Chapter Two: The Cell Flashcards
State the 3 principles of the Modern Cell Theory and their fathers
1) cells are the basic unit of life
2) all living things are composed of cells
Schleiden and schwan
3) all cells arise from preexisting cells
Rudolf virchow
Who coined the term cell
Robert Hooke
Describe the presence of the following between prokaryotes and eukaryotes: Membrane bound organlles Chromosome shape and number Plasmids Ribosome size Type of respiration Cytoskeleton Uni/multi cellular Overall size Tough external cell wall
Yes in pro, no in eu
Single circular loop in pro, multiple linear strands
Yes in pro, no in eu
Small in pro, larger in eu
Both aero and anaero in pro, mostly aero in eu
No cytoskeleton in pro, yes in eu
Most are uni in pro, most multi in eu
Very small pro, larger eu
Yes in pro, only cell membrane in eu mostly
Lay out the Theory of Endosymbiosis
Eukaryotic cell evolved from free prokaryotes which resided in larger prokaryotes. Compartmentalized cells hence are efficient and perhaps more likely to survive
State the composition of the nucleus in detail
DNA wrapped with proteins-histones to make units called nucleosomes. These further coil and supercoil into a chromatin fibre network
What are genes?
They are bits of DNA on chromosomes that code for Polypeptides
What makes the double phospholipid envelope permeable?
Nuclear pores
What are nucleoli?
Prominent regions of undividing cells which are tangles of chromatin and unfinished bits of ribosomes
What is synthesized in tge nucleolus?
Components of ribosomes
What are Ribosomes made of?
Ribosomal RNA and protein
What is the function of ribosomes?
Protein synthesis/translation
What is the ER?
System of membrane channels that traverse the cytoplasm
What makes rough ER rough?
Ribosomes
State 4 functions of smooth ER
Synthesize steroid hormones and other lipids
Connect rough ER to Golgi
Detoxifies cell
Carbohydrate (glycogen) metabolism
What is a vesicle?
Tiny vacuole which carries and release substances
What is a Golgi Apparatus consisted of and what does it do?
Flattened sacs of membranes stacked next to each other like pancakes. Modify, store, and package proteins from ER
What is a lysosome?
A sad of hydrolytic enzymes enclosed by a single membrane
What is the principle site of intracellular digestion?
Lysosome
How does a lysosome help a cell?
Renewal by breakdown and recycling
What is Apoptosis?
Programmed cell death
What goes on in a mitochondrion?
Cellular respiration
What makes up the outer membrane in mitochondria
Phospholipid bilayer
What are the folds on the inner membrane called?
Cistae
What are embedded in the cistae?
Enzymes such as ATP synsthase
Whats the space in cistae called
Matrix
What is the general function of vacuoles (especially in plant cells and adipose cells)
Storage
Protista have contractile vacuoles. What does this mean?
Pump excess water out of the cell
How are the membranes of plastids?
Double
What are plastids?
Organelles found in animals and algae for special metabolic activities
Name 2 organelles which have their own DNA and can replicate
Mitochondria
Chloroplasts
State the structure of inner membranes of chloroplasts
Series of grana, which in stroma
What is the name, colour, and function of plastids in roots?
Colourless leucoplasts store starch
What do chromoplasts store? And how does it aid in pollination
Cartenoid pigment (red-orange-yellow) Attracts insects
What is the cytoskeleton?
Complex network of protein filaments
State some functions of cytoskeletal elements
Cell shape
Movement
Organization (transport of materials)
What are microtubules made of
Tubulin
How do microtubules look
Thick hollow tubes
What are microfilaments made of
Actin
Discriminate the functions of microtubules and microfilaments and examples
MT - movement (such as cilia, spindles and flagella)
MF - shape (allow skeletal muscle to contract by sliding along myosin filaments)
What do centrioles and centrosomes do?
Organise spindle Fibers for cell division
What makes up a centrosome?
