Cell Biology

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Cell Biology Bio 2.8

• Cell structure and function
• Bacterial cells, protist cells, plant cells,
  animal cells
• Cell components and functions
• Microscopy
• Cell processes
• Transport of materials into and out of cells
• Enzymes
• Respiration
• Photosynthesis
• DNA structure and cell replication
• Mitosis, meiosis
• DNA replication

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All living things are made of cells!
Living things
Viruses
Prokaryotes Before the nucleus No
nucleusSingle, circular chromosome No
organelles Small cells
Eukaryotes True nucleus Contain a
nucleus Linear chromosomes Contain
organelles Larger cells
Bacteria
Protists
Plants
Animals
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Eukaryotic cells (continued)
Eukaryotic cells
Protists - Mostly single celled - Some
autotrophic - Some heterotrophic
Plants - Multicellular - Autotrophic - Contain
chloroplasts - Rigid cell wall made ofcellulose
Animals - Multicellular - Heterotrophic - No
cell wall
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Organelles

• Organelles are little organs structures with
  particular functions within cells
• Organelles common to all eukaryotic cells
• Nucleus
• Ribosomes
• Cell membrane
• Cytoplasm
• Mitochondria

Use the text to find the functionof each of
these organelles.Include a sketch of the
organelleto help you identify it later
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Example

• Cell membrane
• Also known as the plasma membrane
• Keeps the cell separate from its environment
• Controls what goes into and out of the cell
• Receives information from outside the cell (e.g.
  from hormones)

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Homework

• Due next Monday
• Tonight study for ecology topic test!
• Rest of week (Biozone pages)
• pages 261, 262, 263
• find the structure/function/diagram of the
  following organelles using your textbook
• Chloroplasts
• Endoplasmic reticulum
• Golgi apparatus
• Cell wall
• Lysosomes

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Monday 30.04.2007

• This week
• Monday
• Cell membranes and the transport of materials
• Active and passive transport
• Osmosis (part one)
• Tuesday
• Osmosis (part two)
• Details of practice experiment for internal AS
• Wednesday
• Set up practice internal AS experiment
• Friday
• Measure practice experiment
• Write up practice experiment

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Organelles

• Organelles are little organs structures with
  particular functions within cells
• Organelles common to all eukaryotic cells
• Nucleus
• Ribosomes
• Cell membrane
• Cytoplasm
• Mitochondria

Use the text to find the functionof each of
these organelles.Include a sketch of the
organelleto help you identify it later
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Definitions

• Metabolism all the chemical reactions going on
  in the cells of an organism
• Respiration process in living cells where large
  food molecules are broken down to release energy

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Organelles structure and function
NUCLEUS
Contains genetic material (DNA) Controls the
functioning of the cell DNA contains
instructions needed to produce proteins that
control metabolism and other cell functions
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Organelles structure and function
MITOCHONDRIA
Site of aerobic respiration Produces much of the
ATP (energy) for the cell Two membranes
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Do Now

• Put the follwing particles in order from smallest
  to largest
• Molecule
• Cell
• Organ
• Tissue
• Atom
• Organelle

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Answer

• Atom smallest
• Molecule
• Organelle
• Cell
• Tissue
• Organ largest

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Organelles structure and function
PLASMA MEMBRANE (Cell Membrane)
1. Regulates the flow of materials in and out of
the cell 2. Receives signals from outside the
cell and relays them to the inside 3.
Separates the cell and its contents from the
environment
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Organelles structure and function
RIBOSOMES
The site of protein synthesis Often found
associated with the endoplasmic reticulum
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Organelles structure and function
GOLGI APPARATUS GOLGI BODY
Modifies, packages anddistributes proteins
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Do Now

• Write what each of the following letters stands
  for
• M
• R
• S
• G
• R
• E
• N
• MRS GREN represents the life functions that
  living things carry out. If an object carries out
  the life functions it is considered to be alive.
• Discuss this statement with regard to cells.

