ap bio unit 4: feedback mechanisms, cell cycle, and regulation of the cell cycle

feedback mechanism

when the output of a system is also the input

positive feedback

amplifies a process

negative feedback

counters a process tries to maintain homeostasis

stimmulus

something that triggers a reaction

sensor/receptor

biological structure that detects a stimulus

effector

responds to stimulus changes bodily function

response

change that responds to he stimulus

insulin

body releases this when low levels of glucose signals for body to turn stored sugar into glucose negative feedback

set points

value around which a homeostatic process fluctuates

disease

when homeostasis is disrupted

cell cycle

how the cycle duplicates itself

mitosis

cell division for body cells

interphase

where cells are for most of their lives, growing, DNA replication, and cell functions

G1

cell is growing, part of interphase

S

DNA is replicated, part of interphase

G2

cells continue to grow

prophase

nucleus is still present, chromosomes are condensing, spindles start to form

metaphase

nucleus is gone, chromosomes line up in the middle, spindles attach to centromeres

anaphase

chromosomes are pulled to opposite sides of the cell

telophase

chromosomes are on opposite sides of the cell, new nuclei form

cytokinesis

cytoplasm splits between two nuclei creating 2 new daughter cells

centriole/centriole pair

where spindle fibers come out of

chromsome

condensed units of DNA

replicated chromosome

when chromosomes are replicated during the S phase of the cell cycle, sister chromatids form and each chromosome is doubled

histones

proteins that the DNA is wrapped around

pole(s)

the ends of the cell where the spindle fibers pull chromosomes to

spindle fiber

attach to the centromeres of chromosomes during metaphase

condense

DNA is usually unbound and loose in the nucleus but for mitosis it condenses into chromosomes

spindle apparatus (mitotic spindle)

small structures that attach to kinetochores of chromosomes and pull them to each pole

midline

where chromosomes line up durmetaphase

sister chromatid

each identical half of a chromosome

cleavage furrow

when the cytoplasm pinches during cytokinesis to prepare for cytoplasmic division

decondense/unwind

after mitosis the DNA in the daughter cells begins to decondense back into a more loose form

kinetochore

center of a chromosome where the spindles attach

centrosome

structure that contains the spindles and the centrioles

checkpoints

several times throughout the cell cycle activity stops so that the cell can be examined for errors helping prevent erroneous cell from being made

cyclin

internal regulator of the cell cycle, the binding of cyclins and CDKS signals for new phases of the cell cycle to commence and end. They are not always present their abundance depends on the abundance of CDKS

CDK (cyclin dependent kinase)

internal regulator of the cell cycle, their activation helps progress the cell cycle. CDKS are always present

G0

phase where cells never divide, like nerve and muscle cells

G2 checkpoint

after S phase, checks all spindles are properly attached

contact inhibition

when normal cells touch each other, their replication rate slows until they fill up a certain space. For cancer cells, contact inhibition does not stop them and they continue to grow controllably

cancer

uncontrolled cell growth

tumor

a clump of cancer cells

malignant

mass of cancer cells that can leave the tumor site and travel throughout the body

benign

abnormal cells, not considered cancerous yet, these cells are unable to leave the tumor site

metastasis

when cells spread throughout the body away from the initial tumor site