Cells Chapter 4 2009 course

Cells Chapter 4 2009 course - Chapter 4 Cells and cellular...

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Chapter 4. Cells and cellular states 4.1 What are cells? Driving through the lush vineyards that cover almost every acre of arable land in California’s Sonoma valley one can’t but marvel at how mixing grape juice with a few living yeast cells has brought unimagined wealth to this parched corner of California and inspired poems, songs and tales that have shaped Western culture. How does yeast transform crushed grapes that would go bad in days to a nectar that improves in taste as it is stored for decades? To understand what yeast does when thrown into vats of grape juice we will explore the nature of the yeast cell, what’s in it, how it functions and how it differs from the combinations of cells that make up the vine from which the grapes came and those constituting our bodies that enjoy the wine. 4.2 Are all cells the same? Differences between eukaryotes and prokaryotes. The information for producing proteins is found in the cell’s DNA. The DNA in yeast cells as well as in animal and plant cells is enclosed in the nucleus, which also has a membrane around it. A key difference between yeast, plant and animal cells and those of bacteria is that bacteria don’t have a nucleus inside the cell. Instead, their DNA is free floating within the cell. Cells with a nucleus are called Eukaryotes, while those without a nucleus are called Prokaryotes. 2.2 How do cell’s compartmentalize functions? For yeast, the cell is everything. Its life is spent nourishing itself and dividing to make more yeast cells. So what constitutes a cell? All cells are enclosed by a membrane, which can be thought of as a balloon made up of water repellent molecules called lipids. The membrane surrounds an aqueous environment called the cytoplasm (See Fig. 1.1). To bring nutrients through the membrane into the cell, specialized protein transporters are located in the membrane. They recognize molecules such as sugars and allow them to selectively cross the membrane. Floating in the cytoplasm are proteins that catalyze chemical reactions as well as the substrates and products of those reactions (See Fig. 1.1).. The cytoplasm is so densely packed with proteins and other macromolecules that it has been characterized as having the consistency of wet cement. Cellular membranes Lipid bilayers Roles of membranes Different compartments Proteins in membranes
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Transporters Cholesterol in membranes 2.3 What are cellular organelles? Nuclei Mitos Chloroplasts Evolution of organelles 2.4 Secretion 2.5 Cellular macromolecules Cytoskeleton The structural characteristics of the cell are determined by proteins that form long polymers. Together these polymers are called the cytoskeleton as they form the skeletal structure of the cell. 2.2 What do cells do? All cells need a source of energy to grow. The cells in the grape vines get their energy from the sun, yeast cells get their energy by fermenting the sugars in grape juice, human cells get their energy from materials in our blood that come from the food we ingest. Many of the chemical reactions that generate energy
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