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Cells and Tissues
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
Cells: Carry out all the chemical
activities needed to sustain life.

Tissues: provide for a division of labor
among body cells.
Cells

Robert Hooke, “cells” in monastery
 Cube- like structures observed in cork.
Smallest unit, or the building block, of all
living things.
 Contain all the parts necessary to
survive in a changing world.

 Trillions in the body
Basics of Life

Primarily made of 4 Elements
 Carbon, Oxygen, Hydrogen, Nitrogen

Trace Elements are also very important
 Calcium- blood clotting
 Iron- hemoglobin
 Iodine- thyroid hormone
 Calcium, Sodium, Potassium- electrical
charge (ionic form)
 Sodium and Potassium- Nerve impulses
Basics of Life
Cells are 60% water
 Interstitial fluid

 Dilute saltwater solution
 All exchanges between cells and blood

Cells range widely in shape and size
 2 micrometers-1 meter

Vast difference in function and roles
Generalized Cell Anatomy

Although cell types vary, all cells do
have the same basic parts and certain
functions common to all cells.
 Nucleus
 Cytoplasm
 Plasma membrane
The Nucleus
“headquarters” or the “control center”
Gene-containing
 Genetic material, deoxyribonucleic acid (DNA)


 Instructions for building proteins
 Necessary for cell reproduction
Nuclear Envelope (membrane)

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A double membrane barrier that
bounds the nucleus.
Between the two membranes is a
fluid-filled space
 Two layers fuse and Nuclear Pores
penetrate through

Nucleoplasm
 Jellylike fluid inside the nuclear
membrane
 Place where other nuclear elements
are suspended
Nucleoli
Usually 1 or more dark round stained
bodies in the nucleus
 Sites where ribosomes are assembled
 Eventually migrate into the cytoplasm
and serve as actual site of protein
synthesis

Chromatin
When the cell is not dividing, its DNA combines
with protein forming a loose network of bumpy
threads that are scattered throughout the
nucleus.
 When the cell divides, the chromatin threads coil
and condense to form dense, rod-like bodies chromosomes

Plasma Membrane






Fragile, transparent barrier that contains
the cell contents and separates them from
the surrounding environment.
Phospholipids
Cholesterol
Hydrophobic
Hydrophilic
Microvilli
 Greatly increase cell’s surface area for
absorbtion
Plasma Membrane

Tight Junctions
 Impermeable junctions the bind cells
together into leakproof sheets

Desmosomes
 Anchoring junctions that prevent cells
subjected to mechanical stress from being
pulled apart (skin cells)

Gap Junctions
 Allow communication, chemicals can pass
directly from one cell to another ( heart and
between embryonic cells)
Cytoplasm
Material outside the nucleus and inside the
plasma membrane.
 Cite of most cellular activities
 Cytosol- semitransparent fluid that
suspends the other elements
 Organelles

 Metabolic machinery of the cell

Inclusions
 Not functioning units, chemical substances that
may/may not be present depending on specific
cell type.
○ Most are stored nutrients or cell products (lipid
droplets)
Cytoplasmic Organelles
“little organs” are specialized cellular
compartments, each performing their
own job to maintain the life of the cell.
 Many bound by a membrane

 Allows them to maintain an internal
environment apart from surrounding cytosol
Mitochondria
Tiny threadlike organelle, they squirm,
lengthen, and change shape almost
continuously
 Wall is a double membrane=2 plasma
membranes

 Outer is smooth
 Inner protrusions called Cristae

Enzymes dissolved in mitochondria
membrane form cristae membranes
 Carry out reactions where oxygen is used to
break down foods.
ATP in Mitochondria
When foods are broken down, energy is
released- as heat and ATP molecules.
 Provides energy for all cellular
processes to take place
 All living cells require a constant supply
 “powerhouse”
 The more metabolic a cell is the more
mitochondria they have and more ATP
they use. (liver and muscle cells)

Ribosomes
Bilobed, dark bodies made of proteins
and ribosomal RNA.
 The actual site of protein synthesis
 Some free-float in the cytoplasm and
manufacture proteins that function in
cytoplasm.
 Others attach to membranes,
combination of ribosome and membrane
is the rough endoplasmic reticulum.

Endoplasmic Reticulum
“network within the cytoplasm”
 A system of fluid-filled cisterns that coil
and twist through the cytoplasm
 Mini-circulatory system for the cell;
provides a network of channels for
carrying substances (primary proteins)
from one part of cell to another.
 2 forms, not all cells have both

 Rough and Smooth Endoplasmic Reticulum
Rough Endoplasmic Reticulum
Studded with Ribosomes
 All of the building materials of the
cellular membranes are formed either in
or on the ER.
 “cells membrane factory”
 The proteins made on the RER fold into
the tubules and are dispersed to other
areas of the cell in the Transport
vesicles.

Smooth Endoplasmic Reticulum
Plays no role in protein synthesis
 Lipid metabolism

 Cholesterol
 Fat synthesis and breakdown
Detoxification of drugs and pesticides
 Liver cells and body cells that produce
steroid-based hormones – have a large
amount of Smooth ER.

Golgi Apparatus

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“Traffic director” for cellular proteins
Stack of flattened membranous sacs
usually found close to the nucleus
Modify and package proteins sent to it by
the Rough ER via transport vesicles.
Proteins that are ready for transport
accumulate, the sacs swell.
Sacs pinch off and form secretory vesicles.
FIGURE 3.6 PAGE 69
Lysosomes
“breakdown bodies”; cells demolition site
 Membranous pouches containing
powerful digestive enzymes.
 Capable of digesting worn-out or nonusable cell structures and most foreign
substances that enter the cell.
 Enzymes they contain are formed by
ribosomes in the Golgi Apparatus
 Very abundant in the White Blood Cells.

Peroxisomes

Membranous sacs containing powerful
oxidase enzymes that use molecular
oxygen (O2) to detox a harmful or
poisonous substances.
 Alcohol
 Formaldehyde

Most important role is to “disarm” Free
Radicals. (numerous in Liver and Kidney)
 Highly reactive chemicals with unpaired
electrons that can scramble the structure of
proteins and nucleic acids.
○ Convert free radicals to hydrogen peroxide (H2O2)
which is then turned into water
Cytoskeleton
Elaborate network of protein structures
extends throughout the cytoplasm.
 Acts as the cells “bones and muscles”
 Made up of the following:

 Intermediate filaments- stable ropelike help form
desmosomes and provide internal guy wires to
resist pulling forces on the cell.
 Microfilaments- (actin and myosin) involved in
cell motility and in producing changes in cell
shape
 Microtubules- determine the overall shape of a
cell and the distribution of organelles.
Centrioles

Lying close to the nucleus, they are rodshaped bodies that lie at right angles to
each other
 Internally made up of fine microtubules

Cila- whip-like cellular extensions that
move substances along the cell surface.
 Ciliated cells in respiratory system

Flagella- projections formed by centrioles
and substantially longer (tail-like)
 sperm