This will discuss about cell biology

1. CELL BIOLOGY

2. CELL BIOLOGY
• EUKARYOTIC CELL STRUCTURE
MEMBRANE STRUCTURE AND
FUNCTIONS
MOVEMENT ACROSS
MEMBRANE
• ENERGY CONVERSION IN
EUKARYOTIC CELLS

3. CELL MEMBRANE

4. CELL MEMBRANE
• The cell membrane (plasma membrane) is a thin semi-
permeable membrane that surrounds the cytoplasm of a cell.
• Its function is to protect the integrity of the interior of the cell
by allowing certain substances into the cell while keeping
other substances out.
• It also serves as a base of attachment for the cytoskeleton in
some organisms and the cell wall in others. Thus, the cell
membrane also serves to help support the cell and help
maintain its shape.

5. • Another function of the membrane is to
regulate cell growth through the
balance of endocytosis and ​exocytosis.
• In endocytosis, lipids and proteins are
removed from the cell membrane as
substances are internalized. In
exocytosis, vesicles containing lipids
and proteins fuse with the cell
membrane increasing cell size.
• Animal cells, plant cells, prokaryotic
cells, and fungal cells have plasma
membranes. Internal organelles are
also encased by membranes.

6. CELL MEMBRANE STRUCTURE
• The cell membrane is primarily
composed of a mix
of proteins and lipids. Depending on
the membrane’s location and role in
the body, lipids can make up anywhere
from 20 to 80 percent of the
membrane, with the remainder being
proteins.
• While lipids help to give membranes
their flexibility, proteins monitor and
maintain the cell's chemical climate and
assist in the transfer of molecules
across the membrane.

7. CELL MEMBRANE LIPIDS

8. • Phospholipids are a major component
of cell membranes.
• Phospholipids form a lipid bilayer in
which their hydrophilic (attracted to
water) head areas spontaneously
arrange to face the aqueous cytosol
and the extracellular fluid, while their
hydrophobic (repelled by water) tail
areas face away from the cytosol and
extracellular fluid.
• The lipid bilayer is semi-permeable,
allowing only certain molecules
to diffuse across the membrane.

9. • Cholesterol is another lipid component of animal cell
membranes. Cholesterol molecules are selectively
dispersed between membrane phospholipids. This helps to
keep cell membranes from becoming stiff by
preventing phospholipids from being too closely packed
together. Cholesterol is not found in the membranes
of plant cells.
• Glycolipids are located on cell membrane surfaces and
have a carbohydrate sugar chain attached to them. They
help the cell to recognize other cells of the body.

10. CELL MEMBRANE PROTEINS
• The cell membrane contains two types
of associated proteins. Peripheral
membrane proteins are exterior to and
connected to the membrane by
interactions with other
proteins. Integral membrane
proteins are inserted into the
membrane and most pass through the
membrane. Portions of these
transmembrane proteins are exposed
on both sides of the membrane. Cell
membrane proteins have a number of
different functions.

11. • Structural proteins help to give the cell support and shape.
• Cell membrane receptor proteins help cells communicate with their
external environment through the use of hormones,
neurotransmitters, and other signaling molecules.
• Transport proteins, such as globular proteins, transport molecules
across cell membranes through facilitated diffusion.
• Glycoproteins have a carbohydrate chain attached to them. They
are embedded in the cell membrane and help in cell to cell
communications and molecule transport across the membrane.

12. ORGANELLE MEMBRANES
• Some cell organelles are also surrounded by protective
membranes.
• The nucleus, endoplasmic reticulum, vacuoles, lysosomes,
and Golgi apparatus are examples of membrane-bound
organelles. Mitochondria and chloroplasts are bound by a
double membrane. The membranes of the different organelles
vary in molecular composition and are well suited for the
functions they perform. Organelle membranes are important
to several vital cell functions including protein
synthesis, lipid production, and cellular respiration.

13. MOVEMENT ACROSS MEMBRANES
Molecules pass through cell membranes in 4 ways
Directly through the phospholipid membrane
Membrane channels
Carrier molecules
-are proteins that extend from one side of a cell membrane to
another.
Vesicles

14. Passive transport
• is a naturally occurring phenomenon and does not
require the cell to exert any of its energy to
accomplish the movement of substances from an
area of higher concentration to an area of lower
concentration.
• Examples include the diffusion of oxygen and
carbon dioxide, osmosis of water, and facilitated
diffusion.