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Organelles structure and function
ENDOPLASMIC RETICULUM A network of fluid filled
membranes running through the cytoplasm Two
types of ER smooth and rough ER acts as a
transport system The synthesis of certain
compounds (lipids, proteins and carbohydrates)
occurs on the membrane Temporary storage
area Surface on which some biochemical reactions
occur
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Organelles structure and function
CELL WALL
Specific to plants Made of cellulose Provides
support and strength
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Do Now

• Match the function to the organelle

Organelle Function
Nucleus
Mitochondria
Ribosomes
Endoplasmic reticulum
Plasma membrane
Centriole
Cytoplasm
Nucleolus
Lysosome
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Cell processes - transport

• Plasma membranes are used in many places within
  the cell
• Chloroplasts
• Mitochondria
• Golgi apparatus
• Nucleus
• Cell membrane
• A major function of plasma membranes is to
  regulate the flow of materials in and out of
  cells.

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Structure of plasma membranes

• Contains lipids called phospholipids in two
  layers (a lipid bilayer)
• Contains cholesterol
• Contains integral membrane proteins
• receptors for hormones
• transport proteins (ion channels etc.)
• structural proteins
• Forms a semi-permeable barrier for the transport
  of materials due to the nature of the
  phospholipids in the membrane

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Structure of a plasma membrane
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Structure of a plasma membrane
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Transport of substances
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Transport processes
Active transport
Passive transport
Movement of materialsdown a concentration
gradient No energy needed
Movement of materialsagainst a concentration
gradient Requires energy
membrane
membrane
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Tuesday 01.05.2007

• Today
• Cell transport
• Osmosis
• Fair tests and experimental plans

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Examples passive transport

• Diffusion movement of substances from an area
  of high concentration to low concentration
• Facilitated diffusion movement of substances
  down a concentration gradient aided by a membrane
  protein
• Osmosis diffusion of water from an area of low
  solute concentration to high solute concentration
  through a semi-permeable membrane

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Examples active transport

• Ion pumps
• Active pumping of ions against a concentration
  gradient(e.g. Na, K)
• Endocytosis
• Phagocytosis ingestion of solids
• Pinocytosis ingestion of liquids
• Exocytosis
• Expelling of substances from the cell

Small process
BIG PROCESSES!
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Examples of transport
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Nerve impulses
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Large-scale transport
PHAGOCYTOSIS
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Osmosis

• Refers only to the movement of water
• Requires a semi-permeable membrane, meaning water
  can move in/out, but solute molecules can not
• Water moves from an area of low solute
  concentration to an area of high solute
  concentration
• The water follows the solute!

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Osmosis effects on animal cells
Isotonic Solution - same solute No water movement
Hypotonic Solution - more solute inside Water
moves in
Hypertonic Solution more solute outside Water
moves out
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Osmosis and plant cells
HYPOTONIC
ISOTONIC
HYPERTONIC
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Osmosis effects on plant cells

• Turgid a plant cell in a hypotonic solution has
  taken in water causing it to swell.
• Plasmolysis a plant cell in a hypertonic
  solution has lost water causing the cell membrane
  to detach from the cell wall.

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Summary transport processes
Transport

• Passive transport
• No energy required
• Driven by diffusion
• Movement down a conc. gradient

• Active transport
• Energy required
• Movement against a conc. gradient

Diffusion
Ion pumps
Endocytosis
Osmosis - Water only
Facilitateddiffusion
Exocytosis
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Internal assessment
Fair test planning sheet

• Task To investigate water movement in and out
  of living plant cells
• Materials apples, containers, sucrose
  solutions, balances
• Questions/issues to think about
• What are the variables? independent?
  dependent?
• What needs to be controlled?
• What method will you use?
• How will you process the data and graph it?

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Wednesday 02.05.2007

• Today
• Writing an experimental plan
• Setting up a practice experiment

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Experimental plan/method
You should be able to answer yes to ALL of the
following questions.
YES NO
Has the independent variable been identified?
Has the dependent variable been identified?
Has a prediction, aim or hypothesis been stated?
Have at least 2 other variables been identified and controlled?
Is there a description of how all other variables are going to be measured or controlled?
Has sufficient data been collected?
Could your METHOD be followed by any other person?
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Organelles structure and function
NUCLEUS
Contains genetic material Controls the
functioning of the cell
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Organelles structure and function
MITOCHONDRIA
Site of aerobic respiration Produces much of the
ATP (energy) for the cell Two membranes
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Organelles structure and function
PLASMA MEMBRANE
1. Regulates the flow of materials in and out of
the cell 2. Receives signals from outside the
cell and relays them to the inside 3.
Separates the cell and its contents from the
environment
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Organelles structure and function
RIBOSOMES
The site of protein synthesis Often found
associated with the endoplasmic reticulum
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Organelles structure and function
GOLGI APPARATUS GOLGI BODY
Modifies, packages anddistributes proteins
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Organelles structure and function
CELL WALL
Specific to plants Made of cellulose Provides
support and strength
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Homework due Friday

