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Anatomy and Physiology 1. Organization of Cells and Beyond. The Bigger Picture Where do the atoms and molecules that we have talked about fit into the bigger picture?. The Basic Unit of Life is the Cell. Nucleus. Chromosomes. Lysosome. Ribosome. Mitochondria. Energy production - PowerPoint PPT Presentation
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The Bigge
r Pictur
e
Where do the atoms
and molecules
that we have talked about fit into
the bigger picture?
The Basic Unit of Life is the CellThe Basic Unit of Life is the Cell
Endoplasmic reticulum
Ribosome
Golgi
Lysosome
Plasma membrane
Energy production
Synthesis of proteins
Maintain intracellular environment
Transport across the membrane
Mitosis (DNA replication)
Recycling old cellular components
Mitochondria
NucleusChromosomes
Membrane proteins
Organelles are made from Organelles are made from macromoleculesmacromoleculesStructural components
– Proteins
– Glycolipids
Information/communication
– DNA
– Proteins
Energy sources
– Carbohydrates
– Lipids
– ATP
Carbohydrates are used for energy and for macromolecules
Amino acids make proteins
Lipids make plasma and
organelle membranes
Plasma Membrane: separates the intracellular environment from the extracellular (interstitial) fluid
Extracellular fluid (ECF): includes plasma and interstitial fluid
Extracellular matrix: jellylike nonliving mesh containing proteins and carbohydrates secreted by cells. Self organizes into a mesh (varies from soft to rock hard) that glues the body together.
Intracellular environment: also water based environment with salts, sugars, amino acids, proteins, membrane bound organelles
Proteins Proteins
• 3D structure of protein determines its function. Disturb shape and loose function
• All proteins are made from a mixture of the 20 amino acids. DNA sequence of genes codes for amino acid sequence
• Each amino acid has chemical personality which influences the way the protein folds
• Some amino acids are polar while others are hydrophobic. The hydrophobic amino acid are found in transmembrane sections of proteins
Crossing the membrane: what does semi-permeable mean?
Simple diffusion Carrier mediated
Channel mediated Osmosis
The chemical properties of a molecule determine how that molecules moves across the plasma membrane.
May be active or passive
May be active or passive
• Monosaccharides are building blocks. Only form that crosses the membrane
– 6 carbon (hexoses) such as glucose
– 5 carbon (pentoses) such as ribose
• Disaccharides are food made of two monosaccharides
– sucrose, lactose and maltoses
• Polysaccharides large carbohydrate storage molecules
– Glycogen, cellulose
Polar molecules cross via facilitated diffusion or active transportCarbohydratesCarbohydrates
Concentrations do NOT have to be equal on both sides of the membrane.
In many cases life depends on concentrations be different across membranes!
• Think about the generation of electricity by hydroelectric power
– Membranes can act as dams preventing molecules from crossing.
– When the concentration is higher on one side of the membrane there is drive toward equilibrium (same concentration on each side)
– When molecules move from higher concentration to lower concentration energy can be captured
– Pushing molecules up there concentration gradient requires energy input
– Water in biological systems freely moves through membranes and never accumulates in a concentration gradient
– Water is at the mercy of other concentration gradients and will move to achieve equilibrium
Concentrations inside the cells are NOT always equal to concentrations outside for many solutes.
Higher concentration Na+
Lower concentration Na+
Energy is needed to
move across
membrane
Outside cell
Inside cell
Higher concentration Na+
Lower concentration Na+
No energy needed to
move across
membrane
Outside cell
Inside cell
Lower concentration K+
Higher concentration K+
No energy needed to
move across
membrane
Lower concentration K+
Higher concentration K+
Energy is needed to
move across
membrane
• Water freely diffuses across membranes (through aquaporins)
• The direction of water movement is determined by the relative solute concentration inside and outside the cell
• Water always moves down its concentration gradient
Water
Higher concentration of solutes (hypertonic)
Lower concentration solutes
Cell will dehydrate
Lower concentration of solutes (Hypotonic)
Higher concentration solutes
Cell will swell
Outside cell
Inside cell
Selective permeability of membranes is necessary for life
• Selective permeability is a characteristic of healthy, intact cells. When a cell (or its plasma membrane) is severely damaged, the membrane becomes permeable to virtually everything, and substances flow into and out of the cell freely. This phenomenon is evident when someone has been severely burned. Precious fluids, proteins, and ions "weep" from the dead and damaged cells
• Selective permeability maintains concentrations of molecules on both sides of the membrane
• The cells in our body have both a plasma membrane surrounding the cell and a series of membrane bound internal structures called organelles that house the everyday functions of the cell. Internal membranes create microenvironments needed for reactions inside the cell.
