2.

1 Organisms are made up of Cells

*All living organisms are made up of units called CELLS. Some take on specialised
functions–but all cells have certain common features.

Animal Plant
Cell membrane Cellulose cell wall
Cytoplasm Vacuole
Nucleus Chl oroplast

*The nucleus of an animal cell is seen

better when stained with methylene
blue. Plant cells in seen better when
stained with iodine solution.
Structure of an Animal Cell Measured length
Vacuoles Magnification =

Actual Length
(Small & Temporary)
Cytoplasm
↑ Glycogen:
Storage form of
I
Secretory Vesicles:

..
carbohydrates.
Contains cell products
.....
ex) horomones,
enzymes 0

I
Cell membrane:
I Nucleus:
Contains genetic
Surrounds the cytoplasm material ex) DNA,
and controls entry and exit. chromosomes
-
Structure of a Plant Cell

Cytoplasm
(Contain
water and
dissolved
substances)
8500 Large
O

Chloroplasts
(Contain permanent
vacuole Starch Cellulose Cell Wall
pigments called (feely permeable to
chlorophyll) water and dissolved
Structures within the Cytoplasm substances)

Mitochondria 20
Nucleus

080
Rough Endoplasmic Reticulum
 Mitochondria • Made up of membranes

&
#
that provide a large
surface area for *
aerobi
-
-
c respiration.
• Like powerhouses
• Muscle cells, nerve cells,
and liver cells have
many mitochondria.
2.2 The Organisation of Living Organisms
*Large Organisms are MULTICELLULAR. = They are SPECIALISED.
wh

Appearance Function

Red- • Transportation of oxygen from

Blood the lungs to tissues
Cell • Has NO NUCLEUS for more
space for haemoglobin
↑

fl • Has a layer of cilia which move and

Ciliated push mucus
Cell • The muscus transports trapped
④
dust and microbes when pushed by
cilia.

Motor
Nerve
Cell
For •
•
Conducts Nerve Impulses.
The cell has a long fibre along which
impulses travel and a many-branched
ending which connect with other cells.
37.
& "
Root • Absorbs minerals and water from soil
Hair • Has a long extension which increases the
Cell surface area for more absorption of
materials

• Transports water and supports the

jjp,
Xylem plant
Vessel • This cell has NO CYTOPLASM, NO END
WALL
• This lets water pass freely and cells to
create a continuous tube.
Specialised Cells Combine to form Tissues: Cells with similar structures or functions
are massed together to form tissues.

Tissues combine to form organs: several tissues combine to form an organ. An organ
is a complex structure with a particular function.

Organs combine to form organ systems: organs work together to form a particular
task. These organs form an organ system.

ogun
57.
1 di
10
cell

A
Fig Organ
 nucleus ciliatedpine,unge a
Questions
1. Organelle, cell, tissue, organ, organ system 3
2. Micrometre, mil imetre, metre, kilometre 50 micrometres = 50 10 = 0.05mm -

3. a) The epithelial cell has no cell wall while the palisade cell has a cellulose cell wall. Also,
the palisade cell has a vacuole and cytoplasm while the epithelial cell does not.
However, they both have a nucleus, a cell membrane, and mitochondria. They have
this difference because the epithelial cell is an animal cell while the palisade cell is a
plant cell.
b) i) 1:35 1.8: x:.63Nm iii) 1:12 2.1:x
= =

Zum
i.25.

ii) 1:35
2.6:x:-9pm iv) 1:35 0.5:x:.17.50m
=

1) I: R 0.2:x
2.4um
=

:.

4. ~
5.
~ 6
~
3
~
V I

~ ~ 4
w
5
w
v
~ 7
~
2

6. a. i) D i ) contains genetic material and controls the cell.

