cell structure and function chapter 7. characteristics of living things page 16
TRANSCRIPT
Cell Structure and Function
Chapter 7
Characteristics of Living Things
Page 16
Levels of OrganizationPage 21
Cell Size and how we know
The Diversity of Cellular Life
Unicellular - single celled organisms, exhibit all the characteristics of life
Can be both Eukaryotic and Prokaryotic
Multicellular - made up of many cells and all cells are interdependent
Each has a specific function that contributes to the whole (specialization of roles)
The Cell Theory
All living things are composed of cellsCells are the basic units of structure and function in living thingsNew cells from existing cells
Two Categories of Cells
Prokaryotes no Nucleussmaller, simpler cellsExample: Bacteria
Eukaryotes Have a NucleusHave Organellesexamples: Plant cells and animal cells (pg 174 fig 7.5)
Cell Project
Cell Membrane
The cell membrane regulates what enters and leaves the cell and provides protection and support
Cell Membrane (pg 184 fig 7-15)
Phospholipid bilayer
Semi-permeableSome substances can cross and others can’t
Protein molecules run through the lipid bilayerCarbohydrate molecules attached to outer surfaces of proteins
Concentration - mass of solute in a give volume of solutionIsotonic - same strengthHypertonic - above strengthHypotonic - below strength
DiffusionMolecules in solution move constantly and spread randomly through space.They naturally move from an area of high concentration to an area of low concentration until equilibrium is reached.
Equilibrium is reached when the solute is the same throughoutDiffusion does not require energy
Osmosis
The diffusion of water molecules through a biological membraneNaturally moves from a higher concentration to a lower concentration
Will continue until Equilibrium is reachedDoes not require energyOsmotic pressure is on the hypertonic side of a selectively permeable membraneAlmost all cells are hypertonic to fresh water
Facilitated Diffusion
Diffusion that occurs through protein channels in the cell membraneEach channel is specific and allows only certain molecules into the cell
Does not require energyMolecules must flow from a higher concentration to a lower concentration
Active Transport
Molecules move against the concentration difference and flow from a lower concentration to a higher concentrationRequires energy
Examples: Sodium - Potassium pumpEndocytosis - the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane to make a vacuole
Phagocytosis - taking in large particles by endocytosis
Exocytosis - the removal of large amounts of material from a vacuole that fuses with the cell membrane forcing it’s contents out of the cell
Every living cell contains a liquid interior and is surrounded by liquid. Cytosol - a solution of many different substances in waterCytoplasm = cytosol + organelles
Cytoplasm
Cytosol + OrganellesFills the entire cellMade of water, salt and organic substances, also contains enzymes
Cytoplasm
Functions to hold organelles, allows for storage of chemicals, and provides pathways for molecular movement (cytoplasmic streaming)
Cell Wall
Not found in all cellsOutside the cell membraneMade of cellulose – a tough carbohydrate fiber
Cell Wall
Porous enough to allow water, oxygen, carbon dioxide and some other substances through easilyMain function is to provide support and protection for the cell
Nucleus
Largest organelleControl CenterContains DNA
Instructions for everything that goes on in the cell
Nucleic acid that stores and transmits genetic information from one generation to another
DNA
Has to be able to carry info from one generation to another
Structure of DNA
That info needs to determine characteristics Needs to be easy to
copy
Structure of DNA
A long molecule made of nucleotides 5 carbon sugar (ribose) Phosphate group Nitrogenous base
DNA is…
Adenine Cytosine Guanine Thymine
4 Bases
Any sequence is possible Base order = the coded genetic information
Base order
The amount of Adenine is always equal to the amount of Thymine and
Chargaffs’ rule
The amount of Cytosine is always equal to the amount of Guanine
Chargaffs’ rule
Adenine will always pair up with Thymine Cytosine will always pair up with Guanine
Base Pairing
Took x-ray defraction photographs of DNA molecules Noticed a spiral shape