• Pages 286-289, Biozone
• Notes on the structure and function of the
  following organelles
• Chloroplasts
• Endoplasmic reticulum
• Centrioles
• Flagellum

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Cell processes - transport

• __________ membranes are used in many places
  within the cell
• Chloroplasts
• ______________
• Golgi apparatus
• ______________
• Cell membrane
• A major function of plasma membranes is to
  ___________ the flow of ___________ in and out of
  cells

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Structure of plasma membranes

• Contains __________ called phospholipids in two
  layers (a lipid __________)
• Contains cholesterol
• Contains integral membrane __________
• receptors for hormones
• transport proteins (ion channels etc.)
• structural proteins
• Forms a _______________ barrier for the transport
  of materials due to the nature of the
  phospholipids in the membrane

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Experimental plan/method
You should be able to answer yes to ALL of the
following questions.
YES NO
Has the independent variable been identified?
Has the dependent variable been identified?
Has a prediction, aim or hypothesis been stated?
Have at least 2 other variables been identified and controlled?
Is there a description of how all other variables are going to be measured or controlled?
Has sufficient data been collected?
Could your METHOD be followed by any other person?
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Monday 07.05.2007

• This week
• Monday
• Apple experiment writeup
• Cell structure and function
• Tuesday
• SAV ratio regulating cell transport
• Wednesday
• 2.4 Achievement standard planning day
• Friday
• 2.4 Achievement standard setup day

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Processing/Interpreting data
Has your data been presented in a well constructed table?
Has your data been processed in some way?
Are any graphs completely self explanatory?
Has a CONCLUSION been written that links the purpose of the investigation with the results obtained?
Does the DISCUSSION link your findings with the process of osmosis?
Has the EVALUATION described all sources of possible error?
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Apple experiment

• Apple experiment exemplar

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All living things are made of cells!
Living things
Viruses
Prokaryotes Before the nucleus No
nucleusSingle, circular chromosome No
organelles Small cells
Eukaryotes True nucleus Contain a
nucleus Linear chromosomes Contain
organelles Larger cells
Bacteria
Protists
Plants
Animals
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Cell organelles

• List of the most common organelles
• Nucleus
• Cell membrane
• Endoplasmic reticulum
• Golgi apparatus
• Ribosome
• Mitochondria
• Chloroplast (plants only)
• Cell wall (plants only)

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Cell structure and function

• Plant cells page 268
• Animal cells page 270
• Protists page 274
• Tasks
• Complete exercises on each page
• Use information to draw a Venn diagram
  showing the common organelles
• Complete pages 276/277 for homework

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Tuesday 07.05.2007

• Today
• Diffusion and the limits to cell transport
• Cell organelles

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Matching definitions of organelles

1. Packaging, modification and distribution of
   proteins
2. Vacuole regulating water balance in protozoans
3. Found in plant cells, a rigid structureoutside
   the cell membrane, composed of cellulose
4. Series of membranes attached to the nucleus,
   often associated with ribosomes
5. Only found in animal cells, involved in cell
   division
6. Allows autotrophic protists to sense the light
7. Contains genetic material, controls the cell
8. Hair-like projections in animal and protist cells
   thatprovide motility

1. Nucleus
2. Endoplasmic reticulum
3. Eye spot
4. Contractile vacuole
5. Cell wall
6. Golgi apparatus
7. Cillia
8. Centriole

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Matching definitions of organelles

1. Packaging, modification and distribution of
   proteins
2. Vacuole regulating water balance in protozoans
3. Found in plant cells, a rigid structureoutside
   the cell membrane, composed of cellulose
4. Series of membranes attached to the nucleus,
   often associated with ribosomes
5. Only found in animal cells, involved in cell
   division
6. Allows autotrophic protists to sense the light
7. Contains genetic material, controls the cell
8. Hair-like projections in animal and protist cells
   thatprovide motility