b. i) C, E i ) E
7. a. A b. Cell wall, cilium, chloroplast
8. a. E b. A c. D d. C e. B
9. a. Large numbers of cells that have the same structure and function are grouped
together to form tissues, for example, epithelium.
Several separate tissues may be joined together to form an organ which is a complex
structure capable of performing a particular task with great efficiency. In the most
highly developed organisms, these complex structures may work together in organ
systems, for example the digestive system in humans in responsible for the removal of
the waste products of metabolism.
b. The structure of cells may be highly adapted to perform one function, i.e. the
cells may become specialised. One excellent example is the red blood cell which is highly
adapted to carry oxygen in mammalian blood. If the different cells, tissues and
organs of a multicellular organsim perform different functions they are said to show
movement. One consequence of this is the need for close co-ordination between
different organs – this function is performed by the brain and the organ systems in
mammals.
c. In plants, an example of a cell highly specialised for photosynthesis is the palisade
cell which contains many chloroplasts. These cells are located in the organ called the
leaf which also contains other tissues such as epidermis which limits water loss and
vascular tissues which transports water and mineral ions to the leaf.
 3. 1 Movement in and out of cells: Diffusion
*The cell cytoplasm is surrounded by a cell surface membrane. This acts as a boundary
between the cell contents and its surroundings.
Materials can pass through cells by:
• Diffusion
• Osmosis
• Active Transport

Diffusion - 'mixing molecules'

The particles collide often when they are concentrated so they tend to diffuse. The
random movement of the particles is due to its own kinetic energy. If there is an area
of high concentration or an area of low concentration, we say there is a concentration
gradient between regions. Diffusion is:
• the net movement of molecules within a gas or liquid
• from a region of high concentration to a region of lower concentration (down a
concentration gradient)
• as a result of their random movement
• until an equilibrium is reached

Partial y permeable membranes

Sometimes the particles are too big, or they have the wrong electrical charge on them,
or the chemical composition of the membrane prevents them passing across.
11

Partial y Permeable membrane

Diffusion and life processes - Living organisms' adaptations to
speed up diffusion

Diffusion distances are Concentration gradients

-

are maintained Diffusion surfaces are large

Short
the membranes in glucose molecules that the surface of the
the lungs, for cross from the gut into placenta, for example, is
example, are very the blood, for example, highly folded to increase the
thin so that are quickly removed by surface area for the
oxygen and carbon the circulating blood so diffusion of molecules
dioxide can diffuse that their concentration between a pregnant female
between the does not build up and and the developing fetus in
blood and the lung equilibrium is not reached. her uterus.
air spaces.

*Many life processes depend on diffusion to move substances around. Diffusion has no
'energy cost' to a living organism.
 3.2 Movement in and out of cells: Osmosis
Osmosis is a special case of diffusion
The chemical processes in living cells always take place in a form of a solution. A solution is
made up of a solvent (the dissolving fluid) and a solute (the particles dissolved in the
solvent). In organisms, the solvent is water and the solution is called an aqueous solution.
Living cells are separated from their surroundings by the partial y permeable cell surface
membrane.
L- Water can move from the right to the left because
there is a lower concentration of water molecules.

This particular diffusion process is called osmosis. N

-
-

Osmosis can be defined as:

• the diffusion of water molecules
• From a region of higher concentration of water
molecules to a region of lower concentration of
water molecules
• down a water potential gradient
• Through a partial y permeable membrane
 Cells and osmosis
A cell is surrounded by a partial y permeable membrane, and water may cross this
membrane easily. If a cell is placed in a solution of lower water potential, water leaves the
cell by osmosis. If the cell is placed in a solution of higher water potential, water enters by
osmosis.
Plant cells and osmosis
If water enters a plant cell by osmosis, the cytoplasm wil swell but only until it pushes
against the cellulose cell wall, as shown below.

If water leaves a plant cell by osmosis, the cytoplasm wil shrink but the cellulose cell
wall wil continue to give some support. Plant cells rarely suffer permanent damage
through the loss of water

so 0000
Flaccid (floppy)

Animal cells and osmosis

Normal Turgid (Firm)

Osmosis is potential y damaging to animal cells, and animals have mechanisms to keep the
body fluids at the same water potential as the cytoplasm of cells. In mammals, the
kidney plays a vital part in this process of osmoregulation.
 5 C.
In a solution of lower In a solution of the In a solution of higher water
water potential- same water potential-the cell takes in
shrinks and becomes potential- equilibrium.
mo water and swells, eventually
crenated.
m bursting. (Haemolysis). The
ma

'ghost' of a red blood ; just

the membrane is left.

3.2 Movement in and out of cells: Active Transport

Active transport requires energy to move materials.
Active transport:
• Can move molecules against a concentration gradient
• Requires energy*
• Involves protein carriers in membranes

0 particle recognised by 0

proteienace
carer
membrane
0
o
O

a
⑦
⑥
Energy
2
Respiration supplies
1. i) Turgid means the state when plant cells are fully inflated by water.
i ) If the cell loses turgor, it loses its firmness and turn flaccid.
i i) Beaker A
iv) chip B
v) the chip would be straight. The water would be absorbed by the chip for the
water concentration to be in equilibrium and the potato cells would become turgid.

