Unit 1 - Cell biology

Cell Theory

Theory that states that all organisms are composed of cells, that all cells come from pre-existing cells, and the cell is the smallest unit of life

3 Statements of Cell Theory

-All living things are composed of 1 or more cells
-The cell is the smallest unit of life
-Cells only arise from pre-existing cells

Coarse Focus Dial

Used to initially focus a light microscope specimen

Differentiation

the alteration of a cell's morphology and physiology through changes in gene expression

Emergent property

A property of a system that emerges from the interaction of the elements of that system

Gene Expression

The synthesis of a functional gene product, often protein, but also rRNA, tRNA or snRNA

Homeostasis

The process in which an organism regulates activities within cells and their bodies to keep conditions stable

Magnification

Ratio of image size to actual size

Micro-

1x10^-6

Milli-

1x10^-3

Nano-

1x10^-9

Objective lens

The part of the microscope that gathers light from the specimen and focuses it to produce a real image

Paramecium

Genus of single-celled ciliated organisms

Reductionism

An approach to science that holds that a complex system can be best understood as the sum of its parts, and that variables can be studied in isolation

response

In behavioral science, the behavior that is the consequence of a stimulus

Scale Bar

A means of visually indicating the magnification of an image

Stargardt's Disease

A degenerative eye disease that has been the target of stem cell research

Stem Cells

A relatively undifferentiated cell that can give rise to other types of cells and retains the ability to divide

SA:VO Ratio

A variable that decreases as cells grow, so that it sets a limit to the size of cells

System

A level of organization that emerges due to the interaction of elements

Tissue

A group of cells with a common function and structure

Advantage of Multicellular Organisms over Unicellular Organisms

Severe cell damage in multicellular organisms does not mean organism death

Calculating Magnification Formula

Convert units to the same unit of measurementScale bar measurement/Scale bar label \= Measured length/Magnification

Mitosis

The process of division of a cell which results in genetically identical diploid daughter cells

Meiosis

The process where a single cell divides twice to produce four cells containing half the original amount of genetic information, or haploids. These cells are our sex cells - sperm in males, eggs in females.

Striated Muscle

-Challenges the idea that a cell has 1 nucleus
-Muscle cells have more than 1 nucleus per cell
-Muscle fibres can be very long (300mm)

Giant Algae (Acetubularia)

-A single celled organism that challenges the idea that cells must be simple in structure and small in size
-Gigantic in size (5-100mm)
-Complex in form, consists of 3 anatomical parts

Aseptate Fungal Hyphae

-Challenges the idea that a cell is a single unit
-Very large with many nuclei and a continuous cytoplasm
-Cytoplasm is continuous along the Hyphae with no end cell wall or membrane

Excretion

The removal of metabolic waste

Functions of Life (MR. H. GREN)

-Metabolism
-Response
-Homeostasis
-Growth
-Reproduction
-Excretion
-Nutrition

Advantages of a Larger SA:VO important?

A larger SA:VO ration means the cell can act more efficiently

for every unit of volume that requires nutrients or produces waste, there is more membrane to serve it

What Type of Thinking does Systems Biology use?

Systems biology uses inductive thinking it is realized the importance of emergent properties. Inductive reasoning is a logical process in which multiple premises, all believed true or found true most of the time, are combined to obtain a specific conclusion. Inductive reasoning is often used in applications that involve prediction, forecasting, or behavior.

Disadvantages of Large SA:VO ratio

-Small, warm blooded animals lose heat very quickly (they need to eat constantly)
-Desert plants would lose water quickly with flat leaves (they minimize SA:VO ratio)

What Happens if the Metabolic Rate is Greater than the Exchange of Vital Materials and Wastes?

The cell will eventually die

The Rate of Metabolism is a Function of What?

The rate of metabolism is a function of its mass/volume

What do all Diploid Cells of an individual organism have in Common?

All diploid cells of an individual organism share an identical genome- each cell contains the entire set of genetic instructions for that organism

Not all Genes are \_____________ in a cell

Expressed/Activated

In Embryonic Stem Cells, the Entire Genome is \_____________ .

Expressed/Activated

Euchromatin

The name for when active genes are packaged in expanded and accessible form

The Fewer Genes a Cell Possesses, \_________________

The more specialized it will become

Humans have how many Specialized Cells?

220

Gene Expression and Cell Differentiation Cause a Change in the Cell's What?

