Chapter 6


Anu Singh-Cundy • Michael L. Cain

Discover  Biology



Cell  Structure  and  Internal


© 2012 W. W. Norton & Company, Inc.

Cells:  The  Smallest  Units  of  Life

• The  cell  is  the  smallest  and  simplest  unit  of  life

• well-­‐coordinated  unit

cell  theory

• A  unifying  principle  of  biology

• Based  on  two  concepts:

– Every  living  organism  is  composed  of  one  or  more cells

– All  cells  living  today  came  from  a  preexisCng  cell

Cells:  The  Smallest  Unit  of  Life

• Cytoplasm  contains   cytosol

• An   organelle  structure  that  performs  a  unique funcCon

• The   nucleus  contains  the  DNA  enveloped  in  double membranes

• The   mitochondrion  (plural:  mitochondria)  provides the  energy  that  fuels  all  cellular  funcCons

• Ribosomes  are  important  protein-­‐manufacturing organelles

The  Microscope  Is  a  Window into  the  Life  of  a  Cell

• The   light  microscope

The  RaCo  of  Surface  Area  to

Volume  Limits  Cell  Size

• ProkaryoCc  cells  smaller  than  eukaryoCc  cells

Cell  size  is  limited

MulCcellularity  Enables  Larger  Body  Size and  Efficiency  through  Division  of  Labor


Different parts “expressed”

The  Plasma  Membrane

• selecCvely  permeable  barrier

– Capturing  needed  molecules  and  bringing  them  into  the cell

– Removing  waste  from  the  cell

– CommunicaCng  with  other  cells  and  the  environment

– Anchoring  the  cell  in  place

The   fluid  mosaic  model proteins  driQ

– Transport  proteins

– Receptor  proteins

– Adhesion  proteins

ProkaryoCc  and  EukaryoCc  Cells

• Prokaryotes  tough  cell  wall  outside  the plasma  membrane

(Some  bacteria  have   capsule)

Eukaryotes –membrane-bound organelles - division of labor

The  Nucleus  Houses  GeneCc  Material

• nuclear  envelope


• double  helix chromosomes

The  Nucleus  Houses  GeneCc  Material

• nuclear  pores

RNA  carry  direcCons for  making  proteins to  the  ribosomes

The  Endoplasmic  ReCculum

• endoplasmic  reDculum  (ER)

• smooth  ER

– produce  lipids

– breaks  down  toxins

– rough  ER

– doTed  with  ribosomes

Transport  Vesicles  Move  Materials

• membrane-­‐enclosed


• fuses  with target  desCnaCon

The  Golgi  Apparatus  Sorts  and  Ships


Lysosomes  Disassemble


• Lysosomes    -­‐interior  highly  acidic

Vacuoles   Disassemble  Macromolecules

• Plants

• storage

• poisons

• water

Mitochondria  Power  the  Cell

• extract  energy  from  food  molecules

• The  process  of  turning  food  molecules  into

ATP  energy  is  called   cellular  respiraDon

Chloroplasts  Capture  Energy from  Sunlight

• Plants  and  algae  use  chloroplasts  to  capture  energy from  sunlight  to  produce  ATP

• The  ATP  is  then  used  to  assemble  sugar  molecules from  carbon  dioxide  and  water  in  a  process  called photosynthesis

• The  energy  in  plant  sugars  is  used  directly  by  plants and  indirectly  by  all  organisms  that  eat  plants

• Oxygen  is  a  by-­‐product  of  photosynthesis  and sustains  life  for  humans  and  many  other  organisms

The  Cytoskeleton

• Movement  and  strength

1. Microtubules

2. Intermediate  filaments

3. Microfilaments

Microtubules rigid, hollow cylinders of protein used for:

• Positioning organelles

• Moving transport vesicles and other organelles

• Generating force to propel the cell

Intermediate filaments are ropelike cables of protein that provide mechanical reinforcement to the cell

Microfilaments are thin, flexible proteins that create cell shape and generate crawling movements in some cells

Microtubules  Support  Movement inside  the  Cell

• Microtubules  are  made  of  protein  subunits called   tubulin

• Disrupted  in  AD

• Disrupted  in  CBI


• AcDn

Cell  crawling

– amoebas  and  slime  molds

– Wound  healing

– embryonic  development

Cilia  and  Flagella  Enable

Whole  Cell  Movement

• Many  proCsts  and  animals  have  cells  covered in  hairlike  projecCons  called  cilia

Cilia  and  Flagella  Enable

Whole  Cell  Movement

• Some  bacteria,  archaeans,  proCsts,  and  sperm cells  use   flagellum   (plural:  flagella)  to  propel themselves  through  fluid

The  EvoluCon  of  Eukaryotes

• EukaryoCc  organelles  are  believed  to  have originally  been  free-­‐living  prokaryotes  that were  engulfed  by  a  predatory  cell

Concept Quiz

Where is the secreted protein insulin synthesized?

A. In the Golgi apparatus

B. On the rough ER

C. On ribosomes in the cytoplasm

D. In the nucleus

Concept Quiz

The boundary structure that physically defines a cell is the .

A.Cell wall

B.Selective permeability

C.Plasma membrane

D.Protein coat