Transcript Cellular Biology I

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 individuals
4. Resources are limited – competition
5. 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 protons
in 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
protons
Shells 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 tension
2. 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)
-monosaccharides2. Proteins – amino acids
3. 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 diffusion
2. Osmosis
3. Facilitated transport
4. 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 membrane
Electrons 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