Cell structure

Cell theory

1. smallest units ( survival on their own )

2. all living things are made of cells ( unicellular, multicellular)

3. all cells come from pre-existing cells no spontaneous generation

Microscopy

Two types:

• light microscope

• electron microscopes

-transmitting TEM internal image

-scanning SEM the surface

Freeze fracture electron microscopy

• Images of surfaces in the cell

• frozen using liquid propane -190

• fractured using steal blade

• etching (enhancing the surface of the specimen by vaporizing the ice)

• coating the surface in platinum or carbon vapor to get a replica

• facilitated the discovery of the membrane structure of a cell

Cryogenic electron microscopy:

• mostly used to find structure of protein

• protein solution poured on to a grid

• frozen using ethane

• due to different orientation of proteins 3D model can be rendered using algorithms

• can capture change in proteins

Staining of a specimen

• Fluorecent stains:

-binds to specific cellular components and not others

• Immunofluorescence:

-Development of fluorescent stains

-links antibodies to fluorescent stains which then bind to specific antigens

Functions of life:

• metabolism

• replication

• movement

• excretion

• response

• growth

• nutrition

• homeostasis

Structures present in all cells:

• Plasma membrane(border that maintains inner environment)

• DNA(all the genetic information)

• Cytoplasm(internal fluid for metabolic reaction)

Prokaryotic cell:

• membraine(homeostasis)

• dna- nucleoid

• ribosomes 70s

• cytoplasm

• pili used for communication

• flagella (slime capsule)

• plasmid extra dna

Eukaryotic cells

• membrane

• ribosomes 80s free, rER (rough endoplasmie reticulum)

• dna- nucleus

• cytoplasm

• cell wall - plants

• mitochondria

• chloroplast- plants

• vacuole - plants (temp in animals)

 Different eukaryotic cell structures

Atypical cell structure

• Red blood cells:

-no nucleus and mitochondria during mutation

-decreases the surface area to volume ratio

• Aseptate fungal hyphae:

-projections that form an underground filamentous network

-no clearly defined individual cell

• Skeletal muscles:

-one large cell with multiple nuclei

-fiused cells

• Phloem sieve tube element:

-part of phloem(organic transport in plants)

-lose nucleus and organelles during development

Endosymbiosis

• Processes for eukaryotic cells form

• Infolding

-plasma membrane folding inward giving organelles(endoplasmic reticulum, golgi apparatus, nuclear envelope)

• Endosymbiosis

Symbiosis - two different organisms living together

Endosymbiosis - cell within a cell dependent on each other

• mitochondria engulfed aerobic bacteria, cell respiration in host cell

• chloroplast engulfed photosynthetic bacteria photosynthesis in host cell

Mitochondia and Chloroplast:

• similar shapes and size as bacteria

• double membrane

• 70s ribosomes

• circular naked DNA

• reproduce by process similar to binary fission

• act independently of host cell

Cell differentiation:

• all cells contain the same genome

• differentiation happens when some genes are expressed but others are not

• allows for the formation of cell types

• stem cells can differentiate into any type of cells

Gene expression:

• gene expression is due to proteins binding to specific sequences in the DNA

• external world affects gene expression

• external environmental factors that can determine genes that turn on and off are: drugs, chemicals, temperature and light

• influences affect how an organism develops and function

Benefits of cell specialization and differentiation :

• can focus on fewer tasks at once and do the work more efficiently while saving energy by not performing other tasks

• can have specialized structures and metabolism

• As they do one (or few) things all the time, they evolve faster in that particular tasks 

Multicellular organisms:

• In multicellular organisms the cells differentiate

• All animals and plants are multicellular and many fungi and eukaryotic algae

Evolution of multicellular

Two steps required:

• the formulation of cellular clusters form unicellular organisms

• differentiation within the cluster for specialized function

Two hypothesis:

1. individual cells come together

2. failure to separate the daughter cells after mitosis

Exercise:

Describe characteristics of paramecium or chlamydomonas that enable it to preform the functions of life

Paramecium:

Movement: covered in tiny hair like structures called cilia that move through the water and sweep food into its oral grove

Nutrition: uses cilia to direct food particles into the oral grove and then forms food vacuoles to digest it

Homeostasis: uses contractile vacuoles to pump out excess water

Response to stimuli: can seance or avoid obstacles by reversing the movement of cilia

Excretion: waste is eliminated through the anal pore

Reproduction: reproduces asexually through binary fission (splinting into two) or sexually

Growth: grows by making new cell material from digested food

Metabolism: brakes down food in vacuoles and uses mitochondria for respiration

Chlamydomonas:

movement: uses flagella to swim towards light and nutrition

Nutrition: uses photosynthesis to create its own food

Homeostasis: uses contractile vacuoles to regulate water balance

Response to stimuli: possess and eye spot

excretion: removes metabolic waste through diffusion of the cell membrane

reproduction : asexually in good conditions and sexually under stress

growth: builds biomass from sugars that it makes

metabolism: metabolites through photosynthesis in chloroplasts and respiration in the mitochondria