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Cell biology Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Cell theory

A
  • Cells are the smallest unit of life
  • All living things come from cells
  • Cells only arise from pre-existing cells
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2
Q

Exceptions of the cell theory

A

Fungal Hyphae- Don’t contain dividing walls and are made up of multiple fused tread-like cells
Skeletal muscles- Are made of muscle fibers which are Fused, elongated cells longer than most cells (300 or more mm long) with multiple nuclei
Aseptate fungai- Has thread-like structures called hyphae. This is divided into subunits each coating a single nucleus
Gaint Algae- Can also grow to a length of 100mm however, they are not divided into subunits. Instead, they are undivided sections with multiple nuclei.

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3
Q

Functions of life

A

Metabolism- All chemical reactions occurring in a cell
Growth- Irreversible increase in size
Nutrition- Obtaing food to provide energy and other materials needed for growth
Reproduction- Producing offspring sexually or asexually
Response- Ability to interact and respond to its surroundings
Excretion- Removal of waste products from metabolism
Homeostasis- Keeping levels within the organism within tolerable limits

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4
Q

Cell Size

A

Cell needs to exchange material with the environment to produce chemical energy for survival(metabolism)
As cell grows, V increase faster than SA.
If cell volume exceeds cell SA the cell would die.
So cells stay small or increase SA:VOL ratio.

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5
Q

Rate of metabolism

A

A function of cell mass/volume
Small SA:Vol Ration
Increased metabolic rate & decreased material exchange
Low chances of survival

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6
Q

Rate of material exchange

A

Function of cell surface area
Large SA:Vol Ration
Decreased metabolic rate & Increased material exchange
High survival chances

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7
Q

Calculating Magnification

A

Magnification= Image size ÷ Actual size

MIA

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8
Q

Calculating Actual Size

A

Actual size= Image size ÷ Maganification AIM

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9
Q

Light Microscope

A
  • Have a lower resolution and magnification

- Can view specimens in natural color

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10
Q

Electron Microscope

A
  • Can create images of smaller specimens with great resolutions
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11
Q

Cell Organization

A

Cells- Tissues- Organ- System

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12
Q

Stem Cells

A
  • Unspecialized cells that have two main qualities
    Self Renewal - Can divide and replicate
    Potency - Can differentiate
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13
Q

Types of Stem Cells

A

Totipotent- Can form any cell type including Extra embryonic tissue
Pluripotent- Can form any cell type (embryonic stem cells (Fetal stem cells)
Multipotent- Can differentiate into closely related cell types (Fetal and adult stem cells)
Unipotent- Cannot differentiate, are capable of self-renewal (Adult stem cells)

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14
Q

Stem cells Therapy

A

Stem cells can replace damaged/ diseased cells

  1. Harvesting stem cells from sources
  2. Using biochemical solutions to trigger cell differentiation
  3. Surgically implanting new cells into a patient’s tissue
  4. Suppressing the host immune system to prevent rejection
  5. Monitoring new cells to ensure they don’t become cancerous.
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15
Q

Stem cells use Stargardt’s disease

A

Degenerative disease of the eye (retinal cells) leads to blindness.
- Human embryonic stem cells are obtained from unsuccessful in-vitro
fertilization.
- Cells are differentiated in the lab into retinal cells and injected into the eye of patients.
- The new cells replace the degenerate cells in the retina and restore vision
Example.

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16
Q

Stem cells use Leukemia

A

Cancer of white blood cells (immune cells).
- Human cord blood is collected after childbirth.
- The cord blood contains stem cells that differentiate into white blood cells.
- A patient with leukemia is irradiated and given chemotherapy to
kill all cancerous white blood cells.
- The killed cells are then replaced by the matching cord blood cells which are able to differentiate into different white blood cells in the patient

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17
Q

Ethics of Stem Cells

A

Embryo-

  • Pluripotent, has a higher risk of developing into a tumor
  • Is harvested by generating it artificially by SCNT
  • For it to be harvested the embryo needs to be destroyed
  • Embryo cannot give consent

Umbilical cord blood

  • Multipotent, has a lower risk of developing into a tumor
  • Can easily be obtained and preserved
  • Cells must be stored from birth- raising the issue of financial accessibility

Adult tissue

  • Multipotent, has a lower risk of developing into a tumor
  • Invasive to extract
  • It is hard to locate them
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18
Q

Differentiation

A
  • Differentiation is the expression of specific genes in the cell genome
  • This expression causes the gene to develop differently from other similar cells (cell specialization).
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19
Q

