Chapter 3 Cells Flashcards
What’s cell theory?
A cell is the structural and functional unit of life.
How well the entire organism functions depends on all its cells’ individual and combined activities.
Structure and function are complementary. Continuity of life has a cellular basis
Cell diversity
Over 250 different types of human cells
Types differ in size, shape, and subcellular components; these differences lead to differences in functions
Plasma membrane
flexible outer boundary
cytoplasm
intracellular fluid containing organelles
Nucleus
DNA containing control center
Extracellular materials
Substances found outside cells
Cellular secretions (e.g., saliva, mucus)
Classes of extracellular materials include:
-Extracellular fluids (body fluids), such as:
-Interstitial fluid: cells are submersed (bathed) in this fluid
-Blood plasma: fluid of the blood
-Cerebrospinal fluid: fluid surrounding nervous system organs
Extracellular matrix
a substance that acts as a glue to hold cells together
Plasma membrane (cell membrane)
Acts as an active barrier separating intracellular fluid (ICF) from the extracellular fluid (ECF)
Plays a dynamic role in cellular activity by controlling what enters and what leaves the cell
Plasma membrane (fluid mosaic)
Consists of membrane lipids that form a flexible lipid bilayer
Specialized membrane proteins float through this fluid membrane, resulting in constantly changing patterns
Membrane lipids (lipid bilayer)
75% phospholipids, which consist of two parts:
Phosphate heads: are polar (charged), so are hydrophilic (water-loving)
Fatty acid tails: are nonpolar (no charge), so are hydrophobic (water-hating)
5% glycolipids
Lipids with sugar groups on the outer membrane surface
20% cholesterol
Increases membrane stability
Membrane Proteins
Allow cell communication with environment
Make up about half the mass of plasma membrane
Most have specialized membrane functions
Some float freely, and some are tethered to intracellular structures
Integral proteins
Firmly inserted into the membrane
Most are transmembrane proteins (span membrane)
Have both hydrophobic and hydrophilic regions
Hydrophobic areas interact with lipid tails
Hydrophilic areas interact with water
Function as transport proteins (channels and carriers), enzymes, or receptors
Integral proteins
Firmly inserted into the membrane
Most are transmembrane proteins (span membrane)
Have both hydrophobic and hydrophilic regions
Hydrophobic areas interact with lipid tails
Hydrophilic areas interact with water
Function as transport proteins (channels and carriers), enzymes, or receptors
Peripheral proteins
Loosely attached to integral proteins
Include filaments on an intracellular surface used for plasma membrane support
Function as:
Enzymes
Motor proteins for shape change during cell division and muscle contraction
Cell-to-cell connections
Transport
A protein (Left) that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute
Receptors
A membrane protein expose to the outside of the cell may have a binding site that sits the shape of a specific chemical messenger, such as a hormone, when bound the chemical messenger may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell
Enzymes
A membrane protein may be an enzyme with its active site exposed to substances in the adjacent solution, which may catalyze sequential steps of a metabolic pathway as indicated
Cell-cell recognition
Some glycoproteins serve as identification tags that are specifically recognized by other cells
Attachment to the cytoskeleton and ECM
Elements of the cytoskeleton and the extracellular matrix may anchor to membrane proteins. Helps maintain shape, fixed the location of certain membrane proteins, and plays a role in cell movement
Cell-to-cell joining
Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions. Binding sites that guide cell migration and other cell-to-cell interactions
Glycocalyx
Consists of: sugars
Every cell type has different patterns: of this “Sugar coating”
Functions as: specific biological markers for cell-to-cell recognition
Tight junctions
Integral proteins on adjacent cells fuse to form an impermeable junction that encircles the whole cell. Prevent fluids and most molecules from moving in between cells
Rivet-like cell junctions
are formed when linker proteins (cadherins) of neighboring cells interlock like the teeth of a zipper. Linker protein is anchored to its cell through thickened “button-like” areas on the inside of the plasma membrane called plaques
Gap Junctions
Transmembrane proteins (connexons) form tunnels that allow small molecules to pass from cell to cell. Used to spread ions, simple sugars, or other small molecules between cells. Allows electrical signals to be passed quickly from one cell to the next cell
Transport Across the Membrane
The plasma membrane only allows certain molecules to pass through so it is called: Selectively permeable
Passive transport
NO energy is required
The direction of transport always: follows the concentration gradient
Active transport
energy ( ATP ) is required
The direction of transport can: go against the concentration gradient
Diffusion
the natural movement of molecules from areas of HIGH concentration to areas of LOW concentration
Also referred to as: Moving down a concentration gradient
Simple diffusion
A type of Nonpolar lipid-soluble (hydrophobic)
Substance diffuses directly through the phospholipid bilayer
Substances must be hydrophobic
Or very small amounts of very small polar substances like Water
Facilitated Diffusion
A type of Passive transport
the diffusion of substances across the membrane using: membrane proteins
Carrier-mediated facilitated diffusion
Substances bind to protein carriers
Channel-mediated facilitated diffusion
substances move through water-filled channels
Leakage channels- Always open
Gated channels- Controlled by chemical or electrical signals
Osmosis
Movement of WATER across a Selectively permeable membrane.
