This document summarizes key concepts from a biology textbook. It discusses cholesterol and its role in cell membranes. It then covers proteins, noting they are made of amino acids and serve various functions. It discusses enzymes as proteins that catalyze reactions by lowering activation energy. Finally, it discusses nucleic acids DNA and RNA, noting DNA stores genetic information in base pairs and RNA translates this into proteins.

1. Day 4 September 4th
2014 Chapters 2 and 3
Dr. Amy B Hollingsworth
Natural Science Biology
TEST NEXT THURSDAY

2. Cholesterol
• Important component of most cell membranes.
• Can attach to blood vessel walls and cause
them to thicken.
• Cells in our liver produce almost 90% of the
circulating cholesterol.

4. • Cholesterol and phospholipids are lipids that
are not fats.
• Both are important components in cell
membranes.
• Cholesterol also serves as a precursor to
steroid hormones, important regulators of
growth and development.

5. 2.14–2.18
Proteins are
versatile
macromolecules
that serve as
building blocks.
Hair and
feathers are
made of
proteins

6. 2.14
Proteins are
bodybuilding
macro-molecules.

7. Amino Acids
• Twenty different amino acids
• Strung together to make proteins

9. • Unique combinations of 20 amino acids give
rise to proteins, the chief building blocks of
physical structures that make up all organisms.
• Proteins perform myriad functions, from
assisting chemical reactions to causing blood
clotting to building bones to fighting
microorganisms.

10. 2.15 Proteins are an
essential dietary component.
• Growth
• Repair
• Replacement

11. • Complete Proteins (as milk, eggs, fish, chicken, and
beef )
• Have all essential amino acids
• Incomplete proteins (vegetables, fruits, and grains)
• Complementary proteins (eating two incomplete
proteins together)

12. Insert new fig 2-38

13. 2.16 A protein’s function is influenced by
its three-dimensional shape.

14. • Egg whites contain a lot of protein.
• Why does beating them change their texture,
making them stiff?

15. Why is wet hair easier to style
than dry hair?

16. Why do some people have curly hair and
others have straight hair?

17. 2.17 Enzymes are proteins that
initiate and speed up chemical
reactions.

20. Activation Energy
• Chemical reactions occurring in organisms can
either release energy or consume energy.
• In either case, the reaction needs a little
“push” in order to initiate the reaction―called
activation energy.
• Enzymes act as catalyst by lowering the
activation energy.

21. • Enzymes are proteins that help initiate and
speed up chemical reactions.
• They aren’t permanently altered in the process
but rather can be used again and again.

22. The rate at which an enzyme catalyzes a
reaction is influenced by several
chemical and physical factors.
Insert new figure 2-43, preferably broken into 4 stepped segments

23. Insert fig 2-43, pt 2

24. Insert fig 2-43, pt 3

25. Insert fig 2-43, pt 4

26. “Misspelled” Proteins
• Incorrect amino acid
sequence
• Active site disruptions
• Phenylketonuria
Insert fig 2-44 to right

27. Why do some adults get sick when they
drink milk?

28. 2.19 Nucleic acids are macromolecules
that store information.
Insert fig 2-45

29. Two Types of Nucleic Acids
Deoxyribonucleic
acid (DNA)
Ribonucleic acid
(RNA)
Both play central roles
in directing the
production of proteins.
Insert fig 2-45 to right

30. Information Storage
• The information in a molecule of DNA is
determined by its sequence of bases.
• Adenine, guanine, cytosine, and thymine
• CGATTACCCGAT

31. 2.20 DNA holds the genetic
information to build an organism.
Insert new fig 2-46

32. Base-Pairing
• A & T, G & C
• What is the complimentary strand to
this strand: CCCCTTAGGAACC?

33. • DNA is shaped like a ladder in which the long
vertical sides of the ladder are made from a
sequence of sugar-phosphate-sugar-phosphate
molecules and the rungs are pairs of nucleotide
bases.
• The sequence of nucleotide bases contains the
information about how to produce a particular
protein.

