Cells`

1
Cells
The smallest functional unit of life
2
Cell theory

• Cells are the structural and functional unit of
  life
• What an organism does is determined by the
  activity of its cells
• the biochemical activities of cells are
  dictated by the relative number of their specific
  subcellular structures
• Reproductive activities are cell based

p. 62
3
Components of the membrane
Proteins as receptor, channel, carrier, marker,
anchoring spot to surrounding cells, enzymes
(acting inside or outside the cell), anchoring
internally for cystoskeleton- about ½ total
membrane mass Some proteins are integral-
extending through the entire membrane Other
proteins are peripheral- inside or outside the
cell. -supporting filaments -enzymes
See 64,65
4
Cell Components

• Plasma membrane
• Cytoplasm
• Nucleus

5
Components of the membrane
Lipids phospholipds, most are unsaturated,
which because of molecule shape, makes the
membrane more fluid
Glycolipids
Cholesterol helps form membrane precursor for
hormones some 20 of the lipid p. 64
See 65
6
Components of the membrane
Proteins (surface) superficial proteins are
glycoproteins- sugarprotein forming the
glycocalyx a region around the cell surface
with many carbohydrates. The variability of the
glycoproteins causes this layer to act as an
identifier- specific markers identify specific
cells. This plays a role in immune cell function
(recognizing foreign cells) and reproduction
(sperm recognizing egg)
See 65
7
Components of the membrane
Carbohydrates joined with proteins as
glycoproteins, joined to lipids as glycolipids.-
found on the outer layer, can serve as markers
for cell recognition
See 65
8
Junctions with other cells/tissue
Membrane appendages

• Tight junctions- prevent leakage going between
  cells

Tight
Not so tight
9
Junctions with other cells/tissue
Membrane appendages

• Desmosomes- lock cells together where cells are
  under mechanical stress (skin, heart).
  Connections are made not just between adjacent
  cells, but through a cell, distributing stress
  more broadly

See p. 67
10
Junctions with other cells/tissue
Membrane appendages

• Gap junctions- allow passage of ions and other
  small molecules (simple sugars) between cells.
• Recall the depolarization of heart cells

See p. 70
11
Transport through the membrane.
12
Cells
Transport through the membrane is selective, and
occurs via passive and active processes.
Passive processes
Diffusion
Facilitated diffusion Osmosis
Filtration
13
Cells
Passive processes
Diffusion depends on concentration gradients.
High concentration--gt Low concentration ?
with temperature, smaller particle size
14
Cells
Diffusion Driven by kinetic energy of matter
Solute moves from area of high concentration to
low concentration
15
Cells
Diffusion
The route a substance takes through the membrane
depends on its size, shape, charge and
solubility. In cells, non-polar and lipid
soluble substances can pass through (alcohol,
fatty acids, steroids.., CO2, O2) the membrane
w/o a channel or gate)
Water soluble substances require a channel in the
membrane These channels may let substances
through on the basis of size or shape
See p. 69
16
Cells
Passive processes
Facilitated Diffusion depends on concentration
gradients. High concentration--gt Low
concentration Depends on carriers (proteins in
the cell membrane) or channels (water filled
allows smaller particles)
17
Cells
Passive processes
Facilitated diffusion specific carriers exist
for certain essential, large, non-lipid soluble
substances.
Transportation depends on binding to, being
recognized by a receptor A passive process- no
ATP required. Ex glucose
See p. 69
18
Cells
Passive processes
See p. 69
19
Cells
Osmosis water moves through a semi-permeable
membrane to equalize concentrations
20
Cells
Passive processes
Osmosis
Think of this either of 2 ways 1) there may be
a higher concentration of water on one side of a
membrane and it moves towards the other side.
(High concentration--gt low concentration)
2) water moves to equalize concentrations on
either side of a semi permeable membrane. That
is, water is drawn to the side where solute is
more concentrated.
Think salting a slug.. Sugaring berries
See p. 70
21
Cells
Filtration driven by hydrostatic pressure
22

• Note that water is able to move through the
  phospholipid bilayer by osmosis not just through
  channels in the membrane

p. 70
23
New words

• Osmolarity- the total concentration of all solute
  particles in a solution
• Hypotonic- a solution having lower concentration
  (compared to cells introduced to the solution)
• Hypertonic- a solution having higher
  concentration (compared to cells introduced to
  the solution)

