Day 4 September 4th 2014 Chapters

2 and 3

Dr. Amy B HollingsworthNatural Science Biology

TEST NEXT THURSDAY

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.

• 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.

2.14–2.18

Proteins are

versatile

macromolecules

that serve as

building blocks.

Hair and feathers

are made of

proteins

2.14 Proteins are bodybuilding macro-molecules.

Amino Acids• Twenty different amino acids

• Strung together to make proteins

• 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.

2.15 Proteins are an essential dietary component.

• Growth

• Repair

• Replacement

• 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)

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

• Egg whites contain a lot of protein.• Why does beating them change their

texture, making them stiff?

Why is wet hair easier to style than dry hair?

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

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

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.

• 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.

The rate at which an enzyme catalyzes a reaction is influenced by several chemical and physical factors.

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“Misspelled” Proteins• Incorrect amino acid

sequence

• Active site disruptions

• Phenylketonuria

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Why do some adults get sick when they drink milk?

2.19 Nucleic acids are macromolecules that store information.

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Two Types of Nucleic AcidsDeoxyribonucleic acid (DNA)

Ribonucleic acid (RNA)

Both play central roles in directing the production of proteins.

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Information Storage• The information in a molecule of DNA is

determined by its sequence of bases.

• Adenine, guanine, cytosine, and thymine

• CGATTACCCGAT

2.20 DNA holds the genetic information to build an organism.

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Base-Pairing• A & T, G & C

• What is the complimentary strand to this strand: CCCCTTAGGAACC?

• 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.

2.21 RNA is a universal translator, reading DNA and directing protein production.

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RNA differs from DNA in three important ways.

The sugar molecule of the sugar-phosphate backbone

Single-stranded

Uracil (U) replaces thymine (T)

Chapter 3: Cells

The smallest part of youLectures by Mark Manteuffel, St. Louis Community College

• 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.

3.1–3.3

What is a cell?

3.1 All organisms are made of cells.

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

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).

How to See a Cell

Cell Theory1. All living organisms are made up of one

or more cells.

2. All cells arise from other pre-existing cells.

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.

• eukaryotes2. A prokaryotic cell

• does not have a nucleus; its DNA simply resides in the middle of the cell.

• prokaryotes

3.3 Eukaryotic cells have compartments with specialized functions.

Eukaryotic cells have organelles.

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

Humans, deep down, may be part bacteria.

How can that be?

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

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

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

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

There are four primary types of membrane proteins, each of which

performs a different function.

3-6. Faulty membranes can cause disease.

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.

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.

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.

3.8–3.11

Molecules move

across membranes in

several ways.

There are two types of passive transport:1. Diffusion2. Osmosis

3.8 Passive transport is the spontaneous diffusion of molecules across a membrane.

Diffusion and Concentration Gradients

• Solutes• Solvents

Simple Diffusion

Facilitated Diffusion

• Most molecules can’t get through plasma membranes on their own.

• Carrier molecules• Transport proteins

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

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

Cells in SolutionTonicity

• The relative concentration of solutes outside of the cell relative to inside the cell

Hypertonic

Hypotonic

Isotonic

How do laxatives relieve constipation?

Milk of magnesia and magnesium salts

Water moves via osmosis from the cells into the intestines.

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.