Transcript Ch 1 - Morgan Community College

CHAPTER 1
CELL STRUCTURE AND FUNCTION
PRELECTURE QUIZ (TRUE FALSE)
F

The endoplasmic reticulum is the control center of the
cell.
T

Cells communicate with each other by means of chemical
messenger systems.
T

The glycolytic pathway does not require oxygen to produce
cellular energy.
F

Examples of passive movement across the cell membrane
include diffusion, osmosis, and active transport.
T

Cells with a similar embryonic origin or function are often
organized into larger functional units called tissues.
PRELECTURE QUIZ
ATP
Connective


muscle
Phagocytosis

Ribosomes


__________ 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.
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?
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
º
Which are handed to electron carriers like NAD and FAD
H+ follow the electrons
 Afterwards,
they are put back on the 2-carbon
chunks
º
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
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).
MUSCLE CONTRACTION
Na+ enters cell
and muscle cell
depolarizes
Ca2+ released
from sarcoplasmic
reticulum into the
sarcoplasm
Ca2+
attaches to
troponin
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
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.
a.