Chapter 4 Cell Structure and Function Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. What Are the Basic Attributes of Cells? All cells share common features DNA and RNA plasma membrane cytoplasm consists of all the fluid and structures that lie inside the plasma membrane but outside of the nucleus The fluid portion of the cytoplasm (cytosol) contains water, salts, and organic molecules Most of the cells metabolic activities occur in the cell cytoplasm Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. The Plasma Membrane carbohydrate
extracellular fluid (outside) Functions: isolates the cells contents from the external environment regulates the exchange of essential substances allows communication between cells creates attachments within and between cells regulates biochemical reactions glycoprotein A phospholipid bilayer helps to isolate the cell's contents Proteins help the cell communicate with its environment
cholesterol membrane protein channel protein cytoskeleton cytoplasm (inside) Biology: Life on Earth, 9e Fig. 4-2 Copyright 2011 Pearson Education Inc. EUKARYOTIC CELLS Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. A Generalized Animal Cell microfilaments nuclear envelope nuclear pore
nucleus chromatin (DNA) nucleolus cytosol micro- (cytoskeleton) tubules flagellum basal body rough endoplasmic reticulum vesicle intermediate filaments (cytoskeleton) cytoplasm Golgi apparatus centriole ribosomes on rough ER
lysosome smooth endoplasmic reticulum mitochondrion Biology: Life on Earth, 9e plasma membrane free ribosome exocytosis of material from the cell Fig. 4-3 Copyright 2011 Pearson Education Inc. A Generalized Plant Cell nuclear envelope nuclear pore nucleus
central vacuole mitochondrion cell wall plasmodesmata cytosol Biology: Life on Earth, 9e Golgi apparatus vesicle plasma membrane plastid free ribosome Fig. 4-4 Copyright 2011 Pearson Education Inc. What Are the Major Features of Eukaryotic Cells? Cell walls outer surfaces of plants, fungi, and some protists Plant cell walls are composed of cellulose Fungal cell walls are made of chitin Cell walls are porous, allowing oxygen, carbon dioxide, and water carrying dissolved molecules to flow easily
through them Plasmodesmata - openings that connect adjacent cells in plants The plasma membrane is located just beneath the cell wall Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. What Are the Major Features of Eukaryotic Cells? intermediate filaments Cytoskeleton provides shape, support, movement, cell division The cytoskeleton is composed of three types of protein fibers: microfilaments intermediate filaments microtubules microtubules microfilaments
(a) Cytoskeleton microtubules (red) nucleus microfilaments (blue) (b) Light micrograph showing the cytoskeleton Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Cytoskeleton Table 4-2 Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Cilia and Flagella central pair of microtubules
protein arms Functions: move the cell through fluid move fluid past the cell Both cilia and flagella are slender extensions of the plasma membrane supported by microtubules. section of cilium 0.1 micrometer cilium Paramecium plasma membrane basal body Biology: Life on Earth, 9e
Copyright 2011 Pearson Education Inc. How Cilia and Flagella Move propulsion of fluid (a) Cilium power stroke plasma membrane direction of locomotion (b) Flagellum return stroke propulsion of fluid continuous propulsion cilia lining trachea
flagellum of human sperm surface of human egg cell Fig. 4-7 Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. The Nucleus Control center Nuclear envelope - consists of a double membrane perforated by nuclear pores Chromatin Nucleolus nuclear envelope nuclear nucleolus pores ribosomes nucleus
chromatin nuclear pores with nuclear pore complex Biology: Life on Earth, (a)9e The nucleus Copyright yeast 2011 Pearson Education Inc. (b) Nucleus of a cell Ribosomes small particle composed of ribosomal RNA and proteins site of protein synthesis in the cytoplasm ribosome polyribosome mRNA
growing protein amino acid Biology: Life on Earth, 9e Fig. 4-10 Copyright 2011 Pearson Education Inc. Endoplasmic Reticulum Vesicles are membranous sacs that transport substances The endoplasmic reticulum (ER) is a series of interconnected membranes that form a labyrinth of interconnected flattened sacs and channels within the cytoplasm All the proteins and phospholipids of cell membranes are synthesized in the ER Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Endoplasmic Reticulum There are two forms of ER: Smooth endoplasmic reticulum has no ribosomes,
detoxifies drugs, and synthesizes lipids like steroid hormones made from cholesterol Rough endoplasmic reticulum is studded with ribosomes and synthesizes proteins destined for other membranes or for secretion smooth ER ribosomes rough ER smooth ER rough ER Biology: Life on Earth, 9e vesiclesCopyright 2011 Pearson Education Inc. The Golgi Apparatus Functions: sorts, chemically alters, and packages important molecules It synthesizes some polysaccharides used in plant cell walls, such as
cellulose and pectin It packages the finished molecules into vesicles that are then transported to other parts of the cell (lysosomes) or to the plasma membrane for export Vesicles from the ER merge with the Golgi apparatus Golgi apparatus Biology: Life on Earth, 9e Vesicles carrying modified protein leave the Golgi apparatus Copyright 2011 Pearson Education Inc. Lysosomes Serve as the cells