2. a)

50 53.5 + 7.2%
49.5 52.5 + b%.
50 51.5 2.6%
+

50 49 -
2%.
50 47.5 -

5.4%
50.6 46
-
a.1Y-

b) 0.5 per mm (difference in mean length / percentage change)

c) Percentage change is useful when comparing statistical data over time. We can also
calculate difference rates.
 b
28
Exam Revision

Palisade Mesophyll Cells:Photosynthesis

Binary Fisson:asexual
reproduction -

prokaryotes
usually

d
use

Mitosis:Cell division used for

two
growth. Splitinto Tissues
lof an organism) -

of chloroplasts

Ciliated Cells - movement of

·

mucus in
bronchi
the tracken and
Epithetare I
-
Nervous
·
Roof hair cells absorption
-

Palademesophthese Connective
·

e
se
impulse Give of
· Red blood cells -

transport of oxygen 2.9 an ex

sperm
and egg cells (gametes) -

reproduction a

teus"Tissue

cell -> Tissue -

-
Organ
]]
Organ
Organism 8
system
-
 ↑iffusion
location for aerobic
2.9 identify
the respiration:mitochondria

Describe andexplain diffusion

solutemoving across the
semipermeable membrane
Description
due to concentration gradient.
Explanation the

The random of cells will if

movement increase temperature
heat the kinetic
rises because increases
energy of the
random movement molecules & ions.
of

02 CO2 (Lipid horomores)

(metabolic
Diffusion allows cells to waste)

gain energy
and get rid of
waste products.
Factors that increase rate of diffusion:
diffin one
pointsofcontact
·surfaceareaor
for

·
concentration the
gradient:greater concentration gradient
the faster
the rate

· Distance
 -
Osmosis

4 moves
Water across the membrane. partially
permeable

move
Water through a (getting help) diffusion
Y
Partially
permeable
-
in channels
&i
tubing partially permeablemembrane
-

Selectively Permeable is Partially/Semi permeable

Allows to
Actively
selectwhat

I
some come

come
to in or not through

Hypertonic Isotonic Hypotonic

t - -
(Turgid/
(plasmalysed/ (Flaccid/ burst)
created) equilibrium)

Turgor Pressure is the force inside the cell which

pushes outwards, pushing the cell membrace against
the cell wall.
 transport
Active transport requires energy to move materials.
Active transport:
• Can move molecules against a concentration gradient
• Requires energy*
• Involves protein carriers in membranes
Active
transport the movement of particles through a cell
·
is

membrace from a
region of lower concentration to a
region of higher concentration.
 4.1 Biological Molecules
Organic Molecules:
Organisms need organic molecules to:
nee
Biological molecules are often • Provide energy to drive life processes
called organic molecules, • Provide raw materials for the growth
because many of them were and repair of tissues
discovered in living organisms.
The four main groups of organic chemicals
Carbon atoms bond strongly to used by living things are:
other carbon atoms, so organic Carbohydrates
molecules can be large and show Lipids
a wide variety of chain and ring Proteins
structures. Nucleic acids
Basic biochemistry

The study of the organic and inorganic molecules that make up living organisms is called
biochemistry. The sum of all the chemical reactions in living organisms is sometimes
called metabolism.
-
-

Large organic molecules are usually made up of lots of similar smaller molecules called
subunits. The subunits can be split apart by a reaction called hydrolysis.
me

uses
Water!
They can be joined together again, perhaps in new combinations, by a reaction called
condensation.
nee

Produceen
 Carbohydrates

Monosaccharides are the simplest

carbohydrates, for exmaple, glucose.
-

Glucose is soluble so it is easily

transported in blood and dissolves in the
cytoplasm of cells.

They are the main source of energy

for many cells.

Lipids
Polysaccharides Lipids are formed by the condensation
of three molecules of fatty acid with
Polysaccharides are formed from many one molecule of glycerol.
monosaccharide molecules e.g starch &
glycogen. Fats (solid at room temp) and oil (liquid
at room temp) are insoluble in water.
They are both made of thousands of
glucose molecules. Therefore they are excellent stores of
They are insoluble, thus good stores of energy, and mee
they form barriers between
energy and form important structures watery environments such as between

m
like cellulose cell walls. a cell and its surroundings.

