Cell Structure and Function Chapter 7

Characteristics of Living Things Page 16

Levels of Organization Page 21 Cell Size 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 cells Cells are the basic units of structure and function in living things New cells from existing cells

Two Categories of Cells Prokaryotes no Nucleus smaller, simpler cells Example: Bacteria

Eukaryotes Have a Nucleus Have Organelles examples: Plant cells and animal cells (pg 174 fig 7.5)

Comparing Cells Chart on page 183

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-permeable Some substances can cross and others can’t Protein molecules run through the lipid bilayer Carbohydrate molecules attached to outer surfaces of proteins

Concentration - mass of solute in a give volume of solution Isotonic - same strength Hypertonic - above strength Hypotonic - below strength

Diffusion Molecules 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.

EquilibriumEquilibrium is reached when the solute is the same throughout Diffusion does not require energy

Osmosis The diffusion of water molecules through a biological membrane Naturally moves from a higher concentration to a lower concentration

Will continue until Equilibrium is reachedEquilibrium Does not require energy Osmotic pressure is on the hypertonic side of a selectively permeable membrane Almost all cells are hypertonic to fresh water

Facilitated Diffusion Diffusion that occurs through protein channels in the cell membrane Each channel is specific and allows only certain molecules into the cell

Does not require energy MoleculesMolecules 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 concentration Requires energy

Examples: Sodium - Potassium pumppump Endocytosis - the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane to make a vacuole

PhagocytosisPhagocytosis - 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 water Cytoplasm = cytosol + organelles

Cytoplasm Cytosol + Organelles Fills the entire cell Made 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)cytoplasmic streaming

Cell Wall Not found in all cells Outside the cell membrane Made of cellulose – a tough carbohydrate fiber

Cell Wall Porous enough to allow water, oxygen, carbon dioxide and some other substances through easily Main function is to provide support and protection for the cell

Nucleus Largest organelle Control Center Contains 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 Song We love DNA Made of nucleotides Sugar, phosphate and a base Bonded down one side

Adenine and thymine Make a lovely pair Cyotsine without guanine Would 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 proteins Sequence 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 proteinsproteins

Step 1 – make RNA What is RNA? To make a protein

Required for protein synthesis Disposable copies of DNA Long 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 RNA Transcribed from DNA Single stands of three kinds M & T & R

M is the messenger T does the transfer R is in the ribosome For translation to occur

RNA and DNA Make 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 Acids Bases 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 codons There 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 202 Figure 8-2 Adenosine Triphosphate Used to store energy needed for life processes

ADP page 203 Figure 8-3 Adenosine Diphosphate Similar in structure to ATP but has only 2 phosphates

Phosphate groups can be added or taken away according to cell supply and need Energy stored in ATP is released when it is converted into ADP and 1 phosphate group

Uses for ATP in cells Movement within the cell organelles along microtubules Active Transport sodium/potassium pump 1 ATP molecule can move 3 sodiums and 2 potassiums

Glucose and ATP Cells only keep a small amt of ATP Glucose can store 90x the chemical energy of ATP They keep larger amounts of glucose

Glucose ATP more value less value less mass more mass

Where does the cell get the energy it needs? energy Photosynthesis Cellular Respiration

Where do they get it? Autotrophs Heterotrophs (carnivore, herbivore, omnivore, decomposer, scavenger)