15. DIFFUSION
• is a passive process of transport
where a single substance moves
from a high concentration to a low
concentration until the
concentration is equal across space.
• Materials move within the cell’s
cytosol by diffusion, and certain
materials move through the plasma
membrane by diffusion.
• Diffusion expends no energy.

16. • The left part of Figure 7-1
shows a substance on one side
of a membrane only in the
extracellular fluid. The middle
part shows that, after some
time, some of the substance
has diffused across the plasma
membrane, from the
extracellular fluid, and into the
cytoplasm. The right part
shows that, after more time, an
equal amount of the substance
is on each side of the
membrane.

17. OSMOSIS
• Osmosis is the movement of water through a semipermeable
membrane according to the water's concentration gradient
across the membrane, which is inversely proportional to the
solutes' concentration.
• While the term diffusion refers to the transport of material
(other than water) across membranes and within cells, the
term osmosis refers specifically to the transport only of water
across a membrane.
• Not surprisingly, the aquaporins that facilitate water
movement play a large role in osmosis, most prominently in
red blood cells and the membranes of kidney tubules.

19. • The movement of water through a
semi-permeable membrane. In
osmosis, water always moves from an
area of higher water concentration to
one of lower concentration. In the
diagram, the solute cannot pass through
the selectively permeable membrane,
but the water can. Note at the beginning,
the volume of water is the same, but the
concentration of solute-unbound water is
greater on the left because there is less
solute. There are fewer solute-unbound
water molecules on the right because
there is so much more solute. Therefore,
there is a higher concentration of “free”
water molecules on the left than on the
right of the membrane in the first beaker.

20. FACILITATED TRANSPORT
• In facilitated transport or facilitated
diffusion, materials that cannot use simple
diffusion, are transported passively across
the plasma membrane with the help of
membrane proteins.
• A concentration gradient exists that would
allow these materials to diffuse into the cell
without expending cellular energy.
However, these materials are polar
molecules or ions that the cell membrane's
hydrophobic parts repel.
• Facilitated transport proteins shield these
materials from the membrane's repulsive
force, allowing them to diffuse into the cell.

21. ACTIVE TRANSPORT
• A fourth method for movement across the membrane is active
transport.
• When active transport is taking place, a protein moves a certain
material across the membrane from a region of lower
concentration to a region of higher concentration. Because this
movement is happening against the concentration gradient, the
cell must expend energy that is usually derived from a substance
called adenosine triphosphate, or ATP
• An example of active transport occurs in human nerve cells. Here,
sodium ions are constantly transported out of the cell into the
external fluid bathing the cell, a region of high concentration of
sodium. (This transport of sodium sets up the nerve cell for the
impulse that will occur within it later.)

22. EXAMPLE OF ACTIVE TRANSPORT
• The Na+/K+ pump uses the
energy of ATP to create and
maintain ion gradients that are
important both in maintaining
cellular osmotic pressure and
(in nerve cells) for creating the
sodium and potassium
gradients necessary for signal
transmission. Failure of the
system to function results in
swelling of the cell due to the
movement of water into the
cell through osmotic pressure

23. ENDOCYTOSIS AND EXOCYTOSIS
• Endocytosis, a process in which a small
patch of plasma membrane encloses
particles or tiny volumes of fluid that are at
or near the cell surface.
• The membrane enclosure then sinks into
the cytoplasm and pinches off from the
membrane, forming a vesicle that moves
into the cytoplasm.
• When the vesicle contains solid particulate
matter, the process is called phagocytosis.
• When the vesicle contains droplets of fluid,
the process is called pinocytosis.

24. • Along with the other mechanisms for
transport across the plasma membrane,
endocytosis ensures that the internal
cellular environment will be able to
exchange materials with the external
environment and that the cell will
continue to thrive and function.
• Exocytosis is the reverse of
endocytosis, where internally produced
substances are enclosed in vesicles and
fuse with the cell membrane, releasing
the contents to the exterior of the cell.

25. ENERGY CONVERSION IN EUKARYOTIC CELLS
• Scientists use the term bioenergetics to describe the concept of energy
flow through living systems, such as cells.
• Cellular processes such as the building and breaking down of complex
molecules occur through stepwise chemical reactions..

