Lecture Quiz: 10.13.25 (Photorespiration, Mitosis, Meiosis)

Photorespiration

when there is high oxygen content, plants will begin to use oxygen as a reactant than carbon dioxide

• Rubisco will bind of O2 rather than CO2

Bundle-sheath cells

underneath the mesophyll cells that help C4 plants offset the wastefulness of photorespiration

• CO2 fixed in the normal Calvin Cycle by rubisco

• enzymes in the Calvin cycle are only here

PEP carboxylase

enzyme in C4 and CAM plants that fixes CO2 into an organic acid

• C4 pathways: CO2 → oxaloacetate 

• CAM pathways: CO2 → malate

Malate

a 4C molecule that can go into the bundle sheaths and gets decarboxylated into pyruvate to go back into the mesophyll cell (C4 plants & CAM (during the night)) 

phosphoenol pyruvate (PEP)

A 3C molecule that accepts carbon molecules from CO2, and when attached to PEP carboxylase which will be converted to oxaloacetate

C4 Plant

type of tropical plants that has CO2 get fixed in the mesophyll cell by PEP carboxylase forming oxaloacetate

• organic acid will be transported to bundle sheath cell and CO2 is released

• in the bundle sheath cell → CO2 is fixed in the Calvin Cycle by rubisco

CAM Plant 

type of plants that fix CO2 to oxaloacetate then produce CO2 for the Calvin cycle both occuring in the mesophyll cells 

• desert plants 

• PEP carboxylase works at night and the Calvin cycle is during the day  

C3 Plant

most plants that use the pathway of photosynthesis where G3P is produced from the Calvin Cycle 

germ cells

gametes and spores

• essentially another name reproductive cells 

• cells that give rise to gametes (mature reproductive cells like sperm and egg) 

gametes

genome

binary fission

chromosome

a linear structure composed of a single DNA molecule complexed with protein

• in prokaryotes → singular with few to no associated proteins

chromatin

the supercoiles of DNA and proteins (50/50)

histones

small positively charged protein that is complexed with DNA in the chromosomes of eukaryotes 

• help with the folding of DNA 

somatic cells

body cells

• produced in mitosis 

sister chromatids

one of two exact copies of a chromosome duplicated during replication

centromere

part of a chromosome where two DNA molecules are hooked together

• a single chromosome will have this structure as well

cytokinesis

the division of the cytoplasm into two daughter cells following nuclear division in mitosis or meiosis

cell cycle

mitotically active 

• events related to DNA molecules going from one episode of cell division to the next

• the series of events that a cell goes through as it grows and divides into two new daughter cells

Interphase

the first stage of the mitotic cell cycle where the cell grows and replicates it DNA before undergoing mitosis and cytokinesis

• when cells are accumulating Energy and matter from its surroundings → growing and increasing in size 

• INcreasing in size 

• longest period of a cell cycle 

• contains three phases 

mitosis

series of events in the eukaryotic cell cycle that results in two nuclei being formed, each containing one complete set of genetic information

G1 Phase

the growth phase of interphase 

• when the two cells come out of mitotic cell division

• smaller than the parent cell

• actively increasing in size → taking up material from its surroundings

• biosynthesis

S phase

phase of interphase where the synthesis of DNA occurs (where DNA is replicated)

• DNA content doubled 

• contains sister chromatids

• anticipates cell division 

• 10 chromosomes (single) in G1 → 10 DNA molecules by the end (20 DNA but 10 chromosomes more like sister chromatids 

G2 phase

phase in interphase where duplication of cell division occurs

• mitochondria and chloroplast will replicate 

• end of this phase 

  • nucleus is intact 

  • 1-2 nucleoli are present 

  • two centrosomes adjacent to nucleus 

• chromosomes are not visible 

  • very loose 

centrosome

where microtubules originate

• forms the cytoskeleton and the mitotic spindle during cell division

centrioles

a cylindrical, microtubule-based cellular organelle found in animal cells that is primarily involved in cell division and the formation of cilia and flagella

