Today’s topics

-cell building blocks (proteins, lipids, nucleic acids, carbohydrates)

-cell structure (plant vs. animal)

-cells and herbivory

Building Blocks of Life• Protons (positive charge), electrons (negative charge), &

neutrons (neutral charge) are building blocks of atoms• Atoms are building blocks of elements (the most basic

“substances”) – Atoms = smallest part of a element that retains the

element’s traits– 92 natural elements– Living organisms mostly: C,O,H,N,P,K,Ca,Mg,S, with

lesser amounts of Fe,Cl, Mn, Zn, B, Cu, Mo, etc.– Atoms held together with chemical bonds

• E.g., covalent, ionic, hydrogen• Elements are building blocks of molecules (made from

one or more atoms) and compounds (made from one or more elements)

Figure 1.7

Figure 1.8a

Figure 1.8b

The processes of life are based on the chemical nature and interactions of:

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids

• Secondary metabolites/compounds

Carbohydrates

• Comprised mostly of carbon (C), hydrogen (H), and oxygen (O), in the proportion (CH2O)n (where n = 3-7 for simple sugars)

• Many functions; e.g., fuel, storage, structural, signaling

• Simple sugars (e.g., glucose, fructose = monosaccharides) to complex macromolecules (cellulose, glycogen, starch = polysaccharides)

Figure 1.9

Lipids

• Comprised mostly of C & H (so often called hydrocarbons)

• Insoluble in water

• Several major classes (fats & oils = triglycerides; phospholipids; fatty acids; sterols, e.g. cholesterol; waxes)

• Many functions (e.g., energy/storage, structural, signaling/hormones)

Proteins

• Comprised of amino acids (AAs)• Chain of amino acids = oligo- or poly-

peptide, cause amino acids held together by covalent peptide bonds

• Polypeptides (one or more) make proteins/enzymes; oligo-peptides common signaling molecules

• AAs built from C,H,O,N, and sometimes S• 20 common AAs used for most proteins

Figure 1.10

Figure 1.11

Nucleic Acids• Comprised of nucleotide building blocks

containing C,H,O,N,P• Nucleotides contain a sugar (ribose, for RNA, or

deoxyribose for DNA), phosphate (PO4), and nitrogenous base (5 kinds)

• Arranged in long chains in DNA (double helix) and some RNA (single chain), or in other shapes

• Major function is storage and expression of genetic code (DNA,RNA) and energy (ATP)

Figure 1.13

All living organisms share certain characteristics

• growth and reproduction

• ability to respond

• ability to evolve and adapt

• metabolism

• organized structure

• organic composition

Cell theory

• Cell is basic unit of life

• Organisms are composed of cells

• Cells arise from pre-existing cells

Figure 27.1  The three major lineages of life

Nucleus

Membrane-bound organelles

Types of cellseukaryotes vs. prokaryotes

• Have a nuclear envelope

• DNA double-stranded• Have 2+

chromosomes• Have membrane-

bound organelles• Have asexual reprdn

by mitosis• Have sex by fusion

• No nuclear envelope• Have single strand of

DNA• No chromosomes• No organelles• Asexual reproduction

by fission• No sexual

reproduction

Figure 2-6

Fig. 5.10a

Fig. 19.1

Mitosis in a plant cell

Mitosis in an onion root

Cytokinesis in animal and plant cells

Fig. 5.22

The mitochondrion, site of cellular respiration

Fig. 5.13

Fig. 5.15

Fig. 5.28

Figure 7.19  Peroxisome

Fig. 5.29

Fig. 7.1

Fig. 7.22

Plant vs. animal cell: structure?

Plant vs. animal cells• Plant

– Cell wall– Plastids– Tonoplast

– Divide by inserting wall– Plasmodesmata– Ergastic deposits common

– Modular construction– Stem cells common– Totipotent cells common

• Animal– No cell wall– No plastids– No tonoplast

• (lysomes instead)

– Divide by pinching– Gap junctions– Deposits rare

– Non-modular– Stem cells rare– No totipotency

Plant vs. animal cell: consequences for eating?

Eating a plant cell-Dealing with the cell wall.

-the most abundant food on earth,

but nutritionally poor food

-the best defense

-What to eat? Where’s C & N?

-Eat wall, cytoplasm, or both?

-how?

-Specialist or generalist?

-Dealing with low [N] of plants.