organization of the cell ch04 lecture

Biology, Seventh Edition Solomon • Berg • Martin

Chapter 4

Organization of the Organization of the CellCell

Biology, Seventh Edition CHAPTER 4 Organization of the Cell

• Cell theory• Cells are the basic living units of

organization and function• All cells come from other cells• Work of Schleiden, Schwann, and

Virchow contributed to this theory• Each cell is a microcosm of life

Biological size and cell diversity

• Cell surface area-to-volume ratio• Plasma membrane must be large

enough relative to cell volume to regulate passage of materials

• Cell size and shape related to function

Cell surface area-to-volume ratio

• Microscopes• Light microscope, referred to as

compound microscope, used by most students

• Two features determine how clearly an object is viewed–Magnification–Resolution

• Light microscope has 500 times more resolution than human eye

• Special optical mechanisms for light microscopes• Bright-field microscopy• Phase contrast microscopy• Differential-interference-contrast

microscopy• Fluorescence microscope, including

confocal fluorescence microscope

• Electron microscope• Developed in the 1950s• Allows study of the ultrastructure of

cells• 10,000 times more resolution than

human eye

• Types of electron microscope• Transmission electron microscope• Scanning electron microscope

Comparing light and electron microscopy

• Cell fractionation• Used to determine function of

organelles • Cells broken apart and the resulting

cell extract spun in a centrifuge• Centrifugal force separates extract

–Pellet–Supernatant

Cell fractionation

• Prokaryotic• Bacteria and archaea • DNA not enclosed in a nucleus

• Eukaryotic• All other known organisms• Highly organized membrane-enclosed

organelles–Cytoplasm–Nucleoplasm

• Functions of cell membranes• Divide cell into compartments,

allowing for specialized activities• Interacting membranes form

endomembrane system• Vesicles transport materials between

compartments

Diagram ofa plant cell

Diagram ofan animal cell

• The cell nucleus• Contains DNA• Bounded by

–Nuclear envelope–Double membrane perforated with

nuclear pores

• DNA forms chromatin, which is organized into chromosomes

• Nucleolus–RNA synthesis and ribosome assembly

The cellnucleus

• Endoplasmic reticulum (ER)• Network of folded internal

membranes in the cytosol• Smooth ER

–Site of lipid synthesis–Site of detoxifying enzymes

• Rough ER–Ribosomes manufacture proteins–Proteins may be moved into the ER

Endoplasmicreticulum (ER)

• Golgi complex• Cisternae that process, sort, and

modify proteins • In animal cells, Golgi complex also

manufactures lysosomes

• Glycoproteins transported to the cis face

• Golgi modifies carbohydrates and lipids and packages into vesicles

Golgi complex

• Lysosomes break down worn-out cell structures, bacteria, and other substances

• Peroxisomes• Involved in lipid metabolism and

detoxification• Contain enzymes that produce and

degrade hydrogen peroxide

Lysosomes

• Mitochondria • Sites of aerobic respiration• Organelles enclosed by a double

membrane• Place important role in apoptosis• Cristae and matrix contain enzymes

for aerobic respiration–Nutrients broken down and energy

packaged in ATP–Carbon dioxide and water by-products

Mitochondria

• Chloroplasts • Plastids that carry out photosynthesis• Inner membrane of chloroplast

encloses the stroma• During photosynthesis, chlorophyll

traps light energy• Energy converted to chemical energy

in ATP

Chloroplast

Cellular respiration and photosynthesis

• Cytoskeleton • Internal framework made of

–Microtubules–Microfilaments–Intermediate filaments

• Provides structural support• Involved with transport of materials in

the cell

TheCytoskeleton

• Cilia and flagella • Thin, movable structures that project

from cell surface• Function in movement• Microtubles anchored in cell by basal

Structureof cilia

• Glycocalyx, cell coat formed by polysaccarides extending from plasma membrane

• Many animal cells also surrounded by an extracellular matrix (ECM)

• Most bacteria, fungi, and plant cell walls made of carbohydrates

Extracellular matrix

Plantcell walls

organization of the cell ch04 lecture

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