• forms the core of a centrosome

aster

radiating array produced as microtubules extending from the centrosomes of cells grow in length and extent 

prophase

the beginning phase of mitosis where the duplicated chromosomes within the nucleus condense from a greatly extended state into compact rodlike structures

• nucleoli will disappear 

  • in order to have access to the genes they need to disappear to be at a level of relaxation 

  • rRNA are shut down

• chromatin condenses 

• centrosomes move apart 

• mitotic spindles grow 

mitotic spindle

the structure that separates sister chromatids and moves them to opposite spindle poles

Prometaphase

transition period between prophase and metaphase during which the microtubules of the mitotic spindle attach to the kinetochores and the chromosomes shuffle until they align in the center of the cell

• nucelar membrane breaks down

• no division between condensing chromosomes and cytoplasm

• the spindle poles are on opposite sides

kinetochore

a structure consisting of proteins attached to a centromere that mediates the attachment and movement of the chromosomes along the mitotic spindle 

kinetochore microtubules

in mitotic and meiotic spindles, where a microtubule originating from a spindle pole and binding to a kinetochore of a chromosome

• are attached to both poles north and south 

• one is attached to each sister chromatid 

nonkinetochore microtubules

a microtubules originating from a spindle pole that doesn’t bind to a kinetochore of a chromosome

metaphase

a phase in mitosis where the mitotic spindle reaches its final form and the spindle microtubules move the chromosomes into alignment at the spindle midpoint

• centromeres line up in the middle (on the metaphase plate) 

metaphase plate

the spindle midpoint

anaphase

phase in mitosis where the centromeres divide and the sister chromatids are pulled to opposite spindle poles 

• no longer a chromatid → daughter chromosome which consists of 1 chromatid 

• kinetochore microtubules start to shorten 

• poles will begin to move apart and the cell elongates 

telophase

the final phase of mitosis, where the mitotic spindle disassembles and the chromosomes decondense and the nuclei form (rRNA genes can be accessed) 

• happens in the metaphase plate

• cells continue to elongate 

• daughter chromosomes are at the poles 

• vesicles start to fuse together and the nuclear envelope redevelops around the chromosomes 

• 2 daughter cells at the end 

cleavage furrow

in cytokinesis where a contractile ring of microfilaments are in the plasma membrane are along with metaphase plate and tightens constricting the cell forming a groove

clone

individual that is genetically identical to an original cell from which it descended

autosome

any chromosome that isn’t a sex chromosome

sex chromosome

chromosomes that differs between sexes → males and females

homologous chromosome

chromosomes that have the same

• size 

• centromere location (metacentric, submetacentric, acrocentric) 

• staining pattern (light and dark banning pattern) 

• carrying the genes in a linear sequence 

  • different alleles help with genetic diversity 

diploid

2n

• 2 sets of chromosomes (one from mom other from dad) 

• 2 copies of the genome 

haploid

n 

• 1 set of chromosomes (1 of chromosome 1, 1 of chromosome 2, 1 sex chromosome set etc) 

• human set → 22 autosomes + 1 sex chromosome 

asexual reproduction

a mode of reproduction in which a single individual gives rise to offspring without the fusion of gametes 

sexual reproduction

form of reproduction that shuffles genetic information

• important for evolution as it helps organisms adapt to changing conditions 

• inheriting genetic information from both parents 

• gametes fuse together → fertilization

fertilization

where an egg and a sperm fuse together to form a zygote

zygote

a cell that is produced from the fertilization of an egg and sperm

• contains 1 set from egg and another set from sperm

spore

a type of germ cell that are in plants where they can start dividing on their own without fusing together

sporophyte

an individual of the diploid generation produced through fertilization in organisms that undergo alternation of generations producing haploid spores 

• their gametes are a dead end unless they fuse together 

gametophyte

produces gametes

• in organism where alternation of generations occur in plants in green algae mainly 

Meiosis

the division of diploid cells to haploids

• consisting of 2 rounds of nucelar and cellular division

meiosis I

the first division of the meiotic cell cycle in which homologous chromosomes pair and undergo an echange of chromosome segments and then the homologous chromosomes separate resulting in two cells