See p. 71
24
Cells
Active processes require ATP
Carriers bind to the substance being transported
and move it against the substances
concentration gradient In primary active
transport, the ATP directly powers the particle
movement. In secondary active transport, the
particle movement is indirectly powered by ATP
See steps on p. 76
25
Cells
Active processes require ATP
Primary- analogy a truck carries water up
hill. Secondary- a truck carries water up
hill, then the water flows back downhill, causing
a water wheel to turn.
See steps on p. 76
26
Cells
Active processes (example of primary)
Na-K pump maintains a low intercellular Na
level, and high potassium level, inside a cell
See steps on p. 74
27
Cells
Active processes require ATP
Vesicular transport- a vesicle with walls like
the cells membrane encloses a substance (large
particle or liquid) for transport into or out of
a cell.
See steps on p. 78
28
Cells
Active processes require ATP
Related terms Phagocytosis cell
eating Pinocytosis cell drinking
(sampling) Endocytosis taking into the
cell Exocytosis secreting from the
cell Transcytosis moving from one side of the
cell to another
See steps on p. 76
29
Cell Membrane potential

• We have seen that the membrane is selectively
  permeable

• Among the substances selected for are ions,
  resulting in different ion compositions
  intracellular compared to extracellular

30
Cell Membrane potential

• We have seen that the membrane is selectively
  permeable

• This selectivity results in the inside of the
  cell being negative (collected more negatively
  charged ions) compared to the outside

31
Cell Membrane potential
Players in the membrane potential are K, Na,
Cl- and proteins inside the cell that carry a
negative charge. Also different ions move
through the membrane at different rates- both
actively and passively AND these ions move
with both concentration gradients AND electrical
gradients
32
Cell Membrane potential
Because there are many different ions involved,
both positive and negative, we will refer to an
electrochemical gradient, which includes (for
example) the notion that an paricle might not
reach a concentration equality because there is a
resistance based on a ionic gradient pushing
the other way.
33
Cell adhesion molecules (CAM)
Cell Membrane interactions with other cells
Functions

• anchors to surrounding cells
• Used by moving cells to grab stationary cells and
  pull past them
• Signal WBCs to an affected area
• Other functions

34
Contact vs Signal communication
Cell Membrane interactions with other cells

• Cells can communicate by physical contact with
  each other, as in the case of immune cells
  checking out a target cell
• Cells can communicate via some chemical signal-
  like a hormone or neurotransmitter- this may
  involve a 2nd messenger system in the target
  cell (p. 81,82)

35
Cytoplasm

• The broth of the soup or the water of the fish
  tank
• The semi-fluid surroundings and support of the
  organelles of the cell
• Stored sugars, pigment lipids and other
  substances are included here
• P. 84

36
Organelles
Mitochondria

• Powerhouse of cell, producing ATP aerobically
• More numerous in cells that are active
• Cells may have hundreds of mitochondria
• Two membranes
• The outer is fairly smooth
• The inner membrane is folded (forming cristae)

37
Organelles
Mitochondria

• A gel matrix fills the mitochondrion. Enzymes
  in the matrix and on the cristae participate in
  oxidation of fuel molecules
• Have their own DNA and RNA and replicate based on
  this genetic material when there is increased
  demand for energy by the cell.

38
Organelles
Ribosomes

• Function in protein synthesis
• May be free floating in the cytoplasm or attached
  to the endoplasmic reticulum (rough ER)
• Free floating make proteins for use in the
  cytosol
• ER bound make proteins for the cell membrane or
  for export
• May be free or bound, depending on the protein
  being assembled ( the same ribosome can be
  either)

39
Organelles
Endoplasmic reticulum

• A fluid-filled system of tubes/membranes located
  near and continuous with the membrane around the
  nucleus
• Rough ER packages proteins made with the
  ribosomes for export.
• Makes membrane parts for the cell

40
Organelles
Endoplasmic reticulum

• Smooth ER make cholesterol and steroid
  hormones, metabolize fats, participate in drug
  detox and glycogenolysis
• In striated muscle (cardiac and skeletal) the
  smooth ER forms the sarcoplasmic reticulum that
  stores calcium ions

41
Organelles
Golgi Apparatus

• another membranous organelle
• major function is to modify , concentrate, and
  package the proteins and lipids made at the rough
  ER. (p. 85)
• Transport vesicles from the ER are received by
  the Golgi Apparatus. Modifications (sugars are
  added/subtracted, phosphates added) are made,
  then the proteins are repackaged in one of 3
  forms on the far side of the Golgi apparatus form
  the ER

