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Mader: Biology 8th Ed.

Cell Structure and Function

Chapter 4

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Outline

• Cell Theory

• Cell Size

• Prokaryotic Cells

• Eukaryotic Cells

– Organelles

!Nucleus

!Endomembrane System

!Cytoskeleton

!Centrioles, Cilia, and Flagella

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Cell Theory

• Cell theory states all organisms are composed of cells and that cells come only from preexisting cells.

– One of unifying concepts of biology.

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Cell Size

• Most cells are much smaller than one millimeter.

– Some as small as one micrometer.

• Small cells are likely to have an adequate surface area for exchanging wastes for nutrients.

– Cells that specialize in absorption have modifications that greatly increase the surface area per volume of the cell.

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Organism Sizes

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Prokaryotic Cells

• Lack a membrane-bounded nucleus.• Structurally simple.• Can be divided into two domains:

– Bacteria !Three Shapes

"Bacillus (rod)"Coccus (spherical)"Spirilla (spiral)

– Archaea!Live in extreme habitats.

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Prokaryotic Cells

• Cell Envelopes

– Includes plasma membrane, cell wall, and glycocalyx (layer of polysaccharides outside cell wall).

!Capsule – Well-organized layer.

– Form internal pouches (mesosomes).

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Prokaryotic Cells

• Cytoplasm

– Cytoplasm is a semifluid solution encapsulated by plasma membrane.

!Inclusion Bodies - Stored granules of various substances.

• Appendages

– Flagella

– Fimbriae

– Sex Pili

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Prokaryotic Cells

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Eukaryotic Cells

• Members of domain Eukarya.

• Contain membrane-bounded nucleus.

• Contain specialized organelles.

• Contain plasma membrane.

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Organelles

• Organelles of endomembrane system communicate with one another.

– Basically self-sufficient

• Compartmentalization allows eukaryotic cells to be larger than prokaryotic cells.

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Animal Cell Anatomy

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Plant Cell Anatomy

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Nucleus

• Contains chromatin in semifluid nucleoplasm.

– Condense to form chromosomes.

• Separated from cytoplasm by double-membrane nuclear envelope.

– Nuclear pores permit passage in and out of the nucleus.

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Anatomy of Nucleus

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Ribosomes

• Composed of large and small subunits that serve in protein synthesis.

– Subunits made in nucleolus.

• Occur singly and in groups, and may become attached to endoplasmic reticulum.

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Endomembrane System

• Consists of nuclear envelope, membranes of endoplasmic reticulum, Golgi apparatus, and several types of vesicles.

– Restrict enzymatic reactions to specific compartments within cell.

• Endoplasmic Reticulum

– Rough - Studded with ribosomes.

– Smooth - No ribosomes.

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Endoplasmic Reticulum

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Endomembrane System

• Golgi Apparatus

– Consists of flattened, curved saccules.

– Modifies proteins and lipids and packages them in vesicles.

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Endomembrane System

• Lysosomes

– Membrane-bounded vesicles produced by the Golgi apparatus.

!Engage in digestion of molecules and apoptosis (programmed cell death).

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Peroxisomes and Vacuoles

• Peroxisomes are membrane-bounded vesicles that enclose enzymes.

– Enzymes are cell-specific

• Vacuoles are membranous sacs that are larger than vesicles.

– Store substances

– Plants cells typically have a central vacuole that functions in storage of nutrients and waste products.

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Energy-Related Organelles

• Chloroplasts use solar energy to synthesize carbohydrates.– Photosynthesis

!Cellular Respiration– Adenosine triphosphate (ATP) is used for

all energy-requiring processes in cells.• Chloroplasts are green due to the green

pigment chlorophyll.– Stroma– Granum

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Chloroplast Structure

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Energy-Related Organelles

• Mitochondria are involved in cellular respiration.

• Produce most of ATP utilized by the cell.

– Cristae - Inner membrane that encloses matrix.

– Matrix - Enzymes that break down nutrient molecules.

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Mitochondrion Structure

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Cytoskeleton

• Cytoskeleton serves as internal skeleton that maintains cell shape and assists in movement of its parts.

– Actin Filaments

!Pseudopods

– Intermediate Filaments

– Microtubules

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Fig. 4.18

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Centrioles, Cilia, and Flagella

• Centrioles are short cylinders with a 9 + 0 pattern of microtubule triplets that may give rise to basal bodies of cilia and flagella.

• Cilia and flagella are hairlike projections with a 9 + 2 pattern of microtubules that aid in cell movement.

– In eukaryotes, cilia are much shorter than flagella.

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Review

• Cell Theory

• Cell Size

• Prokaryotic Cells

• Eukaryotic Cells

– Organelles

!Nucleus

!Endomembrane System

!Cytoskeleton

!Centrioles, Cilia, and Flagella

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