the cell biosci 105 lecture 4 read chapter 3 (pages 47 – 62)
TRANSCRIPT
The Cell
BioSci 105
Lecture 4
Read Chapter 3 (Pages 47 – 62)
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Outline
I. Prokaryotic vs Eukaryotic
II. Eukaryotic
A. Plasma membrane – transport across
B. Main features of animal cells and their functions
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Cells
Cells are the basic unit of life
Cells are highly structured
They are enclosed in a membrane—the Plasma Membrane
Cells vary in size but there is a limit on how big a cell can be and survive
There are different types of cells – specialized cells
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Some organisms are just one cell - yeast
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Multi-celled organisms have specialized cells
Blood CellsBlood Cells Nerve CellsNerve Cells
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Some cells are very small
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Prokaryotic vs Eukaryotic
Prokaryotic – Pro (before) karyotic (nucleus) Eukaryotic – Eu (true) karyotic (nucleus)
The presence or absence of a nucleus is the biggest difference between these types of cells.
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Prokaryotic vs Eukaryotic
Prokaryotic cells = bacteria and archaea have
no nucleus, no organelles, have ribosomes
In eukaryotic cells the DNA is contained within the nucleus Animal cells, Plant cells, Fungi, Protists
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Figure 3.1 Prokaryotic cells, such as bacterium, lack internal membrane-bound organelles.
Ribosome
Cytoplasm
Cell wall
Plasma membrane
DNA region(no nucleus)
1–10 m
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Table 3.1 Review of Features of Prokaryotic and Eukaryotic Cells
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Which are examples of prokaryotic organisms?
1. Animals
2. Plants
3. Bacteria
4. Protists
5. Fungus
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Prokaryotic cells have a nucleus.
1. True
2. False
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Major Features of Eukaryotic Cells
Figure 3.2 (2 of 2)
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Cell size
Cells vary in size, but they can never exceed the volume that can be nourished by materials passing through the surface membrane
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Cell Size
Figure 3.3
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Major Features of Animal Cells
Plasma membrane – controls entry in/out of cell
Cytoplasm – semi-fluid matrix (liquid is cytosol)
Cytoskeleton – gives shape, structure, transport
Ribosomes - assembling polypeptide chains
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Major Features of Animal Cells
Organelles – membrane bound compartments
Nucleus – contains the DNA
Mitochonria – energy production
Endoplasmic reticulum – Rough: modifies new polypeptide chains Smooth: synthesizes lipids
Golgi body – modifies, sorts, ships new proteins and lipids
Vesicles – storage, transport, digestion
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Organelles
Organelles are membrane-bound internal compartments in cells for specialized functions
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Plasma Membrane
Fluid Mosaic model Molecules are free to move around mixture of phospholipids, steroids (cholesterol),
and proteins
Selectively permeable
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Plasma Membrane
Bilayer
Phospholipids arrange to have the polar head on the outside and the non-polar, lipid portion on the inside
Proteins and sterols (cholesterol) are arranged on surfaces and can form channels
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Table 3.2 Review of Plasma Membrane Functions
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Four main components in membrane
1. Phospholipid bilayer
Phosphate head (hydrophilic) Fatty acid tail (hydrophobic) Function – controls what passes through
membrane
2. Cholesterol – maintains fluidity of membrane
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Four main components in membrane
3. Proteins – transport, support, communication, recognition
4. Glycoproteins: chains of sugars attached to a protein Functions – attachment sites, cell recognition
5. Glycolipids: chains of sugars attached to a lipid Function - attachment sites, cell recognition
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Plasma Membrane
Figure 3.6
Cytoplasm
Extracellularfluid
Carbohydrate
Cholesterol
Surfaceprotein
Filaments ofcytoskeleton
Embeddedprotein
Plasma membrane
Outer surface of plasma membrane
Inner surface of plasma membrane
Plasma membrane
Phospholipidbilayer
Glycoprotein
Glycolipid
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Hydrophilic: Water loving = lipophobicHydrophobic: Water hating = lipophilic
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Simple Diffusion
Figure 3.7
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Concentration gradient Molecules will go from higher concentration to
lower concentration.
If you add molecules to water it will disperse (diffuse) until it is equally distributed in the water
Movement through the membrane
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The plasma membrane divides inside the cell from outside the cell
It is semi-permeable – not everything can freely pass through it
Movement through the membrane
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What can freely pass through the membrane
1.Gases – oxygen, carbon dioxide
2.Hydrophobic compounds (non-polar)
3.Very small uncharged molecules (Water, even though water is polar, it is small enough to pass)
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What can not freely pass through the membrane
1. Ions
2. Hydrophillic (polar compounds) (larger than water)
3. Charged compounds
4. Macromolecules compounds (ex: large proteins, complex carbohydrates, triglycerides)
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Osmosis
The cell membrane is semi-permeable:
This means that some things can pass while others can not pass through.
The cell membrane is somewhat permeable to water, but not to charged ions and molecules
Water will travel across the membrane to try to restore the balance of solutes = Osmosis
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Hypertonic: Concentration of solutes is higher outside than inside
Isotonic: Inside and outside have same conc.