2 centrioles a lr right angles to each other
State the structure of a centriole
9 triplets of microtubules
What are cilia and flagella made of? State how the vary in length
9 pairs of microtubules organized around 2 singlet microtubules
Cilia short
Flagella long
What are fungi cell walls made of
Chitin
What are plants/algae cell walls made of?
Cellulose
What happens between plant cells walls as the cell divides?
A gluey layer forms and becomes the middle lamella which keeps the daughter cells connected
What is the cytoplasm?
Regions between nucleus and cell membrane
What is cytosol?
Semiliquid portion of the cytoplasm
What is the process wherein organelles get carried around the cell in cytoplasm cycles?
Cyclosis
What does it mean to say the plasma membrane is selectively permeable?
Controls what enters and leaves the cell
What is fluid mosaic?
Made of many small particles that are able to move around in order to control contents
Why are cholesterol molecules embedded within the cell membrane?
To make it stable/less fluid
Why are there carbohydrate chains on the external surface of the plasma membrane?
For cell-to-cell recognition
How much percent of an average cell membrane is protein?
60% approx
What is the meaning of: selectively permeable
Substances that pass through change with the cell’s needs
What is the meaning of: solvent
A substance that can dissolve others
What is the meaning of: solute
A substance that dissolves
What is the meaning of: hypertonic
Higher concentration of solute
What is the meaning of: hypotonic
Lower concentration of solute
What is the meaning of: isotonic
Two solutions containing equal concentrations of solute
What is passive transport?
Movement of molecules down a concentration gradient, from a region of higher to lower concentration and never requires energy
What is simple diffusion?
Movement of particles from a region of higher to lower concentration
State an example of simple diffusion
Moist alveoli membrane to capillaries
Relate gradient steepness to rate of simple diffusion
The steeper the gradient, the faster the rate
What is facilitated diffusion?
It os diffusion that relies on a special protein membrane channel to assist in transporting specific substances across a membrane
Eg calcium ion channels in neurons axon membrane
What is osmosis?
Diffusion of water across a membrane, down a gradient, from low to high solute concentration
Where does water always diffuse toward?
Hypertonic
What does it mean when we say A is hypertonic to B?
A has more solute than B
As water continues to leave a cell it shrinks. What’s the term for this?
Plasmolysis
Why do animal cells burst and plant cells don’t on the entry of water?
Presence of a cell wall keeps the cell turgid and swollen
What happens to a plant if it’s dehydrated and turgor pressure is lacked?
It wilts
What happens when a solution and cell are isotonic?
Water diffuses in and out but with no net change in the cell
What’s active transport?
Movement of molecules against a gradient, which requires energy, usually in the form of ATP.
When is active transport especially important in organisms and their habitat?
When they live in a hypotonic environment.
Such as freshwater protista whose contractile vacuoles pump out excess water that diffuses inward because of the hypotonic surrounding
What is exocytosis?
The active release of molcules from a cell.
Eg : vesicles release neurotransmitter into the synapse in order to pass an impulse
What is endocytosis?
Process by which cells take in particles/molecules by forming new vesicles made from the plasma membrane
What are the 3 types of endocytosis?
Pinocytosis
Phagocytosis
Receptor-mediated endocytosis
What is pinocytosis aka cell drinking?
Uptake of large, dissolved molecules. The plasma membrane invaginates around tiny particle and encloses them in a vesicle
What is phagocytosis?
Engulfing of large particles or small organisms by pseudopods (pseudopodium). The cell membrane wraps around them and forms a vacuole
Why is receptor-mediated endocytosis important to a cell?
And how does it work?
It enables a cell to take up large quantities of very specific substances.
