Exam III Flashcards
Photosynthesis
- the process that converts solar energy into chemical energy within chloroplasts
- nourishes almost the entire living world directly or indirectly
Autotrophs
“self-feeders” that sustain themselves without eating anything derived from other organisms
- producers of the biosphere
Heterotrophs
obtain organic material from other organisms; they are the consumers of the biosphere
the pigment that gives leaves their green color, resides in the thylakoid membranes
Plants and other photosynthetic organisms contain organelles called chloroplasts
Chloroplasts are found mainly in cells of the ____, the interior tissue of the leaf
mesophyll
CO2 enters and O2 exits the leaf through microscopic pores called
stomata
A chloroplast has an envelope of two membranes surrounding a dense fluid called the
stroma
____ are connected sacs in the chloroplast that compose a third membrane system
thylakoids
Wavelength
a measure of the distance between crests of electromagnetic waves•
electromagnetic spectrum
the entire range of electromagnetic energy, or radiation
Visible light
drives photosynthesis and produces the colors seen by the human eye
Light also behaves as though it consists of discrete particles, called
photons
spectrophotometer
measures a pigment’s ability to absorb various wavelengths
absorption spectrum
a graph plotting a pigment’s light absorption versus wavelength
action spectrum for photosynthesis
a profile of the relative effectiveness of different wavelengths, confirms the effectiveness of violet-blue and red light
carotenoids
yellow or orange because they absorb violet and blue-green light
photosystem
consists of a reaction-center complex surrounded by light-harvesting complexes
reaction-center complex
an association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor
light-harvesting complex
transfer the energy of photons to the chlorophyll a molecules in the reaction-center complex
primary electron acceptor
the reaction center accepts excited electrons and is reduced as a result
Linear electron flow
the primary pathway, involves both photosystems and produces ATP and NADPH using light energy
cyclic electron flow
photoexcited electrons cycle back from Fd to the cytochrome complex instead of being transferred to NADP+
Interphase
- the cell grows
- in preparation for cell division
- chromosomes are duplicated
- DNA duplicated
Prophase
genetic materials inside the nucleus condenses and chromosomes become visible
Pro-metaphase
- nuclear membrane breaks down
- spindle fibers attach to the centromere of the sister chromatids
metaphase
spindle fibers move the mitotic chromosomes to the middle of the cell
- line up at the cell plate
anaphase
sister chromatids are separated and pulled apart. The cell lengthens
- chromosomes at opposite poles
telophase
spindle fibers disappear and chromosomes uncoil
Cytokinesis
the cell divides into two daughter cells, genetically identical to each other and to the parent cell.
- the division of the cytoplasm
mitosis
the chromosome copies are separated from each other and moved to opposite ends of the cell
- the division of the genetic material in the nucleus
Somatic cells
(non-reproductive cells) have two sets of chromosomes
Gametes
(reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells
joined copies of the original chromosome
sister chromatids
Centromere
the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached
mitotic (M) phase
mitosis and cytokinesis
Divisions of interphase
–G1 phase(“first gap”)
–S phase(“synthesis”)
–G2 phase(“second gap”)
mitotic spindle
a structure made of microtubules that controls chromosome movement during mitosis
In animal cells, assembly of spindle microtubules begins in the ____
centromere
aster
a radial array of short microtubules
extends from each centrosome
spindle
includes the centrosomes, the spindle microtubules, and the asters
kinetochore
a protein complex associated with centromeres
metaphase plate
an imaginary plane midway between the spindle’s two poles
Cohesins
a ring of protein complexes that keep the sister chromatids together along their length.
