2- Cells And Cell Theory Flashcards
Are the formation of amino acids, nucleic acids, carbohydrates and lipids sufficient for life by themselves?
No
Do you need living things to make organic compounds?
No
The evolution of cells requires what?
Early organic molecules to assemble into a functional, interdependent unit
What was Stanley L. Miller and Harold C. Urey’s experiment and what did they obtain?
They recreated the primitive oceans and reducing atmosphere (little oxygen) of Earth in the lab.
-They obtained a lot of the basic molecules for life
Amino acids & nitrogenous bases can be created by…
Lightning & primitive oceans
What is the Panspermia hypothesis?
Life came from extraterrestrial origins:
-Life may have originated elsewhere in the solar system or galaxy and arrive on Earth
-In this theory, we would all be descendants from extraterrestrials
Who first observed living cells?
Anton van Leeuwenhoek
What is cell theory?
1) All organisms are made of 1 or more cells
2) Cells are smallest living things — basic unit life
3) Cells only arise by division from a pre-existing
Why are most cells relatively small?
Due to a reliance on diffusion of substances in and out of cells
What is rate of diffusion affected by?
- Surface area available
- Temperature
- Concentration gradient
- Distance
As a cell’s size increases, its volume ________ much more rapidly than its _________
1) increases
2) Surface area
What are the basic structural and functional units of an organism
Cells
What are the main parts of a cell?
1) Plasma Membrane
2) Nucleus
3) Cytoplasm
Characteristics of the plasma membrane?
-Flexible outer surface
-Seperates cell’s internal environment from its external environment
(It is like a container)
Characteristics of the nucleus?
-DNA contains all the information of the cell
-It is surrounded by a membrane
In prokaryote there is no ______, only a circular DNA that is called a _______
1) membrane
2) nucleoid
What are the characteristics of the cytoplasm?
-All parts inside the plasma membrane
-Cytosol: liquid portion of cytoplasm (water + solutes)
-Organelles: biological machines
What is the function of the plasma membrane?
-Encloses a cell and separates its contents from its surroundings
-This separation permits the maintenance of stable chemistry inside the cell
- Allows some substances to move into and out of the cell but stops others (selective permeability)
-Transmits signals between intra and extracellular spaces
What is the structure of the plasma membrane?
-Lipid bilayer (back to back layers made up of phospholipids)
-The thickness of the bilayer is about 5 to 10 nm
-Within the plasma membrane there are proteins (channels, carriers, receptors)
What are organelles?
-Specialized structures inside cells
-Each has a characterized shape and specific function
-8 main organelles of interest
What are the 8 main organelles of interest?
1) Nucleus
2) Endoplasmic reticulum
3) Ribosomes
4) Golgi complex
5) Lysosomes
6) Cytoskeleton
7) Mitochondria
8) Cell membrane
What are the functions of the nucleus?
-Stores genetic material DNA (blueprint)
-‘’Information centre’’
-Contains nucleolus (where ribosome are made)
In eukaryotes, the DNA is divided into multiple ____ chromosomes
Linear
What is the structure of the nucleus?
-Largest organelle in cell (round)
-Is surrounded by a nuclear envelope which is composed of two phospholipid bilayer membranes
-The outer layer of the nuclear envelope is connected to the Endoplasmic Reticulum (ER)
-The nuclear pores allow ions and small molecules to diffuse freely, while controlling the passage of proteins and RNA- protein complexes
What is the function of Ribosomes?
-Site of protein synthesis
-‘’builder’’
What is the structure of Ribosomes?
-Each ribosome is composed of two subunits, each of which is composed by a combination of RNA, called ribosomal RNA (rRNA) and proteins
-Ribosomes can be attached to Endoplasmic reticulum or free in cytosol
-Ribosomes are made in the nucleolus (inside the nucleus)
How do ribosomes make protein?
-They take the m-RNA coming from the nucleus and make a polymer of amino acids named protein
- The sequence of the protein being synthesized determines if the ribosome will become associated with the ER or remain in the cytosol
What are the steps to signalling (protein synthesis
) (5)
1) Signal sequence is synthesized by ribosome
2) Signal sequence binds to signal recognition particle (SRP).
3) Signal recognition particle binds to SRP receptor in ER membrane
4) SRP is released. Protein synthesis continues. Protein enters ER.
5) Signal sequence is removed. Protein synthesis is complete
What is the structure of the Endoplasmic reticulum?
-Network of folded membranes attached to the nucleus
What are the functions of the Endoplasmic reticulum?