Wilkins and Franklin
Looked at Chargaffs research and photos by Wilkins and Franklin Built a 3 dimensional model of DNA
Watson and Crick
Discovered the shape = Double Helix (2 strands wound around each other) Page 294
Watson and Crick
The DNA SongWe love DNA
Made of nucleotidesSugar, phosphate
and a baseBonded down
one side
Adenine and thymineMake a lovely pair
Cyotsine without guanineWould feel very bare
Sugar and phosphate make sides of the ladder The bases are held together with hydrogen bonds to make the rungs (C=G and A=T)
Like a Ladder
This structure explains how DNA can be copied Each half has the info needed to make the other half (complimentary strands)
Replication
Enzymes unzip the molecule by breaking hydrogen bonds (DNA Polymerase)
Replication
Starts at one point and goes along entire molecule (can go in both directions) Each strand serves as a template for complementary bases
Replication
The result is two DNA molecules identical to each other and to the original molecule
Replication
Coded DNA instructions that control production of proteinsSequence of bases are in the DNA molecule
Genes
Mutations Changes in the DNA
sequence that affect the genetic information
Changes the kind of protein made
Proteins are the keys to almost everything that living cells do
Enzymes, growth regulators, building materials
Proteins
Nucleolus
Makes Ribosomes
Ribosome
Assemble proteins
Step 1 – make RNA
What is RNA?
To make a protein
Required for protein synthesis
Disposable copies of DNALong chains of nucleotides
RNA
Sugar is ribose instead of deoxyribose
Single strand not double Uracil replaces thymine
Different from DNA
Messenger – carries copies of DNA instructions Ribosomal – found in the ribosome Transfer – transfers amino acids to the ribosome
3 Types
The RNA Song
We love RNATranscribed from DNA
Single stands of three kindsM & T & R
M is the messengerT does the transferR is in the ribosome
For translation to occur
RNA and DNAMake a lovely pair
Synthesizing proteins and
Copying part of the nucleotide sequence of DNA into a complementary sequence of RNA
Transcription
Proteins are made of chains of Amino AcidsBases are read in groups of three to code for different Amino Acids
Transcription
the three letter “words” are called codons
Transcription
the three letter “words” are called codonsThere are 64 possible codons that can be made with the 4 bases
Transcription
The decoding of mRNA to form a protein (polypeptide chain)Happens in the Ribosome
Translation
1.mRNA is transcribed from DNA and released into cytoplasm (transcription), then attach to ribosome
To Make a Protein
2. tRNA brings amino acids to the ribosome to match codons
3.Ribosomes form peptide bonds between amino acids and breaks bonds between amino acids and tRNA
To Make a Protein
4. Peptide chain continues to grow until it hits a stop Peptide chain continues to grow until it hits a stop codon that causes it to release from the ribosome and the mRNA molecule
To Make a Protein
Proteins are the keys to almost everything that living cells do
Enzymes, grow regulators, building materials
To Make a Protein
Mutations Changes in the DNA
sequence that affect the genetic information
Changes the kind of protein made
Changes sunlight into food
Changes food into energy
Create Energy
Chloroplasts & Mitochondria
Energy
The ability to do work
All living things depend on Energy
ATP
page 202Figure 8-2Adenosine TriphosphateUsed to store energy needed for life processes
ADP
page 203Figure 8-3Adenosine DiphosphateSimilar in structure to ATP but has only 2 phosphates
Phosphate groups can be added or taken away according to cell supply and needEnergy stored in ATP is released when it is converted into ADP and 1 phosphate group
Uses for ATP in cellsMovement within the cell
organelles along microtubules
Active Transportsodium/potassium pump1 ATP molecule can move 3 sodiums and 2 potassiums
Glucose and ATPCells only keep a small amt of ATP Glucose can store 90x the chemical energy of ATPThey keep larger amounts of glucose
Glucose ATPmore value less valueless mass more mass
Where does the cell get the energy it needs?
PhotosynthesisCellular Respiration
Where do they get it?
AutotrophsHeterotrophs
(carnivore, herbivore, omnivore, decomposer,
scavenger)