1. Nucleus
2. Endoplasmic reticulum
3. Eye spot
4. Contractile vacuole
5. Cell wall
6. Golgi apparatus
7. Cillia
8. Centriole

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Cell size and cell transport page 292

• Diffusion limits the size of cells
• The larger a cell, the smaller thesurface area
  volume ratio
• For diffusion to work for getting substances in
  and out of cells, the SAV ratio needs to be
  large
• Surface area provides a surface for molecules
  to diffuse in and out
• Volume larger volumes make it harder for
  molecules to diffuse through the entire cell

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Wednesday 16.05.2007

• Today
• Ecology topic test, exemplars
• Introduction to enzymes
• Friday
• Enzymes and their regulation
• Next week
• Microscopes
• respiration and photosynthesis
• DNA replication

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A/M/E whats the difference?

• Grade the answers from the Ecology test
• In groups, highlight the parts of the answers
  that you think are good for some reason
• Write down what you think is different between
  the A/M/E answers

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The stuff of life

• Components of the cell are made of four different
  basic things
• Nucleic acids (DNA, RNA)
• Carbohydrates (glucose, sucrose, starch,
  cellulose)
• Lipids (phospholipids, triacyl glycerides)
• Proteins

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Metabolic reactions

• Metabolism is the total of all chemical reactions
  in living things
• Some reactions are anabolic they build things
  up HINT anabolic steroids build up your
  muscles
• Some reactions are catabolic they break things
  down

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Cell metabolism
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Enzymes what are they?

• Most enzymes are proteins
• Enzymes are biological catalysts
• Enzymes speed up the rate of metabolic reactions
  without being consumed in the reaction

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How do they work?

• The substance(s) that an enzyme works on are
  called the substrate
• The substrate fits into a place on the enzyme
  called the active site
• The active site is unique to that enzyme and
  specific for that substrate
• At the active site, the enzyme helps catalyse
  reactions between the substrate molecules

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Models of enzyme action
Specific 3D shape
Active site
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Enzymes have a specific shape

• Enzymes have a unique 3-dimensional shape
• Each enzyme is specific for a particular chemical
  reaction
• Anything that changes the shape of the enzyme
  destroys its catalytic activity

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Real-life examples

• Haemoglobin

Phenylalanine
Tyrosine
Melanin
para-Hydroxyphenylpuruvate
Homogentisate
Phenylalanine hydroxylase
4-Malylacetoacetate
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Controlling enzyme activity

• The rate of an enzyme-catalysed reaction is
  sensitive to the following things
• Enzyme concentration
• Substrate concentration
• Temperature
• pH
• Enzymes are optimised for a particular
  temperature and pH

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Enzyme activity

• Temperature is an important factor
• controlling enzyme activity
• Think of cooking a poached egg!

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Enzyme activity

• pH is an important factor controlling enzyme
  activity

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What happens to the enzyme?

• Enzyme activity is decreased in the wrong
  temperature or wrong pH environment
• The enzyme can become denatured, where its
  structure breaks down. This happens, in
  particular, at high temperature

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Monday 21.05.2007

• Today
• Introduction to microscopes
• Viewing material with a microscope
• Drawings in biology

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A quick quiz

• Name three organelles of plant cells that you
  would not find in animal cells
• What is the term for the transport of substances
  in and out of cells against a concentration
  gradient?
• In your own words, how do enzymes speed up
  metabolic reactions?

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A quick quiz

• Name three organelles of plant cells that you
  would not find in animal cells
• Cell wall, large vacuole, chloroplasts
• What is the term for the transport of substances
  in and out of cells against a concentration
  gradient?
• Active transport
• In your own words, how do enzymes speed up
  metabolic reactions?
• Act as catalysts, bind specifically to substrate
  molecules through an active site and increase the
  rate of formation of products without being
  consumed

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Microscopes pages 264/265
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Specimen drawings in biology

• Use pencil only.
• Make the drawing large, it should fill up most of
  the available space (approximately 2/3 of the
  page).
• All drawings should have a heading which contains
  title, magnification (or scale), aspect (what
  direction you are looking from).
• Use continuous lines with no shading remember
  each line represents a viewable object. Use
  double lines for things like blood vessels or
  insect legs.
• Only draw what you can see.
• Place all labels to the sides with ruled lines to
  the structures that they indicate. (do not use
  arrows as this indicates flow).
• It is not necessary to draw every cell, you only
  need to draw a representative groups of them.
• Do not draw incomplete cells (unless that is all
  you see).
• Remember it is a diagram not a photo or work of
  art.