So what do cells do all day?
• Maintain concentration gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
• Maintain concentration gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
Mitochondria
Hormone Receptors/Second Messengers
Receptors• Maintain concentration
gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
Ribosomes/Endoplasmic Reticulum/Golgi
• Maintain concentration gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
Making of macromolecules
• Macromolecules are polymers of smaller molecules• ~ 30 small precursors are combined into a diversity of macromolecules• Biosynthesis is highly regulated• Proteins are the doers in the cell.• All information in DNA is about making proteins • Proteins are not made directly from DNA, but rather from RNA (transcription
is making RNA from DNA; translation is making proteins from RNA)• After translation, proteins may be cut, glycosylated (sugars added), and
packaged
Macromolecule Precursors
Polysaccharides (e.g., glycogen starch)
Monosaccharides (e.g., glucose)
Proteins Amino acids (20 different ones)
Nucleic Acids (DNA, RNA) Nucleotides (4 different ones)
Peptidoglycan cell wallAmino acids and monosaccharides
tRNAs bring in amino acids
AUG CUG GGG GUA CUC GCG CUA CCC GGG UAA
mRNA
tRNARibosom
eMet
Leu
GAC
AUG CUG GGG GUA CUC GCG CUA CCC GGG UAA
mRNA
tRNARibosom
eMet
Leu
GACUAC
UAC
tRNAs bring in amino acids
Pro
GGG
MetLeu
GlyVal
Leu AlaLeu
GAU
AUG CUG GGG GUA CUC GCG CUA CCC GGG UAA
mRNA
tRNA with
amino acidGrowing peptide
chain (peptidyl transferase makes peptide
bonds)Ribosom
e
CGC
Empty tRNA
Stop signal
Aminoacyl-tRNA transferase attaches amino acid to its tRNA
Lysosomes
• Maintain concentration gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
Glycogen and certain lipids in the brain are degraded by lysosomes at a relatively constant rate. In Tay-Sachs disease, an inherited condition seen mostly in Jews from Central Europe, the lysosomes lack an enzyme needed to break down a glycolipid abundant in nerve cell membranes. As a result, the nerve cell lysosomes swell with the undigested lipids, which interfere with nervous system functioning. Affected infants typically have doll-like features and pink translucent skin. At 3 to 6 months of age, the first signs of disease appear (listlessness, motor weakness). These progress to mental retardation, seizures, blindness, and ultimately death within 18 months.
Cytoskeleton
• Maintain concentration gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
Microtubules/Centrioles
• Maintain concentration gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
Tissues
• Maintain concentration gradients
• Metabolism to generate energy
• Respond to chemical messages in the blood
• Make useful proteins
• Digest debris in the cytoplasm
• Transport stuff around within the cell
• Divide into 2 daughters cells
• Organize into structural units called tissues
Cells – the basic structural and functional units of the organismCells specialize in particular jobs, e.g., muscle cells are specialized for contracting
Tissue levelGroups of different cell types cooperate to perform specific functions
Essential Concepts: The Hierarchy of Structural Organization
What does a highly organized body do?
What do cells do? What does the body do?
Maintain concentration gradients
Maintain boundaries with outside
Metabolize nutrients to generate energy
Digest nutrients
Respond to chemical messages in the blood
Respond to changes in the environment
Make useful proteins Grow Digest debris in the cytoplasm Excrete (get rid of wastes)Transport stuff around within the cell
Move relative to external environment and move substances internally
Divide into 2 daughters cells ReproduceOrganize into structural units called tissues
Stay the same while constantly changing (homeostasis)