Chapter 2: The Nature of Life

What makes something alive, or

“living”?

Characteristics of Living Things

Composition (made of cells) Structure (cell wall) Growth (increase in mass and number of cells) Reproduction Response to stimuli Metabolism (all chemical reactions within cells:

respiration, photosynthesis, digestion, etc.) Movement Organization (molecules cells tissues organs,

etc) Evolution

Chemical and Physical Bases of Life Matter: anything that takes up space Made of elements Atom: smallest stable unit of an element Molecules: two or more atoms held together by

chemical bonds Chemical reactions are controlled by enzymes 3 types of Chemical bonds:

Hydrogen Covalent Ionic

Polarity of Molecules Uneven distribution of electrons (charges)

on a molecule Affects the way molecules interact with each

other Capillarity of water Cohesion of water molecules Adhesive properties of water

Acids, Bases, and Salts Due to polarity of water molecules Acids: pH <7, excess hydrogen (H+) ions Bases: pH>7, excess hydroxide (OH-) ions pH scale is used to measure # H+ in a

solution **pH of soil can drastically affect the growth

of a plant

Energy The ability to do work *We will discuss with photosynthesis

Chemical Components of Cells

Organic: molecules make up 96% of cytoplasm

Carbon, hydrogen, oxygen, and nitrogen Inorganic: molecules with no carbon

Can you name the 4 main groups of

organic molecules?

Monomers and Polymers Polymer: macromolecule “large molecules” Monomer: smaller molecules that build

polymers Carbohydrates: main source of energy

Monosaccharides, disaccharides, polysaccharides

Cellulose: makes up cell walls of plants

Monomers and Polymers Lipids: insoluble in water; store energy

Fats, oils, waxes, phospholipids Proteins: regulate chemical reactions, chains

of amino acids Plants use storage proteins in some cases ex: legumes, gluten Enzymes: organic catalysts, names end in –ase

Nucleic Acids: made of nucleotides, store genetic information; ex: DNA and RNA

Chapter 3: Cells

History Robert Hooke: named cells; looked at cork

cells Cell Theory

All organisms are made of cells Cells are the basic unit of life New cells come from pre-existing cells

What are the two main classifications

of cells?

Cell Classification Prokaryotic: no nuclei and lack membrane-

bound organelles Ex: bacteria

Eukaryotic: have nuclei and other organelles Ex: protists, plants, fungi, and animals

Cells are very small and can be various shapes

Bacteria < Animal <Plant (Usually)

Plant Cells Have cell wall outside cell membrane Mostly cellulose in bundles called

microfibrils Also contains pectins and lignins for strength Some plant cells have thicker cell walls

depending on their function Cells are connected by structures called

plasmodesmata: used for communication and movement

Cell Components Cytoplasm: jellylike fluid holding organelles

in place Plasma or Cell Membrane: semipermeable,

allows materials in and out, made of phospholipids and proteins

Nucleus: control center of the cell, contains the DNA Nuclear envelope, nucleolus, chromatin

Cell Components Endoplasmic Reticulum: cell communication

and transport of materials Rough and Smooth ER

Ribosomes: site of protein synthesis, made of RNA and proteins

Golgi apparatus: synthesize and package

Cell Components Mitochondria: powerhouse of the cell, site of

cellular respiration Vacuoles: maintain pressures inside cell and

hold cell sap: mostly water with dissolved salts, sugars, proteins, etc.

Cytoskeleton: movement and structure of cell Microtubules and microfilaments

Plastids Chloroplast: site of photosynthesis

Contains pigment chlorophyll Chromoplast: similar to chloroplast but have

carotenoids: yellow, orange, and red pigments; abundant in carrots, tomatoes, and red peppers

Leucoplast: colorless, synthesize starches and oils; can develop into chloroplasts

How do existing cells make new cells?

The Cell Cycle Cell division Interphase: mostly growth and DNA

replication Mitosis: division of the cell nucleus

Prophase, Metaphase, Anaphase, and Telophase Cytokinesis: division of the cytoplasm,

formation of the cell plate Results in two identical daughter cells

Plant cells vs. Animal cells Structures unique to plant cells:

Cell wall Plasmodesmata Cell plate

Minor differences: No centrioles in plant cells Plant cells contain plastids Vacuoles small or absent in animal cells