Chapter two Biomolecule.ppt

Copyright © 2010 Pearson Education, Inc.
BIOCHEMISTRY
 CHAPTER TWO: BIOMOLECULES
SECTION 2.1
What Does Life Require
A Definition of Life
There is no simple definition of life.
But, all Earth organisms…
 Require liquid water
 Have a common set of biological molecules
 Can maintain homeostasis
 Can evolve

2.1 What Does Life Require?
Additional Characteristics of Life
 Cellular organization
 Growth and metabolism
 Reproduction
 Heredity

Physical Properties of Chemicals
 Elements: fundamental forms of matter
 EXP: carbon, hydrogen, oxygen, etc
 Atoms: the smallest units of an element

 Protons (positive
charge) + neutrons
form atomic nucleus
 Electrons (negative
charge) are outside
the nucleus.
Atoms are composed of protons,
neutrons, and electrons

The Chemistry of Water
Molecule:
Two or more atoms held together by chemical bonds
Example: Water
Water molecule: two hydrogen atoms bonded to one
oxygen atom

The Properties of Water
 Water is a polar molecule:
 Oxygen side is slightly
negative
 Hydrogen side is slightly
positive
 Electronegativity = how
strongly the atoms pull
electrons
 When molecules have no
charges, they are
nonpolar

 Hydrogen bond: the weak attraction
between the hydrogen atom of one water
molecule and the oxygen atom of another
 Water molecules tend to stick together:
cohesion

 Due to its polarity, water is a good solvent
 Solute: what is being dissolved
 Solution: the solute in the solvent

The Properties of
Water
 Water can dissolve
salts and hydrophilic
(water–loving)
molecules because it
is polar.

The Properties of Water CONTINUE.
 Water can dissolve acids and bases.
 Acid = a substance that donates H+ ions to
solution
 Base = a substance that accepts H+ ions
Animation—Chemistry and Water
PLAY

 The pH scale is a measure of
the relative amounts of acids
and bases in a solution.
 pH greater than 7 = basic
 Pure water pH = 7 = neutral
 pH lower than 7 = acidic

Organic Chemistry =
The Chemistry of Carbon
Organic Chemistry
 All life on Earth is based on organic
chemistry: the chemistry of the element
carbon.
 Carbon makes up most of the mass of living
organisms.
 Why?

Carbon as a building block
 Carbon forms Covalent bonds: strong bonds
from sharing electrons
 Carbon is like a molecular TinkerToy
 Can bond to 4 different atoms at once
 Carbon can make macromolecules

Nonpolar & Hydrophobic Molecules
 Nonpolar molecules, such as oil, do not
contain charged atoms.
 These atoms are called hydrophobic
(water–hating).

Types of Macromolecules
1. Carbohydrates
2. Proteins
3. Lipids
4. Nucleic Acis
Figure 2.12
Structure and Function of Macromolecules

 Carbohydrates: molecules of carbon,
oxygen, and hydrogen
 Major source of energy for cells

Proteins: polymers of
amino acids; joined
by peptide bonds

Proteins
 There are 20 different common amino acids,
with different chemical properties.
 Amino Acids are made up of carbon, oxygen,
hydrogen, and nitrogen.
 Different combinations of amino acids give
proteins different properties.

 Lipids: hydrophobic; composed mostly of
carbon and hydrogen
 Three important types:

 Nucleic acids = polymers of nucleotides
 Nucleotide = a phosphate + sugar + a
nitrogenous base

 Nucleotides are of two types, depending on the
sugar
 RNA = ribonucleic acid
 DNA = deoxyribonucleic acid
 DNA is the hereditary material in nearly all
organisms.

 The structure of a
DNA molecule is a
double helix made
up of nucleotides.
Figure 2.15a

 Bonding between
bases on opposite
strands follows strict
base-pairing rules:
 A with T
 G with C

Section 2.2
Life on Earth: Part 1 Cells
Cells – the smallest living unit
 All cells on Earth are either:
 Prokaryotic or Eukaryotic.
 Prokaryotic cells are smaller and simpler in
structure.
 EXP: bacteria
 They probably resemble the earliest cells to arise
on Earth.
 Some structures in the Martian meteorite resemble
them.

Cells – the smallest living unit
 All cells on Earth are either:
 Prokaryotic or Eukaryotic.
 Prokaryotic cells are smaller and simpler in
structure.
 EXP: bacteria
 They probably resemble the earliest cells to
arise on Earth.
 Some structures in the Martian meteorite
resemble them.

Characteristics of Cells
 Cells have a cell membrane (plasmalemma)
 a phospholipids bilayer: hydrophobic tails
orient inside the membrane, away from water

 Plasma membrane (plasmalemma) properties.
 Fluid mosaic model: lipids and proteins can
move about within the membrane
 Semipermeable: some molecules can cross
and some can’t

Characteristics of Prokaryotic Cells
 Prokaryotes are simpler than eukaryotes
 Prokaryotes have cell membrane
 Prokaryotes do not have a true nucleus

Characteristics of Cells
 Eukaryotic cells are much more complex.
 Have true nuclei surrounded by a membrane
 Also have membrane-bound organelles with
specialized jobs

Eukaryotic Cell Organelles
 Mitochondria: provide energy for the cell, using
oxygen
 Chloroplasts: sites of photosynthesis in plants
 Endoplasmic reticulum: involved in protein
and lipid synthesis
 Golgi apparatus: modifies and sorts proteins

Prokaryotic and Eukaryotic Cells
Animation—A Comparison of Prokaryotic
and Eukaryotic Cells
PLAY

Animal versus Plant Cells

Section 2.2 Life on Earth
Part 2 Tree of Life
The Tree of Life and Evolutionary Theory
 All Earth organisms share many similarities:
 Same basic biochemistry, with same types of
macromolecules
 All organisms consist of cells
 Cells always have phospholipid bilayer plasma
membrane
 Eukaryotes share most of the same organelles

Prokaryotic and Eukaryotic Cells
 This unity of life is best explained by a tree
of life, with modern species having evolved
from common ancestors.

Section 2.2 Life on Earth
Part 3: Homeostasis
 Homeostasis – a dynamic state of equilibrium in which
internal conditions remain relative stable (Steady State)
 homeostasis maintains constant conditions in the
internal environment
 A homeostatic control system has
 a receptor – can sense internal conditions
 a set point – what conditions should be maintained
at.
 a control center – processes information & sends
instructions to effectors
 an effector – can make changes to internal
conditions

Steve McCommas
Southern Illinois State University
PowerPoint lecture prepared by
LE 40-11
Response
No heat
produced
Room
temperature
decreases
Room
temperature
increases
Set point
Too
hot
Set
point
Heater
turned
off
Too
cold
Set
point
Control center:
thermostat
Heater
turned
on
Response
Heat
produced

Two Types of Regulatory Systems
 Negative Feedback – Homeostatic mechanism
that stops or reduces a change in internal
conditions
 Causes a change in the variable in the opposite
direction as the initial stimulus
 Positive feedback – a physiological mechanism
that disrupts homeostasis and causes dramatic
swings in physiological parameters
 Causes a change in the variable in the same direction
as the initial stimulus

Chapter two Biomolecule.ppt

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