26. Figure 4.2 Ultimately, most
life forms get their energy
from the sun. Plants use
photosynthesis to capture
sunlight, and herbivores
eat the plants to obtain
energy. Carnivores eat the
herbivores, and eventual
decomposition of plant and
animal material
contributes to the nutrient
pool.

27. METABOLIC PATHWAYS
• Consider the metabolism of sugar. This is a classic example of one of
the many cellular processes that use and produce energy. Living
things consume sugars as a major energy source, because sugar
molecules have a great deal of energy stored within their bonds.
For the most part, photosynthesizing organisms like plants produce
these sugars. During photosynthesis, plants use energy (originally
from sunlight) to convert carbon dioxide gas (CO2) into sugar
molecules (like glucose: C6H12O6). They consume carbon dioxide
and produce oxygen as a waste product. This reaction is
summarized as:
• 6CO2 + 6H2O + energy ——-> C6H12O6+ 6O2

28. • Because this process involves synthesizing an energy-storing molecule, it
requires energy input to proceed.
• During the light reactions of photosynthesis, energy is provided by a
molecule called adenosine triphosphate (ATP), which is the primary
energy currency of all cells. In contrast, energy-storage molecules such as
glucose are consumed only to be broken down to use their energy.
• The reaction that harvests the energy of a sugar molecule in cells
requiring oxygen to survive can be summarized by the reverse reaction
to photosynthesis. In this reaction, oxygen is consumed and carbon
dioxide is released as a waste product. The reaction is summarized as:
• C6H12O6 + 6O2 ——> 6CO2 + 6H2O + energy
• ******anabolic pathways (building polymers) and catabolic pathways
(breaking down polymers into their monomers

29. Catabolic pathways are those that generate energy by breaking down
larger molecules. Anabolic pathways are those that require energy to
synthesize larger molecules. Both types of pathways are required for
maintaining the cell’s energy balance

30. • Thermodynamics refers to the study of energy and energy transfer
involving physical matter. The matter relevant to a particular case of
energy transfer is called a system, and everything outside of that
matter is called the surroundings.
• There are two types of systems: open and closed. In an open
system, energy can be exchanged with its surroundings.
• Biological organisms are open systems. Energy is exchanged
between them and their surroundings as they use energy from the
sun to perform photosynthesis or consume energy-storing
molecules and release energy to the environment by doing work
and releasing heat.

31. • The first law of
thermodynamics states
that the total amount of
energy in the universe is
constant and conserved.

32. • However, the second law of
thermodynamics explains why
these tasks are harder than
they appear. All energy
transfers and transformations
are never completely efficient.
• In every energy transfer, some
amount of energy is lost in a
form that is unusable. In most
cases, this form is heat energy.
Thermodynamically, heat
energy is defined as the energy
transferred from one system to
another that is not work

33. • An important concept in physical systems is that of order and
disorder. The more energy that is lost by a system to its
surroundings, the less ordered and more random the system is.
• Scientists refer to the measure of randomness or disorder within a
system as entropy.
• High entropy means high disorder and low energy. Molecules and
chemical reactions have varying entropy as well. For example,
entropy increases as molecules at a high concentration in one place
diffuse and spread out. The second law of thermodynamics says
that energy will always be lost as heat in energy transfers or
transformations.
• Living things are highly ordered, requiring constant energy input to
be maintained in a state of low entropy.

34. EXERGONIC AND ENDERGONIC REACTIONS IN
METABOLISM
• EXERGONIC
-ENERGY OUTWARD
-PROCEEDS WITH A NET RELEASE OF FREE ENERGY
• ENDERGONIC
-ENERGY INWARD
-ABSORBS FREE ENERGY FROM THE SURROUNDINGS
-STORES FREE ENERGY FROM THE MOLECULES

35. THE STRUCTURE AND HYDROLYSIS OF ATP
• Adenosine triphosphate, or ATP, is
a small, relatively simple molecule.
It can be thought of as the
main energy currency of cells, much
as money is the main economic
currency of human societies. The
energy released by hydrolysis
(breakdown) of ATP is used to power
many energy-requiring cellular
reactions.
•

36. • . ATP is hydrolyzed to ADP in the
following reaction:
• ATP+H20⇋ADP+Pi​+energy
• Like most chemical reactions, the
hydrolysis of ATP to ADP is
reversible.. Regeneration of ATP
is important because cells tend to
use up (hydrolyze) ATP molecules
very quickly and rely on
replacement ATP being
constantly produced.

