CHAPTER 1
CELL STRUCTURE AND FUNCTION
CHAPTER 1
CELL STRUCTURE AND FUNCTION
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
T
F
T
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
CELL STRUCTURE
CELL COMPONENTS Nucleus and nucleolus Cytoplasm and cytoplasmic
organelles Ribosomes Endoplasmic reticulum Golgi complex Lysosomes, peroxisomes Mitochondria
Cytoskeleton Microtubules, microfilaments
THE PLASMA MEMBRANE
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?How does this relate to their function?
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
ANSWER
c. 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.
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
º Which are handed to electron carriers like NAD and FAD
º H+ follow the electrons Afterwards, they are put back on the 2-carbon
chunksº Forming lactic acid
AEROBIC ENERGY METABOLISM—KREBS CYCLE
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
The 2-Carbon molecules don’t make lactic acid but
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
QUESTION
Tell whether the following statement is true or false:
ATP is produced in the mitochondria.
ANSWER
True
The Krebs cycle occurs in the mitochondria. Each Krebs cycle produces one molecule of ATP.
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
QUESTION
Your patient has been given an intravenous solution of water. What will happen to this patient’s red blood cells?
a. They will burst/lyse.b. They will shrink.c. They will not be affected by the water
solution.
ANSWER
a. 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.
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
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
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)
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
QUESTION
Tell whether the following statement is true or false:
An action potential is the result of K+ movement out of the cell.
ANSWER
FalseAn 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).
Na+ enters cell and muscle cell
depolarizes
Ca2+ released from sarcoplasmic reticulum into the
sarcoplasm
Ca2+ attaches to
troponin
MUSCLE CONTRACTION
QUESTION
What happens to the sarcomere when myosin slides across the actin binding sites?
a. It gets longer.b. It gets shorter.c. There is no change in length.d. It releases acetylcholinesterase.
ANSWER
a. 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.