CH 2 - Cells

human body has between

50-100 trillion cells (smallest living units)

cells are the basic

structural and functional units of an organism

• make molecules needed for survival

cells obtain

nutrients, build molecules, generate and dispose of wastes (metabolism)

cells contain

organelles (subunits with specific functions)

replicate

cells have three main components

cytoplasm, nucleus, plasma membrane

cytoplasm -

contains most organelles

nucleus -

controls cellular activities

plasma membrane

the outer boundary

• defines the extent of the cell

  • separates the intracellular fluid within cell from extracellular fluid outside and in between cells

plasma membrane provides

barrier against substances outside cells

some plasma membranes act as

receptors

• determines which substances enter or leave the cell (selectively permeable)

types of membrane proteins

integral and peripheral proteins

intergral proteins

firmly imbedded within the lipid bilayer

• short chains of carbs attach to integral proteins, forms the glycocalyx

peripheral proteins

attack to the membrane surface

• support plasma membrane from the cytoplasmic side

simple diffusion

tendency of molecules to move down their concentration gradient

osmosis

diffusion of water molecules across a membrane

facilitated diffusion

movement of molecules down their concentration gradient through an integral protein

active transport

integral proteins move molecules across the plasma membrane against their concentration gradient

endocytosis

mechanism by which particles enter cells

phagocytosis =

cell eating

pinocytosis

cell drinking

receptor-mediated endocytosis

1. plasma proteins bind to certain molecules

2. invaginates and forms a coated pit

3. pinches off to become a coated vesicle

   1. method by which insulin, other hormones, enzymes, and low-density lipoproteins enter cells

exocytosis

mechanism that moves substances out of the cell

1. substance is enclosed in a vesicle

2. vesicle migrates to the plasma membrane

cytoplasm

• internal to plasma membrane

• consists of cytosol and organelles

cytosol

• jelly-like fluid in which other cellular elements are suspended

• consists of water, ions, and enzymes

ribosomes

constuctured of proteins and ribosomal RNA; not surrounded by a membrane

• site of protein synthesis; the “assembly line” of the manufacturing plant

free ribosomes function

within the cytosol

ribosomes attached to ER

• make proteins to renew plasma membrane

• make proteins that are exported from the cellE

ER -

system of membrane-walled envelopes and tubes throughout cytoplasm

rough ER -

ribosomes stud the external surfaces

smooth ER -

consists of tubules in a branching network

• no ribosomes are attached; therefore no protein synthesis

Golgi apparatus

a stack of 3-10 disc-shaped envelopes

• packaging and shipping division the manufacturing plant

Golgi apparatus functions

• sorts products of rough ER and sends them to proper destination

  • products of rough ER move through the Golgi from the convex (cis) to the concave(trans) side

lysosomes

cell’s demolition crew

• membrane-walled sacs containing digestive enzymes

  • digest unwanted substances

mitochondria

surrounded by double-walled membrane

mitochondria functions

• generate most of the cell’s energy

• cells with high energy requirements have more mitochondria - e.g., muscle cells

• most complex organelle

• contain some maternally inherited DNA

peroxisomes

membrane-walled sacs of oxidase enzymes

• enzymes neutralize free radicals and breakdown poisons

• numerous in the liver and kidneys

• the “toxic waste removal system”y

cytoskeleton

cell skeleton

• an elaborate network of rods

cytoskeleton contains three types of rods

microtubules, microfilaments, intermediate filaments

microtubules -

cylindrical structures made of proteins

microfilaments -

filaments of contractile protein actin

intermediate filaments -

proteins fibers

centrosomes and centrioles are closely related that help

organize a cell’s internal “skeleton” and are especially important during cell division

centrosome

a spherical structure in the cytoplasm

• composed of centrosome matrix and centrioles

centrioles

paired cylindrical bodies

• consists of 27 short microtubules

• ct in forming cilia

• necessary for karyokinesis (nuclear division)

nucleus is the

control center of the cell

nuclear envelope -

two parallel membranes separated by fluid-filled spaces

nuclear pore penetrate the

nuclear envelope

nuclear pores

allow large molecules to pass in and out of the nucleus

nucleolus

little nucleus - in the center of the nucleus

• site of ribosome subunit assembly

DNA double helix composed of

four subunits

• A, T, C, and G

DNA is packed with

protein molecules

DNA plus the proteins from

chromatin

each cluster of DNA and histone proteins is a

nucleosome

extended chromatin

active region of DNA where DNA’s genetic code is copied into mRNA in transcription

condensed chromatin

tightly coiled nucleosomes, inactive

chromosomes

highest level of organization of chromatin

• a typical human cell contain 46 chromosomes

the cell life cycle is the

series of changes a cell undergoes

interphase =

G1, synthesis, G2

g1 phase (growth)

cell metabolically active (makes proteins and grows rapidly)

• centrioles begin to replicate near the end

  • variable in length from hours to YEARS (egg cells)