Extracellular substances bind to specific receptors on the cell membrane and are drawn into the cell into vesicles
Explain the sodium-potassium pump
Nerve cells actively transport particles/ions across a membrane against a gradient. A nerve cells carries Na+ and K+ across the axon membrane in opposite direction so to return the nerve to it’s resting state after an impuse has passed
What is a characteristic of all cells
They carry out certain life processes
State the 12 life process
1) ingestion-intake of nutrients
2) digestion-enzymatic breakdown, hydrolysis, of food so it is small enough to be assimilated
3) respiration-metabolic processes that produce energy for other processes
4) transport-distribution of molecules (within cells or to others)
5) regulation-ability to maintain internal environment aka homeostasis
6) synthesis-combining of small molecules into larger complex ones
7) excretion-removal of metabolic waste
8) egestion-removal of undigested waste
9) reproduction-ability to generate offspring
10) irritability-responding to stimuli
11) locomotion-moving from places (animals)
12) metabolism-sum total of all the life functions
How many km in a m
Or kg in a g
0.001 or 1×10^-3
How many micrometers/micrograms in a millimetre/milligram?
1000
How many cm in an inch?
2.5
How to distinct between exact and approximate values?
Exact: 26.0mm
Approx: 26mm (it could be 25.9 or 26.1!)
What is the difference between accurate and precise?
Accurate: correct
Precise: exact
Where should your eye level rest when measuring using a graduated cylinder?
The meniscus or bottom of the curve
What is the best tool for studying cytology?
Compound microscope
What is cytology
Cell structure
What are the 2 characteristics of a good microscope?
Magnification
Resolution (image clarity)
Who developed the first microscope?
Anton van Leeuwenhoek
How do you determine magnification?
Magnification of tge ocular lens (normally 10×)
× magnification of the objective lens
How does the image from a microscope appear?
Upside down and backward
The higher the magnification, the ______ the field because a ______ area is being viewed
The higher the magnification, the darker the field because a smaller area is being viewed
What does a phase contrast microscope do
It’s a uses a beam of light to enhance contrast when examining living, unstained cells
What is transmission electron microscope useful for?
Studying the interior of cells
What is the source of electrons for TEM
Tungsten filament within a vacuum column
What are the drawbacks (5) of studying specimens under (T)EM
- tissue is dead after processing
- specimen preparation is elaborate; tissue must be fixed, dehydrated, sectioned on a special machine-it takes many hours and expertise
- TEM is a delicate machine and requires special engineers to maintain it
- specimens must be sliced so thin to study a small portion of the sample at one time
- machine can cost thousands of dollars
What is the scanning electron microscope useful for studying?
Surface of cells
How do images from SEM appear?
3D
What is a drawback when using SEM?
Tissue can be examined only after killing it
What does a ultracentrifuge enable scientists to do?
Isolate specific components of cells in large quantities by cell fractionation
What is the first step of cell fractionation?
Tissue is mashed in a blender
What is the resulting liquid of the blending called?
Homogenate
What is homogenation?
Homogenate is spun at a high speed in an ultracentrifuge and separated into layers on differences in density
State how nuclei, mitochondria and ribosomes settle after homogenation
Nuclei are forced to the bottom first, followed by mitochondria, and then Ribosomes with clear liquid above the organelles
Outline the process of differential centrifugation
Tissue is lysed to remove cell membranes. The lysate is then subjected to repeatedcentrifugations, where particles that sediment sufficiently quickly at a given centrifugation force for a given time form a compact “pellet” at the bottom of the centrifugation tube. After each centrifugation, thesupernatant(non-pelleted solution) is removed from the tube and re-centrifuged at an increasedcentrifugal forceand/or time
What is an ultracentrifuge
An ultracentrifuge consists of a refrigerated, low-pressure chamber containing a rotor which is driven by an electrical motor capable of high speed rotation.
What is freeze fracture/freeze-etching
Complex technique used to study details of membrane structure under an EM.
After preparation, only a cast of the original tissue is available to examine
What is tissue culture?
- A technique to study the properties of specific cells in vitro (in lab)
- Living cells are seeded onto a sterile culture medium to which a variety of nutrients and growth stimulating factors have been added.(Different cells require different growth media)
- While cell lines are growing in culture they can be examined unstained under a phase-contrast light microscope
Suggest 2 reasons why plant cells do not have lysosomes?
- cell wall keeps out most large foreign molecules
- vacuole carries out most lysosomal functions
