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Transcript
Unit 2:Cell Structure and Function
Section 1 The History of Cell Biology
Section 2 Introduction to Cells
Section 3 Cell Organelles and Features
Section 4 Unique Features of Plant Cells
Objectives
• Name the scientists who first observed living and nonliving cells.
• Summarize the research that led to the development of the cell
theory.
• State the three principles of the cell theory.
• Explain why the cell is considered to be the basic unit of life.
Sect 1: Discovery of Cells
• All living things are made up of one or more cells.
• A cell is the smallest unit that can carry on all of the
processes of life.
Discovery of Cells
Robert Hooke
• 1665 used microscope to
examine cork.
• Coined the term “cell”.
Discovery of Cells
Anton van Leeuwenhoek
• 1673, observed living cells.
• Called cells animalculescurrent day protists.
Cell Theory
• All living organisms are made of one or more cells.
• Cells are the basic unit of structure and function in an
organism.
• Cells come from the reproduction of existing cells.
Cellular Basis for Life
All living things:
• are made of organized parts
• obtain energy from their surroundings
• perform chemical reactions
• change with time
• respond to their environment
• reproduce.
• maintain constant internal environment
Sect. 2: Objectives
• Explain the relationship between cell shape and cell
function.
• Identify the factor that limits cell size.
• Describe the three basic parts of a cell.
• Compare prokaryotic cells and eukaryotic cells.
• Analyze the relationship among cells, tissues, organs, organ
systems, and organisms
Sect 2: Cell Diversity
Shape: reflects function
Sect 2: Cell Diversity (cont’d)
• Size: limited by surface-to-volume ratio
-allows for quick transport of materials into and out of
the cell
Basic Parts of a Cell
The three basic parts of a cell:
• plasma membrane: covers cell’s surface; acts as a barrier
between inside and outside of cell.
• cytoplasm: region within plasma membrane; includes the
fluid, the cytoskeleton, and all organelles except the nucleus
• nucleus: membrane-bound organelle that contains cell’s
DNA.
Two Basic Types of Cells
Prokaryotes: lack a nucleus
and membrane-bound
organelles.
Two Basic Types of Cells
• Eukaryotes: have a nucleus
and membrane-bound
organelles
Prokaryotes vs Eukaryotes
Prokaryote
Eukaryote
Cellular Organization
• Colonies: collection of
genetically identical cells that
exist together.
Cellular organization (cont’d)
• True multicellularity: specialized cells- tissue- organs- organ
system, organism
Sect 3 Objectives:
• Describe the structure and function of a cell’s plasma
membrane.
• Summarize the role of the nucleus.
• List the major organelles found in the cytosol, and describe
their roles.
• Identify the characteristics of mitochondria.
• Describe the structure and function of the cytoskeleton.
Sect. 3: Cell Organelles and Features
Plasma Membrane: consists of
a phospholipid bilayer and
embedded membrane proteins
• Polar, hydrophilic head points
outward toward water
• Two hydrophobic tails point
inward away from water
• Sterols make membrane firm
and prevent freezing
Plasma Membrane
Nucleus
Nucleus: directs the cell’s activities and stores DNA;
surrounded by a double membrane called the nuclear
envelope
Nucleolus
Nucleolus: place within nucleus where DNA is concentrated
when it is in the process of making ribosomal RNA.
Mitochondria
Mitochondria: harvest energy from organic compounds and transfer it
to adenosine triphosphate- ATP.
• have own DNA
• may be a result of a symbiotic relationship between prokaryote and
eukaryote cells.
Ribosomes
Ribosomes: either free in cytoplasm or attached to the rough
ER; play a role in protein synthesis.
Endoplasmic Reticulum- ER
ER: system of membranous tubes-cisternae; functions as an
intracellular path molecule transport. Two types:
• rough ER: makes phospholipids, proteins; most abundant in
digestive glands and antibody-producing cells.
• smooth ER: builds lipids, helps detoxify drugs, poisons in liver,
kidney cells; produces estrogen and testosterone in ovaries
and testes.
Golgi Apparatus
Golgi apparatus/body/complex: stacks of flattened
membranes, processes and packages proteins
Vesicles
Vesicles: small, migrating “packages” of needed materials.
• Lysosomes: bud from golgi body, carry digestive enzymes
needed for breakdown of proteins, nucleic acids, or wornout cells.
Protein Synthesis
• Major function of cell
• Requires work of ribosomes, rough ER, Golgi apparatus, and
vesicles…
1. Ribosomes assemble proteins on rough ER.
2. Vesicles transport proteins to Golgi apparatus.
3. Golgi modifies proteins, repackages them in new vesicles.
4. Vesicles release proteins for trip outside cell.
5. Vesicles with enzymes stay within cell.
Cytoskeleton
Cytoskeleton: protein fibers that help cells move and maintain
their shape.
• cilia and flagella: hairlike structures that extend from cell
surface; aid in movement.
• centrioles: microtubules in animal cells, play role in cell
division.
Sect 4: Unique Features of Plant Cells
• Cell walls, central vacuoles, and plastids
Cell Wall
• Rigid layer outside of cell membrane
• Contains cellulose, proteins, pores for water ions.
Central Vacuole
• Reservoir for water, enzymes, wastes
• Can make up to 90% of cell interior
• Loss of water causes plants to wilt
Plastids
• Surrounded by double membrane
• Contain their own DNA
• most important: chloroplasts, chromoplasts
Chloroplasts
• Use light energy to make carbohydrates from CO₂ and H₂O
• Thylakoids contain chlorophyll, main molecule that traps
light energy for photosynthesis
Chromoplasts
• Contain colorful pigments
ex.s: carotene, xanthophyll