S (synthesis) phase

DNA replicates itself

• ensures that daughter cells receive identical copies of the genetic material (chromatin extended)

G2 (growth) phase

• centrioles finished copying themselves

• enzymes needed for cell division are synthesized

during S and G2 phases, cells

carries on normal activities

M (mitotic) phase

cell divide

• follows interphase

cells division involves

mitosis and cytokinesis

mitosis -

division of the nucleus during cell division

• chromosomes are distributed to the two daughter nuclei

cytokinesis

division of the cytoplasm

• occurs after the nucleus divides

mitosis - prophase

the first and longest stage of mitosis

mitosis - early prophase

chromatin threads condense into chromosomes

• chromosomes are made up of two threads Called chromatids (sister chromatids)

• chromatids are held together by the centromere

• centrioles pairs separate form one another

• the mitotic spindle forms

mitosis - late prophase

centrioles continue moving away from each other

• nuclear membrane fragments

mitosis - metaphase

the second stage of mitosis

• chromosomes cluster at the middle of thece’ll

  • centromere are aligned along the equator

mitosis - anaphase

the third and shortest stage of mitosis

• centromere of chromsomes split

mitosis - telophase

begins as chromosomal movement stops

• chromosomes at opposite pole of the cell uncoil

• resume threadlike extended-chromatin form

• a new nuclear membrane forms

mitosis - cytokinesis

complete the division of the cell into two daughter cells

cellular diversity - cells that connect

body parts of cover organs

cellular diversity - cells that move organs and body parts

skeletal and smooth muscle cells

• elongated and filled with actin and myosin

  • contract forcefully

cellular diversity - cells that store nutrients

fat cell - shape is produced by large fat droplet in its cytoplasm

cellular diversity - cells that fight disease

macrophage - moves through tissue to reach infection sites

cellular diversity - cells that father information

neutron - has long processes for receiving and transmitting messages

cellular diversity - cells of reproduction

sperm(male) - possesses long tail for swimming other the egg for fertilization

dysplasia

abnormal development of cells within tissues or organs (size, shape, displacement); from long-term irritation or inflammation

hyperplasia

excessive cell proliferation (normal shape and arrangement)

hypertrophy -

enlargement of an organ or tissue from the increase in size of its cells (cells it already has)

necrosis -

death of cells or groups of cells due to injury or disease (not controlled)

aging

a complex process caused by a variety of factors

aging - free radical theory

• damage from byproducts of cellular metabolism

• “radicals” build up and damage essential molecules of cells

aging - mitochondrial theory

decrease in production of energy by mitochondria weekends and ages our cells

genetic theory proposes that aging is

programmed by genes

telomeres

end caps on chromosomes

telomerase

prevents telomeres from degrading

The __________ is (are) the protein assembly
line.
a. cytosol
b. ribosomes
c. smooth endoplasmic reticulum
d. Golgi apparatus

b - ribosomes

What works with the rough ER to package and
ship new proteins to appropriate sites within
the cell?
a. Golgi apparatus
b. smooth endoplasmic reticulum
c. Centrioles
d. lysosomes

a - Golgi apparatus

These are paired cylindrical bodies that
organize microtubule networks during mitosis
and form the bases of cilia and flagella.
a. microfilaments
b. centrioles
c. nucleoli
d. plasma membrane

b - centrioles

These are membranous sacs of oxidase
enzymes that detoxify many substances.
a. peroxisomes
b. lysosomes
c. vesicles
d. nuclear envelope

a - peroxisomes

These are membranous sacs of acid
hydrolases that act as the cell’s “stomach.”
a. peroxisomes
b. lysosomes
c. vesicles
d. nuclear envelope

b - lysosomes

Which membranous system of sacs and
tubules functions as a site of lipid metabolism,
steroid synthesis, and drug detoxification?
a. rough endoplasmic reticulum
b. smooth endoplasmic reticulum
c. Golgi apparatus
d. ribosomes

b - smooth ER

Which cell type has extended processes for
receiving messages and transmitting them to
other structures in the body?
a. hair cell
b. muscle cell
c. epithelial cell
d. nerve cell

d - nerve cell

A cell’s life cycle can be divided into what two
major periods?
a. mitosis and metaphase
b. living or dying
c. innerphase and meiosis
d. interphase and cell division

d - interphase and cell division

Interphase is the portion of a cell’s life span in
which it carries out normal life-sustaining
function as well as __________.
a. preparation for apoptosis
b. preparation for cellular division
c. preparation for endocytosis
d. preparation for cell death

b - preparation for cellular division

The S, or synthetic, part of interphase is
marked by __________.
a. vigorous growth
b. synthesis of separation enzymes
c. mitosis
d. replication of DNA

d - replication of DNA

The final part of interphase is __________.
a. G2, enzymatic preparation for cell division
b. I2, enzymatic preparation for cell death
c. G1, immense cell growth
d. H1, mitotic cell division

a - G2