lecture 3 ; cell structure, function, organelle and mitosis Flashcards
- smallest living unit in the body
- obtain nutrients
- makes molecules needed to survive
- dispose of wastes
- maintain shape of cell
- replicate (mitosis)
without energy; all of that stops
cells
cells organized into 3 areas
- plasma membrane
- cytoplasm
- nucleus
- outer boundary
- separates the intracellular fluid within cell form extracellular fluid outside and between cells
- transport substances across the membrane
- fluid mosaic model (lipid bilayer)
plasma membrane
4 methods of membrane transport
- simple diffusion
- osmosis
- facilitated diffusion
- active transport
- contains most organelles
- lies internal to plasma membrane
- consists of cytosol, organelles and inclusions
cytoplasm
controls cellular activities
nucleus
- subunits of cells with specific function
- most cells contain the same basic organelles
- not all cells have all organelles in the same abundance
organelles
relate to location at the interface of cell’s exterior and interior
- provides barrier against substances outside cell
- some plasma membranes act as receptors
- determines which substances enter or leave the cell
- membrane is selectively permeable
functions of the plasma membrane
tendency of molecules to move down their concentration gradient
simple diffusion
diffusion of water molecules across a membrane
osmosis
movement of molecules down their concentration gradient through an integral protein
facilitated diffusion
integral proteins move molecules across the plasma membrane against their concentration gradient
active transport
mechanism by which particles enter cells
endocytosis
cell eating
phagocytosis
cell drinking
pinocytosis
- plasma proteins bind to certain molecules
- invaginates and forms a coated pit
- pinches off to become a coasted vesicle
- this is the method by which insulin, other hormones, enzymes and low density lipoproteins enter cells
receptor- mediated endocytosis
a mechanism that moves substances out of the cell
- substance is enclosed in a vesicle
- vesicle migrates to the plasma membrane
exocytosis
- jelly like fluid in which other cellular elements are suspended
- consists of water, ions, and enzymes
cytosol
constructed of proteins and ribosomal RNA; not surrounded by a membrane
- site of protein synthesis
- assembly of proteins called translation
- are the “assembly line” of the manufacturing plant
- attahed to ER
ribosome
system of membrane walled envelopes and tubes throughout cytoplasm
endoplasmic reticulum
ribosomes stud the external surfaces
rough Er
consists of tubules in a branching network
-no ribosomes attached; therefore no protein synthesis
smooth er
stack of 3 to 10 disc-shaped envelopes
- sorts products of er and sends them to proper destination
- products of rough er move through the ____ from the convex to the concave side
- “packaging and shipping” division of the manufacturing plant
Golgi apparatus
membrane walled sacs containing digestive enzymes
- digest unwanted substances
- are the cells “demolition crew”
lysosomes
surrounded by double walled membrane
- generate most of the cells energy
- “power plant” of the cell
- release energy stored in chemical bonds and transfer energy to produce atp
- cells with high energy requirements have more
- most complex organelle
mitochondria
membrane walled sacs of oxidase enzymes
- enzymes neutralize free radicals and break down poisons
- break down long chains of fatty acids
- numerous in the liver and kidneys
- “toxic waste removal system”
peroxisomes
"cell skeleton" an elaborate network of rods contains 3 types of rods: 1. microtubules 2. microfilaments 3. intermediate filaments
cytoskeleton
cylindrical structures made of proteins
microtubules
filaments of contractile protein actin
microfilaments
protein fibers
intermediate filaments
- a spherical structure in the cytoplasm
- composed of centrosome matrix and centrioles
centrosome
paired cylindrical bodies
- consist of 27 short microtubules
- act in forming cilia
- necessary for karyokinesis
centrioles
found in liver cell and fat cells
lipid droplets
store sugar in the form of glycogen
glycosomes
- control center of the cell
- dna directs the cells activities
- provides instructions for protein synthesis
- nucleus is approximate 5 um in diameter
nucleus
two parallel membranes separated by fluid-filled space
- nuclear pores penetrate the nuclear envelope
- pores allow large molecules to pass in and out of the nucleus
nuclear envelope
- “little nucleus” in the center of the nucleus
- contains parts of several chromosomes
- site of ribosome subunit assembly
nucleolus
DNA double helix is composed of 4 subunits
Thymine, adenine, cytosine and guanine
dna plus protein molecules form
chromatin
each cluster of dna and histone proteins is a
nucleosome
active region of dna where dan’s genetic code is copied onto mRNA in transcription
extended chromatin
- tightly coiled nucleosomes
- inactive form of chromatin
condensed chromatin
highest level of organization of chromatin
- contains a long molecule of DNA
- typical human cells contains 46 chromosomes
chromosomes
series of changes a cell undergoes
cell life cycle
Cell life cycles
- interphase g1
- S phase
- G2 phase
- mitosis
- cytokinesis
- prophase
- metaphase
- anaphase
- telophase
- cytokinesis
G1 phase
- first part
- cell metabolically active
- -makes protein and grows rapidly
- variable in length from hours to years
- centrioles begin to replicated near the end of G1
interphase
DNA replicates itself
-ensures that daughter cells receive identical copies of the genetic material
S (synthetic) phase
Growth 2
- centrioles finish coping themselves
- enzymes needed for cell division are synthesized in G2
-During these phases cell carries on normal activities
G2 phase
cells divide during the stage
-follows interphase (g1, s and G2)
M (mitotic) phase
division of the nucleus during cell division
-chromosomes are distributed to the two daughter nuclei
mitosis
division of the cytoplasm
-occurs after the nucleus divides
cytokinesis
first and longest stage of mitosis
- early ___ ; chromatin threads condense into chromosomes
- chromosomes are made up of 2 threads called chromatids
- chromatids are held together by centromere
- certriole pairs separate from one another
- the mitotic spindle forms
prophase
chromosomes are made up of 2 threads
chromatids
chromatids are held together by
centromere
centrioles continue moving away from each other
-nuclear membrane fragments
late prophase
second stage of mitosis
- chromosomes cluster at the middle of the cells
- centromeres are aligned along the equator
metaphase
the 3rd and shortest stage of mitosis
-centromeres of chromosomes split
anaphase
begins as chromosomal movement stops
- chromosomes at opposite poles of the cell uncoil
- resume threadlike extended- chromatin form
- a new nuclear membrane forms
telophase
completes the division of the cell into 2 daughter cells
cytokinesis
they are temporary structures in the cell. can contain energy in the form of glycogen or lipids
inclusions
proteins or minerals
crystals
hemoglobin or melanin
pigments