digestive system A lysosome fuses with a food vacuole and digests food into basic nutrients Digest worn-out organelles (extracellular fluid) (cytoplasm) food food vacuoles 5 A lysosome fuses with a food vacuole, and the enzymes digest the food 4 The enzymes are packaged into lysosomes, which bud from the
Golgi apparatus lysosome 3 The Golgi apparatus modifies the enzymes as they pass through its compartments Golgi apparatus digestive enzymes 2 The enzymes are packaged into vesicles and travel to the Golgi apparatus 1 Digestive enzymes are synthesized on ribosomes and travel through the rough ER
Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Vacuoles Serve many functions, including water regulation, support, and storage Most cells contain one or more sacs of cell membrane filled with fluid containing various molecules Many freshwater organisms possess contractile vacuoles composed of collecting ducts, a central reservoir, and a tube leading to a pore in the plasma membrane that carries excess water out of the organism Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Contractile Vacuoles contractile vacuole
(a) Paramecium Water enters the collecting ducts and fills the central reservoir collecting ducts central reservoir pore (b) Contractile vacuole Biology: Life on Earth, 9e The reservoir contracts, expelling water through the pore Fig. 4-15 Copyright 2011 Pearson Education Inc. cytoplasm central vacuole Vacuoles
Central vacuoles Found in plants Functions: To maintain water balance To store hazardous wastes, nutrients, or pigments To provide turgor pressure on the cytoplasm to keep cells rigid When water is plentiful, it fills the central vacuole, pushes the cytoplasm against the cell wall, and helps maintain the cell's shape (a) Turgor pressure provides support cell wall plasma membrane When water is scarce, the central vacuole shrinks and the
cell wall is unsupported Biology: Life on Earth, 9e Water pressure supports the leaves of this impatiens plant Deprived of the support from water, the plant wilts Copyright 2011 (b) Loss of turgor pressure causes the plant Pearson to wilt Education Inc. Mitochondria Extract energy from food molecules to make ATP Powerhouse of the cell
Double membrane with cristae outer membrane inner membrane matrix cristae 0.2 micrometer Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Chloroplast Site of photosynthesis Double membrane The thylakoid membranes contain the green pigment chlorophyll, which capture sunlight and make sugar from CO2 and water (photosynthesis) outer membrane inner membrane stroma
thylakoid channel interconnecting thylakoids Biology: Life on Earth, 9e granum (stack of thylakoids) Copyright 2011 Pearson Education Inc. 1 micrometer Plastids Storage Only in plants and photosynthetic protists Double membrane Storage containers for various molecules, such as pigments or starch Biology: Life on Earth, 9e
plastid starch globules 0.5 micrometer Copyright 2011 Pearson Education Inc. Review Questions 1. Describe the structures and features shared by all cells. 2. Define organelle. 3. Which organelles are found in plants not animals? 4. Describe each major structure and know its function. Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. PROKARYOTIC CELLS Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Prokaryotic Cells Are Simpler Than Eukaryotic
cytoplasm capsule or slime layer cell wall plasma membrane photosynthetic membranes (a) Generalized prokaryotic cell (bacillus) (e) Photosynthetic prokaryote Fig. 4-19 Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. What Are the Major Features of Prokaryotic Cells? Most prokaryotic cells (bacteria) are less than 5 m long, with a simple internal structure compared to eukaryotic cells They usually have a stiff cell wall Prokaryotic cells can take several shapes: Rod-shaped (bacilli)
Spiral-shaped (spirilla) Spherical (cocci) Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. What Are the Major Features of Prokaryotic Cells? Prokaryotic cells Some bacteria and archaea are propelled by flagella Infectious bacteria may have polysaccharide adhesive capsules and slime layers on their surfaces Pili are protein projections in some bacteria that further enhance adhesion In the central region of the cell is an area called the nucleoid, which is separate from the cytoplasm Within the nucleoid is a single, circular chromosome of DNA Small rings of DNA (plasmids) are located in the cytoplasm Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. What Are the Major Features of Prokaryotic Cells?
Prokaryotic cells No nuclear membrane or membrane-bound organelles Some have internal membranes used to capture light Extensive cytoskeleton The cytoplasm may contain food granules ribosomes Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc. Review Questions 1. Explain the major differences between prokaryotic and eukaryotic cells. 2. Describe the structure and function of the major surface features of bacteria. 3. Describe the internal features of bacteria. Biology: Life on Earth, 9e Copyright 2011 Pearson Education Inc.
The Beginnings of Informatics at the University of Utah The First Few Years. Reed M. Gardner, PhD. Emeritus Professor and Former Chair, Department of Biomedical Informatics. Biomedical Informatics 50th Anniversary Celebration. 18 April 2015
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