Chapter 2 Flashcards
First person to observe and document the living cell
Anton van Leeunwenhoek
Developed a microscope to study cork tissue
Robert Hooke
Concluded all plants are made of cells
Matthias Schleiden
Concluded all animals are made of cells
Theodor Schwann
Stated ‘where a cell exists there must be a pre-existing cell’
Rudolf Virchow
Modern cell theory states
All living things are composed of cells, cells are the basic unit of all organisms, all cells arise from preexisting cells
Most plant/animals cells have diameters between
10-100 micrometers (um)
RBCs have a diameter of
8 micrometers (um)
Prokaryotes
No internal membranes, all bacteria = prokaryotes
Eukaryotes
Have a nucleus and are more complex cells, make up every life form other than bacteria (human cells are eukaryotic)
P & E: chromosomes
P: contain a single, circular chromosome
E: chromosomes are linear, human cells have 46 in nucleus
P & E: plasmids
P: contains plasmids ,
E: doesn’t contain plasmids
P & E : ribosomes
P: ribosomes are small
, E: ribosomes are larger
P & E : respiration
P: respiration can be aerobic or anaerobic
E : aerobic
P & E : cytoskeletal elements
P:cytoskeletal elements, such as microfilaments, are absent
E: c.e. like microfilaments and microtubules are present
P & E: uni- or multi- cellular
P: most are unicellular
E: some like euglena and paramecium are single-celled, many are multicellular w/ specialized cell types such as. muscle, blood, skin
P & E : size
P: very small; 1-10 um
E: larger: 10-100 um
P & E: cell walls
P: most have tough external cell walls
E: most (except plant cells and protists) are surrounded by only a cell membrane
Radioactive dating indicates that the Earth is about
4.6 billion years old
All organisms are believed to have descended from a
A common ancestral prokaryotic cell about 3.5 billion y/a
Theory of Endosymbiosis
Eukaryotic cells containing organelles like mitochondria and chloroplast evolved when free-living prokaryotes took up permanent residence inside other larger prokaryotic cells about 2 billion years ago
Cell’s form is dictated by
It’s function
Nucleus contains chromosomes made of DNA that is
Wrapped w/ special proteins called histones into a chromatin network
Chromosomes contains genes:
Bits of DNA that code for polypeptides
Nucleus is surrounded by a
- Selectively permeable double membrane that contains pores
- pores allow for the transport of large molecules such as RNA out of the nucleus and into the cytoplasm
The nucleolus is
A region inside the nucleus of a cell that is not dividing
What is synthesized here? (in nucleolus)
Components of ribosomes
Nucleoli are not membrane-bound but are
Tangles of chromatin and unfinished ribosomes
1 or 2 nucleoli are
Commonly visible in a non-dividing cell
Ribosomes are
Particles made of ribosomal RNA and protein and are the site of protein synthesis
Ribosomes are suspended
Freely in the cytoplasm or bound to endoplasmic reticulum
A cell that produces large amounts of protein
Contains millions of ribosomes
ER is a
System of membrane channels across the cytoplasm
Rough ER
- Studded with ribosomes
- site of protein synthesis
- transport throughout the cytoplasm
Smooth ER
- Synthesizes steroid hormones+other lipids
- connects rough ER to golgi apparatus
- detoxifies cell
- carb (glycogen) metabolism
Golgi apparatus
- Lies near nucleus
2. consists of flattened sacs of membranes stacked next to each other and surrounded by vesicles
Golgi apparatus (function)
- Modifies, stores, and packages substances produced in rough ER
- secretes substances to other parts of the cells and cell surface for export to other cells
Lysosome
- A sac of hydrolytic (digestive) enzymes enclosed by a single membrane
- main site of intracellular digestion
With the help of the lysosome, the cell
Continually renews itself by breaking down and recycling cell parts
Apoptosis is critical to
- Embryonic development of multicellular organisms
- is carried out by a cell’s own hydrolytic enzymes
Plant cell usually
Don’t have lysosomes
Mitochondria
Site of cellular respiration, all cells have many
A very active cell should have about
2500 mitochondria
Mitochondria consist of an
Outer double membrane and folded inner membranes called cristae
What is embedded in cristae?
Enzymes important to cellular respiration
Mitochondria contain their own
DNA and can self-replicate
Vacuoles
Single, membrane-bound structures that store substances
Contractile vacuoles Function.
Where are they found?
Pump excess water out of the cell
Freshwater protista like (amoeba, paramecium)
Which cells have large central vacuoles for storage?
(some specialized human ) fat or adipose cells , plant cells
Vesicles Definition
Where are they found?
