Transcript Chemistry of Life

Chemistry of
Life: Part 1
AHSGE Science Standards (See
Handout)
2a Identify functions of
carbohydrates, lipids, proteins
and nucleic acids in cellular
activities.
3 Identify reactants and
products associated with
photosynthesis and cellular
respiration and the purposes of
these two processes.
I. Chemistry of the Cell : Key Elements
A.
An element is a type
of matter composed of
only one kind of atom
which cannot be broken
down to a simpler
structure.
I. Chemistry of the Cell : Key Elements
B.
The following six
elements are commonly
found in living cells: sulfur,
phosphorous, oxygen,
nitrogen, carbon, &
hydrogen (SPONCH). See
Figure 3.1 Key Elements of
Living Cells
I. Chemistry of the Cell : Key Elements
C.
These elements
make up 99% of all
living tissue & combine
to form the molecules
that are the basis of
cellular function.
I. Chemistry of the Cell : Key Elements
D. Carbon
–1. Carbon is especially important
because 1 carbon atom can make
covalent bonds with 4 other
atoms, resulting in the formation
of very stable & complex
structures.
–2. Carbon is in all living things
as well as in the remains of living
things.
I. Chemistry of the Cell : Key Elements
E.
Molecules containing
carbon are called organic
molecules, while those without
carbon are called inorganic
molecules.
F. Cellular reactions occur in
great part between biological
molecules called biomolecules.
I. Chemistry of the Cell : Key Elements
G.
The 4 primary classes of
cellular biomolecules are
carbohydrates, lipids, proteins
and nucleic acids.
H. Each of these is a polymer,
a long chain of small repeating
units called monomers.
II. Carbohydrates
II. Carbohydrates
A.
Carbohydrates are often
called sugars and are an energy
source.
B. Structurally, they are chains
of carbon units with hydroxyl
groups (-OH) attached.
C. The simplest carbohydrates
are monosaccharides.
II. Carbohydrates
D.
The ends of these
sugars bond & unbond
continuously, so that the
straight chain & cyclic (ringlike) forms are in
equilibrium. See Figure 3.2
Fischer diagram of glucose
& Figure 3.3 Ribose
E.
II. Carbohydrates
These monosaccharides
may join together to form
disaccharides (2),
oligosaccharides (3-10) or
polysaccharides (10+),
depending on how many
monosaccharides make up the
polymeric carbohydrate.
II. Carbohydrates
 F.
Examples
–1. Monosaccharides – fructose &
glucose
–2. Disaccharides – sucrose (table
sugar)
–3. Oligosaccarides – no common
names
–4. Polysaccarides – starch &
cellulose (complex carbs)
III. Lipids
III. Lipids
A.
Lipids are fats, made up of
chains of methylene (-CH2)
units.
B. The chains may be long or
short, & they may be straight
or fused into rings (cyclic).
C. They function as fat
molecules that store energy.
III. Lipids
D.
They are structural
components of the cell
membrane.
E. Important lipids include:
waxes, steroids, fatty acids &
triglicerides. See Figure 3.4
Lipids
F. Example – butter
A.
IV. Proteins
Proteins consist of long,
linear chains of polypeptides.
–1. The polypeptide is a chain
of amino acids monomers.
B. There are 20 standard amino
acids which combine to form
every single protein needed by
the human body. See Figure 3.5
Polypeptide & Figure 3.6 Protein
IV. Proteins
C.
Since mammals cannot
make all 20 amino acids
themselves, they must eat
protein in order to maintain a
healthy diet.
D. Examples – animals
(meat) & vegetables (beans)
V. Nucleic Acids
V. Nucleic Acids
A.
Nucleic acids are found in the
nucleus of a cell.
B. The nucleic acid polymer is
made up of nucleotide
monomers.
–1. The nucleotide monomer
consists of a sugar, a phosphate
group & a nitrogenous base.
See Figure 3.7 A Nucleotide
V. Nucleic Acids
C.