Through-specific water channels called aquaporins
Through-lipid bilayer
Flow occurs when water/solute concentration is different on the two sides of a membrane that won’t allow the movement of Solutes
Osmolarity
the measure of the concentration of the total number of solute particles in a solvent
When solute concentration goes up, water concentration goes: DOWN
Water moves from: osmosis from areas of low solute concentration to high areas of solute concentration
Isotonic solution
has the same osmolarity as inside the cell, so volume remains unchanged
Water moves: in-between
Effect on cell: unchanged
Hypertonic
the solution has Higher osmolarity than inside cell
Water moves: Outside of the cell
Effect on cell: Cell shrinking is referred to as crenation
A hypotonic solution
has lower osmolarity than inside cell
Water moves: into cell
Effect on cell: cell swelling can lead to cell bursting, referred to as lysing
Primary Active Transport
Energy come directly from: the hydrolysis of ATP causing change in the shape of transport protein
Pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell per ATP
Sets up gradient
Na+ at high concentration- outside of cell/ low inside
K+ at high concentration- inside of cell/ low outside of cell
Secondary active transport
Depends on ion gradient that was created by primary active transport system
Requires cotransporters- proteins that transport: more then one substance
Antiporters transport one substance: into cell while transporting different substance out of cell
Symporters transport two different substances in the: same direction
Vesicular Transport
Involves transport of large particles, macromolecules, and fluids across membrane in membranous sacs called: Vesicles
Endocytosis
transport: into cell
Can be hijacked by: Receptor for transport into cell
Once vesicle is pulled inside cell, it may:
Fuse with lysosome or
Undergo trancytosis
Phagocytosis
The cell engulfs a large particle forming a projecting pseudopod around it within a membranous sac called a phagosome. The phagosome combines with a lysosome and its contents are digested. The vesicle has receptors capable of binding to microorganisms or solid particles
Pinocytosis
The cell “gulps” a drop of extracellular fluid containing soulutes into tiny vesicles. No receptors are used, so the process is nonspecific
Receptor Mediated Endocytosis
Extracellular substances bind to specific receptor proteins, enabling the cell to ingest and concentrate specific substances in protein coated vesicles. Substances may be released inside the cell or digested in a lysosome
Exocytosis
transport: Process where material is ejected from cell
Substance being ejected is enclosed in Secretory vesicle
Ex: Hormones, neurotransmitters, mucus, cellular wastes
Cell-Environment Interactions
Every cell has thousands of sticky glycoproteins called: Glycoprotein CAMs
Functions of Cell-Environment Interactions
Anchor cell to: Extracellular matrix or eachother
Assist in movement: Of cell past one another
Attract: WBCs to injured or infected areas
Stimulate synthesis or degradation of: Adheasive membrane junctions
Transmit intracellular signals to direct: Cell migration, proliferation, and specialization
Roles of Plasma Membrane Receptors
Contact signalling- cell that: Touch recognize eachother by each cells unique surface membrane receptors
Used in: Normal development and immunity
Roles of Plasma Membrane Receptors
Chemical signaling: interaction between: Receptors and ligands (chemical messengers) that cause changes in cellular activities
In some cells, binding triggers enzyme activation; in others, it opens: Chemically gated ion channels
Same ligand can cause: different responses in different cells depending on chemical pathway that the receptor is part of
G protein linked receptors
Activated G proteins can:
Affect: Ions channels
Activate: Other enzymes
Cause release of internal: Second messenger chemicals such as cyclic AMP or calcium
Cytoplasm
all cellular material that is located between: The plasma membrane and the nucleus
Cytosol
gel-like solution made up of water and soluble molecules such as proteins, salts, sugars, etc.