- Tiny vacuoles
2. found in many places in cells including axon of a neuron where they release neurotransmitters into a synapse
Plastids
Have a double membrane and are found in plants/algae
3 types of plastids
Chloroplasts, leucoplasts, chromoplasts
Chloroplasts
Green because they contain chlorophyll, sites of photosynthesis
Chloroplasts have a double outer membrane and an
Inner one that forms a series of structures called grana
Grana lie in the
stroma
How are chloroplasts like mitochondria?
Both contain their own nuclear material and can self-replicate (free-living prokaryotes billions of years ago)
Leucoplasts
Colorless and store starch, found in roots like turnips or tubers like potatoes
Chromoplasts
Store carotenoid pigments and are responsible for the red-orange-yellow coloring of carrots, tomatoes, etc.
How are bright pigments in petals useful?
Attract pollinating insects to flowers
Cytoskeleton
- A complex network of protein filaments that extends throughout the cytoplasm
- gives cells its shape/enables it to move
2 types of structures in cytoskeleton:
Microtubules, microfilaments
Microtubules
Thick hollow tubes that make up cilia, flagella, and spindle fibers → formed from protein tubulin
Microfilaments enable
- Animal cells to form a cleavage furrow during cell division
- amoeba to move by sending out pseudopods,
- skeletal muscles to contract by sliding along myosin filaments
Centrioles and centrosomes
Location + Function
- Outside nuclear membrane
2. organize spindle fibers required for cell division
Which cells have centrioles/centrosomes?
Animal cells
Plants cells have
Microtubule organizing regions instead
2 centrioles at right angles
Make up one centrosome
Centrioles and spindle fibers have
The same structure
Cilia and flagella have
The same internal structure, both are made of microtubules
The difference between the 2 is
Cilia and flagella
Their lengths , cilia = short, flagella = long
Cell wall of fungi consist of? Of plant and algae?
Chitin, cellulose
Where is the primary cell wall located in plant cells?
Immediately outside the plasma membrane
Some cells produce a
Second cell wall underneath the primary cell wall called the secondary cell wall
What happens when a plant cell divides?
A thin gluey layer is formed between the 2 cell walls, which becomes the middle lamella and keeps the 2 daughter cells attached
Cytoplasm
Entire region between the nucleus and plasma membrane
Cytosol
Refers to the semiliquid portion of the cytoplasm
In eukaryotic cells, organelles are suspended in the
Cytosol and get carried around the cell as the cytoplasm cycle around the cell, a process called cyclosis
Plasma membrane is described as a
Fluid mosaic because it is made of many small particles that are able to move around in order ot control what enters and leaves the cell
What molecules are embedded within the membrane?
Molecules of cholesterol make the membrane less fluid and more stable
What is attached to the surface of the plasma membrane?
Carb chains that are important for cell-cell recognition
An average cell membrane consists of
About 60% protein , provide a wide range of functions
Some membrane proteins like ______ act as an enzyme.
ATP synthetase
Some, like ________, transport ions into and out of cells.
Sodium-potassium pump
Animal vs. Plant Cells: centrioles/centrosomes
A: contain them , P: none
Animal vs. Plant Cells: chloroplast/plastids
A: no chloroplast and other plastids, P: contain both
Animal vs. Plant Cells: vacuoles
A: most have small vacuoles (specialized fat storage cells are an exception) ,
P: large central vacuoles
Animal vs. Plant Cells: plasma membrane
A: plasma membrane only
P: cell walls+plasma membrane
Animal vs. Plant Cells: lysosomes
A: have them , P: don’t have them
The substances that pass through a selectively permeable membranes
Change with the needs of a cell
Solvent
Substance that does the dissolving
Solute
The substance that dissolves
Hypertonic
Have greater concentration of solute than another solution
Hypotonic
Have lower concentration of solute than another solution
Isotonic
2 solutions containing equal concentrations of solute
Passive transport
Movement of molecules down a concentration gradient from a region of higher concentration to a region of lower concentration
Passive transport NEVER
Requires energy, occurs either by diffusion or osmosis
Simple diffusion
movement of particles from higher to lower concentration
The steeper the gradient, the
Faster the rate of diffusion
How do earthworms breathe?
Oxygen from the air is absorbed by simple diffusion across their moist skin into capillaries directly beneath the skin
How do humans obtain oxygen?
By simple diffusion across moist membranes in air sacs, alveoli
Facilitated diffusion
Relies on special protein membrane channels to assist in transporting specific substances across a membrane
The normal functioning of a neuron requires calcium ions
To be transported by facilitated diffusion through calcium ion channels within the axon membrane
Facilitated diffusion does
Not require ATP/energy
Osmosis
Diffusion of water across a membrane, water flows down a gradient toward a region w/ high solute concentration
Water diffuses toward
The hypertonic area
Plasmolysis
Water leaves the cell causing the cell to shrink
If 5% sodium chloride is dropped onto a living cell (such as elodea)
The cell will shrink
When water flow into a cell, this causes an animal cell
To burst
If water flows into a plant cell,
the cell wall will prevent the cell from bursting , plant cells merely swell or become turgid
Turgid pressure is what keeps vegetables like
Celery or green peppers crisp
If a plant loses too much water (dehydrates),
It loses turgor pressure and wilts
In an isotonic solution, water diffuses in and out
But there is no net change in the cell
Why must solutions for contacts or saline solutions be isotonic?