Nucleic acids are the backbone
of the following genetic material:
–1. DNA (deoxyribonucleic acid)
directs the activities of the cell &
contains the sugar deoxyribose.
–2. RNA (ribonucleic acid) is
involved in protein synthesis &
contains the sugar ribose.
V. Nucleic Acids
D.
The bulk of the
cell is made up of
water. See Figure
3.8 Composition of
the Cell
Complete the Section
Review 1: The
Chemistry of the Cell
Cells & Cellular
Transport:
Part 2
VI. Solutions
A.
A solution is a liquid
mixture of solute dissolved in
solvent.
–Example – Think of salt
water, a solution in which
salt (solute) is dissolved in
water (solvent).
VI. Solutions
B.
The interior of a cell is
also a solution.
C. The cytoplasm is a
watery jelly-like substance
(solvent) that contains a
variety of substances
(solutes).
VI. Solutions
D.
Maintaining the concentration
of solutes in the cytoplasm is
critical to cell function.
E. This ideal balance of solutes
within the cell is a state the cell
strives to maintain through a
variety of mechanisms.
–1. This process is called
homeostasis.
VII. Cell Membrane
VII. Cell Membrane
A.
The main purpose of the cell
membrane is to regulate the
movement of materials into &
out of the cell.
B. The membrane is semipermeable, or selectively
permeable, meaning that only
certain substances can go
through.
VII. Cell Membrane

C. The cell
membrane is
composed of a
phospholipid bilayer.
See Figure 2.9
Phospholipid Bilayer
– 1. Each
phospholipid layer
consists of
phosphate groups
attached to 2 fatty
acid tails.
VII. Cell Membrane
–2. The layers arrange
themselves so that the
phosphate heads are on the
outer edges of the
membrane, & the fatty acid
tails compose the interior of
the membrane.
VII. Cell Membrane
–3. Globular proteins used for
various functions are
embedded in the cell
membrane.
–4. The phospholipids are free
to move around allowing the
membrane to stretch & change
shape.
VIII. Cellular Transport
A.
Passive Transport
–1. Passive transport is
spontaneous & does not require
energy.
–2. Molecules move
spontaneously through the cell
membrane from areas of higher
concentration to areas of lower
concentration.
VIII. Cellular Transport
–3. They move with the
concentration gradient.
–4. The 3 types of passive
transport are diffusion,
facilitated diffusion, &
osmosis.
VIII. Cellular Transport
B.
Diffusion is the process by
which substances move directly
through the cell membrane. See
Figure 2.10 Diffusion
C. Facilitated diffusion involves
the help of a carrier protein to
move a substance from 1 side of
the cell wall to the other.
VIII. Cellular Transport
E.
Osmosis is the movement
of water from an area of high
water concentration to an
area of low water
concentration through a semipermeable membrane. See
Figure 2.11 Osmosis
VIII. Cellular Transport
–1. Osmosis is the
diffusion of water.
–2. Osmosis can occur in
either direction depending
on the concentration of
dissolved material inside &
outside the cell.
VIII. Cellular Transport
–3. Defining the solution
concentrations relative to 1
another will predict the
direction in which osmosis will
occur.
–4. Diffusion of water
(osmosis) across a cell
membrane always occurs from
hypotonic to hypertonic.
VIII. Cellular Transport
–5. 3 situations are
possible:
a. Hypotonic Solution
b. Hypertonic Solution
c. Isotonic Solution
a. Hypotonic Solution
–1) The solution surrounding the cell
membrane has a lower concentration
of dissolved substances than the
solution inside the cell membrane.
–2) The solution outside the
membrane is hypotonic with respect
to the solution inside the cell
membrane.
–3) The cell will experience a net gain
of water & swell. See Figure 2.12
Possible Results of Osmosis
b. Hypertonic Solution
–1) The solution surrounding the cell
membrane has a higher concentration
of dissolved solute than the solution
inside the cell membrane.
–2) The solution outside the
membrane is hypertonic with respect
to the solution inside the cell
membrane.