The cell's metabolism and shape changes as a result of gene expression and cell differentiation

Totipotent Stem Cell

A stem cell that can differentiate into any type of cell

Pluripotent Stem Cell

A stem cell that can differentiation into many different types of cells

Multipotent Stem Cell

A stem cell that can differentiate into a few closely-related types of cells

Unipotent Stem Cell

A stem cell that can regenerate but can only differentiate into their associated cell type

Arguments for Therapeutic Cloning

-Stem cell research influences future discoveries and technologies that would not have occurred if their use had been banned
-May be used to cure serious diseases or disabilities
-Transplants are less likely to be rejected as they are genetically identical to the parent
-Transplants do not require death of another human being
-Stem cells can be taken away from embryos that have stopped developing and would've died anyway (abortions)
-Stem cells are taken at a stage when the embryo has no nervous system and can arguably feel no pain

Arguments Against Therapeutic Cloning

-Involves the creation and destruction of human embryos
-ESCs are capable of continued division and may develop into cancerous cells and cause tumors
-More embryos are generally produced than needed, so excess embryos are killed
-Alternative programs could fill this role
-Religious or moral objections as "playing God"

Size of Prokaryotic Ribosomes

70S

Size of Eukaryotic Ribosomes

80S

Archaea

A domain of prokaryotes

Bacteria

A domain of prokaryotes

Binary Fission

Method of asexual production common among prokaryotes where one cell divides, giving rise to two cells, each having the potential to divide the size of the original cell

Cell Wall

A rigid layer of polysaccharides lying outside the plasma membrane of the cells of plants, fungi, and bacteria used for structure and protection. In the algae and higher plants, it consists mainly of cellulose.
-An extracellular component, NOT AN ORGANELLE
-Secreted by all plant cells (fungi and some protists also secrete cell walls)
-Plant cell walls consist mainly of cellulose which is
-Permable: does not affect transport in & out of cell
-Strong: prevents plasma membrane from bursting under pressure
-Hard to digest: lasts a long time without the need for replacement/maintenance

Compartmentalization

Seen in eukaryotes, consequence of organelles being membrane bound

Eukaryote

Organisms with membrane bound nuclei

Exocrine Glands

Glands that secrete their products into ducts

Extracellular Matrix

A network of material that is secreted by cells that serves to support, strengthen and organize cells

Histone

A protein associated with DNA that plays a role in gene expression and the packing of DNA

Naked DNA

DNA not associated with histones or histone-like proteins

Organelle

A sub-cellular structure or membrane-bound compartment with a distinct structure and function

Palisade Mesophyll

Photosynthetic tissue below the epidermis in a leaf

Pilli

Extensions of the prokaryotic cell surface membrane used for reproduction

Plasmid

Extra Chromosomal DNA in a prokaryote

Prokaryote

-Category of a cell without a membrane bound nucleus

archaea and bacteria
-Smaller than eukaryotes and came first in evolution
-DNA is replicated semi-conservatively

Resolution

The ability to see an object or structures as distinct from each other

Scanning Electron Microscope

An electron microscope that generates a 3-D image

Svedburg Unit

Unit of molecule size based on the position that material settles out in a centrifuge tube after spinning. Larger particles tend to settle out faster and therefore have higher Svedburg values

Transmission Electron Microscope

An electron microscope that produces 2-D images

Ultrastructure

the detailed structure of a biological entity

Describe the Division of Prokaryotic Cells

-The DNA loops to attach to the membrane
-The membrane elongates and pinches off (cytokinesis) forming two separate cells
-The two daughter cells are genetically identical

Advantages of Compartmentalization

-efficiency in metabolism: enzymes and substrates can be localized and much more concentrated
-Localized conditions: pH and other such factors can be kept at optimal levels. The optimal pH level for one process in one part of the cell.
-Toxic/damaging substances can be isolated: Example, digestive enzymes are stored in lysosomes
-Numbers and locations of organelles can be changed dependent on the cell's requirements

Mitochondrion (Pl. Mitochondria)

-Has a double membrane
-A smoother outer membrane and a folded inner membrane
-The folds are referred to as cristae
-Variable in shape
-Site of ATP production by aerobic respiration (if fat is used as an energy source it is digested here)

Free Ribosomes

-80S (larger than ribosomes found in prokaryotes)
-No membrane
-Appear as dark granules in the cytoplasm
-Synthesizes proteins to function in the cytoplasm, for use within the cell

Nucleus

-Generally spherical with a double membrane
-Pores (holes) are present in the membrane
-Contains genetic information in the form of chromosomes (DNA and associated histone proteins)
-Uncoiled chromosomes are referred to as chromatin- they stained dark color and are concentrated at the edges of the nucleus
-mRNA is transcribed in the nucleus (prior to use in protein synthesis in the cytoplasm)
-mRNA leaves the nucleus via pores (DNA is too large to move through the pores)

