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Transcript
Cell Biology Revision
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
Animal Cell
Nucleus
Cell
membrane
Cytoplasm
Mitochondria
Ribosomes
Plant Cell
Chloroplasts
Mitochondria
Vacuole
Cell
membrane
Cytoplasm
Nucleus
Cell wall
Ribosomes
Plant Cell
Mitochondria
Chloroplasts
Vacuole
Cell membrane
Cytoplasm
Nucleus
Cell wall
Ribosomes
Chloroplasts are found in leaf cells,
they are NOT found in root cells!
Yeast/ Fungal Cell
Mitochondria
Cytoplasm
Cell wall
Cell
membrane
Vacuole
Nucleus
Ribosomes
Bacterial Cell
Ribosomes
Cytoplasm
Plasmid
Free floating
DNA
Cell
membrane
Cell wall
Cell Part
Function
Cells
Ribosomes
Site of protein synthesis.
All
Cytoplasm
Where chemical reactions occur.
All
Cell membrane
Controls what enters and leaves
the cell.
All
Nucleus
Controls all cell activities.
Animal, plant and yeast
Mitochondria
Site of aerobic respiration.
Animal, plant and yeast
Cell wall
Supports the cell.
Plant, bacteria and yeast
Vacuole
Stores cell sap.
Plant and yeast
Chloroplasts
Site of photosynthesis.
Plants only
Passed naturally between
Plasmids
bacteria. Extra circular piece of
DNA.
Free floating DNA Genetic material that codes for
protein.
Bacteria only
Bacteria only
Quick Quiz 1
1. Which cell structure controls all cell activity?
2. Which cell structure is found in plant leaf cells
but not yeast cells?
3. Which type of cell does not store its DNA
inside a nucleus?
4. What is the function of the ribosomes?
5. What is the function of the mitochondria?
6. Which 3 cell structures are found in all cell
types?
7. What is the function of the cell wall?
8. Which structure stores cell sap in plants and
yeast cells?
Quick Quiz 1 - answers
1. Nucleus
2. Chloroplasts
3. Bacteria
4. Site of protein synthesis
5. Site of aerobic respiration
6. Cell membrane, cytoplasm & ribosomes
7. Supports the cell
8. Vacuole
Problem Solving
Calculating cell size
Calculate the average cell length and
breadth using the diagram below.
Average cell
length;
Average cell
breadth;
5 cells across
2mm
10 cells across
2mm
2/5 = 0.4mm
2mm
2/10 = 0.2mm
Total Magnification
Eyepiece
Lens
Objective
Lens
Eyepiece
Lens
Objective
Lens
Total
Magnification
10x
10x
100x
5x
20x
10x
50x
20x
800x
30x
900x
10x
400x
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
Membrane Structure
protein
phospho
-lipid
Selectively Permeable Membrane
• Only small molecules can pass through
• Larger molecules cannot fit through.
Small
O2, CO2, glucose, water.
Large
Starch/protein/fat
(need to be digested)
Transport across Membrane
1. Passive Transport (diffusion/osmosis)
2. Active Transport
Passive Transport
• Does not require energy to cross membrane.
• Molecules move from high concentration to low
concentration, down a concentration gradient.
High concentration
Low concentration
Concentration Gradient
• Difference between high & low
concentration.
• Steeper difference – quicker diffusion rate.
Real Diffusion Examples
Slow process – happens naturally.
No energy required.
Air sac - gas
exchange
Stomata in leaves
– gas exchange
Small intestine
- villus
Air sac gas exchange
Air sac
Blood capillary
O2 IN
CO2 OUT
Blood capillary
Air sac
Gas Exchange Stomata (plants)
CO2 IN
Air
Mesophyll cells
O2 OUT
Mesophyll cells
Air
Small Intestine - Villus
Fatty acids & glycerol
Lacteal
Glucose & Amino Acids
Blood capillary
Diffusion in Respiration
Glucose
Water
Oxygen
Carbon
Dioxide
IN
OUT
Osmosis
Movement of water from HIGH water
concentration to LOW water concentration
through a selectively permeable membrane.