–3) The cell will lose water to its
surroundings causing it to shrink. See
Figure 2.12
c. Isotonic Solution
–1) The concentration of dissolved
solutes is the same inside the cell
as it is outside the cell.
–2) These solutions are said to be
isotonic with respect to each
other.
–3) There will be no net
movement of water across the cell
membrane. See Figure 2.12
VIII. Cellular Transport
F.
Placing plant cells in a
hypotonic solution causes the
plant cell membranes to
shrink away from the cell
wall.
–1. This process is called
plasmolysis.
VIII. Cellular Transport
–2. Plasmolysis can result
in plant cell death due to
water loss.
–3. A wilted plant is
showing signs of
plasmolysis.
VIII. Cellular Transport
G.
Placing a plant in a
hypertonic solution has an
opposite effect:
–1. The cell will swell until the
cell wall allows no more
expansion.
–2. The plant now becomes
very stiff & turgid.
Turgid & Plasmolysed
VIII. Cellular Transport
 H.
Active Transport
–1. The cell may need to move
material across the cell membrane
against the concentration
gradient.
–2. The cell must expend energy.
–3. The movement of substances
from an area of low concentration
to an area of high concentration is
called active transport.
VIII. Cellular Transport
–4. The movement
is characterized by
its directionality.
a. Exocytosis
b. Endocytosis
a.
VIII. Cellular Transport
Exocytosis
–1) Exocytosis is a form of
active transport that removes
materials from the cell.
–2) A sac stores the material
to be removed from the cell,
& then moves near the cell
membrane.
VIII. Cellular Transport
–3) The cell membrane opens, &
the substance is expelled from
the cell.
–4) Waste materials, proteins, &
fats are examples of materials
removed from the cell this way.
See Figure 2.13 Schematic of
Exocytosis & Endocytosis
VIII. Cellular Transport
 b.
Endocytosis
–1) Endocytosis, another form of
active transport, brings materials
into the cell without passing
through the cell membrane.
–2) The membrane folds itself
around the substance, creates a
vesicle & brings the substance into
the cell.
VIII. Cellular Transport
–3) Some unicellular
organisms, such as an
amoeba, obtain food this
way. See Figure 2.13
Schematic of Exocytosis
& Endocytosis
Exocytosis & Endocytosis
IV. Factors Affecting Cellular Activity
 A.
Cellular activity (metabolism,
reproduction, & movement) is
affected by several factors:
–1. Cells cannot grow to extremely
large sizes due to the ratio
between cellular surface area &
internal cell volume.
–2. Environmental factors
(temperature, light, & pH) affect
cellular activity.
V. Fluid Pressure
A.
Fluids
–1. Fluids are liquids & gases.
–2. The collisions of the
particles against the surface of
the container cause the gas or
liquid to exert pressure upon
the container. See Figure 2.14
Particle Motion in Gases
V. Fluid Pressure
B.
Pressure
–1. Pressure is a force (push or
pull) applied uniformly over an
area.
–2. Examples of how pressure
affects humans & plants:
a. Blood pressure in humans
b. Turgor pressure in plants
a.
V. Fluid Pressure
Blood pressure
–1) Blood is moved throughout
the human body through the
use of pressure.
–2) Blood pressure is the
pressure exerted by the blood
on the walls of the blood
vessels.
V. Fluid Pressure
–3) The
continuous cycle
of the heart
contracting &
relaxing creates
the blood
pressure
measured in
millimeters of
mercury (mm
Hg).
b.
V. Fluid Pressure
Turgor pressure
–1) Plants must take up water
from the surrounding
environment through the use of
osmosis.
–2) Once a plant cell is filled with
water, its vacuoles become
swollen & large. The cell has a
large amount of fluid inside
causing a higher pressure.
V. Fluid Pressure
–3) The cell wall begins to exert
pressure on the neighboring cell.
The internal pressure inside the
cell is called turgor pressure. See
Figure 2.15 Turgor pressure from
within the cell
Complete Section
Review 2: The Cell
Membrane & Cellular
Transport
Complete Review