-‘’Assembly line’’ (factory)
- Synthesis
- Intracellular transport
What are the 2 types of ER (Endoplasmic reticulum)?
-Rough E.R
-Smooth E.R
What are the characteristics/functions of Rough E.R?
-Covered wth ribosomes
-Involved in protein synthesis
-Proteins can be modified by the addition of short-chain carbohydrates to form glycoproteins
-Those proteins bound for secretion are separated from other products and packaged into vesicles that move to the Golgi for further modification and packaging for export.
What are the characteristics/functions of smooth E.R?
-Has no ribosomes
-Involved in lipid and carbohydrate synthesis
-The majority of membrane lipids are assembled in the smooth E.R
-Stores Ca^2+ which keeps the cytoplasmic level low, allowing Ca^2+ to be used as a signalling molecule (muscle contraction).
-Detoxification of foreign substances (medication, drugs, alcohol, etc.)
What is the endomembrane system and what is its function?
-Series of membranes throughout the cytoplasm (surround the organelles)
-Divides cell into compartments where different cellular functions occur
What is one of the fundamental distinctions between eukaryotes and prokaryotes?
The presence of endomembrane
What is the function of the golgi complex?
-Collection, packaging and distribution
-Modifies proteins and lipids
-Synthesized at one location (ex.: ER), received by the Golgi and sent to another place within the cell or even outside the cell
Everything that leaves the cell passes through the…
Golgi
How many golgi’s are there in protists, animals, and plants?
Protist: 1 to a few
Animal: >20
Plants: >100
What is the structure of the Golgi Complex?
-Flattened membranes with bulging edges
-Cis face: Receiving side located near the ER
-Trans face: Exit side where they are discharged in secretory vesicles
How are glycoproteins and glycolipids formed?
Glycoprotein: Addition of a polysaccharide to the protein
Glycolipid: Addition of a polysaccharide to the phospholipid
What is the structure of the vesicle?
-Small membrane sac made of bilayer of phospholipid
What are the functions of the vesicles?
-Transporting material within the cell
-Transporting material in and out of cell
What are the two types of transport for vesicles?
-Endocytosis: importing material into the cell
-Exocytosis: exporting material out of the cell
What is the structure of lysosomes?
-Small round vesicles
-Arise from the Golgi apparatus
What is the function of lysosomes?
-‘’Recycling truck’’ of the cell
-Contains digestive enzymes that can breakdown proteins, nucleic acids, lipids, and carbohydrates
-They digest and remove old structures and organelles
-Recycle their component molecules, allowing room for newly formed organelles
-The very low pH inside the lysosomes activate the enzymes (thus important have a vesicle to not digest the entire cell).
What is the structure of peroxisomes?
Similar to lysosomes but smaller
What do peroxisomes do?
-Oxidize fatty acids and some amino acids
-Produce hydrogen peroxide as a byproduct of the activities of oxidative enzymes
-Contain enzyme catalase, which catalyzes the decomposition of hydrogen peroxide into water and oxygen
Note: peroxide is dangerous to the cell
What is the structure of the mitochondria?
-Rod shaped (size of bacteria)
-Have two phospholipid bilayer membranes
-Outer membrane
-Inter-membrane space
-Inner membrane shaped into folds called cristae
-Matrix (most inner part)
What is the function of the mitochondria?
- ‘’Powerhouse of the cell’’
-Generate ATP (energy currency of the cell)
-Uses oxygen and glucose for energy
-Produces CO2 & H20
What are some facts about mitochondria?
-Mitochondria contain their own circular DNA
-However some necessary genes are coded by the nucleus
-They can divide themselves
-You inherit the mitochondria from your mother
What is the structure of cytoskeleton?
-network of protein fibres found in all eukaryotic cells
What is the function of the cytoskeleton?
-supports the shape of the cell
-keeps organelles in fixed locations
What are the three types of fibres (cytoskeleton)?
1) Actin filaments (microfilaments)
2) Microtubules
3) Intermediate filaments
What is the function of actin filaments (microfilaments)?
-Maintain cell shape by resisting tension (pull)
-Move cells via muscle contraction or cell crawling
-Divide animal cells in two
-Move organelles and cytoplasm in plants, fungi and animals
What is the function of microtubules?
-Maintain cell shape by resisting compression (push)
-Move cells via flagella or cilia
-Move chromosomes during cell division
-Assist formation of cell plate during plant cell division
-Move organelles
-Provide tracks for intracellular transport
What is the function of intermediate filaments?