Rough Endoplasmic Reticulum (rER)

-Consists of flattened membrane sacs, called cisternae
-often located near the nucleus
-80S ribosomes are attached to the outside of the cisternae
-rER synthesizes proteins which are transported, by vesicles, to the golgi apparatus for modification before secretion outside the cell

Golgi Apparatus

-Also consists of flattened membrane sacs called cisternae
-Different to rER
-No attached ribosomes
-Often sited close to the plasma membrane
-The cisternae are shorter and more than those of rER
-Processes (modifies) proteins from the rER. The proteins are then repackaged in vesicles for secretion outside the cell

Vacuoles

-Single membrane with fluid inside
-In plant cells, vacuoles are large and permanent, often occupying the majority of the cell volume
-In animals, vacuoles are smaller and temporary and used for various reasons, example to absorb food and digest it

Cilia

-Thin projections from the cells surface
-Contains microtubules
-Used to either move the cell or to move the fluids next to the cell

Vesicles

-A single membrane with fluid inside
-Very small in size
-Used to transport materials inside of a cell
-Bud off the rER and the Golgi Apparatus
-Carries proteins produced by ribosomes on the rER to the Golgi Apparatus, where they are prepared for export from the cell via another vesicle

Lysosomes

-Generally spherical with a single membrane
-Formed from golgi vesicles
-Contain digestive enzymes known for breakdown of:
-ingested food in vesicles
-unwanted/damaged organelles
-the cell itself
-High concentration of enzymes (type of protein) cause this organelle to stain heavily and hence appear dark on micrographs

Flagellum (Pl. Flagella)

-Thin projection (usually singular) from the cell surface
-Contains microtubules
-Used to move the cell

Microtubules

-Small cylindrical fibers
-Have a variety of functions (Ex. part of the structure of flagella and they play a role in cell division)

Centrioles

-Consist of two groups of nine triple microtubules
-Are mainly found in animal cells, not present in vascular plants or fungi
-Self-replicating cylindrical organelle that is involved in the process of nuclear division

Chloroplasts

-Found in plant cells
-A double membrane surrounds the chloroplast
-Inside are sacs of thykaloids
-Each thykaloid is a disk composed of a flattened membrane
-The shape of chloroplasts is variable but usually ovoid
-The site of photosynthesis and hence where glucose is produced
-Starch grains may be present if photosynthesis is happening quickly

Amphiphatic

Molecule that has hydrophobic and hydrophilic regions

Cholesterol

-A lipid that prevents the membrane from crystallizing. Cholesterol makes the phospholipids pack more tightly and regulates the fluidity and flexibility of the cell.
-Carbon rings classified as steroid
-Non-polar tail attracted to the hydrophobic tails of phospholipids in the center of the membrane
-Hydroxyl group makes the head polar and hydrophilic

Davson-Danielli Model

-Model of the cell membrane in which the phospholipid bilayer is between two layers of protein
-A protein-lipid sandwich (proteins do not permeate the lipid bilayer)

Fluid Mosaic Model

A model conceived by S. J. Singer and Garth Nicolson in 1972 to describe the observed structural features of biological membranes

Fluidity

Refers to the viscosity of a lipid bilayer of the membrane that allows it to change shape

Glycoproteins

Proteins that contain oligosaccharide chains attached (oligo \= few, saccharide \= sugar)
-Important for cell recognition by the immune system and as hormone receptors
-Organ transplants are possible/not possible due to identifiers

Hormone Mapping Sites

Proteins on the outside of the membrane that allow specific hormones to bind

Integral Proteins

Proteins permanently embedded in the phospholipid bilayer, many go all the way through and are polytopic (poly \= many, topic \= surface). Integral proteins penetrating just one surface are monotopic

Peripheral Proteins

Proteins on the surface of the plasma membrane who have a temporary association with the membrane, they can be monotopic or attached to the surface

Permeability

The rate of passive diffusion of molecules through the membrane, which depends on the electric charge, size and polarity of the molecule

Phospholipid bilayer

Two layers of phospholipids arranged so that their hydrophobic tails are projecting inwards while their polar head groups are on the outside surfaces

Singer-Nicolson Model

-Current model of membrane structure that incorporates a fluid mosaic structure in a discontinuous lipid bilayer

Transport Pumps

Proteins in the plasma membrane that release energy and use it to move substances across the membrane