Inclusions
insoluble molecules; vary with cell type (examples: glycogen granules, pigments, lipid droplets, vacuoles, crystals
Organelles
metabolic machinery structures of cell; each with specialized function; either membranous or nonmembranous
Membranous (list)
Mitochondria
Endoplasmic reticulum
Golgi apparatus
Peroxisomes
Lysosomes
Nonmembranous (list)
Ribosomes
Cytoskeleton
Centrioles
Membranes allow
compartmentalization, which is crucial to cell functioning
Mitochondria
Called the “power plant” of the cell because they produce most of the cell’s: Energy molecules (ATP) via aerobic (oxygen-requiring) cellular respiration
Enclosed by: double membranes
Inner membrane has many folds called: Cristae
Mitochondria contain their own: DNA, RNA, and Ribosomes
Resemble bacteria; capable of same type of cell division bacteria use, called: Fission
Endosymbiont Theory
The theory that mitochondria (and chloroplasts) originated as: free living prokaryotes that were engulfed by proto-eukaryotes
Ribosomes
Nonmembranous organelles that are site of: Protein synthesis
Made up of: Protein and ribosomal RNA (rRNA)
Free ribosomes
free floating; site of synthesis of soluble proteins that function in cytosol or other organelles
Membrane-bound Ribosomes
attached to membrane of endoplasmic reticulum (ER); site of synthesis of proteins to be incorporated into membranes or lysosomes, or exported from cell
Endoplasmic Reticulum
Consists of series of parallel, interconnected cisterns—flattened: membranous tubes that enclose fluid-filled interiors
ER is continuous with: Outer nuclear membrane
Site of: Phospholipid synthesis
Rough ER
External surface appears rough because it is: studded with attached ribosomes
Site of synthesis of proteins that will be: secreted from cell
Site of synthesis of many: plasma membrane proteins
Final protein is enclosed in vesicle and sent to: Golgi apparatus for further processing
Smooth ER
Network of looped tubules continuous with: Rough ER
Enzymes found in its plasma membrane (integral proteins)
integral proteins function in:
Lipid metabolism
cholesterol and steroid-based: Hormone synthesis
making lipids for: lipoproteins
Absorption, synthesis, and transport of: Fats
Detoxification of: certain chemicals
Converting of glycogen to: Free glucose
Storage and release of: Calcium
Sarcoplasmic reticulum is specialized smooth ER found in skeletal and cardiac: Muscle cells
Golgi Apparatus
Stacked and flattened: Membranous cistern sacs
Modifies, concentrates, and packages: Proteins and lipids received from rough ER
Golgi is “traffic director,” controlling which of three pathways final products will take one of three pathways
Pathway A: Secretory vesicles containing proteins to be used: Outside of cell fuse with plasma membrane and exocytosis contents
Pathway B: Vesicles containing lipids or transmembrane proteins fuse with plasma membrane or organelle membrane, inserting contents directly: Into destination membrane
Pathway C: Lysosomes containing: Digestive enzymes remain in cell, holding contents in vesicle until needed
Peroxisomes
Membranous sacs containing powerful detoxifying substances that: Neutralize toxins
Free radicals: toxic, highly reactive molecules that are: Natural by-products of cellular metabolism, can cause havoc to cell if not detoxified
Peroxisomes also play a role in breakdown and synthesis of: Fatty acids
Lysosomes
Spherical membranous bags containing: Digestive enzyme
Considered “safe” sites because they isolate potentially harmful: Intracellular digestion from rest of cell
Lysosomes functions
Digest ingested: Bacteria, viruses, and toxins
Degrade nonfunctional organelles (called: Autophagy
Metabolic functions
break down and release: Glycogen
break down and release release Ca2+ from: Bone
Intracellular release in injured cells causes: Cells to digest themselves (Autolysis)
Endomembrane System
Consists of membranous organelles discussed so far (list): ER, Golgi apparatus, secretory vesicles, and lysosomes, as well as the nuclear and plasma membranes
Endomembrane System function
Produce, degrade, store, and export: Biological molecules
Degrade: Potentially harmful substances
Supply membrane lipids to: Membranous organelles
Cytoskeleton
Elaborate network of : Protein strands that run throughout cytosol
act as cell’s “bones, ligaments, and muscle” by: Playing a role in movement of cell components
Microfilaments
Thinnest of all: Cytoskeletal elements
Semi-flexible strands of the protein : Actin
Functions:
Strengthens cell surface and helps to resist: Compression
Some are involved in: Cell motility, changes in cell shape or endocytosis and exocytosis
Intermediate filaments
Tough, insoluble, ropelike: Protein fibers
Composed of: Tetramer (4) fibrils twisted together, resulting in one strong fiber
Functions:
Help cell resist: Pulling forces
Anchor: organelles in place
Example of special types: Nerofilaments in nerve cells, Keratin filaments in epithelial cells
Microtubules
consist of hollow tubes composed of protein subunits called: Tubulins, are constantly being assembled and dissasembled
Most radiate from: Centrosome area of cell
Functions:
Many organelles are: tethered to microtubles to keep organelles in place
Many substances are: moved throughout cell by monitor proteins, which use microtubules as tracks
Motor proteins
complexes that function in:Motility
Can help in movement of: Organelles and other substances around cell
Use microtubules as: Tracks to move their cargo on
Powered by: ATP
Centrosome and centrioles
It is the organizing center for: Microtubules
Consists of a granular matrix and a pair of: Centrioles- barrel-shaped microtubular organelles that lie at right angles to eachother
Centrioles form the base of: Cilia and flagella
Microvilli
fingerlike projections that extend from the surface of the cell to: Increase surface area
Aids: In the movement of free cells
Have a core of: Actin microfilaments that is used to stiffening of projections
Cilia and flagella
aid in the: Movement of free cells
In attached cells, moves: Materials across the surface of the cell
Cilia are
Whiplike, motile extensions on surfaces of certain cells (Such as respiratory cells)
Flagella are
Longer extensions that propel the whole cell (EX: Tail of sperm)
Both cilia and fagella are made of which type of cytoskeletal filament?
