Chapter 4 A Tour of the Cell. History of Cells u Robert Hooke - Observed cells in cork. u Coined the...
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Transcript of Chapter 4 A Tour of the Cell. History of Cells u Robert Hooke - Observed cells in cork. u Coined the...
Chapter 4 A Tour of the Cell
History of Cells
Robert Hooke - Observed cells in cork.
Coined the term "cells” in 1665.
History of Cells 1833 - Robert Brown,
discovered the nucleus. 1838 - M.J. Schleiden,
all plants are made of cells. 1839 - T. Schwann,
all animals are made of cells. 1840 - J.E. Purkinje, coined
the term “protoplasm”.
Cell Theory
All living matter is composed of one or more cells.
The cell is the structural and functional unit of life.
R. Virchow
“Omnis cellula e cellula” All cells are from other cells.
Why Are Cells So Small?
Cell volume to surface area ratios favor small size.
Big enough to perform all functions but have enough surface area
Nucleus to cytoplasm consideration (control all areas).
Metabolic requirements.
Basic Cell Organization
Membrane Nucleus Cytoplasm Organelles
Animal Cell
Plant Cell
Membrane
Separates the cell from the environment.
Boundary layer for regulating the movement of materials in/out of a cell.
Cytoplasm or Cytosol
Cell substance between the cell membrane and the nucleus.
The “fluid” part of a cell. Exists in two forms: gel - thick sol - fluid
Organelle
Term means "small organ” Formed body in a cell with a specialized function.
Important in organizational structure of cells.
Organelles - function
Way to form compartments in cells to separate chemical reactions.
Keeps various enzymes separated in space.
Nucleus
Most conspicuous organelle. usually spherical, but can be
lobed or irregular in shape.
Structure
Nuclear membrane Nuclear pores Nucleolus Chromatin
Nuclear Membrane
Double membrane Inner membrane supported
by a protein matrix to provide shape
Nuclear Pores
Allow things in and out of nucleus
Ex. mRNA during transcription
Nucleolus
Dark staining area in the nucleus.
0 - 4 per nucleus. Storage area for ribosomes.
Chromatin
Chrom: colored - tin: threads DNA and Protein in a “loose”
format. Will form the cell’s chromosomes.
Nucleus - Function
Contains the genetic instructions to make proteins and more DNA
Ribosomes
Structure: 2 subunits made of protein and rRNA. No membrane.
Function: protein synthesis. Site of translation
Subunits
Large: 45 proteins 3 rRNA molecules
Small: 23 proteins 1 rRNA molecule
Locations
Free in the cytoplasm - make proteins for use in cell.
Membrane bound - make proteins that are exported from the cell. (on rough ER)
Endomembrane System
Membranes that are related through direct physical continuity or by the transfer of membrane segments called vesicles.
Endomembrane System
Endoplasmic Reticulum
Often referred to as ER. Makes up to 1/2 of the total
membrane in cells. Often continuous with the
nuclear membrane.
Structure of ER
Folded sheets or tubes of membranes.
Very “fluid” in structure with the membranes constantly changing size and shape.
Types of ER
Smooth ER: no ribosomes. Used for lipid synthesis,
carbohydrate storage, detoxification of poisons.
Rough ER: with ribosomes. Makes secretory proteins.
Golgi Apparatus or Golgi Body
Structure: parallel array of flattened cisternae. (looks like a stack of pancakes)
3 to 20 per cell. Likely an outgrowth of the ER
system.
Function of Golgi Bodies
Processing - modification of ER products (lipids, carbs).
Distribution - packaging of ER products for transport.
Mailman of the cell
Golgi Vesicles
Small sacs of membranes that bud off the Golgi Body.
Transportation vehicle for the modified ER products.
Lysosome
Structure: Single membrane. Made from the Golgi
apparatus.
Function
Breakdown and degradation of cellular materials.
Contains enzymes for fats, proteins, polysaccharides, and nucleic acids.
Over 40 types known.
Lysosomes
Important in cell death. Missing enzymes may cause
various genetic enzyme diseases.
Examples: Tay-Sachs, Pompe’s Disease
Vacuoles
Structure - single membrane, usually larger than the Golgi vesicles.
Function - depends on the organism.
Protists
Contractile vacuoles - pump out excess water.
Food vacuoles - store newly ingested food until the lysosomes can digest it.
Plants
Large single vacuole when mature making up to 90% of the cell's volume.
Function
Water regulation. Storage of ions. Storage of hydrophilic
pigments. (e.g. red and blues in flower petals).
Function: Plant vacuole
Used to enlarge cells and create turgor pressure.
Enzymes (various types). Store toxins. Coloration.
Microbodies: Peroxisomes
Structure: single membrane. Often have a granular or
crystalline core of enzymes.
Function
Specialized enzymes for specific reactions.
Peroxisomes: use up/break down hydrogen peroxide.
Enzymes in a crystal
End of part 1 Homework
Mitochondria
Structure: 2 membranes. The inner membrane has more surface area than the outer membrane.
