Day 5 September 9th Chapter 3 and Exam

ReviewDr. Amy B HollingsworthThe University of Akron

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.

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

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.

The diffusion of water across a membrane is a special type of passive transport called osmosis.

Water molecules move across the membrane until the concentration of water inside and outside of the cell is equalized.

3.10 In active transport, cells use energy to move small molecules.

Molecules can’t always move spontaneously and effortlessly in

and out of cells.

Two distinct types of active transport:

1. Primary 2. Secondary

(Differ only in the source of the fuel)

Primary Active Transport:Uses Energy Directly from ATP

Secondary Active Transport An indirect method many transporter

proteins use for fueling their activities

The transport protein simultaneously moves one molecule against its concentration gradient while letting another flow down its concentration gradient.

Secondary Active Transport No ATP is used directly.

At some other point and in some other location, energy from ATP was used to pump one of the types of molecules involved against their concentration gradient.

3.11 Endocytosis and exocytosis are used for bulk transport of particles.

Many molecules are just too big to get

into a cell by passive or active transport.

Three types of endocytosis:

1. Phagocytosis

2. Pinocytosis

3. Receptor-mediated endocytosis

Pinocytosis: the process of cells taking in dissolved particles and liquid

Faulty cell membranes are a primary cause of cardiovascular disease.

What modification to them might be an effective treatment?

Cells are

connected and

communicate

with each other.

3.12 Connections between cells hold them in place and enable them to communicate with each other.

Involves numerous types of protein and glycoprotein adhesion molecules

How can a lack of communication between cells lead to cancer?

Contact inhibition

Tumors

Plasmodesmata

Tube-like channels connecting the cells to each other and enabling communication and transport between them

Consider a plant as one big cell?

Nine important

landmarks

distinguish

eukaryotic

cells.

3.13 The nucleus is the cell’s genetic control center.

The nucleus―the largest and most prominent organelle in most eukaryotic cells.

The nucleus has two primary functions:• genetic control center• storehouse for hereditary

information

Insert new fig 3-26 to right

Chromatin

a mass of long, thin fibers consisting of DNA with some proteins attached

Nucleolus

an area near the center of the nucleus where subunits of the ribosomes are assembled

Ribosomes are like little factories.

3.14 Cytoplasm and cytoskeleton: the cell’s internal environment, physical support, and movement

Cytoskeleton: Three Chief Purposes

Cilia and Flagellum

3.15 Mitochondria: the cell’s energy converters

Bag-within-a-Bag Structure:the intermembrane space and the matrix

Endosymbiosis

Mitochondria may have existed as separate single-celled, bacteria―like organisms billions of years ago.

Mitochondria have their own DNA!

We all have more DNA from one parent thanthe other.

Who is the bigger contributor: mom or dad?

Why?

3.16 Lysosomes are the cell’s garbage disposals.

Lysosomesround, membrane-enclosed, acid-filled

vesicles that function as garbage disposals

The Endomembrane System

Endoplasmic reticulum: where cells build proteins and disarm toxins

Rough Endoplasmic Reticulum

The Smooth Endoplasmic Reticulum

Critical Responsibilities of the Smooth ER

How can long-term use of one drug increase your resistance to another, different drug that you have never encountered?

3.18 Golgi apparatus: Where the cell processes products for delivery throughout the body

3.19 The cell wall provides additional protection and support for plant cells.

3.20 Vacuoles: multipurpose storage sacs for cells

The central vacuole can play an important role in five different areas of plant life:

1. Nutrient storage2. Waste management3. Predator deterrence4. Sexual reproduction5. Physical support

3.21 Chloroplasts: the plant cell’s power plant

The stroma and interconnected little flattened sacs called thylakoids

Endosymbiosis Theory Revisited

Chloroplasts resemble photosynthetic bacteria

Circular DNA

Dual outer membrane

Exam One – Chapters 1 – 3 – all ppts are posted

Study Guide is Posted

Will be open from 4pm – 7pm on Thursday, September 11th. No one will be in this room.

Give yourself enough time, plan if there is a line, and bring your zipcard. You cannot take the exam without one.

If you will miss the exam, tell me ahead of time. If there is an emergency, you will have to take the makeup exam during finals week.