Title: Cell Biology
1Cell 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
2All 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
3Eukaryotic 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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6Organelles
- 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
7Example
- 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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10Homework
- 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
11Monday 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
12Organelles
- 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
13Definitions
- 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
14Organelles 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
15Organelles structure and function
MITOCHONDRIA
Site of aerobic respiration Produces much of the
ATP (energy) for the cell Two membranes
16Do Now
- Put the follwing particles in order from smallest
to largest - Molecule
- Cell
- Organ
- Tissue
- Atom
- Organelle
17Answer
- Atom smallest
- Molecule
- Organelle
- Cell
- Tissue
- Organ largest
18Organelles 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
19Organelles structure and function
RIBOSOMES
The site of protein synthesis Often found
associated with the endoplasmic reticulum
20Organelles structure and function
GOLGI APPARATUS GOLGI BODY
Modifies, packages anddistributes proteins
21Do 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.
22Organelles 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
23Organelles structure and function
CELL WALL
Specific to plants Made of cellulose Provides
support and strength
24Do Now
- Match the function to the organelle
Organelle Function
Nucleus
Mitochondria
Ribosomes
Endoplasmic reticulum
Plasma membrane
Centriole
Cytoplasm
Nucleolus
Lysosome
25Cell 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.
26Structure 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
27Structure of a plasma membrane
28Structure of a plasma membrane
29Transport of substances
30Transport processes
Active transport
Passive transport
Movement of materialsdown a concentration
gradient No energy needed
Movement of materialsagainst a concentration
gradient Requires energy
membrane
membrane
31Tuesday 01.05.2007
- Today
- Cell transport
- Osmosis
- Fair tests and experimental plans
32Examples 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
33Examples 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!
34Examples of transport
35Nerve impulses
36Large-scale transport
PHAGOCYTOSIS
37Osmosis
- 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!
38Osmosis 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
39Osmosis and plant cells
HYPOTONIC
ISOTONIC
HYPERTONIC
40Osmosis 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.
41Summary 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
42Internal 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?
43Wednesday 02.05.2007
- Today
- Writing an experimental plan
- Setting up a practice experiment
44Experimental 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?
45Organelles structure and function
NUCLEUS
Contains genetic material Controls the
functioning of the cell
46Organelles structure and function
MITOCHONDRIA
Site of aerobic respiration Produces much of the
ATP (energy) for the cell Two membranes
47Organelles 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
48Organelles structure and function
RIBOSOMES
The site of protein synthesis Often found
associated with the endoplasmic reticulum
49Organelles structure and function
GOLGI APPARATUS GOLGI BODY
Modifies, packages anddistributes proteins
50Organelles structure and function
CELL WALL
Specific to plants Made of cellulose Provides
support and strength
51Homework due Friday
- Pages 286-289, Biozone
- Notes on the structure and function of the
following organelles - Chloroplasts
- Endoplasmic reticulum
- Centrioles
- Flagellum
52Cell 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
53Structure 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
54Experimental 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?
55Monday 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
56Processing/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?