Matrix: inner space. Intermembrane space: area between
the membranes.
Inner Membrane
Folded into cristae. Amount of folding depends
on the level of cell activity. Contains many enzymes. ATP generated here.
Function
Cell Respiration - the release of energy from food.
Major location of ATP generation.
“Powerhouse” of the cell.
Mitochondria notes
Have ribosomes (small size). Have their own DNA. Can reproduce themselves. May have been independent
cells at one time.
Chloroplasts
Structure - two outer membranes.
Complex internal membrane. Fluid-like stroma is around
the internal membranes.
Inner or Thylakoid Membranes
Arranged into flattened sacs called thylakoids.
Some regions stacked into layers called grana.
Contain the green pigment chlorophyll.
Function
Photosynthesis - the use of light energy to make food.
Where does this food go to produce energy?
Chloroplasts notes
Contain ribosomes (small size). Contain DNA. Can reproduce themselves. May have been independent
cells at one time.
Cytoskeleton
Network of rods and filaments in the cytoplasm.
Functions
Cell structure and shape. Cell movement. Cell division - helps build cell
walls and move the chromosomes apart.
Components
Microtubules Microfilaments Intermediate Filaments
Microtubules
Structure - small hollow tubes made of repeating units of a protein dimer.
Level 3-Size - 25 nm diameter with a 15 nm lumen. Can be 200 nm to 25 m in length.
Tubulin
Protein in microtubules. Dimer - and tubulin.
Microtubules
Regulate cell shape. Tracks for motor molecules.
Microtubules
Form cilia and flagella. Internal cellular movement. Make up centrioles, basal
bodies and spindle fibers.
Centrioles
Usually one pair per cell, located close to the nucleus.
Found in animal cells. 9 sets of triplet microtubules. Help in cell division.
Microfilaments
5 to 7 nm in diameter. Structure - two intertwined
strands of actin protein.
Microfilaments are stained green.
Functions
Muscle contraction. Cytoplasmic streaming. Pseudopodia. Cleavage furrow formation. Maintenance and changes in
cell shape.
Intermediate filaments
Fibrous proteins supercoiled into cables
Functions: Maintain cell shape
Anchor organelles
Cytoskeleton
Very dynamic; changing in composition and shape frequently.
Cell is not just a "bag" of cytoplasm within a cell membrane.
Cell Wall
Nonliving jacket that surrounds some cells.
Found in: Plants Prokaryotes Fungi Some Protists
Cell Walls
May be made of other types of polysaccharides and/or silica.
Function as the cell's exoskeleton for support and protection.
Extracellular Matrix - ECM
Fuzzy coat on animal cells. Helps glue cells together. Made of glycoproteins and
collagen. Evidence suggests ECM is
involved with cell behavior and cell communication.
Intercellular Juctions
Plants-Plasmodesmata
Plasmodesmata
Channels between cells through adjacent cell walls.
Allows communication between cells.
Also allows viruses to travel rapidly between cells.
Intercellular Juctions
Animals: Tight junctions Anchoring junctions Gap junctions
Tight Junctions
Very tight fusion of the membranes of adjacent cells.
Seals off areas between the cells.
Lining of digestive tract
Anchoring junctions
Does not close off the area between adjacent cells.
Coordination of movement between groups of cells.
Ex: Tissue subject to stretching (skin and muscle)
Gap Junctions
Open channels between cells, similar to plasmodesmata.
Allows “communication” between cells.
Ex: heart muscle, embryos
Types of Cells
Prokaryotic - lack a nucleus and other membrane bound structures.
Eukaryotic - have a nucleus and other membrane bound structures.
Both Have:
Membrane Cytosol Ribosomes (but the size is
different)
Prokaryotic Eukaryotic
Nucleus
Prokaryotes
Bacteria Capsule- sticky outer layer Cell wall- protects and
maintains shape Plasma membrane- controls
movement of materials
Prokaryotes
Pili- used for attachment Joins bacteria together for
transfer of DNA Flagella- allow for cell motility
(longer than pili)
Prokaryotes
Ribosomes- protein synthesis Nucleoid- Contains the DNA
Calculating in microscopes
Actual size of specimen Measure the field of vision
while looking through the microscope (~1.5mm)
Then figure the % of field the specimen occupies and multiply by field of vision
Continued
Field of vision is 1.4mm or 1400 micrometers
Specimen is 60% of field of vision
1400 x .60 =840 micrometers
Calculating
Magnification Scale bar next to drawing
Magnification= size of image / size of specimen
Size of image = 10 mm or 10000 micrometers
Size of specimen is 10 micrometers
10000 / 10 is 1000x magnified
Magnification
Image size 12.5 cm or
125,000
Micrometers
Specimen size
(using scale)
4.5 micrometers
So 125,000/4.5=
27,777x
Summary
Answer: Why is Life cellular and what are the factors that affect cell size?
Be able to identify cellular parts, their structure, and their functions.