Osmosis in animal cells
Placed in
strong sugar
solution
Water moves OUT
CELL SHRIVELS/SHRINKS
Placed in
pure water
Water moves IN
CELL BURSTS
Osmosis in plant cells
Pure water
Water IN
TURGID
1% Sucrose
No water
movement
95% Sucrose
Water OUT
PLASMOLYSED
Osmosis Exam Tips!
Animal cells
Burst/shrink ONLY
Plant cells
Turgid/plasmolysed
ONLY due to cell
wall
Osmosis is the movement of water.
A – 2% salt
B – 5% salt
A – 98% water
B – 95% water
(movement from high water to low water
= movement from A to B)
Problem Solving
Potato Osmosis Experiment
Changed variable
Concentration of sugar solution
Measured variable
% change mass
Variables kept constant
Volume of solution
Temperature
Type of potato
Surface area of potato
•
•
•
Blotted potato to remove excess water
Used more readings to increase reliability
Used percentages as starting mass not the same.
Graph
Percentage Change in mass
Change/original number x 100
Potato weighed 1g now weighs 3g –
calculate the percentage change in
mass?
Percentage Change in mass
Potato weighed 1g now weighs 3g –
calculate the percentage change in mass?
Change = 3-1 = 2g
Change/original x 100
2/1 x 100 = 200% increase
Active Transport
The movement of molecules from a
region of low concentration to a region
of high concentration against a
concentration gradient
Active Transport – key features
1. Direction
Low
High
2. Specific
Different conc. of different ions inside cell
e.g. K, Na, Mg
3. Mitochondria
Large number needed to produce ATP for
active transport
Concentration Gradient
• Going against the gradient
(low to high)
• Moving along/down gradient
(high to low)
Diffusion
High to low concentration
Active Transport
Need
energy
Low to high concentration
needs energy (ATP)
ATP = Energy
What is ATP???
ATP = Adenosine Tri Phosphate.
Energy made during respiration
adenosine
Pi
Pi
Pi
Summary
Breakdown releasing energy.
ENERGY!!
ATP
(high energy
state)
Build up requiring energy.
ADP + Pi
(low energy
state)
Active Transport
ATP
ADP
P
High
ATP uses
proteins on
the membrane
to carry
molecules
across.
LOW
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
Recap S3 Diploid Body Cell
2 sets of 23 chromosomes
= 46 chromosomes
Cell division = mitosis
1 diploid cell
2 diploid cells
Location of mitosis?
Nucleus
Cytoplasm
Where DNA is found!
In the nucleus
Cell
membrane
Mitochondria
Ribosomes
Need for Mitosis
Unicellular
Multicellular
Reproduction
Growth and Repair
DNA & Chromosomes
• DNA
Gene
Chromatid
Chromosome
Stage 1
Chromosomes in the
nucleus coil up,
replicate and
become visible on
staining.
Stage 2
Chromosomes now
consist of two identical
chromatids joined by a
centromere.
Chromatid
Chromatid
Stage 3
Equator
Chromosomes line up
along the equator of
the cell and spindle
fibres form.
Spindle fibres
Stage 4
Spindle fibres pull
identical chromatids
towards opposite
ends of cell
Stage 5
Nuclear membranes
reform.
Cytoplasm divides.
Stage 6
2 diploid daughter
cells which contain the
same number of
chromosomes as the
original cell.
They are identical to
each other and the
original cell.
Problem Solving
Mitosis Problem Solving
• A bacterial cell divides every 4
minutes. How many bacteria are
present after 24 minutes?
Mitosis Problem Solving
0 mins – 1 bacteria
4 mins – 2 bacteria
8 mins – 4 bacteria
12 mins – 8 bacteria
16 mins – 16 bacteria
20 mins – 32 bacteria
24 mins – 64 bacteria
Mitosis Importance
It is important that every new cell has
exactly the same number of
chromosomes (46) so that no genetic
information is lost.