Gene Packing

A
  • In the nuclei of eukaryotic cells, DNA(gene instructions are packaged as chromatin with proteins.
  • Active genes are loosely packed as Euchromatin
  • Inactive genes are packed tightly as heterochromatin
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20
Q

Structure of Prokaryotic cells

A

Prokaryotes are organisms, that have no nucleus within their cells
- They belong to the kingdom Monera- Bacteria
All prokaryotic cells have;
- A genophore- single circular DNA molecule
- A peptidoglycan cell and 70s ribosomes
Prokaryotic cells may also have
- Pili- Attachment or bacterial conjunction
- Flagella- A long tail used for movement
- Plasmids- Autonomous DNA molecules

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21
Q

Prokaryotic vs Eukaryotic

A

Prokaryotic and eukaryotic cells differ based on the key features:
- DNA- Composition and structure
P-DNA is naked, circular & usually no intron
E- DNA is bound to protein, linear & usually has introns
- Organelles- That are present and their sizes
P- No nucleus & 70S ribosomes
E- Has a nucleus & 80S ribosomes
- Reproduction- How cell division occurs
P- Binary fission, Single chromosome
E- Mitosis and meiosis & paired chromosomes
- Average size
P- Smaller 1-5
E- Larger 10-100

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22
Q

Eukaryotic organelles

A

80s ribosomes- Responsible for protein synthesis- Translation
Nucleus- Stores genetic information, site for transcription
Mitochondria- Site for aerobic respiration- ATP production.
ER- Transports materials between organelles
Golgi complex- Sorts,stores,modifies & exports secretory products
Centrosomes- Aids in cell division- Mitosis and meiosis.
Chloroplasts- Plant cells- Site for photosynthesis
Lysosomes- Animal cells- Breaks Down macromolecules

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23
Q

Phospholipids Bilayer- Stucture

A
  • Contains a polar( hydrophilic) head composed of phosphate(+ glycerol)
  • 2 non-polar(hydrophobic) tails, composed of a fatty acid chain
  • They are amphipathic have both hydrophilic and hydrophobic part
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24
Q

Phospholipids Bilayer- Arrangement

A
  • Phospholipids spontaneously arrange into a bilayer

- The hydrophilic phosphate heads face outward, hydrophobic fatty acids tails face inwards

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25
Q

Phospholipids Bilayer- Properties

A
  • Bilayer held together by weak hydrophobic interaction between tails
  • Individual phospholipids can move within the bilayer( fluid and flexible)
  • Emphatic properties restrict passage of certain Substances( Semi- permeable)
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26
Q

Cholesterol

A
  • found only in animal cell membranes.
  • Reduces membrane fluidity and permeability to some solutes
  • Anchors certain peripheral proteins and prevents crystallization
  • keeps the fluidity of the membrane constant at a variety of temperatures.
  • When cold, increases fluidity - - When hot, makes membrane more rigid.
  • This is important to maintain a constant environment for cellular processes to occur.(Homeostasis
27
Q

Membrane proteins

A

Diverse in structure and position in the membrane
- They serve many functions:
- Insulin receptors are an integral protein that is a hormone receptor
- Cytochrome are peripheral protein used for electron transport
- Calcium pump is an integral protein for the active transport of calcium ions
- Cadherin and integral protein used for cell-to-cell adhesion
- Cytochrome oxidase an integral protein that is an immobilized enzyme
- Nicotinic acetylcholine receptor an integral protein that is both a receptor
for a neurotransmitter and a channel or facilitated diffusion of sodium ions

28
Q

Integral Proteins

A
  • Span the lipid bilayer and are permanently attached to it by polar interactions with the phospholipid heads and nonpolar interactions with the tails.
  • These can be for example receptors or transport proteins
29
Q

Peripheral Proteins

A
  • Attached to the inner or outer side of the membrane by non-covalent interactions with the surface of the membrane or other integral proteins.
  • These are for example enzymes attached to the outside of cells.
30
Q

Membrane Models

A
  • Membranes appear trilaminar (three distinct layers) when viewed on an electron microscope.
  • Davson-Danielli- Proposed a model where a phospholipid bilayer was flanked by two proteins layers
    Model was Falsifies
  • Fluorescent tagging showed the proteins are mobile
  • Not all membranes have a constant lipid: protein ratio
  • Freeze fracturing identified transmembrane proteins
31
Q

Fluid Mosaic Model

A
  • Cell membranes are represented in a fluid-mosaic models
    Fluid- Membrane components can move positions
    Mosaics- Phospholipids Bilyaer is embedded with protein.
  • Proposed by Singer-Nicolson in 1972, after falsification of the Davson-Danielli model
32
Q

Membrane properties

A

The lipid bilayer membrane is semi-permeable and selective,

Semi-permeable: only certain molecules (small, polar) can freely cross the membrane

Selective: transport proteins regulate the material passage

33
Q

Type of membrane transport

A

Active- Movement of molecules from an area of low concentration to an area of high concentration, using ATP (against the concentration gradient)

Passive- movement of molecules from an area of high concentration to an area of low concentration (down the concentration gradient) divided into two types of diffusion, simple and facilitated.

