Chapter 11 Flashcards
Why do cells have to be small?
As cells grow, it will start to place too many demands on the DNA
The volume of the cell will grow too fast relative to the cell’s surface area, making the material exchange insufficient
What is a cell’s volume?
The substance in the cell
What is a cell’s surface area?
The membrane surrounding the cell
What is the surface area to volume ratio?
The amount of surface area the cell has relative to its volume
When does the surface area to volume ratio become a problem?
When the volume increases faster than the surface area
Does the surface area to volume ratio increase or decrease with growth?
Decrease (smaller ratio = larger cell)
Why is a smaller surface area to volume ratio bad?
There’s less area for materials to enter and exit the cell from, making it harder for the cell to absorb nutrients and expel waste products
Why do cells divide? (4) Some reasons may very due to different types of cell division
Keep cells small
Repair and replace old/damaged cells
Make sex cells (meiosis)
Organism growth (multicellular organisms)
Define meiosis
Sexual reproduction and cell cycle/division
Define mitosis
Asexual reproduction and cell cycle/division
How does sexual reproduction differ from asexual reproduction? Are offspring like or unlike (why)?
S - Two separate parent cells fuse, forming unlike offspring with some genetic info from each parent
A - One parent cell splits itself in two, forming genetically identical offspring
What is the advantage of sexual reproduction?
Genetic diversity can be beneficial in a changing environment due to different features and adaptations
What are the disadvantages of sexual reproduction? (3)
Fewer offspring are produced, so growth as a population takes more time
Need to find a mate to reproduce
Offspring may be less well adapted to current conditions
What are the advantages of asexual reproduction? (3)
Many offspring can be produced in a short period of time
No need to find a mate
Genetically identical offspring thrive in stable environments
What is the disadvantage of asexual reproduction?
If conditions change, offspring will not be well adapted
What are chromosomes made up of?
DNA and protein
What do chromosomes do?
Pass genetic info from one generation to the next
How many chromosomes are in a human body cell?
46
What is a sister chromatid?
Two identically replicated chromatids that are joined together at the centromere, forming a chromosome
What is the process of turning DNA into chromosomes? (3)
- DNA starts to coil, condensing into chromatin
- Chromatin coils tighter until you can no longer see the coils, condensing into a chromosome
- The chromosome replicates itself and connects with its copy, forming sister chromatids
When does chromatin turn into chromosomes?
Mitosis
What type of DNA do eukaryotic cells have? What shape does it take?
Linear
Coils and x-shapes
What type of DNA do prokaryotic cells have? What shape does it take?
Circular
Loop
What process do prokaryotic cells go through to divide?
Binary fission
What are the steps of binary fission? (3)
- DNA duplicates
- Cell membrane indents
- Cell divides, forming two cells
What are the two main parts of the cell cycle?
Interphase and M phase
What percent of a cell’s time is spent in interphase?
90%
What percent of a cell’s time is spent in m phase?
10%
What occurs during interphase?
Cells prepare to divide
What occurs during m phase?
Cells divide
What are the stages of cell division in order?
G1
S phase
G2
Mitosis
Cytokinesis
G0
What stages of cell division are included in interpase?
G1
S phase
G2
What stages of cell division are included in m phase?
Mitosis
Cytokinesis
Is G0 phase in interphase or m phase?
Technically interphase, but it is outside of the cell cycle and cells here are not preparing to divide
What happens in G1 phase?
Cell grows
What does S phase stand for?
Synthesis phase
What happens in S phase?
Cell’s DNA replicates
What happens in G2 phase?
Cell prepares for mitosis
What is the goal of mitosis (what happpens)?
The cell’s nucleus and chromosomes divide
What stages are included in mitosis?
Prophase
Metaphase
Anaphase
Telophase
In what stage is the goal of mitosis accomplished?
Telophase
What happens in prophase? (3)
Nucleus disappears
Chromosomes condense and become visible
Spindle fibers form
What happens in metaphase? (2)
Chromosomes line up single file down the middle of the cell
Spindles attach to the centromeres of the chromosomes
What happens in anaphase?
Sister chromatids are pulled apart and moved to opposite side of the cell by the spindles
What are the separated chromatids called?
Chromosomes; they are still individual chromosomes, they just aren’t attached to their duplicate anymore
What happens in telophase? (4)
Nucleus reforms (1 on each side of the cell)
Spindle fibers begin to disappear
Chromosomes begin to no longer be visible
Cell begins to pinch
What happens in cytokinesis in animals? (2)
Cytoplasm divides
Cell membrane pinches, causing a cleavage until fully separated, forming two identical daughter cells
What happens in cytokinesis in plants? (2)
Cytoplasm divides
Cell plate forms down the middle of the cell and turns into a new cell wall, splitting the cell into two identical daughter cells
Why is cytokinesis different in plants than in animals?