42
Organelles
Golgi Apparatus

• the new packages will
• Be sent to the cell membrane to secrete the
  proteins
• OR
• Be sent to the cell membrane for incorporation
  into the membrane
• OR
• Act as a lysosome inside the cell

43
Organelles
Lysosome

• Lysosomes do clean-up work
• old organelles
• bacteria, viruses, etc.
• Glycogen break down
• Unused/modified tissues during fetal development
• Cell self-digestion
• See list on p. 86

44
Organelles
Lysosome

• Lysosomes maintain an acidic environment
  inside, which is where their enzymes work best
• keep the enzymes contained, while releasing
  products of breakdown to the cytosol

45
Organelles
Membranous structures (review) (derived from,
forming or continuous with the cell membrane)

• cell membrane
• endoplasmic reticulum
• Golgi apparatus
• lysosome
• Secretory vesicles
• nuclear membrane/envelope
• mitochondria
• peroxisomes

46
(More) Organelles
Peroxisomes

• Like lysosomes, peroxisomes are membranous
  sacs.
• Unlike lysosomes, peroxisomes bud off from the ER

47
(More) Organelles
Peroxisomes

• Peroxisomes help with detoxification (alcohol and
  formaldehyde) but help extinguish free
  radicals, to protect the cell
• free radicals are highly reactive molecules
  they cause (undesirable) reactions inside the
  cell, causing damage like a fire that has
  escaped the hearth

48
Cytoskeleton

• 3 types of rods passing through the cytoplasm
• These have no membrane
• Provides support and movement of the cell and
  organelles

49
Cytoskeleton

• Microtubules
• Largest of 3 rod types
• Provide shape support for the cell
• Provide attachment points and mechanisms for
  moving organelles (mitochondria, lysosomes) via
  motor proteins
• Continually being formed/reformed as cell needs
  change

50
Cytoskeleton

• Microfilaments
• Smallest of 3 rod types, made of actin
• Involved in cell shape change and cell movement
• Involved in cell cleavage during replication
• Continually being formed/reformed as cell needs
  change

51
Cytoskeleton

• Intermediate filaments
• Relatively permanent within the cell
• Attached to desmosomes, functions to reinforce
  structure of cell

52
(More) Organelles
Centrosome and Centrioles
The centrosome is an attachment point for
microtubules The centrosome contains the
centrioles- pairs of tubes at right angles to
each other which (additionally) help move cell
components during mitosis (p. 89)
53
(More) Organelles
Cilia and Flagella

• Cilia move material across the surface of the
  cell
• In the trachea, shifts mucus up/out of the lungs
• In uterine tubes, moves the egg towards the
  uterus
• Flagella move the cell only in sperm, in humans
• In both, the structures arise from centrioles

54
Membrane appendages
Microvilli- increase surface area Contain
actin Specialized for absorption and
secretion (digestive and urinary tracts)
Cilia- specialized to move material across the
cells surface
microvilli
cilia
(a cell)
(a cell)
55
Organelles
Nucleus

• Stores cells genetic material
• Directs what proteins are made, when and how much
• Most cells have one.
• Some cells have many (skeletal muscle and others)
• One cell type (RBCs) have no nucleus
• So has no repair capacity limited life

56
Organelles
Nucleus

• Three regions/structures
• Envelope (membrane)
• Nucleoli
• Chromatin

57
Organelles
Nucleus

• Regions/structures
• Envelope (membrane)
• A double membrane, the outer layer of which is
  continuous with the ER
• Contains pores allowing movement of particles
  in/out
• Encloses the nucleoplasm- analogous to the
  cytoplasm of the cell

58
Organelles
Nucleus

• Regions/structures
• Nucleoli (1, 2 or more/nucleus)
• Darker regions within the nucleus, having no
  membrane
• Sites of ribosome assembly

59
Organelles
Nucleus

• Regions/structures
• Chromatin
• The genetic material of the cell (DNA)
• AND
• Proteins (histones) involved in the packaging of
  the DNA and regulation of gene expression
• When the cell is preparing to divide, the
  chromatin forms chromosomes- bundles of the
  genetic material

