancient eukaryotic cells.
• Chromoplasts contain colorful pigments

33
Comparing Cells

• All cells share 4 common features
• Cell membrane
• Cytoplasm
• Ribosomes
• Genetic Material
• 3 Main types of Cells
• Prokaryotic
• Eukaryotic
• Differences among eukaryotic
• Plant vs. Animal Cell

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Prokaryote vs. Eukaryote Cells

• Prokaryotes lack nucleus, have nucleoid, lack
  membrane bound organelles, lack internal membrane
  system

35
Plant vs. Animal Cells

• Plants have cell wall, large central vacuole
  plastids