Cellular Nature of Life?

• Cell – fundamental unit of life
• Smallest entity with characteristics of life
• Cells acquire and use energy
• Cells acquire and organize materials

Microscopes made discovery of cells possible

• –Robert Hooke (1662) – built the primitive microscope
• – Anton van Leeuwenhoek (1674) built microscope with 200X
• Excellent quality, could see bacteria

Cell theory – proposed in 1800s

• Matthias Schleiden & Theodor Schwann proposed that

• Cells are the fundamental units of life
• All organisms are composed of one or more cells
• All cells arise from preexisting cells

Chemical Nature of Cells?

• Building blocks of cells are complex molecules based on carbon
• Large organic compounds of cells
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

Biological Macromolecules

• •Carbohydrates (CHOs)
• –Monosaccharide
• Simplest carbohydrates. Single sugar molecule may have from 3-7 Cs

• – Disaccharide

Composed of two monosaccharides joined together by a covalent bond
–Maltose (malt sugar) - 2 glucose units
–Lactose (milk sugar) - 1 galactose unit, and 1 glucose unit

• – Polysaccharide

Long monosaccharide chains - 100s or 1000s
–Starch – made in plants
– Glycogen – made in animals
– Cellulose – made of repeat glucose
•Unbranched found in plants
• Most abundant organic material on earth

•Lipids (fats)

–Heterogeneous, diverse class of molecules
– Share a single property – not soluble in water
– Complex lipids and simple lipids

•Different types of cellular lipids

Complex Lipids
•Fatty acids (bound to glycerol)

–Saturated – have double bonds

•Found in tropical oils & animal fats

–Unsaturated – varying numbers of double bonds

•Triglycerides – contain glycerol
• Phospholipids
Simple Lipids
•Have no fatty acids in structure

–Steroids, Cholesterol, Steroid hormones

Proteins (most complex)

–Direct products of genes
– Function determined by features of primary & higher order structures
– Functions include structural mole-cules, enzymes & cellular messengers

Levels of Structure  - 3D Nature of Proteins

–Primary
– Secondary
– Tertiary

Nucleic Acids

–Polymers of nucleotides
– Two kinds of polymers

•Ribonucleic acid (RNA)
–Contain ribose
•Deoxyribonucleic acid (DNA)
–Contain deoxyribose

• Nucleotides & Nucleic Acids
• Adenosine triphosphate (ATP)

–Ribonucleotide & 2 phosphates

• Nucleotide coenzymes (NAD, FAD)

–Cellular energetics & metabolism

• Nucleotide polymers (RNA, DNA)

–Contain & convey hereditary info.

Membranes Surround all Cells

• •Introduction to structure
• –Membrane surrounding cell separates contents from surroundings
• – 1935 – Membranes composed of lipids and proteins
• •Fluid mosaic – dynamic nature of lipids & proteins in membrane

Types of Membrane

• Protein & Carbohydrates

–Integral proteins - Proteins that penetrate bi-layer

–Peripheral proteins -Do not penetrate bi-layer

–Lipid-anchored proteins - Specialized type of regular proteins

Diffusion & Osmosis

Materials enter and leave cells through membranes

Simple Diffusion -Nonpolar molecules move through spaces in bilayer

Transport Proteins - Integral proteins that regulate movement of substances across the membrane

Facilitated Diffusion - Transport molecules that cannot pass directly through bilayer

Active Transport
•Molecules are moved in direction opposite to concentration gradient
• Accomplished by membrane proteins (carrier proteins)

Endocytosis - Cell membrane engulfs items in bulk, transported in vesicles

Exocytosis - Export of cellular products in bulk

Types of Cells

• More than 200 cell types - Shapes vary – spherical, elongated, box-shaped, flat
• Organelles - Specialized structures in cell that participate in cellular activities
• Two cell types – prokaryotes & eukaryotes

Prokaryotic Cells

• Have few internal parts
• Include true bacteria
• On earth 3.8 million years
• Found nearly everywhere
• Spores in each breath; intestines
•  Naturally in soil, air, hot springs
• Structurally relatively simple

Eukaryotic Cells

• Have numerous internal structures
• Various types & forms – Plants, animals, fungi, protists
• Multicellular organisms

Eukaryotic Cells: Organelles

• Nucleus
• central to cell activities
• Nucleolus
• found in nucleus
• small structure of DNA & RNA
• Cell wall
• Plasma membrane
• fluid mosaic membrane
• Endoplasmic reticulum (ER)
• forms network of membranes
• Rough endoplasmic reticulum (RER)
• Smooth endoplasmic reticulum (SER)
• Golgi complex
• packaging center for the cell
• Energy sources for cell activities
• –Mitochondria
• – Chloroplasts
• found only in photosynthetic cells
• Surface structures
• Flagella
• Cilia
• Cytoskeleton
• internal infrastructure
• Cytoplasm/cytosol
• liquid portion of cells

Plant & Animal Cells

•Similarities

–Both constructed from eukaryotic cells
– Both contain similar organelles
– Both surrounded by cell membrane

•Differences

–Plants have
•Cell wall – provides strength & rigidity
•Have chloroplasts, photosynthetic

Brief Look at Viruses

• •Viruses are acellular
• • Not considered to be living
• • Cause serious diseases in most organisms

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