In animal cells, cytokinesis occurs by a process known as
cleavage
cleavage furrow
a shallow groove in the cell surface near the old metaphase plate
In plant cells, a ___ forms during cytokinesis
cell plate
Prokaryotes (bacteria and archaea) reproduce by a type of cell division called ____
binary fission
In binary fission, the chromosome replicates (beginning at the ____, and the two daughter chromosomes actively move apart
origin of replication
The sequential events of the cell cycle are directed by a distinct
cell cycle control system
The clock has specific ___ where the cell cycle stops until a go-ahead signal is received
checkpoints
Two types of regulatory proteins are involved in cell cycle control:
cyclins and cyclin-dependent kinases (Cdks)
MPF
a cyclin-Cdk complex that triggers a cell’s passage past the G2 checkpoint into the M phase
If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a non-dividing state called the
G0 phase
____ are released by certain cells and stimulate other cells to divide
growth factors
In density-dependent inhibition,
crowded cells will stop dividing
Most animal cells also exhibit _____—to divide, they must be attached to a substratum
anchorage dependence
Cells that acquire the ability to divide indefinitely have undergone
transformation
If abnormal cells remain only at the original site, the lump is called a
Benign tumor
___ invade surrounding tissues and can undergo ___, the spread of cancer cells to other parts of the body, where they may form additional tumors
malignant tumors
metasis
heredity
The transmission of traits from one generation to the next is called inheritance
The study of heredity and inherited variation is called ___
genetics
Genes
the units of heredity and are made up of segments of DNA
Genes are passed to the next generation via reproductive cells called ___
gametes
Humans have __ chromosomes in the nuclei of their ___
46
somatic cells
A gene’s specific position along a chromosome is called its
locus
In asexual reproduction
a single individual passes all of its genes to its offspring without the fusion of gametes
Clone
an individual or group of genetically identical individuals from the same parent
sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from the two parents
life cycle
Is the generation-to-generation sequence of stages in the reproductive history of an organism
karyotype
an ordered display of the pairs of chromosomes from a cell
The two chromosomes in each pair are called
homologs
determine the sex of the individual, are called X and Y
sex chromosomes
Human females have a homologous pair of X chromosomes
(XX)
Male chromosomes
(XY)
The remaining 22 pairs of chromosomes are called
autosomes
Human somatic cells have __ pairs of chromosomes
23
diploid cell
(2n) has two sets of chromosomes
A gamete (sperm or egg) contains a single set of chromosomes and is thus a
haploid cell(n)
Each set of 23 consists of __ autosomes and __ sex chromosome - haploid cell
22
one
For humans, the diploid number is
46 (2n= 46)
Fertilization
the union of gametes (the sperm and the egg)
The fertilized egg is called a ___ and has one set of chromosomes from each parent
zygote
Gametes are the only type of human cells produced by ___
meiosis
Plants and some algae exhibit an alternation of generations
This life cycle includes both a diploid and haploid multicellular stage
Mitosis vs Meiosis: Mitosis
- Occurs in all organisms
- Creates body cells
- One cell division
- no crossing over
- 2 diploid cells
- identical daughter cells
Mitosis vs Meiosis: Meiosis
- animals, plants, fungi
- creates sex cells
- two cell divisions
- crossing over occurs in prophase
- 4 haploid daughter cells
- daughter cells genetically different
meiosis I
–Prophase I
–Metaphase I
–Anaphase I
–Telophase I and cytokinesis
Prophase I
each chromosome pairs with its homolog and crossing over occurs
X-shaped regions called ___ are sites of crossovers
chiasmata
Metaphase I
homologous chromosome line up at the equatorial plate of the cell
Anaphase I
pairs of homologous chromosomes separate
Telophase I and Cytokinesis
nuclear membrane reforms around the separated chromosomes
- two new diploid cells are formed
In animal cells, a__ forms; in plant cells, a __forms
- cleavage furrow
- cell plate
meiosis II
–prophase II
- metaphase II
–anaphase II
–telophase II and cytokinesis
Prophase II
- In prophase II, a spindle apparatus forms
* In late prophase II, chromosomes (each still composed of two chromatids) move toward the metaphase plate
metaphase II
- the sister chromatids are arranged at the metaphase plate
- The kinetochores of sister chromatids attach to microtubules extending from opposite poles
Anaphase II
The sister chromatids of each chromosome now move as two newly individual chromosomes toward opposite poles
Telophase II and Cytokinesis
- In telophase II, the chromosomes arrive at opposite poles
* Nuclei form, and the chromosomes begin decondensing
Crossing Over and Synapsis
A zipper-like structure called the ___holds the homologs together tightly
synaptonemal complex
During synapsis,
DNA breaks are repaired, joining DNA from one nonsister chromatid to the corresponding segment of another
Three events are unique to meiosis, and all three occur in meiosis I
- Synapsis and crossing over in prophase I
–2. Alignment of homologous pairs at the metaphase plate
–3. Separation of homologs during anaphase
- Synapsis and crossing over in prophase I
Three mechanisms contribute to genetic variation:
–Independent assortment of chromosomes
–Crossing over
–Random fertilization
Independent Assortment of Chromosomes
In independent assortment, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs
Crossing over produces ____, which combine DNA inherited from each parent
recombinant chromosomes
Random Fertilization
Random fertilization adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg)
The Evolutionary Significance of Genetic Variation Within Populations
- Natural selection results in the accumulation of genetic variations favored by the environment
- Mutations are the original source of different alleles