57Apple experiment
- Apple experiment exemplar
58All 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
59Cell organelles
- List of the most common organelles
- Nucleus
- Cell membrane
- Endoplasmic reticulum
- Golgi apparatus
- Ribosome
- Mitochondria
- Chloroplast (plants only)
- Cell wall (plants only)
60Cell 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
61Tuesday 07.05.2007
- Today
- Diffusion and the limits to cell transport
- Cell organelles
62Matching definitions of organelles
- Packaging, modification and distribution of
proteins - Vacuole regulating water balance in protozoans
- Found in plant cells, a rigid structureoutside
the cell membrane, composed of cellulose - Series of membranes attached to the nucleus,
often associated with ribosomes - Only found in animal cells, involved in cell
division - Allows autotrophic protists to sense the light
- Contains genetic material, controls the cell
- Hair-like projections in animal and protist cells
thatprovide motility
- Nucleus
- Endoplasmic reticulum
- Eye spot
- Contractile vacuole
- Cell wall
- Golgi apparatus
- Cillia
- Centriole
63Matching definitions of organelles
- Packaging, modification and distribution of
proteins - Vacuole regulating water balance in protozoans
- Found in plant cells, a rigid structureoutside
the cell membrane, composed of cellulose - Series of membranes attached to the nucleus,
often associated with ribosomes - Only found in animal cells, involved in cell
division - Allows autotrophic protists to sense the light
- Contains genetic material, controls the cell
- Hair-like projections in animal and protist cells
thatprovide motility
- Nucleus
- Endoplasmic reticulum
- Eye spot
- Contractile vacuole
- Cell wall
- Golgi apparatus
- Cillia
- Centriole
64Cell 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
65Wednesday 16.05.2007
- Today
- Ecology topic test, exemplars
- Introduction to enzymes
- Friday
- Enzymes and their regulation
- Next week
- Microscopes
- respiration and photosynthesis
- DNA replication
66A/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
67The 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
68Metabolic 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
69Cell metabolism
70Enzymes 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
71How 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
72Models of enzyme action
Specific 3D shape
Active site
73Enzymes 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
74Real-life examples
Phenylalanine
Tyrosine
Melanin
para-Hydroxyphenylpuruvate
Homogentisate
Phenylalanine hydroxylase
4-Malylacetoacetate
75Controlling 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
76Enzyme activity
- Temperature is an important factor
- controlling enzyme activity
- Think of cooking a poached egg!
77Enzyme activity
- pH is an important factor controlling enzyme
activity
78What 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
79Monday 21.05.2007
- Today
- Introduction to microscopes
- Viewing material with a microscope
- Drawings in biology
80A 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?
81A 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
82Microscopes pages 264/265
83Specimen 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
84Magnification 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
85Tasks today
- Mount a leaf of pond weed (Elodea) and practice
biological drawing - Mount a solution containing protozoans and
observe them
86Tuesday 22.5.2007
- Today
- enzymes
- energy in cells
- photosynthesis and respiration
87Controlling 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
88Enzyme activity
- Temperature is an important factor
- controlling enzyme activity
- Think of cooking a poached egg!
89Enzyme activity
- pH is an important factor controlling enzyme
activity
90What 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
91Wednesday 23.05.2007
- Today
- Question about enzymes
- Re-cap Biozone information about enzymes
- Microscope work
- Biological drawings
- Onion cells, stems, staining sections
- Paramecium
92Enzymes 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.)
93Specimen 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
94Tasks 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
95Friday 25.05.2007
- Today
- Energy in metabolic reactions
- Introduction to respiration and photosynthesis
- Photosynthesis, the details
96Energy 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
97What 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
98ATP and ADP energy carriers
P
Energy stored
ATP
ADP
Adenosine
P
P
P
Adenosine
P
P
LOW ENERGY
HIGH ENERGY
Energy released
99Monday 28.05.2007
- This week
- Monday
- Photosynthesis
- Tuesday
- Experiment with enzymes
- Wednesday
- Respiration
- Friday
- Summary questions, cell biology
- Unit Standard on microscopes
100Photosynthesis 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
101Photosynthesis
- 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
102The chloroplast
103Chlorophyll
- Pigment in green plants
- Absorbs light energy
- Found in thylakoidmembranes
104Chlorophyll
105Part one the light phase
2 H2O 2 NADP 2 ADP 2 Pi light ? 2 NADPH
2 H 2 ATP O2
106Part 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
107Melvin Calvin
108Photosynthesis 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
109Starter 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
110Respiration 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
111Stages 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)
112Aerobic 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
113The mitochondrion
- Mitochondrion (singular) or mitochondria (plural)
have a specific internal structure important to
respiration
114Stages 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
115The Krebs cycle
116Stages 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)
117Wednesday 06.06.2007
- Today
- Summary of respiration and photosynthesis
- Overview of the cell biology topic
- DNA structure
118Starter 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.
119Task comparision chart
3 major steps
Both have electrontransport chains
Photosynthesis
Respiration
2 major steps
120Comparing 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
121Cell 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
122DNA 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
123Friday 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?
124Packaging DNA
125Chromosomes
126The 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
127The 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
128DNA 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
129DNA structure
5 5 prime
3 3 prime
3 3 prime
5 5 prime
130The 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
131DNA 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
132The 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
133DNA replication
Original strand
Replication fork
New strand
New strand
134The 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
135Monday 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
136Starter 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
137Bingo
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