37. Photosynthesis and cellular
respiration are connected
through an important
relationship. This relationship
enables life to survive as we
know it. The product of one
process are the reactants of
the other.

38. • Cellular Respiration:
C6H12O6 + 6O2 → 6CO2 +
6H2O
• Photosynthesis: 6CO2 +
6H2O → C6H12O6+ 6O2
• While water is broken down
to form oxygen during
photosynthesis, in cellular
respiration oxygen is
combined with hydrogen to
form water.
• While photosynthesis requires
carbon dioxide and releases
oxygen, cellular respiration
requires oxygen and releases
carbon dioxide. It is the released
oxygen that is used by us and
most other organism for cellular
respiration.
• We breathe in that oxygen,
which is carried through
our blood to all our cells. In our
cells, oxygen allows cellular
respiration to proceed. Cellular
respiration works best in the
presence of oxygen. Without
oxygen, much less ATP would be
produced.

39. • Photosynthesis is the process
in which light energy is converted
to chemical energy in the form of
sugars. In a process driven by
light energy, glucose molecules
(or other sugars) are constructed
from water and carbon dioxide,
and oxygen is released as a
byproduct. The glucose
molecules provide organisms
with two crucial resources:
energy and fixed—organic—
carbon.
•

40. • The light-dependent
reactions take place in the
thylakoid membrane and require
a continuous supply of light
energy. Chlorophylls absorb this
light energy, which is converted
into chemical energy through the
formation of two
compounds, ATP—an energy
storage molecule—
and NADPH—a reduced
(electron-bearing) electron
carrier.
• In this process, water molecules
are also converted to oxygen
gas—the oxygen we breathe!

41. .
• The Calvin cycle, also called
the light-independent reactions,
takes place in the stroma and
does not directly require light.
Instead, the Calvin cycle
uses ATP text and NADPH from
the light-dependent reactions to
fix carbon dioxide and produce
three-carbon sugars—
glyceraldehyde-3-phosphate, or
G3P, molecules—which join up to
form glucose.

42. CELLULAR RESPIRATION

43. 1. GLYCOLYSIS
• -means SUGAR SPLITTING
• Glucose (6-carbon sugar) splits into two 3 C sugars which are oxidized and
rearranged to form 2 molecules of pyruvate
• Net energy produced: 2 ATP and 2 NADH
2. CITRIC ACID CYCLE/ KREB’S CYCLE
• -where pyruvate enters the mitochondria via active transport and converts the
compound called Acetyl coA which is the step junction between Glycolysis and Citric
Acid Cycle
• Acetyl coA is broken down into 2 CO2 molecules
• The cycle generates 1 ATP per turn, but most chemical energy is transferred to
NAD+ and FAD (vit Riboflavin) producing 3NADH and FADH.

44. 3. Oxidative Phosphorylation-
• The electron transport chain: is a collection of molecules embedded in the
inner membrane of mitochondria during chain electron carriers which
alternate between reduced & oxidized states by accepting & donating
electrons.
• Electrons drop in free energy as they go down the chain and are finally
passed to O 2, forming H 2 O.
• Chemiosmosis: a process in which energy stored in the form of hydrogen
ion across a membrane is used to drive cellular work, such as the synthesis
of ATP using enzyme ATP Synthase. (ADP+Pi-----ATP synthase---→ATP)
The net ATP produced are about 32-34 ATP.

45. ATP yield per molecule of glucose at each stage of cellular respiration: Since oxygen is required to
complete the citric acid cycle and oxidative phosphorylation, these two processes are known as
aerobic respiration, and generate about 32-34 ATP per glucose.

46. • A process where organic fuels are oxidized and generate ATP without the
use of oxygen.
• Anaerobic respiration: has electron transport chain, but the final electron
acceptor is other than oxygen → it is sulfide.
• Fermentation: the electrons from NADH are passed to pyruvate,
regenerating the NAD+ required to oxidize more glucose.
• Two types: Alcohol fermentation( yeast is used in baking) & Lactic acid
fermentation (Human muscles)
Fermentation and Anaerobic Respiration