Pages 38-39, Biozone
84
Magnification factors

• Indicate how enlarged an object is
• Simply calculated by multiplying together the
  objective lens magnification factor and the
  eyepiece magnification factor
• e.g. eyepiece 10x, objective 40x
• magnification factor 10 x 40 400x

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Tasks today

• Mount a leaf of pond weed (Elodea) and practice
  biological drawing
• Mount a solution containing protozoans and
  observe them

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Tuesday 22.5.2007

• Today
• enzymes
• energy in cells
• photosynthesis and respiration

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Controlling enzyme activity

• The rate of an enzyme-catalysed reaction is
  sensitive to the following things
• Enzyme concentration
• Substrate concentration
• Temperature
• pH
• Enzymes are optimised for a particular
  temperature and pH

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Enzyme activity

• Temperature is an important factor
• controlling enzyme activity
• Think of cooking a poached egg!

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Enzyme activity

• pH is an important factor controlling enzyme
  activity

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What happens to the enzyme?

• Enzyme activity is decreased in the wrong
  temperature or wrong pH environment
• The enzyme can become denatured, where its
  structure breaks down. This happens, in
  particular, at high temperature

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Wednesday 23.05.2007

• Today
• Question about enzymes
• Re-cap Biozone information about enzymes
• Microscope work
• Biological drawings
• Onion cells, stems, staining sections
• Paramecium

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Enzymes test question

• QUESTION FIVE Enzymes.
• Enzymes are a very important set of protein-based
  molecules that act as catalysts. Enzymes are
  said to be specific and function by using a lock
  and key method. All enzymes are affected by
  changes in temperature and pH, as well as
  substrate concentration within the cell.
• (a) Without enzymes, life as we know it would not
  exist. Explain why enzymes are an important part
  of all living things.
• (b) Describe what it means by the statement that
  Enzymes are said to be specific.
• (c) An enzyme called trypsin splits a double
  amino acid chain into two single amino acids.
  Explain how the enzyme would achieve this.
  (Labelled diagrams may be used.)

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Specimen drawings in biology

• Use pencil only.
• Make the drawing large, it should fill up most of
  the available space (approximately 2/3 of the
  page).
• All drawings should have a heading which contains
  
• Title
• Magnification factor (or scale)
• Use continuous lines with no shading
• Only draw what you can see.
• Place all labels to the sides with ruled lines to
  the structures that they indicate. (do not use
  arrows).
• Draw only enough cells to give a representative
  view
• Do not draw incomplete cells (unless that is all
  you see).

Pages 38-39, Biozone
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Tasks today

• Prepare a slide of some onion cells
• Stain using iodine
• Re-visit the Paramecium, do not use the slow
  down solution
• Make a transverse section of a soft plant stem
• Prepare a biological drawing of either (a) the
  onion cells or (b) the transverse section of the
  plant stem

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Friday 25.05.2007

• Today
• Energy in metabolic reactions
• Introduction to respiration and photosynthesis
• Photosynthesis, the details

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Energy in living things page 296

• Energy for living things ultimately comes from
  sunlight and is converted into mobile chemical
  energy in glucose by plants through
  photosynthesis
• All living things use this chemical energy to
  power their metabolic reactions
• Respiration is the chemical process that releases
  the chemical energy in glucose to be used by the
  cell

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What is ATP?

• ATP is adenosine triphosphate
• It is the energy carrier of the cell, required
  to power many processes
• Many enzyme reactions require it
• Active transport processes require it
• Chemical energy in glucose has to be converted
  into chemical energy in ATP before the cell can
  use the energy

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ATP and ADP energy carriers

P
Energy stored
ATP
ADP
Adenosine
P
P
P
Adenosine
P
P
LOW ENERGY
HIGH ENERGY
Energy released
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Monday 28.05.2007

• This week
• Monday
• Photosynthesis
• Tuesday
• Experiment with enzymes
• Wednesday
• Respiration
• Friday
• Summary questions, cell biology
• Unit Standard on microscopes