Cell Culture
Growing cells (mitosis) on a liquid or
solid media
Types of Cultures
Agar slopes (solid) Broth nutrient(liquid)
Aseptic Techniques
Promote cell division (growth) of 1
micro organism (prevent
contamination from other microbes).
Aseptic Techniques
Examples;
•
•
•
•
•
•
Wearing a lab coat
Washing hands
Disinfect the work surfaces
Open petri dish lid for a very short time
Flame the inoculating loop
Use an autoclave to sterilise equipment
Fermenters
• Large containers used in industry to
grow specific micro organisms by
mitosis for useful products.
Fermenters
Computers monitor the conditions to
ensure optimal...
A) temperature
B) oxygen
C) pH
D) nutrient level
Fermenters
Cleaned by heating to 120 degrees
at high pressure for 20 minutes to
prevent contamination.
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
Chromosomes & DNA
Chromosomes and their genes are made
of a molecule called DNA.
Each chromosome
is a very long molecule
of tightly coiled DNA.
The DNA molecule
looks like a
twisted ladder this
spiral shape is
called a
DOUBLE HELIX
DNA Chromosome Numbers
All cells contain 46 chromosomes with 2
exceptions
1. Gametes (sex cells) contain half the DNA
- 23 chromosomes (haploid)
2. Red blood cells
- No DNA
DNA stands for deoxyribonucleic acid.
What does DNA do?
Genetic code for protein
molecules.
DNA nucleotide
3 parts
phosphate
base
sugar
DNA Bases
The double helix ‘ladder’ of a DNA molecule
is held together by complementary bases.
Adenine (A)
Cytosine (C)
Thymine (T)
Guanine (G)
Complementary Base Pair
Activity
Problem Solving
DNA Calculation
• If there are 2000 bases and
10% are Adenine – how many
Guanine bases are there?
DNA Calculation
• 10% A
• 10% T
= 20% A & T
80% G & C
40% = C
40% = G of 2000 = 40/100 x 2000
= 800 G bases
Proteins
Proteins are made up of different
sequences of amino acids.
20 different types of amino acids –
many different protein sequences.
3 DNA bases
1000’s Amino Acids
1 amino acid
protein
DNA and Proteins
The sequence of bases on DNA
determines the sequence of amino acids
in a protein - 3 bases 1 Amino Acid
A
A
T
C
T
G
C
A
T
G
G
C
A
T
C
A
G
T
Coding for protein
Different sequence of bases on DNA n
produces a different sequence of amino acids
in a protein.
A A
T
C
T
G
C
A
T
G
G
C
A
T
C
A
G
T
Building a protein
DNA is only found in the
nucleus.
Proteins are assembled
using amino acids at
structures called ribosomes
Messenger RNA (mRNA)
DNA instructions in nucleus
Messenger RNA carries a
copy of the genetic code
from the DNA to the
ribosomes.
Assembly of amino
acids at ribosomes
DNA  mRNA  Protein
Same bases as DNA except mRNA has no
T bases - Swap T for Uracil (U) bases
DNA code
AAC GTA
mRNA code AAC GUA
DNA base sequence
Amino Acid sequence
Structure of protein
Function of protein
Proteins
Needed for growth and repair.
1. Hormones - Carry chemical messages in
the blood.
2. Enzymes – act as biological catalysts to
speed up chemical reactions inside
cells.
3. Antibodies – help to protect the body
against infection.
4. Structural – give strength and support
to cell membranes.
5. Receptors – help cells recognize
specific substances.
What do enzymes do?
Enzymes are biological catalysts – they
speed up reactions but are not used up.
Enzymes allow reactions to happen
sufficiently quickly at relatively low
temperatures (37 °C).
Enzymes are specific – they will only
react with one type of substrate.