Microtubules synthesized by centrioles that are called basal bodies
Nucleus
Largest organelle; contains the genetic library of blueprints for: Synthesis of nearly all cellular proteins
Responds to signals that dictate the kinds and amounts of: Proteins that need to be synthesized
Most cells are
Uninucleate (One), But skeletal muscle, certain bone cells, and some liver cells are Multinucleate (Many)
Red blood cells are: Acunucleate (No nucleus)
Nuclear envelope
Double-membrane barrier that encloses the jelly-like fluid, the: Necleoplasm
Outer layer is continuous with: Rough Er, student with ibosomes
Inner layer is called: Nuclear lamina, network mesh of proteins that maintains nuclear shape and acts as scaffolding for DNA
Nuclear pores
allow substances to Pass into and out of the nucleus
Nucleoli
Dark-staining spherical bodies within nucleus that are involved in: Ribosomal RNA, synthesized by ribosome subunit assembly
Associated with nucleolar organizer regions that contain the DNA that codes for: rRNA
Chromatin
Consists of
30% Threadlike strands of DNA
60% Histone proteins
10% RNA
Arranged in fundamental units called nucleosomes, which consist of: DNA wrapped around histones
Chromosomes are
Condensed chromatin
Why are chromosomes in a condensed state during cell division?
It helps protect fragile chromatin threads during cell division
Cell Cycle
Series of changes a cell undergoes from the: time it is formed until it reproduces
Most cells need to replicate continuously for: Growth and repair purposes
Skeletal, cardiac, and nerve cells do not: Divide efficiently; damaged cells are replaces with scar tissue
Two major periods
interphase: Cell grows and carries on its usual activities Cell divsion (Mitotic Phase )- Cell divides into two
nuclear material is in uncondensed
Chromatin state
G1 (gap 1)
Vigorous growth and metabolism
Cells that permanently cease dividing are said to be in
G0 phase
S (synthetic)
DNA replication occurs
DNA Replication
Prior to division, the cell makes a copy of: DNA
Replication fork
Point where strands seperate
Replication bubble
Active area of replication
Each strand acts as a: Template fro a new complementary strand
DNA polymerase
attaches to primer and begins adding: Nucleotides to form new strand
DNA polymerase works only in one direction so
leading strand is synthesized: Continously
lagging strand is “backwards,” so it is synthesized: Discontinuously into segments
DNA ligase
then splices short segments of: discontinous lagging strand together
End result is two identical
“Daughter” DNA molecules are formed fromthe original
Process is called semiconservative replication because each new double-stranded DNA is composed of: One old strand and one new strand
G2 (gap 2)
Preparation for division
M (mitotic) phase
phase in which: Division occurs
2 distinct events:
Mitosis
Cytokenisis
Control of cell division is crucial, so cells: Divide when necessary but do not divide unnecessarily, In which the duplicated DNA distribute to new daughter cells
Mitosis
is the division of the nucleus
Early prophase
Chromatin condenses, forming visible chromosomes
Each chromosome and its duplicate (called sister chromatids) are held together by a centromere Centrosome and its duplicate begin synthesizing microtubules that push each centrosome to opposite poles of cell
Called the mitotic spindle
Other microtubules called asters radiate from centrosome
Late prophase
Nuclear envelope breaks up
Special microtubules attach to specific area on centromeres called kinetochore and serve to pull chromosomes to center (equator) of cell
Remaining nonkinetochore microtubules push against each other, causing poles of cell to move farther apart
Metaphase
Centromeres of chromosomes are precisely aligned at cell’s equator
The imaginary plane midway between poles is called metaphase plate
Anaphase
Shortest of all phases
Centromeres of chromosomes split simultaneously—each sister chromatid now becomes a separate chromosome
Chromosomes are pulled toward their respective poles by motor proteins of kinetochores
One chromosome of each original pair goes to opposite poles
Nonkinetochore microtubules continue forcing poles apart
Telophase
Begins when chromosome movement stops
Each set of chromosomes (at opposite ends of cell) uncoils to form chromatin