Hypotonic: concentration of solutes is lower outside the cell than inside.
How does the salt concentration effect a cell?
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Osmosis
Osmosis is the movement of water across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration
Osmosis restores the solute balance
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Transporting molecules across the membrane
Passive transport – does not require energy, uses concentration gradient Simple diffusion Facilitated diffusion
Active Transport – requires energy, goes against concentration gradient
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Simple Diffusion
Figure 3.7
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Passive Transport – Simple Diffusion
Simple diffusion: molecules that can freely pass through the membrane are controlled by concentration gradient
Gases like oxygen and CO2
Very small molecules that are not charged (H2O) hydrophobic (non-polar) molecules
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Facilitated diffusion
Figure 3.8
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Passive Transport – Facilitated Diffusion
Facilitated diffusion: Aided by a transport protein, still controlled by concentration gradient
Hydrophilic molecules like glucose and amino acids
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Active Transport
Figure 3.10
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Active Transport
Sometimes our cells want to move a molecule across the membrane but there is not a gradient. The cell wants more of the solute on one side of the membrane.
The cell will use energy to maintain the higher concentration
Used to transport sugars, amino acids and ions
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Active Transport
Movement often from a region of lower to higher concentration with the aid of a carrier protein and energy (usually from ATP)
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Can Calcium (Ca2+) pass freely through the membrane?
1. Yes
2. No
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Can glucose pass freely through the membrane?
1. Yes
2. No
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If a transport protein is used to move glucose using a concentration gradient this is called:
1. Simple diffusion
2. Facilitated diffusion
3. Active transport
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Transporting using a vesicle
When the cell needs to transport larger things (i.e. macromolecules, bacteria, fluids) they can use vesicles to transport things in and out of the cell.
Exocytosis: moving things out of the cell using a vesicle
Endocytosis: moving things into the cell using a vesicle
Used to transport macromolecules including: whole cells (bacteria), cholesterol, fluids, and proteins
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Endocytosis
Phagocytosis – when cells transport large particles and cells (bacteria) into the cell using vesicles
Pinocytosis – when cells transport fluid into the cell using vesicles
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Endocytosis - phagocytosis
Figure 3.11a
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Endocytosis - pinocytosis
Figure 3.11b
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Exocytosis
Figure 3.12
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Table 3.3 Review of Mechanisms of Transport Across the Plasma Membrane
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Major Features of Eukaryotic Cells
Figure 3.2 (2 of 2)
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Nucleus
Nucleus contains DNA = instructions for building proteins
Number of DNA molecules vary between species Humans have 46 DNA molecules in each cell Frogs have 26 DNA molecules in each cell
Nucleus protects DNA
Separates DNA from rest of cell
Place where DNA duplicates itself
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Chromosomes
Humans chromosomes They are visible in the light microscope
during cell division when they shorten and condense
At other times the chromosomes are extended uncondensed and are called chromatin
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Nucleus
Figure 3.14a
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Chromatin
Figure 3.14b
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Parts of the Nucleus
1. Nuclear Envelope – Double membrane (two different bilayers) Inside layer contains sites for DNA to attach Outside surface layer has many ribosomes
2. Nucleolus – dense area in the nucleus where ribosomes are produced
3. Nucleoplasm – area inside the nucleus
4. Chromatin – DNA and its associated proteins
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Nucleus
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Ribosomes
Function: Site of protein synthesis
This is where amino acids are chained together with a peptide bond to make a polypeptide chain
Ribosomes are composed of proteins and ribosomal RNA (rRNA)
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Endoplasmic Reticulum
There are two types of Endoplasmic Reticulum:
Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum
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Figure 3.15 The endoplasmic reticulum (ER)
Rough endoplasmic reticulum (RER) has ribosomes attached to its surface and is involved in modifying proteins made by the ribosomes.
Smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in detoxifying certain drugs and in producing phospholipids forincorporation into membranes.
Endoplasmicreticulum
Nucleus
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Rough Endoplasmic Reticulum
Endoplasmic reticulum that has ribosomes associated with it is called rough endoplasmic reticulum
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Rough Endoplasmic Reticulum
Functions: Important in protein modification
1. It is here that polypeptide chains (chains of amino acids) are folded into their shape by chaperones
2. Here carbohydrate tags are added to the proteins
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Smooth Endoplasmic Reticulum
Endoplasmic reticulum that does not have ribosomes associated with it is called smooth endoplasmic reticulum
Functions: 1. Phospholipids and steroids are
synthesized here
2. contain enzymes that detoxify alcohol and some drugs
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Transport vesicles
Membrane bound compartments used for transporting molecules around in the cell, also can be used to transport molecules in and out of cell
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Golgi Complex
The golgi complex – series of flattened membranous sacs
Vesicles from rough and smooth endoplasmic reticulum bring their products to the golgi to be modified and repackaged
Functions: processes, sorts, packages proteins and lipids
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Figure 3.16a The Golgi complex
Golgicomplex
New vesicleforming
(a) Diagram of the Golgi complex. This organelle serves as tsite for protein processing and packaging within the cell.