Lock and Key Mechanism
SUBSTRATE
PRODUCT
ACTIVE
SITE
ENZYME
ENZYME- SUBSTRATE
COMPLEX
Example of Enzymes
Degrading
Synthesising
Catalase
Phosphorylase
Amylase
Lipase
Pepsin
Synthesizing
Small
molecules
Large molecule
Degrading
Large molecule
Small
molecules
Catalase enzyme
• Hydrogen peroxide
(substrate)
water + oxygen
(products)
Amylase enzyme
• Starch
(substrate)
maltose
(products)
Pepsin (stomach)
Protein
Amino Acids
Lipase
Fat
Fatty acids + glycerol
**Phosphorylase**
Only found in plants
Glucose 1 - Phosphate
Starch
Factors affecting Enzymes
1. Temperature
2. pH
Describe what is happening at
points A,B,C and D.
Effect of temperature – on human
enzymes
A - rate of reaction increases very
slowly
B- rate of reaction increases with
temperature
C - Optimum temperature of 37˚C
D- Enzyme denatured above 50˚C and
stops working
Pepsin
amylase
2
7
catalase
Enzyme activity
9
1
2
3
4
5
6
7
pH
8
9
10
11 12
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
Genetic Engineering
Transfer of a gene from 1 organism (human)
to another (bacteria)
Uses
Insulin
(diabetes)
Human Growth Hormone
(dwarfism)
1. Genetically Modified Plants
Tomatoes which keep fresh longer
and do not spoil quickly.
2. Productivity of Rice
Real Life Applications
• Made in fermenters
• Can be expensive
Bacteria need optimum
• pH
• oxygen
• temperature
• nutrient (food) levels.
Why use a Bacterial cell?
1.
DNA is loose in the cytoplasm,
making it easy to modify.
2. Bacteria grow & replicate quickly
by mitosis
3. Plasmids enable foreign DNA to
produce a useful protein.
.
Human cell
Chromosome
Gene
Bacterial cell
Product
Plasmid
Stage
1
2
3
4
5
6
Description
Gene is located on the human
chromosome
Gene is removed from the chromosome
using enzymes
Plasmid removed from bacterial cell and
cut open
Gene is inserted into plasmid
Plasmid is inserted into bacterial cell to
create a GM organism
Bacterial cells multiply and produce
product
Human cell
Chromosome
Gene
Bacterial cell
Product
Plasmid
Stage
1
2
3
4
5
6
Description
Gene is located on the human
chromosome
Gene is removed from the chromosome
using enzymes
Plasmid removed from bacterial cell and
cut open
Gene is inserted into plasmid
Plasmid is inserted into bacterial cell to
create a GM organism
Bacterial cells multiply and produce
product
Advantages of Genetic
Engineering
1.
Large quantities can be produced.
2.
Fast process
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
Summary
Photosynthesis
Plants make their own food (glucose) using
light!
Photosynthesis
2 stages
1. Light dependent stage
2. Carbon fixation
CO2
Glucose (C6)
Energy Conversion
Light energy
Chemical energy
(ATP)
How?
Chlorophyll (in chloroplasts)
traps the light energy.
Light Dependent Stage
Fill in the Blanks
Carbon Fixation
Series of enzyme controlled reactions.
CO2
Glucose
Need H2 & ATP from Light Dependent Stage
Carbon Fixation
Uses of Glucose
• 1. Glucose for Respiration
(use chemical energy to make ATP)
• 2. Converted into larger carbohydrate
molecules
Starch
(energy storage)
Cellulose
(part of cell wall)
Testing Leaf for Starch
The Need for Light
Foil keeps
out the light
Results – The Need for Light
No starch present
No photosynthesis
Measuring Photosynthesis
3 ways
• O2 produced/ time
• CO2 used/time
• Dry mass of carbohydrate
produced/time
Limiting Factor
A factor that increases the rate of
a reaction if it is increased.
Rate of photosynthesis (units)
Light Intensity
limiting
30
Light Intensity
no longer limiting
20
10
0
0
10
20
Light Intensity (units)
Problem Solving
Limiting factor at point...
P = temperature
Q = carbon dioxide concentration
R = light intensity
Key Areas
1.
2.
3.
4.
5.
6.
7.
Cell Structure & Function
Diffusion, Osmosis & Active Transport
Mitosis & Cell Culture
DNA & Proteins (enzymes)
Genetic Engineering
Photosynthesis
Respiration
What is respiration?