Simple diffusion- passive transport of molecules through a membrane, without the need for protein channels (oxygen diffusion)

Facilitated diffusion- passive transport of molecules facilitated by channel
or carrier proteins (sodium transport, calcium transport

34
Q

Active transport

A
  • Requires proteins, proteins use energy in form of ATP to pump molecules against their concentration gradient.
    Types of active transport:
  • Primary: direct use of metabolic energy for transport of molecules against
    a concentration gradient.
  • Secondary: coupling the movement of one molecule against the concentration gradient with the movement of another along the concentration gradient of the second molecule. Often created by primary active transport. Example sodium-potassium pump
  • Exocytosis: Transport of molecules in secretory vesicles that fuse
    with the plasma membrane upon contact to release the contents outside
    of the cell
  • Endocytosis transport of molecules into the cell through invagination of the
    plasma membrane and formation of the phospholipid vesicle
    containing the molecule
  1. Particle enters the pump from the side with a lower concentration
  2. Particle binds to Other types of particles cannot bind
  3. Energy from ATP is used to change the shape of the pump
  4. Particle is released on the side with a higher concentration and the pump then returns to its original shape
    .
35
Q

Osmolarity

A
  • The measure of the number of moles of solute particles per unit volume of solution.
    Solutions can be
    Hypertonic- High solute concentration( gains water)
    Hypertonic- Low solute concentration( loses water)
    Isotonic- Sam solute concentration ( no net flow)

(See how to evaluate mass change on physical flashcards)

36
Q

Potassium Channels in Axons

A
  • Axons of neurons contain potassium channels used during an action potential.
  • Closed when the axon is polarized, open in response to depolarization of the axon membrane.
  • Allows K+ions to exit by facilitated diffusion, which repolarizes the axon.
  • Potassium channels only remain open for a short time before a globular sub-unit blocks the pore.
  • The channel then returns to its original closed conformation

As sodium and potassium are pumped in opposite directions it is an antiporters.
- The energy required is obtained by converting ATP to ADP and
phosphate, so it is an ATPase. It is known to biochemists as Na+ /K+ -ATPase. One
- ATP provides enough energy to pump two potassium ions in and three sodium
ions out of the cell.
- The concentration gradients generated by this active transport are needed for the transmission of nerve impulses in axons.
OUTSIDE 2K+ 3Na+
INSIDE 2K+ 3Na+
-Centre of the pump are two binding sites for K+ ions and three Na+ ions.
- The pump has two alternate states. In one, there is access to the
binding sites from the outside of the membrane and stronger
attraction to K+ ions, so Na+ are discharged from the cell and K+
bind.
- Another state there is access to the binding sites from inside and there is a
stronger attraction or Na+ ions, so K+ ions are discharged into the cell and
Na+ bind.
- Energy from ATP causes this switch

.

37
Q

Osmosis

A

Passive transport that refers to the movement of water.
- Water moves from the area of low concentration to an area of high concentration
- Osmosis is defined in terms of the concentration of dissolved molecules
Osmosis- the movement of water from the area of low solute concentration to
the area of high solute concentration.

38
Q

Accuracy in Osmosis Experiments

A

Dependent on-
- The volume of water used for making solutions should be measured with a volumetric flask

  • The initial and final mass of tissue samples should be measured with the same electronic balance that is accurate to 0.01 grams (10 mg).
39
Q

Avoiding Osmosis In Donor Organs

A

Osmosis can cause cells in human tissues or organs to swell and burst, or shrink due to the gain or loss of water by

osmosis.
- To prevent this, tissues or organs used in medical procedures such as kidney transplants must be bathed in a solution with the same osmolarity as human cytoplasm.
- A solution of salts called isotonic saline is used for some procedures.
- Donor organs are surrounded by isotonic slush when they are being transported, with the low temperatures helping to keep them in a healthy state.

