Download Chapter 3 Cells - Wilkes-Barre Area Career & Technical

Chapter 3
The Cell
Joe Pistack MS/ED

Cell-structural and functional unit of all
living matter.

Cells vary in size, shape, and function.

Cells vary in structure.

Structure and function are closely related.
Typical Cell
Different shapes of cells

Cell membrane-encases the cell.

Separates the intracellular material from
the extracellular material.

Physically holds the cell together.

Chief function- selection of substances
allowed to enter and leave the cell.
Cell Membrane

Semipermeable-ability of the cell
membrane to choose substances allowed
to cross it.

Cell membrane is composed of
phospholipids and protein.

Phospholipids are arranged in two layers.
Cell Membrane

Functions of the protein molecules in the
membrane:
◦ Provide structural support for the
membrane.
◦ Binding sites for hormones.
◦ Pokes holes or pores through the lipid
membrane. These pores form channels
through which water and dissolved
substances can flow.
Typical Cell

The inside of the cell is divided into two
compartments: 1. the nucleus
2. cytoplasm

Nucleus-control center of the cell, controls
the workings of the entire cell.

Nucleus contains genetic information and
controls all protein synthesis.
Inside the Cell

Nuclear Membrane-double layered membrane
that surrounds the nucleus.

Nucleoplasm-substance that fills the nucleus.

Cytoplasm-gel-like substance found inside
the cell but outside the nucleus

Composed primarily of water, electrolytes,
and nutrients.
Inside the Cell

The cytoplasm contains:

Organelles-small organs with a specific
role.

Inclusion bodies-temporary structures
that appear and disappear.
Inside the Cell

Mitochondria-power plant of the cell.

Tiny slipper-shaped organelles.

Number of mitochondria per cell depends
on the metabolic activity of the cell.
(How hard the cell works)
eg. Liver, bone
Cytoplasmic Organelles

Mitochondrial membrane:
Consists of 2 layers.
Smooth outer layer
Inner layer contains many folds or cristae.
Enzymes associated with ATP are located
along the cristae.
 Called the “power plant” of the cell
because of production of ATP.




Cytoplasmic Organelles
Mitochondria
Cytoplasmic Organelles:

Ribosomes-concerned with protein
synthesis.

Endoplasmic Riticulum-network of
membranes within the cytoplasm,
membranes form channels through which
substances move.
Inside the Cell

Endoplasmic Riticulum(ER):

2 types:
- Rough endoplasmic riticulum-(RER)
- sandpaper-like appearance
- concerned with protein synthesis
-Smooth endoplasmic riticulum-(SER)
-concerned with the synthesis of lipids
and steroids
Inside the Cell

Golgi apparatus-series of flatted
membraneous sacs.

Proteins synthesized along the RER are
transported to the Golgi through channels
formed by the ER.

The Golgi apparatus packages the protein
for synthesis.
Inside the Cell

Lysosomes-membranous sacs containing
powerful enzymes.

Lysosomes are digestive organelles.

Lysosomal enzymes break down
intracellular waste and debris.
“clean house”
Inside the Cell

Cytoskeleton-composed of threadlike
structures called microfilaments and
microtubules.

Cytoskeleton helps to maintain the shape of
the cell and assists the cell in cellular
movement.

Centrioles-paired, rod-shaped microtubular
structures, play a key role in cellular
reproduction.
Inside the Cell

Cilia-short, hairlike projections on the
outer surface of the cell.

Cilia use wavelike motions to move
substances across the surface of the cell.

Eg. Resp. tract-cilia help to move mucous
and dust toward the throat, away from
the lungs.
On the Cell Membrane

Flagella-(meaning whip)

Whip-like projections, longer, thicker and
fewer in number than cilia.

Help to move the cell.

Eg. The tail of the sperm enables the
sperm to swim.
On the Cell Membrane

Passive and Active Transport:

Both are transport mechanisms that assist
in the movement of water and dissolved
substances across the cell membrane.

Passive transport-requires no additional
energy in the form of ATP.
Movement Across the Cell
Membrane

Passive transport-water and dissolved
substances move without additional
energy.





