BIOLOGY 11

HUMAN BIOLOGY

The Scientific Method

1. Observation

2. Hypothesis: a testable explanation

3. Experiment: 1). control group

2). repeatability

4. Conclusion: hypothesis supported or disproved

Scientists typically ask lots of questions!

Characteristics of Life

1. Living things reproduce

2. Living things are composed of cells

3. Living things metabolize and grow

4. Living things respond

5. Living things maintain constant internal

conditions (homeostasis)

6. Living things evolve

Evolution in a Nutshell

1. Evolution: the transformation of life on Earth from its earliest beginnings to its diversity today

2. All of life is connected. Life began as a single cell more than 3 billion years ago

3. Genetic variation among individuals4. Resources are limited – competition5. Individuals with useful variations leave

more offspring

CELLULAR BIOLOGY

ATOMIC STRUCTURE

1. Chemistry terms:Atom = smallest chemical unit

Proton (+ charge)Neutron (neutral)Electron (- charge)

Element = atom with specific # of protonsin the nucleus – oxygen – 8 –the atomic number of oxygen is 8

Periodic Table lists elements in order of atomic number

Isotopes are versions of an element with different number of neutrons in the nucleus – some are stable; some are radioactive

2. Electron arrangements Shells = energy levels surrounding

nucleus, where electrons can orbit

The number of electrons = number of protonsShells fill at lowest (innermost) energy level first

First shell holds up to 2 electrons; the next shells can hold 8 electrons:

Helium (AN 2)

Carbon (AN 6)

Chlorine (AN 17) 2 + 8 + 7

Chemical Bonds

Valence shell = the outermost energy level that has any electrons in it

Atoms are most stable when the valence shell is filled – see noble gases of periodic table

Some atoms can “steal” electrons to fill valences shell; they are “ionized” – no longer neutral – Ex. – sodium chloride

Electronegativity measures the ability to attract electrons

Type of bond atoms form depends on their electronegativity

1. Very different electronegativity: IONIC BOND

2. Same electronegativity: COVALENT BOND

Hydrogen bonds are between some molecules with polar covalent bonds, and are relatively weak – water – Fig. 2.7

Example: Water

Unusual properties of water:1. Cohesiveness – surface tension2. High specific heat (vaporization)3. Good solvent for other polar (charged

molecules) When atoms bond to other atoms we have

multiple atoms coming together to form a molecule – water is a molecule

Water and the pH scale: The pH scale measures the concentration of hydrogen ion in solution

Chemical buffers maintain/stabilize a particular pH in a solution by either absorbing or releasing hydrogen ions

Macromolecules

Macromolecules are VERY LARGE molecules.

Many are polymers = long chains of single (monomer) subunits

Biological polymers:1. Polysaccharides (sugars)

-monosaccharides-2. Proteins – amino acids3. Nucleic acids - nucleotides

Macromolecules associated with living organisms

Carbohydrates, lipids, proteins, nucleic acids

1. Carbohydrates – have C, H, O

Two linked together form a disaccharide

Polysaccharides are long chains consisting of 8 or more monomers – usually glucose

A. starch – energy storage in plants

B. glycogen – energy storage in

animals

C. chitin – cell wall of insects and

crustaceans

D. cellulose – cell walls of plants

2. Lipids have C, H, and are not soluble in

water A. Triglycerides = fats and oils – glycerol is

the backbone and fatty acids are

hooked on by dehydration synthesis

The different fatty acids have more or less C’s in their chains, and may have double bonds (covalent sharing of two pairs of electrons

Double bonds put “kinks” in the fatty acid chain

Saturated = no double bonds; pack well;

solid fats

Unsaturated = double bond(s); pack

poorly; liquid oils

B. Phospholipids – Also use glycerol backbone; two fatty acids and one phosphate group is put on

The fatty acid parts are “hydrophobic” = not water soluble

The phosphate group is polar and “hydrophilic”

C. Steroids have four fused rings of carbon,

but attachments vary. Ex.s: cholesterol,

testosterone, estrogen. Not water soluble

3. Proteins are chains of amino acid subunits

There are 20 kinds of amino acids, with the same basic structure but different side chains. The side chains are chemically varied (charge, size, hydrophicity)