40
Q

Endosymbiotic theory

A

This theory explains the characteristics of mitochondria and chloroplasts:

  • Assumes that complex eukaryotic cells evolved from prokaryotic cells through a symbiotic process.
  • They grow and divide like cells.
  • They have a naked loop of DNA, like prokaryotes.
  • They synthesize some of their own proteins using 70S ribosomes, like prokaryotes.
  • They have double membranes, as expected when cells are taken into a vesicle by endocytosis.
41
Q

Transport Using Vesicles

A
  • Fluidity of membranes allows them to move and change shape.
  • Small pieces of plasma membrane are pinched to create a vesicle containing some material from outside the cell.-endocytosis.
  • Vesicles can also move to
    the plasma membrane and fuse with it, releasing the contents of the vesicle outside the cell This is exocytosis.
  • Vesicles move materials from one part of the cell to another. Move Proteins from the rough ER to the Golgi apparatus.
42
Q

Abiogenesis

A
  • Formation of living cells from non-living materials.
    Theorized to involve 4 key processes
  • Non- living synthesis of simple organic molecules
  • Assembly of organic molecules into complex polymers
  • Formation of polymers that can self-replicate
  • Packaging of molecules into membranes to create internal chemistry different from the surroundings
43
Q

Biogenesis

A

Abiogenesis requires specific conditions in order to proceed
- No oxygen and high temperatures(>100) celsius or electrical dischargers.

These conditions no longer exist on earth so cells can only arise from pre-existing cells

44
Q

Pasteur’s soups

A

Louis Pasteur verified this principle in the 19th century
Pasteur’s experiment used swan-necked flasks.
- He placed samples of broth, a medium highly nutritious for microorganisms to thrive.
- Pasteur then boiled the broth to kill any organisms present but left others unboiled as controls.
- Fungi and other organisms soon appeared in the unboiled flasks but not in the boiled ones.
- The broth in the flasks was in contact with air, which it needed for spontaneous generation, yet no spontaneous generation occurred.
- Pasteur snapped the necks of some of the flasks
- Organisms were soon apparent in these flasks.
- He concluded that the swan necks prevented air from getting into the flasks and so no organisms appeared spontaneously.

45
Q

Mitotic Index

A

The ratio between the number of cells in mitosis in a tissue and the total number of observed cells.

46
Q

Formation of organic molecules

A

Miller Urey’s experiment showed
- Water vapor, ammonia, and methane, found in the early atmosphere, could have spontaneously assembled into amino acids and carbon compounds, in the presence of electricity (lightning)

  • If some compounds formed at that time were phospholipids, they would have assembled into bilayers, forming early membranes
  • Formation of nucleic acids such as RNA would have given rise to early enzymatic activities, protein assembly, and the first genetic information.
47
Q

Chromosomes and Condensation

A
  • During mitosis the chromosomes become shorter and fatter. This is condensation
  • Occurs by a complex process of coiling, known as supercoiling.
48
Q

Chromatids and Centrosomes

A

At this stage of mitosis, each chromosome is a double structure.

  • The two parts of the chromosome are called sister chromatids.
  • Held together at one point by a centromere.
49
Q

Endosymbiotic theory

A
  • A larger anaerobic prokaryotic cell engulfed a smaller aerobic cell and co-existed
  • The smaller cells supplied both the cells with energy(ATP)]
  • This gave the larger cell a competitive advantage because aerobic respiration is more efficient than anaerobic.
  • Gradually the aerobic bacterium evolved into mitochondria and the larger cell evolved into heterotrophic eukaryotes alive today such as animals.
  • A heterotrophic cell took in a smaller photosynthetic bacterium, which supplied it with organic compounds, thus making it an autotroph. The photosynthetic prokaryote evolved into chloroplasts and the larger cell evolved into photosynthetic eukaryotes
50
Q

Mitosis

A

is the division of the cell’s nucleus into two identical daughter nuclei
containing the same number of chromosomes as the mother cell.

51
Q

Phases of Mitosis

A

1- Early Prophase

  • Spindle microtubules are growing
  • Chromosomes are becoming shorter & fatter by supercoiling
  1. Late prophase
    - Each chromosome consists of two identical chromatids formed by DNA replication in interphase and held together by a centromere
    - Spindle microtubules extend from each pole to the equator
  2. Metaphase
    - Spindle microtubules from both poles are attached to each
    centromere, on opposite sides
  • The nuclear membrane has
    broken down and chromosomes have moved to
    the equator
  1. Anaphase
    - The centromeres have divided
    and the chromatids have become chromosomes
    - Spindle microtubules pull the
    genetically identical chromosomes to opposite poles.
  2. Early telophase
    - All chromosomes have reached the poles and
    nuclear membranes
    form around them
    - Spindle microtubules break down
  3. Late telophase
    - Chromosomes uncoil and
    are no longer individually
    visible
  • The cell divides (cytokinesis) to form two cells with
    genetically identical nuclei
52
Q