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Figure 3.17 Transport of proteins from RER to Golgi to plasma membrane
Transportvesicle
Secretoryvesicle
Proteinexpelled
Lysosomewithproteins
Proteins
Roughendoplasmicreticulum
Ribosome
Golgi complex
Plasma membrane
Vesicles carrying proteins from the RER arrive at the “receiving” side of the Golgi complex and empty their contents to the inside, where the proteins are modified.
Vesicles containing the modified proteins leave the “shipping” side of the Golgi complex and travel to their specific destinations.
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Lysosomes
Figure 3.18
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Lysosomes
Lysosomes are digestion vesicles that contain strong acids and enzymes, can fuse with plasma membrane to expel waste
Made by the golgi
Functions: Engulf molecules and digest them Fuse with other organelles to destroy them Destroy bacteria
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Tay-Sachs disease
Tay-Sachs is a hereditary disease where people don’t have a enzyme normally found in lysosomes that breaks down lipids in nerve cells.
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Mitochondria
All Eukaryotic cells contain mitochondria
Bound by a double membrane
Outer membrane faces cytoplasm Inner membrane folded = forms cristae that increases
surface area for cellular respiration
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Mitochondria
Functions: 1. Produces energy for the cell (ATP). This process
requires oxygen
2. Important in apoptosis (planned cell death)
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Mitochondria
Figure 3.19
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Where are polypeptide chains/proteins produced
1. Nucleus
2. Ribosomes
3. Golgi complex
4. Rough Endoplasmic Reticulum
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Where are polypeptide chains/proteins folded
1. Nucleus
2. Ribosomes
3. Golgi complex
4. Rough Endoplasmic Reticulum
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What organelle produces energy for the cell?
1. Nucleus
2. Ribosomes
3. Mitochondria
4. Rough Endoplasmic Reticulum
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Cytoskeleton
Interconnected system of fibers and lattices between the nucleus and the plasma membrane
Functions: Gives cells their organization, shape, ability to move, transport things in cell, aid in cell division
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Cytoskeleton
Wide variety of cytoskeleton: Microfilaments microtubules (including cilia and flagella) Intermediate filaments
Some permanent (intermediate) others self assemble and are only present
when needed (microfilaments and microtubules)
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Microtubules - functions
1. Microtubules serve as tracks along which organelles or vesicles move.
2. Aid in cell division
3. Microtubules are also responsible for the structure and movement of cilia and flagella Cilia are numerous short extensions in a
cell that move back and forth Flagella are larger than cilia and move in
an undulating manner
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Microtubules – cilia and flagella
cilia and flagella are composed of microtubules
Cilia are numerous short extensions in a cell that move back and forth
Flagella are larger than cilia and move in an undulating manner
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Cytoskeleton - Microtubules.
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Cytoskeleton - Microtubules serve as tracks along which organelles or vesicles move.
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Cytoskeleton – Microtubules of a centriole
Figure 3.21
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Microtubules - cilia
Figure 3.22a
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Microtubules - flagella
Figure 3.22b
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Cytoskeleton - Microfilaments
Made of the protein actin Functions
1. Important function in muscle contraction
2. Responsible for the movement of pseudopodia
3. Role in dividing cells during cell division
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Intermediate Filaments
A diverse group of ropelike fibers
Functions: maintain cell shape and anchor organelles
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Cilia is made of this type of cytoskeleton
1. Intermediate filaments
2. Microtubules
3. Microfilaments
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Important Concepts
Read Ch 4 Why are most cells small? What are the main differences between
prokaryotic cells and eukaryotic cells, and know examples of prokaryotic cells and eukaryotic cells.
Major features of cells and their function; includes: Plasma membrane, Cytoplasm, Nucleus,
Cytoskeleton, Mitochondria, Ribosomes, Endoplasmic reticulum (smooth and rough), Golgi body, Vesicles, lysosomes
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Important Concepts
What are lysosomes, what disorder is associated with a missing enzyme in lysosomes
What are the functions of cytoskeleton and examples of cytoskeleton
What are the functions of microtubules
What cytoskeleton makes up cilia and flagella
Know the functions of microfilaments, what protein makes up microfilaments
Know the functions of intermediate filaments
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Functions of the plasma membrane
Know the main components in the plasma membrane and the function of each component.
Be able to draw a membrane.
Be able to identify what can pass freely through a membrane and what can’t pass freely.
Important Concepts
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Know how small molecules are transported into the cell, know the differences between passive diffusion, facilitated diffusion, and active transport. Know what molecules each mode can transport
Know how things are transported in and out of a cell using a vesicle
Important Concepts
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Definitions
Prokaryotic cells, eukaryotic cells, semi-permeable, osmosis, hypertonic, hypotonic, isotonic, hydrophobic compounds, non polar, hydrophillic compounds, polar, passive transport, active transport, simple diffusion, facilitated diffusion, exocytosis, endocytosis, phagocytosis, pinocytosis, nucleolus, nuclear envelope, nucleoplasm, chromatin, cristae, apoptosis