Chapter 4: A Tour of the Cell Flashcards
Who were cells first seen by?
Robert Hooke, as he studied the bark of an oak tree
Who first saw living cells?
Antoni van Leeuwenhoek
What is a light microscope?
a microscope in which visible light is passed throguh the specimen and then through glass lenses that refracts the light and magnifies it
What is magnification?
the ration of an objects image size to its real size
How much can light microscopes magnify up to?
1000x
What is resolution?
the measure of the clarity of an image: the minimum distance that two points can be distinguished as seperate points
What is contrast?
the difference in brightness between the light and dark areas of an image. This is usually enhanced by straining
What does the electron microscope do?
focuses a beam of electrons through the specimen allowing scientists to study the membrane-enclosed structures called organelles inside the cells. These images are about 100x more powerful than the light microscope but unfourtunately it kills living cells
How is the scanning electron microscope especially useful?
for a detailed study of the topography of a specimen
How can the Transmission electron microscope be used for?
to look at the interior structure of a cell
What is cytology?
the study of cell structure
What is cell fractionation?
a very useful technique of studying cell structure and function which takes cells apart and spun down to seperate the organelles and other structrues
Explain the timeline of cell theory.
In 1838 Matthias Shielden and Theodore Schwann came up with the first two parts of cell theory, while Rudolf Virchow contributed the third in 1855
What is the first part of cell theory?
Cells are the basic unit of structure and function
What is the second part of cell theory?
All living things are made up of one or more cells
What is the third part of cell theory?
All cells come from pre-existing cells
What domains consist of prokaryotic cells
Bacteria and Archae
What domains consist of eukaryotic cells?
protists, fungi, animals, and plants
What are all cells bounded by?
a selective barrier, called the plasma membrane which surrounds a semifluid, jellylike substance called cytosol
What else do all cells contain?
chromosomes and ribosomes
What do chromosomes do?
carry genes in the form of DNA
What are ribosomes?
tiny complexes that make proteins according to the instructions from the genes
Where is DNA held in a Eukaryotic cell?
in an organelle called the nucleus which has a double membrane surrounding it
Where is DNA concentrated in a Prokaryotic cell?
in a region that is not membrane enclosed called the nucleoid
Which cell evolved first: Eukaryotic or Prokaryotic?
Prokaryotic cells
How long in diameter are typical bacteria?
1-5 micrometers
How long in diameter are typical eukaryotic cells?
10 - 100 micrometers
How does the plasma membrane function?
as a selective barrier that allows the passage of enough oxygen, nutrients and wastes to service the entire cell
What happens as a cell increases in size?
the surface area of a cell grows proportionately less than its volume
T/F: Larger organisms do not have larger cells than smaller organisms
False - they simply have MORE cells
What does the nuclues contain?
most of the genes in the eukaryotic cell.
if not in the nuclues, where are the other genes?
mitochondria and chloroplasts
What are mitochondria and chloroplasts surrounded by?
a nuclear envelope which seperates its contents from the surrounding cytoplasm.
How is DNA organized in the nucleus?
into discrete organisms called chromosomes
What are chromosomes?
structures that carry the genetic information
What are thin strands of uncoiled DNA called?
chromatin
What is chromatin wrapped in?
proteins called histores
What is the nucleolus?
the dark staining, non-dividing region of the nucleus
What happens at the nucleolus?
ribosomal DNA is made from DNA and the subunits of ribosomes are produced
What are ribosomes?
complexes of rRNA and proteins that carry out synthesis of proteins.
Are ribosomes membrane bound?
No - therefore, they are nto considered organelles
In what to locations do ribosomes build proteins?
free proteins, which are suspended in the cytosol, and bound ribosomes, which are attached to the outside of the endoplasmic reticulum or nuclear envelope
Where do most of the proteins produced by free ribosomes function?
inside the cell
Where do most of the proteins produced by bound ribosomes function?
outside the cell - through secretion
What parts are included in the endomembrane system?
Nuclear envelope, endoplasmmic reticulum, golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane
What is the endoplasmic reticulum?
a network of membrane tubules and sacs that is continous with the outer nuclear membrane and is composed of ribosome studded regions (rough ER) and ribosome free regions (smooth ER)
What are the functions of the smooth ER?
Synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, storage of calcium ions
What is the rough er?
the network that has ribosomes attached that are designed to make proteins that will be secreted out of the cell
What are glycoproteins?
proteins that are covalently bonded to carbohydrates and are secreted out of the cell
What is a lysosome?
a membranous sac of hydolytic enzymes that many eukaryotic cells use to digest macromolecules
Who produces the lysosme
the golgi apparatus
How do amoebas and other unicellular eukaryotes eat?
by engulfing smaller organisms or food particles in a process called phagocytosis. Then the food vacuole formed in this way then fuses with a lysosome whose enzymes digest the food
What is autophagy?
a process in which lysosomes use their hydrolytic enzymes to recycle the cell’s own organic material
What are vacuoles?
large vescicles derived from the endoplasmic reticulum and Golgi apparatus
How are food vacuoles formed?
by phagocytosis and contain materials for digesting
What do contractile vacuoles do?
pump out excess water in freshwater unicellular eukaryotes
What is a central vacuole?
a vacuole found in mature plant cells that stores water and other ions
In eukaryotic cells, what are the organelles that convert energy to forms cells can use for work.
Mitochondria and chloroplasts
What does the endosymbiont theory state?
that an early ancestor of eukaryotic cells engulfed an oxygen using prokaryotic cells. The two cells eventually formed a symbiotic relationship and merged into a single organism.
What are mitochondria?
sites of cellular respiration, the metabolic process that uses oxygen to drive generation of ATP by extracting energy from sugar, fats and other fuels. It is a double membrane organelle. Oxidative Phosphorylation– oxidize glucose, reduce intermediates, ADP –> ATP
What is hte inner membrane known as?
cristae
What does cristae do?
increases surface area
What are chloroplasts?
the sites of photosynthesis and are found in plants and algae
What are chlorophyll?
A green pigment in chloroplasts, that function in the photosynthetic prod glucose.
What are thylakoids?
Another membranous system of sacs inside the chloroplasts that are the site of the light reaction of photosynthesis
What are a stack of thylakoids called?
granum
What surround thylakoids?
a fluid called the stroma which is the site of the light independent reaction that produce sugar
What are peroxisomes?
specialized metabolic compartments that contain enzymes that remove oxygen atoms from molecules and the add them to water forming hydrogen peroxide (H2O2). THey then later break down this toxic substance for remoal from the body
What is the cytoskeleton?
a network of fibers extending throughout the cytoplasm that plays a major role in organizing the sturcutres and activities of the cell
What can motor proteins do?
attach to the cytoskeleton to move things withing the cell
What type of fibers is the cytoskeleton made up of?
microtubules, microfilaments, and intermediate filaments
What are microtubules?
hollow tubes (used in centrioles, cilia, and flagella) zip lines for vacuoles
What are microfilaments?
two intertwined strands of actin for movement of the cell, cytokenesis
What are intermediate filaments?
fibrous proteins supercoiled into cables
In animal cells, where do microtubules grow out from?
centrosomes
What are centrosomes?
a structure that functions as a microtubue organization center that is veyr important during cell division. It has two centrioles arranged in 9 microtubule triplets.
What are cilia and flagella?
means of locomotion in cells. Motile cilia usually occur in large numbers over the surface while flagella are usually limited to one or a few per cell.
What is a cell wall?
a rigid covering of a plant cell that is made primarily of cellulose which is a structural polysaccharide
What is the primary cell wall?
the thin and flexible wall secreted by young plants
What is the middle lamella?
a thin layer rich in pectin that helps glue the cells together
What is the secondary cell wall?
the thicker layer found inside of the primary cell wall and outside of the cell membrane; secreted as the cell matures
What are plasmodesmata?
channels between plant cells that allow for communication and transfer of materials between cells (analogous to gap junctions in animals). Communication between plant cells
What are central vacuole?
large storage areas for plants
helps to maintain Turgor Pressure
What is the extracellular matrix (ECM)?
the substance in which animal cells are embedded. It consists of proteins and polysaccharides synthesized and secreted by cells
What are tight junctions?
junctions that form belts around a cell that help to prevent leakage of extracellular fluids. Epithelial linings to prevent fluid leakage.
What are demosomes, or anchoring junctions?
act like rivets holding cells together in storng epithelial sheets
What are gap junctions?
communication junctitions that allow for the passage of materials between cells. (Similar to plasmodesmata in plant cells.)