60
Histone a protein which the DNA is bound
to Nucleosome a clump of gathered DNA and
histones.
The genetic code is contained in the DNA.
The DNA molecule consists of 2 strands, linked
together by many paired nitrogenous bases
See p. 97
61
The genetic information codes for (among other
things) the formation of amino acids. The
information for each amino acid is stored as a
triplet of nitrogenous bases. (see figure3.36,
p. 103). Other triplets give information about
how to read the code (as in start or Stop
messages.)
A gene consists of all the triplets which code
for a specific protein. (bigger proteins require
larger genes longer instructions for assembly)
62
Protein synthesis
First, gene to be copied needs to be accessible-
the strands unravel and separate
then
1. Transcription making an RNA template of the
bases to be copied (the gene) this happens in
the nucleus
2. Translation- ribosomes act on/with the RNA to
construct the new protein--- this happens in the
cytosol.
63
Transcription mRNA (messenger RNA) is made as a
template from which to build the new protein. RNA
polymerase finds the start codon, then moves
along the gene, linking together the pairing
nucleotides stopping when the stop codon is
reached.
See 104, 106, 107
64
The mRNA undergoes some editing before leaving
the nucleus (pre-mRNA ? mRNA) p. 103
65
Translation- assemblage of the protein in the
cytoplasm

• Involves mRNA that came from the nucleus
• ribosomes
• tRNA
• amino acids free floating in the cytoplasm

66
Each tRNA molecule codes for a specific amino
acid, so there are 20 different kinds. tRNA
caries the amino acid coded for on the mRNA to
the mRNA and ribosome, and links on to the
growing protein chain.
67
Once the protein is completed, the tRNA detaches
and the mRNA (eventually) is degraded by enzymes.
68
The assembly of the protein takes place near the
ER, which then packages the completed protein
for transport elsewhere in the cell or to the
Golgi apparatus for transport out of the cell.
69
Tissues
70
4 Types of Tissues Epithelium Connective Muscl
e Nerve
71
Epithelium

• -Named for numbers of layers and cell shape
• -Covers surfaces in contact with the outside
• -Specialized for absorption, secretion,
  protection, sensation, filtration
• Have an apical surface (the free surface) and a
  basal surface (where attached to the basement
  membrane
• -Gland tissues are epithelium

72
Epithelium

• -Have an apical surface (the free surface) and a
  basal surface (where attached to the basement
  membrane)
• Adjacent cells are connected as sheets by
  desmosomes and tight junctions
• The basal layer rests on the basement membrane,
  comprised of the basal lamina and reticular
  lamina (115)
• Nerves, but no blood vessels
• Generally good regenerative capacity

73
All epithelium rests on a basement membrane.
The blood carries nutrients as far as the
basement membrane. From there, nutrients must
diffuse across.
The basement membrane is made of protein fibers
and helps keep materials/cells in their proper
tissue compartments.
Thats why, in stratified epithelium, the upper
layers start dying trickle-up nutrition only
serves those at the bottom
74
Glandular Epithelium

• Exocrine when secretions end up on the surface
  on the skin or on a surface contiguous with the
  skin
• Endocrine secretions are released to the blood,
  lymph or interstitial spaces (Not all are
  epithelium more later)

75
Exocrine glands

• Includes single cell and multicell glands
• Single cell are goblet cells producing mucin,
  which released, dissolves in water to make mucus

See 122
76
Exocrine glands

• Includes single cell and multicell glands
• Multicell glands have ducts and regions
  secreting to those ducts (acinar cells). There is
  generally connective tissue supports and blood
  supplies