The sequence of amino acids determines what shape the protein will fold into; the shape determines function

There are 4 levels of protein structure:

A. Primary: Sequence of amino acids

B. Secondary: Folding over of polymer.

Hydrogen bonds hold the shape together

4. Nucleic acids: RNA and DNA

Monomer unit is called a nucleotide = phosphate, sugar, nitrogen base

Phosphate and sugars join in chain with bases paired in the center

A very special nucleotide monomer is ATP, the molecule that moves ENERGY around the cell

Cell Structure (eukaryotic vs. prokaryotoic)

Plasma membrane, nucleus, and cytoplasm (cytosol + organelles) make up a eukaryotic cell. May or may not have a cell wall

A prokaryotic cell (bacterium) has no nucleus or membrane bound organelles. May or may not have a cell wall

Cell membranes, chemically, are phospholipid bylayers

Membranes are very fluid and can join together or pull off like soap bubbles allowing large substances to enter or leave the cell – phagocytosis and pinocytosis

May have cholesterol present

Molecules are able to move across this membrane using several processes:

1. Simple diffusion2. Osmosis3. Facilitated transport4. Active transport – Na+ and K+ pump

- nerve and muscle cells

Cell Organelles

Nucleus – contains DNA (genetic material)

Double membrane with pores

Nucleolus – makes RNA part of ribosomes

Mitochondrion – processes food molecules into ATP energy

Two membranes; inner highly folded

Ribosomes – factories for making proteins

Very small; made of RNA and protein

Endoplasmic reticulum – Rough: secretion of proteins out of the cell

Smooth: membrane production; detoxification

Membranous network: rough is coated with ribosomes, smooth has none

Golgi complex – processing and routing of some newly made proteins

Stack of flattened membranes

Lysosomes: contain digestive enzymes;

Membranous vesicles with enzymes inside

Cytoskeleton

Helps maintain cell shape. Also anchors and organizes organelles and helps with their movement

1. Microtubules: large diameter hollow fibers made of tubulin protein

2. Actin filaments: thin solid fibers made of actin protein

3. Intermediate filaments: in between other two in size; made of diverse proteins

Actin filaments and intermediate filaments involved in cell shape and motion

Microtubules: cilia, flagella, and the mitotic spindle; 9 + 2 configuration

cilia are short and numerous

flagella are long and usually singular

Cilia and flagella move when the microtubules move – requires ATP

Cell Energetics

Cellular (aerobic) respiration breaks glucose down to carbon dioxide, water, and ENERGY.

The ENERGY released is stored in the form of ATP

C6H12O6 + 6 O2 6 CO2 + 6 H2O + ATP

Carbon-carbon bonds contain energy; when they break, ATP is formed

1. Glycolysis (in cytoplasm): 6C 2 3C

(pyruvate) + 2ATP

2. Transition: each 3C 2C (acetyl CoA) +

CO2

3. Citric acid cycle: each 2C 2 CO2 + 2ATP

4. Electron transport chain: electrons from steps 1-3 bounce down acceptors to

O2 (final electron acceptor) H2O + 36ATP

Mitochondrial structure & ATP production

Electron transport chain: inner membraneElectrons transferred down a variety of electron

carriers – energy conserved

Electron transport chain produces the most ATP of the 4 steps

Oxygen gas required

Fermentation

2 ATP produced

Electron carriers give over electrons to pyruvate to produce products:

Lactic acid, alcohol, CO2 are examples

Examples: overworked muscles, yeasts brewing beer or raising bread

Cell Division

Mitosis (asexual) and cytokinesis

Chromosome: tightly coiled DNA

Humans: 46 per cell – 23 pairs; 2N=46 N=23

2N = diploid cell; N = haploid cell

Each chromosome has a centromere

Steps of Mitosis

1. Prophase – chromosomes seen

2. Metaphase – chromosomes line up in the

middle

3. Anaphase – chromosomes move apart

4. Telophase – the end of chromosome

division

Terms to remember

Nuclear envelope

Chromatin

Mitotic spindle

Sister chromatids

Cytokinesis

Cell Cycle