34. 2.21 RNA is a universal translator, reading
DNA and directing protein production.
Insert fig 2-47

35. RNA differs from DNA in three
important ways.
The sugar molecule of the sugar-phosphate
backbone
Single-stranded
Uracil (U) replaces thymine (T)

36. Chapter 3: Cells
The smallest part of you
Lectures by Mark Manteuffel, St. Louis Community College

37. • Describe what a cell is and the two general types of cells.
• Describe the structure and functions of cell membranes.
• Describe several ways in which molecules move across
membranes.
• Describe how cells are connected and how they communicate
with each other.
• Describe nine important landmarks in eukaryotic cells.

38. 3.1–3.3
What is a cell?

39. 3.1 All organisms
are made of cells.

40. The cell: The smallest unit
of life that can function
independently and perform
all the necessary functions
of life, including
reproducing itself.

41. Cells
• Robert Hooke, a British scientist, mid-1600s
• A cell is a three-dimensional structure, like a
fluid-filled balloon, in which many of the
essential chemical reactions of life take place.
• Nearly all cells contain DNA (deoxyribonucleic
acid).

42. How to See a Cell

43. Cell Theory
1. All living organisms are made up of one or
more cells.
2. All cells arise from other pre-existing cells.

44. 3.2 Prokaryotic cells are structurally simple,
but there are many types of them.
Every cell on earth falls into one of two basic
categories:
1. A eukaryotic cell
• has a central control structure called a nucleus, which
contains the cell’s DNA.
• eukaryotes
2. A prokaryotic cell
• does not have a nucleus; its DNA simply resides in the
middle of the cell.
• prokaryotes

46. 3.3 Eukaryotic cells have compartments
with specialized functions.

47. Eukaryotic cells have organelles.

49. Endosymbiosis Theory
Developed to explain the presence of two
organelles in eukaryotes, chloroplasts in plants
and algae, and mitochondria in plants and
animals.

50. Humans, deep down,
may be part bacteria.
How can that be?

52. 3-4. Every cell is bordered by a plasma
membrane.

53. Why are plasma membranes such
complex structures?
They perform several critical functions.
• Take in food and nutrients
• Dispose of waste products
• Build and export molecules
• Regulate heat exchange
• Regulate flow of materials in and out of cell

55. 3.5 Molecules embedded within the plasma
membrane help it perform its functions.

56. What determines whether a protein resides on
the surface or extends through the bilayer?

57. There are four primary types of
membrane proteins, each of which
performs a different function.

58. 3-6. Faulty membranes can cause
disease.

59. 3.7 Membrane surfaces have a
“fingerprint” that identifies the cell.
Cells with an improper fingerprint are
recognized as foreign and are attacked by
your body’s defenses.

61. Q.Why is it extremely
unlikely that a person
will catch HIV from
casual contact—such as
shaking hands—with an
infected individual?
A. The AIDS-causing HIV
virus uses the molecular
markers on a cell’s plasma
membranes to infect an
individual’s cells.

62. CD4 cells are
found only
on cells
deep within
the body
and in the
bloodstream
, such as
immune
system cells
and some
nerve cells.
Even if millions of HIV particles are present on one
person’s hands, they just can’t gain access to any of
the other person’s surface cells.

63. 3.8–3.11
Molecules move
across membranes
in several ways.

64. 3.8 Passive transport is the
spontaneous diffusion of molecules
across a membrane.
There are two types of passive transport:
1. Diffusion
2. Osmosis

65. Diffusion and Concentration Gradients
• Solutes
• Solvents

66. Simple Diffusion

67. Facilitated Diffusion
• Most molecules can’t get through plasma
membranes on their own.
• Carrier molecules
• Transport proteins

68. Defects in Transport Proteins
• Can reduce or even bring facilitated diffusion to
a complete stop
• Serious health consequences
• Many genetic diseases
• Cystinuria and kidney stones

69. 3.9
Osmosis is
the passive
diffusion of
water
across a
membrane.

70. Cells in Solution
Tonicity
• The relative concentration of solutes outside of
the cell relative to inside the cell
Hypertonic
Hypotonic
Isotonic

72. How do laxatives relieve constipation?
Milk of magnesia and
magnesium salts
Water moves via
osmosis from the cells
into the intestines.

73. The Direction of Osmosis
• Determined only by a difference in total
concentration of all the molecules dissolved
in the water
• It does not matter what solutes they are.