See 123

• Pancreas here

See 122
77
Secretion
Three ways for this to happen
1) merocrine when the substance being produced
by the cell is released by exocytosis (some
cytoplasm is lost)
78
2) holocrine the cell is filled with the
secretion bursts, releasing the material, and
dies.
3) Apocrine present in humans?
79
Connective tissue types
Embryonic mesenchyme
Blood
Connective tissue proper
Bone
Cartilage
Hyaline Fibrocartilage Elastic
Spongy Compact
Loose Dense
Several cell types- details later
80
Connective tissue
Functions
Support and protection
Cartilage and bone (blood and lymph)
Transportation
Blood and lymph
Energy storage
Fat
81
Connective tissue (look at 125)
Characteristics -made up of ( in differing
degrees) cells, matrix of ground substance and
fibers -blood supply varies with the specific
tissue -cartilage very poor -bone very
rich -others in between -an extracellular
matrix lies between cells - contains proteins
that connect tissue, hold water - amount
varies with the tissue
82
Connective tissue fibers
Collagen most common, strong and flexible
Elastic containing the creatively named
elastin protein. These fibers are wavy and
have recoil
Reticular like a lattice- support organ soft
tissue and small vessels
83
Connective tissue
Matrix -an extracellular matrix lies
between cells - contains proteins that connect
tissue, hold water - amount varies with the
tissue
84
Connective tissue cells
Fibroblasts produce and maintain fibers and
matrix Chondroblasts produce cartilage
Osteoblasts- Bone production Hematopoietic
cells- blood cell production
Macrophages tissue pac-men (also WBCs w/
antibodies)
Fat cells
Mast cells contain chemical mediators of
inflammation
85
Connective tissue types
Blood
Connective tissue proper
Bone
Cartilage
Hyaline Fibrocartilage Elastic
Spongy Compact
Loose Dense
Several cell types- details later
86
Connective tissue types
Connective tissue (proper)
Loose
Examples areolar, adipose, reticular
Dense Examples Dense regular, dense
irregular, elastic
87
Connective tissue types
Areolar Fibers support surrounding
tissue Matrix (ground substance) holds
water White blood cells/Macrophages act
defensively Nutrients stored in fat
(adipose) See p. 126
88
Connective tissue types
Adipose (cells are adipocytes)
-Like areolar connective tissue, plus a
predominance of adipocytes
-Acts as padding, shock absorption, insulation
and energy reserves -good blood supply -white
fat vs brown fat
-see p. 127
89
Connective tissue types
Reticular
Think lattice A framework supporting cells,
esp. in the spleen, lymph nodes and marrow
-see p. 133
90
Connective tissue types
Dense Regular connective tissue
-Made up mostly of collagen, with fibers oriented
parallel, in line with the direction of stress
-Think tendon and ligament
91
Connective tissue types
Dense Irregular connective tissue
-Similar components to regular, with thicker
collagen fibers, oriented ad various angles
-Think dermis, joint capsules, organ capsules
92
Connective tissue types
-Fluid connective tissues
Blood and lymph (including RBC, WBC, Platelets
93
Connective tissue types
Cartilage (see pages 131,132)
Maintained by chondrocytes
Poor blood supply and innervation
Types Hyaline
Elastic
Fibrocartilage
94
Connective tissue types
Cartilage
Types Hyaline- at joints, supporting respiratory
tract, connecting ribs to sternum - forms the
template of bones in the developing fetus
Elastic- more flexible at outer ear,
epiglottis, auditory tube
Fibrocartilage- much collagen tough found
intervertebral disks, symphysis joints
95
Connective tissue types
Cartilage
Elastic- like hyaline, more flexible having many
elastic fibers - at outer ear, epiglottis,
auditory tube
Fibrocartilage- much collagen tough found
intervertebral disks, symphysis joints
96
Connective tissue types
Cartilage
Fibrocartilage- much collagen tough found
intervertebral disks, symphysis joints
97
Connective tissue types
Bone (see p. 133)
2 structural types spongy and compact Components
include collagen fibers, with a matrix material
reinforced by calcium salts for great
rigidity Good blood supply
98
Nerve
Nerve tissue consists of two main groups the
neurons which send and receive signals through
the body the neuroglia which are support
cells for the neurons, providing protection and
maintenance for the neurons . More details on
neuroglia later
99
Muscle
Smooth
Cardiac
Skeletal
See 140, 141
100
Muscle- cont
Smooth muscle forms the wall of hollow
organs bladder, stomach/intestines, uterus,
blood vessels is non-striated,
involuntary contracts in response to stretch-
meaning for example- that when the bladder is
stretched (full) it contracts to empty
101
Muscle
Cardiac found only in the heart cells have
single nucleus cells may be branched cells
are connected by gap junctions and communicate
with each other through these junctions
connections between cells are intercalated
disks cardiac muscle is striated,
involuntary
102
Muscle (cont)
Skeletal striated, voluntary what we
usually think of as muscle-- like the biceps
or hamstring group provides posture, generates
heat, provides movement, control of sphincters
(openings of bladder, bowel) multi-nucleate
103
Membranes

• Cutaneous
• Mucous
• Serous

104
Membranes
Mucus- -line body cavities open to the
outside -moisten tissue, generally adapted
for secretion, absorption -varying amounts of
mucus -protective
105
Membranes
Serous- -line outside of organs heart, lungs
and GI tract -provide reduced friction around
these moving organs -composed of two layers of
a simple squamous epithelium on loose connective
tissue layers -between the layers is serous
fluid