Concepts of Biology 2nd Edition

1. Chapter 4
Structure and Function of Cells

2. Cells are the basic units of life
All organisms are composed of cells
• Cell theory states
– A cell is the basic unit of life
– All living things are made up of cells
– New cells arise only from preexisting cells

4. Metabolically active cells are small in size
Why are cells so small?
Cells need a surface area large enough to gain
nutrients and get rid of waste.

5. Prokaryotic cells evolved first
• Prokaryotic (“before” “nucleus”) cells lack a membrane
bound nucleus
• Prokaryotic cells are also much smaller than eukaryotic
• Domains Bacteria and Archaea are prokaryotic
• All cells contain
– Cell membrane (plasma membrane)
– Cytoplasm
– Genetic material

6. • Prokaryotic cells contain
– Cell membrane
• Allows substances in and
out
– Cytoplasm
• Fluid that fills cell
– Ribosomes
• Protein synthesis
– Cell wall
• Holds cell shape
– Pili
• Allows attachment to solid
surfaces
– Flagella (some cells)
• movement
Prokaryotic cells cause disease, decompose dead material, and are used in the
production of food and drugs.

7. Eukaryotic cells contain specialized
organelles
• Eukaryotic (“true” “nucleus”) cells have a membrane
bound nucleus
• Domain Eukarya contains eukaryotic cells
• Larger than prokaryotic cells
• Less surface area to volume
• Contains organelles (“little organs”) that perform specific
functions

8. Animal Cell
Plant Cell – Notice the cell
wall, chloroplasts, and large
central vacuole

9. Protein synthesis is a major
function of cells
The nucleus contains the cell’s genetic information
• Chromosomes
– DNA and proteins
• Chromatin
– Extended chromosomes after cell division
• Nucleolus
– Region of chromatin where subunits of ribosomes are produced
• Nuclear envelope
– Separates nucleus from cytoplasm
• Nuclear pores
– Allows ribosomal subunits out and proteins in

10. The ribosomes carry out protein
synthesis
• Do not have membranes
• Polyribosomes
– Group of ribosomes
• Endoplasmic reticulum
– Rough version has ribosomes attached to it
• Messenger RNA
– Copy of a gene
– Tells cell how to make a particular protein
– Indicates correct sequence of amino acids
– Leaves nucleus via nuclear pore
– Attaches to ribosome
– Protein is produced

11. The endoplasmic reticulum synthesizes
and transports proteins and lipids
• Many ribosomes attach to the endoplasmic
reticulum, making it a site of protein production
• Types of ER
– Rough ER
• Has ribosomes attached
• Make proteins
– Smooth ER
• Does not have ribosomes attached
• Make lipids
• Transport vesicles
– Pinched off portions of ER that contain proteins,
membranes, and lipids going mainly to the Golgi
apparatus

12. The Golgi apparatus modified and
repackages proteins for distribution
• Receives, processes, and packages proteins and lipids,
so that they may be sent to their final destination
• Receives at inner face
• Processes as it moves from inner face to outer face
• Packages into vesicles that leave from the outer face
– Some are secretory vesicles that discharge contents out of the
cell. Also called exocytosis.

13. Vacuoles and vesicles have varied
functions
Lysosomes digest biomolecules and cell
parts
• Vesicles produced by Golgi apparatus
• Have low internal pH that digests old and
worn-out organelles
• White blood cells engulf bacteria and
digest it to protect your body

14. Peroxisomes break down long-
chain fatty acids
• Help produce cholesterol and important
phospholipids
• In germinating seeds, convert fatty acids
and lipids to sugars that are used as
energy

15. Vacuoles are common to plant cells
• Store water, sugars, salts, toxins (protects
plant from herbivory), and water-soluble
pigments (responsible for flower color)
• Central vacuole provides support to the
plant
• Stores waste and breaks down old
organelles like lysosomes in animal cells

16. Vesicles allow the organelles of the
endomembrane system to work together
1. Proteins, produced in the rough
ER are carried in
2. Transport vesicles to
3. The Golgi apparatus, which sorts
the proteins and packages them
into vesicles that transport them to
various cellular destinations
4. Secretory vesicles take proteins to
the plasma membrane, where they
exit the cell when the vesicles fuse
with the membrane
5. In animal cells, lysosomes
produced by the Golgi apparatus
6. Fuse with incoming vesicles from
the plasma membrane and digest
biomolecules and debris

17. A cell carries out energy
transformations
Chloroplasts and mitochondria have opposite
functions
• Chloroplasts are found in plant cells and contain
the green pigment chlorophyll, which is
responsible for the ability to absorb solar energy
• Protists and algae also contain chloroplasts
• Mitochondria carry out cellular respiration
• Mitochondria produce ATP
(Cellular respiration and photosynthesis reactions)

18. The cytoskeleton is dynamic
The cytoskeleton maintains cell shape and assists movement
• Cytoskeleton
– Network of protein fibers within cytoplasm
– Holds organelles in place but allows them to move if needed
– Allows cells to change shape
– Support and movement
• Types of fibers
– Actin filaments
• Support plasma membrane
• Largest
– Intermediate filaments
• Support nuclear envelope, plasma membrane, and cell to cell connections
• Medium
– Microtubules
• Maintain shape of cell and act as tracks along which organelles can move
• Smallest

19. Cilia and flagella permit movement
• Cilia
– Short
– Move an egg along the oviduct
– Move mucus that contains debris out of lungs
• Flagella
– Long tail
– Sperm tail