To protect delicate body cells to prevent damage
Active transport
The movement of molecules against a gradient, which requires energy, usually in the form of ATP
The contractile vacuole pumps out excess water that
Diffuses inward because the organisms live in an environment that is hypotonic
Exocytosis
The active release of molecules from a cell
A good example of exocytosis is found in the
Synapse of nerve cells
Example of exocytosis in synapse cells: Vesicles containing a neurotransmitter such as ACh
Release their contents into the synapse in order to pass an impulse to another cell
Endocytosis
cells take in molecules and particles by forming new vesicles made from the plasma membrane
3 examples of endocytosis are
Pinocytosis, phagocytosis, receptor-mediated endocytosis
Pinocytosis
- ‘Cell-drinking’,
2. absorption of large, dissolved molecules
In pinocytosis: The plasma membrane invaginates around tiny
Particles and encloses them in a vesicle
Phagocytosis
The engulfing of large particles or even small organisms by pseudopods
Phagocytosis: The cell membrane wraps around the particles and encloses
Them forming a vacuole
Phagocytosis: Human white blood cells engulf
Bacteria and also the way amoeba feed
Receptor-mediated endocytosis
Enables a cell to take up large quantities of very specific substances
Receptor-meditated endocytosis: Extracellular substances bind to
Specific receptors on the cell membrane and are drawn into the cell into vesicles
Receptor mediated endocytosis:This is how body cells
absorb cholesterol from the blood
What does the sodium-potassium pump (in nerve cells) do?
Carries Na+ and K+ across the axon membrane in opposite directions to return the nerve to its resting state after an impulse has passed
Life processes all cells must carry out
Ingestion, digestion, respiration, transport, regulation, synthesis, excretion, egestion, reproduction, irritability, locomotion, metabolism
Ingestion
Intake of nutrients
Digestion
Enzymatic breakdown, hydrolysis, of food so it’s small enough to be assimilated by the body
Respiration
Metabolic processes that produce energy (ATP) for all life processes
Transport
Distribution of molecules from 1 part of a cell to another or from one cell to another
Regulation
Ability to maintain homeostasis
Synthesis
Combining of small molecules or substances into larger, more complex ones
Excretion
Removal of metabolic wastes
Egestion
Removal of undigested waste
Reproduction
Ability to generate offspring
Irritability
Ability to respond to stimuli
Locomotion
Moving from place to place (animal cells only)
Metabolism
Sum total of all life functions
Accurate
Correct
Precise
Exact
Main tool for studying cell structure (cytology)
Compound microscope
Important characteristic of good microscopes
Resolution- image clarity
Developed the 1st microscope in the 17th century
Anton van Leeuwenhoek
How do we determine magnification?
Magnification of ocular lens(eyepiece) x magnification of objective lens
When you use the microscope, the image is
Upside down and backward from the actual specimen
The higher the magnification, the
Darker the field will appear because you are viewing a much smaller area
Phase-contrast microscope
- A light microscope that enhances contrast
2. useful in examining living, unstained cells
Transmission electron microscope (TEM)
Useful for?
Source of electrons?
- Useful for studying the interior of cells.
2. a tungsten filament within a vacuum column
Drawbacks of TEM
- Tissue is no longer alive after processing
- preparation of specimens is elaborate
- TEM is a delicate machine/requires special engineers to maintain it,
- specimens must be sliced so thin that only a small portion of a tissue sample can be studied at one time
- machine costs 100s of 1000s of $
Specimens observed under the EM are
Not alive
Scanning Electron Microscope (SEM)
- Useful for studying the surface of cells,
- resulting images have a 3D appearance
- specimens are examined after an elaborate process that kills the tissue
Ultracentrifuge
Enables scientists to isolate specific components of cells in large quantities by cell fractionation
Cell fractionation
- Tissue is mashed in a blender
- resulting liquid (homogenate) is spun at high speed in an ultracentrifuge
- separated into layers based on diff. In density
Freeze Fracture (or freeze-etching)
A complex technique used to study details of membrane structure under an electron microscope
In freeze fracturing, after preparation, only a
Cast of the original tissue is available to examine
Tissue culture is a technique
Used to study the properties of specific cells in vitro (in lab)
Living cells are seeded onto a ….
What is added?
- Sterile culture medium
2. a variety of nutrients and growth-stimulating factors have been added
Different cells require
Different growth media
Growing cells can be examined
Unstained under a phase-contrast light microscope