100
Photosynthesis pages 300/301

• The purpose of photosynthesis is to convert light
  energy into mobile chemical energy (glucose)
• Occurs in chloroplasts
• Overall, converts water and carbon dioxide into
  glucose and oxygen
• H2O CO2 ? C6H12O6 O2

101
Photosynthesis

• The first stage of photosynthesis is called the
  light dependent phase
• Light energy is required
• Chlorophyll is required
• Occurs in the thylakoid membranes within the
  chloroplast (electron transport chain)
• Produces oxygen, ATP and reactive hydrogen atoms

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The chloroplast
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Chlorophyll

• Pigment in green plants
• Absorbs light energy
• Found in thylakoidmembranes

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Chlorophyll
105
Part one the light phase
2 H2O 2 NADP 2 ADP 2 Pi light ? 2 NADPH
2 H 2 ATP O2
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Part two the light independent phase

• Occurs in the chloroplast stroma
• Does not require light energy
• Takes ATP and uses the energy to convert CO2 and
  hydrogen into glucose using a cyclic sequence of
  reactions

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Melvin Calvin
108
Photosynthesis summary
Chemical energy (ATP)
H2O
CO2
Light dependent - Grana/thylakoid membranes -
Water converted to oxygen - Light energy
converted to chemical energy (ATP)
Light independent - Chloroplast stroma - Carbon
dioxide converted to glucose - Requires chemical
energy (ATP) - Requires reactive hydrogen
(eventually)
Reactive hydrogen (NADPH)
O2
C6H12O6
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Starter question

• QUESTION THREE Cell Processes
• Photosynthesis
• 1 Name the main organelle associated with this
  process
• 2 Write an equation for the process
• 3 Membranes play an important role in different
  stages of photosynthesis. Discuss the role of
  membranes in photosynthesis

110
Respiration pages 298/299

• The function of respiration is to break down
  energy-rich molecules to make ATP
• Overall, C6H12O6 O2 ? CO2 H2O
• There are two types of respiration
• Aerobic respiration, occurs in the presence of
  oxygen
• Anaerobic respiration, occurs in the absence of
  oxygen

111
Stages of respiration

• Step 1 Glycolysis
• Occurs in the cytoplasm
• Breaks glucose (C6) down to pyruvate (2x C3)
• Releases a small amount of energy as ATP
• Releases some reactive hydrogen
• Can occur anaerobically in the absence of oxygen
  to produce lactic acid (animals) or ethanol
  carbon dioxide (yeast and plants)

112
Aerobic versus anaerobic respiration

• Anaerobic respiration produced lactic acid
  (animals) or ethanol (plants, yeast) as a
  by-product
• Not much energy is produced by anaerobic
  respiration

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The mitochondrion

• Mitochondrion (singular) or mitochondria (plural)
  have a specific internal structure important to
  respiration

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Stages of respiration

• Step 2 The Krebs Cycle
• Occurs in the matrix of the mitochondrion
• Occurs as a cycle of reactions
• Carbon dioxide is produced as a waste product
• Some ATP is formed
• Reactive hydrogen atoms are produced

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The Krebs cycle
116
Stages of respiration

• Step 3 The electron transport chain
• Occurs on the cristae of the inner membrane of
  the mitochondrion
• Energetic electrons flow between proteins in the
  membrane
• The energy of the electrons is converted to ATP
• Lots of ATP is produced
• At the end of the process, oxygen (O2) is
  converted to water (H2O)

117
Wednesday 06.06.2007

• Today
• Summary of respiration and photosynthesis
• Overview of the cell biology topic
• DNA structure

118
Starter questions

• List FOUR organelles that can be found in plant
  cells and animal cells.
• Muscle cells need to be flexible and elastic to
  allow them to function correctly. Explain how
  this is possible in animal cells, but less likely
  in plant cells
• Muscle cells use a lot of energy for the fibres
  to be able to contract and relax as opposed to
  plant cells.
• (a) Name the cell organelle you would expect to
  see in larger numbers in muscle cells
  compared to plant cells.
• (b) Explain your answer above.