The cell wall is two rigid to pinch inwards like the membrane of an animal cell
What happens in G0 phase?
Cells that cannot divide wait to be fixed
Do all cells leave the G0 phase?
No; some are created at birth and stay permanently
What are some examples of cells that never leave the G0 phase?
Neurons (nerve cells)
What happens if cells that can’t leave the G0 phase get damaged? Example?
They can’t be replaced, so they can cause permanent damage
Example: brain/spine injuries could break neurons, causing paralysis
What is a cancer cell?
Cells that grow and divide uncontrollably and don’t respond to normal regulatory signals
What causes a cancer cell to occur?
When a defect in genes that control cell growth occurs, causing control over the cell cycle to break down
How can you tell that a cancer cell is present?
Abnormal cell division, which can often appear as tumors
What regulates the cell cycle?
Internal regulators and external regulators
Examples of internal cell regulators?
Cyclin
CDKs
p53
Example of external cell regulators?
Stopping division when the cell touches another cell
What are the checkpoints in the cell cycle? (3)
G1, G2, and M
What does the G1 checkpoint check for? (4)
Enough room around the cell for division
Cell has grown enough to divide
Cell has enough energy and nutrients to support cell functions during division
No damage has been done to the DNA
What does the G2 checkpoint check for? (3)
DNA is fully replicated
No damage has been done to the DNA
The cell has all the materials needed for M phase ready
When does the M checkpoint occur?
During metaphase
What does the M checkpoint check for? (1)
All chromosomes have spindles correctly attached
What two structures work together to manage checkpoints?
Cyclin and CDK
What is cyclin?
The proteins used in regulating the cell that only show up when needed at checkpoints
What does CDK stand for?
Cyclin Dependent Kinase
What are CDKs?
Enzymes that are always present but need cyclin to be present to function
How do CDK and cyclin work together?
Cyclins bind to the CDK
Is the same cyclin used throughout the cell cycle?
No; each checkpoint tends to have a different type of cyclin
When fixing an injury (e.g. a bone break), in what direction do the cells work to fix the injury?
Outside in (e.g. from the healthy bone next to the break in towards the center of the break)
What is apoptosis?
The self-destruction of a cell that is too old or damaged beyond repair and cannot be allowed to divide
What does p53 do?
Causes apoptosis when necessary
What are proto-oncogenes? (Definition and simple terms)
Genes that play a role in regulating the cell cycle
The “go” signal for the cell cycle to start
What is an example of a proto-oncogene?
Cyclin
What are oncogenes? What cause them to form?
Cancer causing genes that don’t give correct signals to regulate the cell cycle
A mutation in a proto-oncogene
What are tumor suppressor genes?
Genes that cause apoptosis and regulate the cell cycle by causing it to slow down or stop
What is an example of a tumor suppressor gene?
p53
What are stem cells?
The unspecialized cells from which differentiated cells develop
What are the three types of stem cells?
Totipotent
Pluripotent
Multipotent
Define totipotent
Stem cells that can develop into any type of cell in the body (including the cells that make up structures outside the body, such as the placenta)
Define pluripotent
Stem cells that are capable of developing into most, but not all, of the body’s cell types
Define multipotent
Stem cells that can only develop into a certain few kinds of specialized cells
Define embryonic stem cell
Stem cells found only when an embryo is forming
What are some examples of embryonic stem cells?
Totipotent and pluripotent cells
What are adult stem cells?
Stem cells that can be found in adults’ bone marrow, hair follicles, brain, heart, and skeletal muscle
What is an example of adult stem cells?
Multipotent cells
How are specialized cells different from each other?
They have different amounts of certain organelles based on their job and function in the organism
What is the order that stem cells appear in the human life cycle?
Totipotent (early embryo stages)
Pluripotent (later embryo stages)
Multipotent (child/adult)
Why do stem cells appear in the order they do?
When an embryo is first forming, it needs to be able to turn into anything, including outer structures (toti). After a few divisions, once these outer structures have been formed, the stem cells can focus on becoming different types of body cells (pluri). By birth, most of these body cells have already been created, so not many more need to be produced from the stem cells (multi).
Define blastocyst
The hollow sphere of cells formed after fertilization
What is the inner cell mass?
The mass of embryonic stem cells found inside the blastocyst that will later differentiate into specialized cells