New nuclear membranes form around each chromatin mass
Nucleoli reappear
Spindle disappears
Cytokinesis
Division of the: Cytoplasm
Begins during: Late anaphase and continues through mitosis
Ring of actin microfilaments contracts to form: Clevage furrow
Control of cell division
Go” and “Stop” signals direct when a cell: should and should not divide
Go signals include:
Critical surface-to-volume ratio of cell, when: area of membrane becomes inadequate for exchange
Chemicals (example: Growth factors, hormones)
Stop signals include
Availability of space; normal cells stop dividing when: they come into contact with other cells
Referred to as: contact inhibition
Cell Cycle Checkpoints
key events in the cell cycle where cell division processes are checked and, if faulty: stopped until repairs are made
Protein Synthesis
DNA is master blueprint that holds the code for: Protein synthesis
DNA directs the order of: Amino acids in a polypeptide
A segment of DNA that holds the code for one polypeptide is referred to as a: Gene
Codons
Code consists of: Three sequential bases
Each triplet specifies the code for a: particular amino acid
Genes are composed of
exons and introns
Exons are
Part of ene that actually codes for amino acids (EXpressed)
Introns are
noncoding segments interspersed amongst exons (INbetween)
Protein synthesis occurs in two steps
Transcription- DNA information coded in RNA
Translation- mRNA decoded to assemble polypeptides
This process (DNA->RNA->Protein) is referred to as
Central Doogma or Gene Expression
The Role of RNA
RNA is the “go-between” molecule that links: DNA to proteins
RNA copies the DNA code in: the nucleus
Carries it into: the cytoplasm to the ribosomes
how is RNA different from DNA?
Uracil is substituted for thymine in RNA , RNA has ribose instead of deribose sugar
Initiation
RNA polymerase separates DNA strands
Elongation
RNA polymerase adds complementary nucleotides to growing mRNA matching sequence of based on DNA template strand
Termination
Transcription stops when RNA polymerase reaches special termination signal code
Which enzyme is responsible for transcription?
RNA polymerase
Where does transcription occur in the cell?
nucleus
Messenger RNA ( mRNA )
Code from DNA template strand is copied with: complementary base pairs
Introns are spliced out, leaving: Exons
mRNA maintains the triplet code (codon) from DNA, which determines the: Amino acid sequence of the polypeptide
Ribosomal RNA ( rRNA )
Structural component of: ribosomes, the organelle where protein synthesis occurs
helps to: Translate message from mRNA into polypeptide
Catalyzes: Peptide bond formation (ribozyme)
Transfer RNA ( tRNA )
Carrier of: Amino acid
Have special areas that contain a specific triplet code ( Anticodon )
complementary base-pair with: codon of mRNA at ribosome, adding its specific amino acid to growing polypeptide chain
Each three-base sequence on DNA is represented by a complementary three-base sequence on mRNA called
a codon
Each codon codes for an: amino acid or stop of translation (stop codon) AUG (start codon) codes for
the amino acid methionine and the start of translation
Redundancy helps protect against:
against transcription errors
There are ____ possible codons but only____ possible amino acids
64, 20
Autophagy ( Self-eating ) is the process
of disposing of nonfunctional organelles and sweeping up cytoplasmic bits by forming: autophagosomes, which can then be degraded by Lysosomes
Ubiquitin-Proteasome Pathway
Unneeded, misfolded, or damaged proteins can be marked for destruction by a protein called: ubiquitin
Proteasomes disassemble ubiquitin-tagged proteins, recycling the: amino acids and ubiquitin
Apoptosis
Also known as programmed cell death, causes certain cells (examples: cancer cells, infected cells, old cells) to neatly self destruct
adipose Process begins with mitochondrial membranes leaking chemicals that activate enzymes called
caspases
Dead cell shrinks and is phagocytized by
and is phagocytized by macrophages
All cells of body contain the same
DNA, but not all cells are identical or carry out same function
Chemical signals in embryo channel cells into specific developmental pathways by
turning some genes on and others off
The development of specific and distinctive features in cells is called
cell differentiation