Passive Transport Mechanisms:
Diffusion
Facilitated diffusion
Osmosis
Filtration
Movement across the Cell
Membrane

Diffusion-most common transport
mechanism.

Movement of a substance from an area of
higher concentration to an area of lower
concentration.

Equilibrium-point at which no further net
diffusion occurs.
Passive Transport Mechanisms

Facilitated diffusion-form of diffusion
responsible for the transport of many
substances.

Substances move from an area of higher
concentration to an area of lower
concentration but requires a helper
molecule.
Transport Mechanisms

Osmosis-diffusion of water through a
selectively permeably membrane.

Semipermeable or selectively permeable
membrane allows the passage of some
substances while restricting the passage of
others.

The strength of the osmotic pull is directly
related to the concentration of the solution.
The greater the concentration, the greater
the pulling or osmotic pressure.
Transport Mechanisms

Edema-accumulation of water in the
tissue spaces.

Osmotic pressure pulls water into a
compartment causing swelling.

Tonicity-ability of a solution to affect the
volume and pressure within a cell.
Transport Mechanisms

Isotonic Solution-”iso=same”.

Same concentration as intracellular fluid.
Movement Across a Cell Membrane

Hypotonic Solution-solution containing no
solute.
Movement Across a Cell Membrane

Hypertonic Solution-very concentrated
solution, causes cells to shrink or crenate.
Movement Across the Cell
Membrane

Isotonic Solutions do not cause the cells
to swell or shrink.

Most IV solutions are isotonic.




Commonly used isotonic solutions:
Normal saline (0.9% NaCl)
5% D/W (dextrose or glucose in water)
Ringers lactate
Isotonic Solutions

Filtration-water and dissolved substances
cross the membrane in response to
differences in pressure. (Pressure pushes
the substance across the membrane.)
Filtration

Active transport-transport mechanism
requires an input of energy ATP to achieve
its goal.

Endocytosis-intake of food or liquid by the
cell membrane.

Particle is too large to move across the
cell membrane by diffusion.
Active Transport Mechanisms

Endocytosos:
Particle surrounds the cell membrane, engulfs
it and takes it into the cell.

2 types:

Phagocytosis-the cell eating solid particles.
 Pinocytosis-ingestion of water droplets,
cellular drinking.

Active Transport Pumps

Exocytosis-moving of substances out of
the cells.
Active Transport Mechanisms

Cell division-necessary for growth and
repair.

Some cells reproduce frequently, whereas
others do not reproduce at all.

Most cells grow in an orderly manner, cells
that grow abnormally may be tumors
which may be benign or malignant.
.
Cell Division


Rate of cell division depends on type of tissue:
Some cells don’t divide but are replaced at
incredible rates:
◦ Cells of digestive tract replace every few days
◦ Red blood cells-2 million per second
◦ Nerve cells-not at all


Two types of cell division-Mitosis and Meiosis
Mitosis
Mitosis is involved with bodily growth and repair
Mother cell splits into two identical “Daughter Cells”

Meiosis
◦ Special type of cell division only found in sex cells
Cell Division


Cell Cycle has two major parts
Interphase
◦ Cell carries on normal functions
◦ Prepares for mitosis through growth and DNA
replication

Mitosis
◦ The splitting of a cell into two cells with exactly the
same genetic information
◦ Divided into four phases
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Prophase
Metaphase
Anaphase
Telophase
Cell Cycle

Prophase
◦ Chromosomes coil tightly and are composed of two identical
strands of DNA

Metaphase
◦ DNA align in a narrow central zone

Anaphase
◦ DNA split into pairs and move to opposite ends of the cell

Telophase
◦ Cell wall pinches together forming the daughter cells and both
cells enter interphase
Mitosis
Stem cells are cells that have not differentiated
 Cells differentiate due to the addition of different
enzymes
 Sometimes cells reproduce in an uncontrolled
and disorganized way and form tumors - there
are two types:
◦ Benign-noncancerous
◦ Malignant-cancerous

 Metastasis is when cancer cells spread.
 A widespread invasion of cancer can cause death
Stem Cells