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Chapter 1 Cell Structure and Function

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1 Chapter 1 Cell Structure and Function

2 Prelecture Quiz (True False)
The endoplasmic reticulum is the control center of the cell. Cells communicate with each other by means of chemical messenger systems. The glycolytic pathway does not require oxygen to produce cellular energy. Examples of passive movement across the cell membrane include diffusion, osmosis, and active transport. Cells with a similar embryonic origin or function are often organized into larger functional units called tissues. F T

3 Prelecture Quiz __________ tissue is the most abundant tissue type in the body. Three types of __________ tissue exist: skeletal, cardiac, and smooth. __________ literally means “cell eating” and involves the engulfment and subsequent killing or degradation of microorganisms and other particulate matter. The __________ serve as sites of protein synthesis in the cell. Cell metabolism is the process that converts carbohydrates, proteins, and fats into __________, which is the major source of energy for all body cells. ATP Connective muscle Phagocytosis Ribosomes

4 Cell Structure

5 Cell Components Nucleus and nucleolus
Cytoplasm and cytoplasmic organelles Ribosomes Endoplasmic reticulum Golgi complex Lysosomes, peroxisomes Mitochondria Cytoskeleton Microtubules, microfilaments

6 The Plasma Membrane

7 Red Blood Cells Start Out with All the Organelles
As they mature, they: Lose their lysosomes Produce hemoglobin Have small Golgi bodies Have enlarged endoplasmic reticulum When they are mature, they: Lose their endoplasmic reticulum Lose their mitochondria How does this relate to their function?

8 Question By the time a red blood cell (RBC) is mature, it has lost all but which of the following? a. lysosomes b. endoplasmic reticulum c. hemoglobin d. mitochondria

9 Answer Hemoglobin Because the function of the RBC is to carry oxygen, hemoglobin is an essential component of the cell (each hemoglobin molecule can carry four molecules of oxygen) . Lysosomes, endoplasmic reticulum, and mitochondria all exert some metabolic function in other cells. But, if they remained in the RBC, the oxygen on board would be consumed before reaching its destination.

10 Anaerobic Energy Metabolism— Glycolysis
In the cytoplasm, molecules are broken into chunks, 2-carbons each Glycolysis breaks sugar  2 ATP molecules formed Other pathways break fatty acids or amino acids Breaking molecules involves removing electrons Which are handed to electron carriers like NAD and FAD H+ follow the electrons Afterwards, they are put back on the 2-carbon chunks Forming lactic acid

11 Aerobic Energy Metabolism—Krebs Cycle
The 2-Carbon molecules don’t make lactic acid but 2-carbon molecules enter the mitochondrion matrix space Krebs cycle breaks them down  1 ATP molecule formed Carbon is lost as CO2 Energy is extracted from nutrients and used to form ATP from ADP Energy is released to do cellular work when ATP is broken back down to ADP

12 Krebs Cycle Occurs within Mitochondria
Breaking molecules involves removing electrons Handed to electron carriers like NAD and FAD H+ follows the electrons Many of these electron carriers are loaded up with electrons by the Krebs cycle

13 Question Tell whether the following statement is true or false: ATP is produced in the mitochondria.

14 Answer True The Krebs cycle occurs in the mitochondria. Each Krebs cycle produces one molecule of ATP.

15 Diffusion Is Movement of Molecules
Passive diffusion: molecules move randomly away from the area where they are most concentrated Facilitated diffusion: molecules diffuse across a membrane by passing through a protein Osmosis: diffusion of water molecules

16 Question Your patient has been given an intravenous solution of water. What will happen to this patient’s red blood cells? They will burst/lyse. They will shrink. They will not be affected by the water solution.

17 Answer They will burst/lyse. Osmosis causes movement from “more watery” to “less watery.” Because water is “more watery” than the RBC (it’s water, after all), water moves into the cell, causing it to expand and burst/lyse.

18 Cell Communication A messenger molecule attaches to receptor proteins on cell surface Receptor proteins cause cell to respond by: Opening ion channels to let ions in or out Causing a second molecule to be released inside the cell Turning on enzymes inside the cell Stimulating the transcription of genes in the nucleus

19 The Basics of Cell Firing
Cells begin with a negative charge: resting membrane potential Stimulus causes some Na+ channels to open Na+ diffuses in, making the cell more positive

20 The Basics of Cell Firing (cont.)
At threshold potential, more Na+ channels open Na+ rushes in, making the cell very positive: depolarization Action potential: the cell responds (e.g., by contracting)

21 The Basics of Cell Firing (cont.)
K+ channels open K+ diffuses out, making the cell negative again: repolarization Na+/K+ ATPase removes the Na+ from the cell and pumps the K+ back in


23 Question Tell whether the following statement is true or false: An action potential is the result of K+ movement out of the cell.

24 Answer False An action potential occurs when Na+ moves into the cell, making it more positive on the inside (depolarization). When K+ leaves the cell, it becomes less positive (more negative) until it returns to resting membrane potential (repolarization).

25 Muscle Contraction Na+ enters cell and muscle cell depolarizes
Ca2+ released from sarcoplasmic reticulum into the sarcoplasm Ca2+ attaches to troponin

26 Question What happens to the sarcomere when myosin slides across the actin binding sites? It gets longer. It gets shorter. There is no change in length. It releases acetylcholinesterase.

27 Answer It gets shorter. When the myosin binds with exposed actin sites (myosin “reaches” forward like your hands do when pulling end-over-end on a rope), the Z lines get pulled closer together, and the muscle cell shortens/contracts.

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