-Maintain cell shape by resisting tension (pull)
-Anchor nucleus and some other organelles
What is the most durable element of the cytoskeleton?
Intermediate filaments
What is the function of cilia and flagella?
Both used for motion
-Flagellum: longer than cilia, few of them (ex: only found in the tail of sperm)
-Cilia: shorter than flagellum, more of them (ex: uterine tubes move the egg, respiratory system moves mucus, protists…)
What is the structure of cilia and flagella?
-Circle of nine microtubule pairs surrounding two central microtubules
-Extension of the cytoplasm and plasma membrane outward
-This arrangement is referred to as the 9 + 2 structure
-As pairs of microtubules move past each other using arms composed of the motor protein dynein
-Eukaryotic flagellum undulates, or waves up and down, rather than rotates
What is the structure of centrosome?
Two centrioles arranged perpendicular to each other
What is the function of centrosome?
Moves chromosomes to ends of cell during cell division
What is the special structure of a plant cell?
-Central vacuole
-Cell wall
-Chloroplast
-No centrioles
What is the function of the vacuole (plant cell)
-Stores sugar, ions and pigment
-Stores waste
-Can also function as lysosomes
-Involved in water balance
What is the structure of the vacuole?
Plasma membrane surrounding the vacuole is called the tonoplast bc it contains channels for water that are used to help maintain is tonicity, or osmotic balance.
What is the structure of chloroplast?
-Organelles present in cells of plants and some other eukaryotes
-Surrounded by two membranes
-Contain chlorophyll for photosynthesis
-Thylakoids are membranous sacs within the inner membrane
-Have their own DNA and ribosomes
What are landmarks in the evolution of metabolism?
-Oxygenic photosynthesis
-Carbon fixation (12C isotope)
-Nitrogen fixation
What is nitrogen fixation?
-Nitrogen gas is essential for life but is not bio available to most organisms (plants and animals)
-Nitrogen fixation is an important process by which microbe (nitrogen fixing bacteria) take gaseous nitrogen (N2) of the atmosphere and make it biologically accessible to plants (ammonia NH3)
Why is RNA hypothesized to predate DNA?
It can store genetic information and catalyze chemical reactions (ribozyme) and serve as a structure molecule (ribosome)
How do cell membranes affect the evolution of metabolism?
Increase the probability of metabolic reactions
What is the mitochondria endosymbiosis theory?
Ancestral eukaryotic cell wasn’t able to digest the mitochondria, so it became a part of the cell
What is the chloroplast endosymbiosis theory?
The origins of the chloroplast in eukaryotes
What are characteristics of prokaryotes?
-The simplest organism
-No nucleus
-Consists of a cytoplasm surrounded by a plasma membrane and encased within a rigid cell wall
-Free circular DNA
-May have a capsule
-No membrane bound organelle
-Have ribosomes
What are the two types of prokaryotes?
1) Bacteria
2) Archaea
Characteristics of bacteria (prokaryote)
-Strong cell wall
-Composed of petidoglycan
-Cell walls of plants, fungi and most protists are different
-Protects the cell, maintains its shape, and prevents excessive uptake or loss of water
-Susceptibility of bacteria to antibiotics often depend on the structure of their cel walls
Characteristics of archaea
-Cell walls are composed of various chemical compounds, including polysaccharides and proteins and possibly even inorganic components
-Archaea lack peptidoglycan
-A common feature distinguishing archaea from bacteria is the nature of their membrane lipids including saturated hydrocarbons that are covalently attached to glycerol
-These features seem to confer greater thermal stability to archaea membranes
-The cellular machinery that replicates DNA and synthesized proteins in archaea is more closely related to eukaryotic systems than to bacterial systems
What are flagella for prokaryotes?
-Some prokaryotes move by means of rotating flagella
-There may be one or more per cell, or none, depending on the species
-The rotary motor uses the energy stored in a gradient that transfers protons across the plasma membrane to power the movement of the flagellum
What are the differences between a prokaryote and eukaryote
Eukaryotes:
-Possess a membrane-bound nucleus
-More complex than prokaryotic cells
-Compartmentalizations is achieved through membrane-bound organelles and endomembrane system
-Possess a cytoskeleton for support and to maintain cellular structure
What is bacteria divided by?
Binary fission
Characteristics of asexual reproduction (binary fission)?
-No exchange on chromosomes
-Reproduction is clonal (identical DNA)
What are the steps to binary fission?
-Single,circular bacterial chromosome is replicated
-Replication begins at the origin of replication and proceeds in two directions to site of termination
-New chromosomes are partitioned to opposite ends of the cell