119
Task comparision chart
3 major steps
Both have electrontransport chains
Photosynthesis
Respiration
2 major steps
120
Comparing photosynthesis and respiration
Both require membranes P.S. thylakoid Resp
inner mitochondrialmembrane
3 major steps
Occurs in chloroplasts
Occurs in cytoplasmand mitochondria
Produces O2 Consumes H2O
Both have electrontransport chains
Photosynthesis
Respiration
Both involve energy conversion
Converts lightenergy to mobilechemical energy
Produces H2O Consumes O2
Both involveATP and reactivehydrogen atoms
Converts mobile chemical energy to ATP
2 major steps
121
Cell Biology Overview
Animal
Plant
Cell organelles
Eukaryotic cells
Protists
Cell Specialisation
Cell Types and Structures
Prokaryotic cells
Cell Biology
DNA structureand replication
Cell Processes
Cell Transport
Enzymes
Energy in Cells
SAV ratio
pH
Active transport
Photosynthesis
Temp.
Osmosis
Respiration
Passive transport
122
DNA the basic facts, page 302

• DNA is deoxyribose nucleic acid
• DNA is found in the nucleus of eukaryotic cells
• DNA is packaged with proteins called histones to
  form chromatin
• DNA in an organism is divided into lengths called
  chromosomes
• Chromosomes themselves are divided into genes
  that carry information for making proteins

123
Friday 08.06.2007

• Today
• DNA structure
• DNA replication
• Genes and protein synthesis
• Starter questions
• What are the 46 long lengths of DNA in human
  cells called?
• What are the rules for pairing up the four DNA
  bases?
• What is the function of DNA in the cell?

124
Packaging DNA
125
Chromosomes
126
The structure of DNA

• DNA is composed of building blocks called
  nucleotides
• Sugar (deoxyribose)
• Phosphate
• Base (Adenine, Thymine, Cytosine, Guanine)
• DNA is a double helix containing two strands of
  nucleotides
• The bases match up in a specific way
• A always pairs with T
• C always pairs with G

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The structure of DNA - discovery

• 1953, Cambridge
• Watson and Crick
• A/T and G/C contents of DNA always the same
• X-ray crystallography data suggests a helix
• It has not escaped our notice that the specific
  pairing we have postulated immediately suggests a
  possible copying mechanism for the genetic
  material

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DNA structure

• DNA strands have a direction, defined by the
  position on the sugar (5 and 3)
• Each strand of the double helix runs
  anti-parallel to the other

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DNA structure
5 5 prime
3 3 prime
3 3 prime
5 5 prime
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The functions of DNA

• DNA is an information store, a master
  instruction manual for the cell
• Information for making proteins is stored as
  lengths of DNA called genes
• When a cell needs to make a particular protein,
  it reads off the relevant gene in the master
  instruction manual

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DNA replication

• DNA is always replicated prior to cell division,
  both for mitosis and meiosis
• DNA replication occurs so that new cells receive
  a complete set of correct instructions
• DNA replication is calledsemi-conservative as
  the original DNA strand becomes part of the new
  DNA strand

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The steps

• Step One
• DNA unwinds with the help of enzymes
• Step Two
• DNA strands separate
• Step Three
• Each original strand acts as a template
• New nucleotides are incorporated
• Step Four
• Two new DNA molecules are formed that are exact
  copies of the original

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DNA replication
Original strand
Replication fork
New strand
New strand
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The bare minimum!

• DNA is a double helix
• DNA is made up of nucleotides
• In DNA, A pairs with T, C pairs with G
• The strands in DNA are anti-parallel
• DNA is replicated during cell division
• DNA replication is semi-conservative

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Monday 11.06.2007

• This week
• Today
• Revision, cell biology
• Individual interviews
• Tuesday
• Revision, cell biology, your questions
• Wednesday
• Cell Biology Topic Test
• Friday
• Genetics and Evolution

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Starter question

• (a) Using the bases G, T, C and A, describe which
  base-pairs bond together.
• (b) Explain why the process of DNA replication is
  necessary for the growth of living things

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Bingo
1. Thylakoid 2. Active transport 3. Enzyme 4.
Catalyst 5. Osmosis 6. ATP 7. Mitochondria 8.
Chloroplast 9. Nucleus 10. Passive transport
11. Exocytosis 12. Endocytosis 13. Golgi
apparatus 14. Light dependent 15. Substrate 16.
Semi-permeable 17. Diffusion 18. Light
independent 19. Centriole 20. Contractile
vacuole