The process by which chemical energy
(ATP) is released during the breakdown of
food, such as glucose.
When food is burned, its chemical energy
is released rapidly as heat and light.
In a living cell, the chemical energy is not
released as quickly. This helps to protect
the cell.
Chemical energy in food released
through a series of enzyme
controlled reactions.
Respiration = making energy (ATP)
an energy
store
Adenosine
Pi
Adenosine
triphosphate
Pi
Pi
ATP
Adenosine
Pi
Pi
Pi
Made from…
ADP
+
Pi
Adenosine
Pi
Pi
Pi
(Adenosine diphosphate)
(Inorganic phosphate)
Role of ATP;
Transfers chemical energy from food
to other reactions.
• Muscle
contraction
• Protein
synthesis
• DNA replication
• Mitosis
• Nerve impulse transmission
• Active transport
Breakdown releasing
energy.
ATP
(high
energy
state)
ENERGY!!
Build up requiring
energy.
ADP + Pi
(low energy
state)
CO2 +
water
Respiration
Glucose +
oxygen
energy
ATP
Amino acids
Chemical energy
transfer
energy
ADP +
Pi
Work
Protein
Types of Respiration
1. Aerobic Respiration –requires oxygen
Location - mitochondria
2. Fermentation – does not require oxygen
Location – cytoplasm
Aerobic respiration
Very active cells (muscle, sperm,
etc) have lots of mitochondria &
therefore can produce lots of
energy that it needs.
Aerobic respiration
glucose
+ oxygen
Raw
materials
energy
+ CO2 +
Products
water
1.
Glycolysis
– occurs in
1x
glucose
the
cytoplasm
2 ATP
Pyruvate
2. Aerobic
+O
2
36 ADP + Pi
respiration
– occurs in
mitochondria
2 ADP + Pi
36 ATP
CO2
+
Water
Step 1 Glycolysis
1 x glucose
2 ADP + Pi
 Splitting of Glucose
 Location – cytoplasm
2 ATP
Pyruvate
 Does not require oxygen
 Turns 1 glucose molecule (6c) into 2
pyruvate molecules (3C) and produces 2
molecules of ATP.
Step 2 – Aerobic
respiration
Pyruvate
+O
2
 Location – mitochondria
36 ADP + Pi
 Requires oxygen (aerobic)
36 ATP
CO2
+
Water
 Turns the pyruvate molecules into CO2, water
and produces 36 molecules of ATP.
Aerobic respiration summary
1 x glucose
2 ADP + Pi  Glucose is broken down
2 ATP
Pyruvate
+
O2
 O2 is required
 1 glucose releases 38
ATP
36 ADP + Pi  Produces CO2 and water
36 ATP
CO2
+
 Glycolysis occurs in
cytoplasm, aerobic
Water
respiration completed in
the mitochondria.
Aerobic
Respirometer experiment
respiration –
common exam
question!!!
Experiment
to measure
respiration
rate (i.e. the
volume of O2
consumed per
unit of time).
Oxygen drawn up the tube – measured in
mm per min
Q. Why use a chemical such as sodium
hydroxide?
A. To absorb CO2 that is produced.
Q. How would you set up a control?
A. Exact same set up but with a dead worm
(no respiration).
Q. What variables would need to be kept
constant?
A. Temperature, diameter of tube, volume of
chemical.
Fermentation
animals
Respiration in the
absence of O2.
lactic acid + ENERGY
glucose
plants and
yeast
ethanol + CO2 + ENERGY
Fermentation in animals
1 x Glucose
2 ADP + Pi
Pyruvate
+
Lactic acid
2 ATP
Fermentation in plants and yeast
1 x Glucose
2 ADP + Pi
2 ATP
Alcohol builds
up & kills
plant/yeast.
Pyruvate
Ethanol
+ CO2
Respiration summary;
Net
energy
Location
Products
Aerobic
Fermentation
38 ATP
2 ATP
Cytoplasm &
Cytoplasm
mitochondria
CO2 & water Animal – lactic acid
Plants – ethanol &
CO2