Cytokinesis

A

is the division of the cell’s cytoplasm and organelles, forms 2 cells, follows mitosis

  • In plants, the transport of vesicles to the cell equator leads to fusion and formation of the plasma membrane. The vesicles bring cellulose to form the cell wall around the new plasma membrane. This divides the cell in two
  • In animal cells, an invagination(membrane at the equator is pulled inwards till it meets the center of the cell,
    dividing it in two. Actin and myosin are the contractile
    fibers that create this invagination called cleavage furrow.
53
Q

Sodium-Potassium Pump

A

Found in many cells including neurons.
- Sodium-potassium pump is an integral protein, uses ATP to transport molecules across a membrane;
- Transports sodium out of the cell, and potassium into the cell
- Works against the concentration gradients of both sodium and potassium;
- For every three sodium molecules it transports out, two potassium molecules are
transported in.

54
Q

Cell cycle

A

Sequence of events between one cell division and the next. Has 2 main phases: interphase
and cell division.
Interphase- many metabolic reactions occur. reactions of cell respiration occur during cell division, but DNA replication in the nucleus and protein synthesis in the cytoplasm happens during interphase.

Mitochondria in the cytoplasm increase, as they grow and divide. In-plant cells the numbers of chloroplasts increase in the same way.

55
Q

Phases of the inerphase

A

G1 - Cells spend the majority of their lifespan- period of growth and performance of daily functions.

S- Occurs when the cell has decided to undergo mitosis-
period of DNA synthesis (replication)

G2- Cell does its last preparations for mitosis- cell duplicates organelles and prepares enzymes and proteins needed for mitosis

G(rowth)1, S(ynthesis of DNA),
and G(rowth)2.
56
Q

Cyclins

A

Proteins that regulate the cell cycle

concentrations of the proteins vary throughout the cell cycle in response to internal and external
signals
Varying the concentration of cyclins influences progression of the cell cycle.

  • Cyclins are the cell cycle checkpoints
  • First checkpoint is between G1 and S phase
  • Another during S phase before the beginning of DNA replication
    • If cyclins are not produced or activated, the cell cannot pass the
    checkpoint

Tim Hunt discovered this out of luck while researching protein synthesis in seas urchin eggs

57
Q

Cyclin-dependent kinases- CDK

A
  • CDKs- Enzymes that depend on concentrations of cyclins for their activity.
  • CDKs allow progression through the cycle via phosphorylation specif molecules

Cyclins bind to enzymes called CDKs

kinases become active and attach phosphate groups to other proteins in the cell.

The attachment triggers other proteins to become active and
carry out tasks specific to the phases of the cell cycle.

58
Q

Oncogenesis

A

Formation of tumors

  • Mutagens cause mutation in DNA
  • Mutations are missed by proofreading machinery leads to gene mutations

UV light is a known mutagen, caused DNA mutations. Often cannot be repaired

59
Q

Oncogenes

A

Genes of cells responsible for normal dell division.

Mutation of this gene leads to the formation of Cancer

Proto-oncogenes are oncogenes, when mutates they become overactivated and promote cell division leading to tumor growth

60
Q

Tumors

A

Tumor suppressor genes negatively regulate the cell cycle, when mutated they fail to prevent uncontrollable cell divisions

  • When control of the cell cycle is lost cells undergo uncontrolled division called Primary tumors, which don’t grow rapidly or spread (Benign)
  • Some of these become malignant as cells detach from them and carried somewhere else, developing into a secondary tumor
61
Q

Metastasis

A

Movement of primary cancerous cells to a new formation where they continue to form tumors.

62
Q

Smoking and Cancer

A

Positive correlation

More cigarettes = a higher chance of developing concern in lungs and other areas

Chemicals in tobacco smoke are mutagenic= Carcinogenic- Cancer causing

63
Q

Mitosis

A

Prophase- nuclear envelope is
fractured, chromosomes are becoming thick,
centrioles are located and the poles of the cell.

Metaphase- chromosomes align at the equator of the cell and are ordered in one single row. Spindle fibres originate at the poles and attach to the centromeres centres, one chromosome having one spindle from each pole

Anaphase- fibres drag the chromosomes towards opposite sides of the poles. Equal number of chromosome legs are moving to each pole.

Telophase- two nuclei beginning
to form at each pole, and the chromosomes uncoiling and becoming longer.

Biology (6 decks)

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