Condensation
 Proteins

Do
Proteins are made up of long chains of
subunits called amino acids. The sequence of
~ e
amino acids determine the shape of the
protein molecule - thus some are long and
thin like keratin while others are more egg
shaped or spherical. *

1)
The function depends on their shape. E.g the
active site of enzymes and the binding site Hydrolysis Condensation
of antibodies are the areas of the two egg-
shaped proteins.

Amino acids are soluble so they are easily [0od]

transported in living organisms. They also take
-

part in reacitonse
mor
r in the watery cytopl
e asm of
the cell.
*All organic molecules contain the elements carbon and hydrogen. The simplest organic
molecule is methan, cH4. More complex organic molecules also contain oxygen. The
biologicaln
function of aemolecule depends
a on its shape
r ande
structure.
 4.2 Testing for Biochemicals
A special test for lipids

Important: fats and oils are insoluble in water. Therefore one cannot make an aqueous
solution of a fat or oil on which to carry out a biochemical test. However, a physical
test is available.
Emulsion Test:
• 2cm^3 of ethanol are added to the unknown solution, and the mixture is
gently shaken.
• The mixture is poured into a test tube containing an equal volume of distil ed
water.
• If a lipid is present, a milky-white emulsion is formed.

I
Testing for Vitamin C: using DCPIP

E
As

E
Protein, few drops Starch, a few drops Glucose, a few drops of
of Biuret reagent is of iodine solution is Benedict's reagent are
added. A mauve/ added. A deep blue- added. An- orange/brick-red
we
purple colour is a ne
black colour is a colour is a positive result.
positive result positive result.
(protein is present)
 5.1 Enzymes Control Biochemical Reactions in
Living Organisms
Enzymes are biological catalysts.
All the chemical reactions within a living organism is known as metabolism.
-

Anabolic reactions build up large molecules Catabolic reactions break down large
form smaller ones, and usually require molecules into smaller ones, and often
energy. release energy.

Ex: The condensation of glucose molecules Ex: The breakdown of glucose into carbon
into the polysaccharide glycogen. dioxide and water by respiration.
Enzymes determine whether glucose molecules are built up into glycogen or brokern down
into carbon dioxide and water. Enzymes are proteins that function as biological catalysts.
The molecules that react in the enzyme-catalysed reaction are called substrates, and
the molecules produced in the reaction are products.

Enzymes and cells

Enzymes that work inside the cell are intracellular enzymes. An example of this is catalase
e

(it breaks down harmful hydrogen peroxide in liver cells).

Enzymes which are made inside cells and then released from the cell to perform are called
extracellular enzymes. Ex: lipase (it breaks down fats to fatty acids and glycerol) / amylase
ne ne

(converts starch to maltose)

kind of substrate
only!
*
Enzymes are SPECIFIC most work
-

on one
This results from the and fitof the
specificity
active and the substrate.
site
complementary shape
 Factors affecting enzyme activity
1. Temperature
Temperature affects the activity of enzymes. The activity increases with a rise in
temperature up to a point. This is because:
• A higher temperature speeds up the movement of substrate molecules, so that
when they collide with the enzyme they have more kinteic energy and are more likely
to bind.
Optimum
Temp • The enzyme molecules also gain in kinetic

*
diner
p
energy as the temperature rises so that
they begin to vibrate. The enzyme
astaile molevules vibrate so much that they
become denatured. They lose their 3D
-

shape and can no longer bind to their

-

substrate. So high temperatures reduce

-

Temp enzyme activity. Enzymes each have an

-

optimum temperature which is mostly

around 37 degrees.
-

2. PH
Changing the pH conditions around an enzyme molecules affects its three dimensional
shape and can denature the enzyme.
Each enzyme has its own optimum pH.

3. Activators and inhibitors

Some molecules change the likelihood of an enzyme being able to bind to its substrate.
Activators make this binding more liekly. For ex, chloride ions are essential for the
activity of salivary amylase. Inhibitors make it more difficult for the enzyme to bind in
to the substrate, for example, cyanide ions block the active sites of enzymes involved in
respiration.
Humans exploit enzymes
Enzymes are specific and can be used over and over again. They are very useful in the
fields of industry, food preparation and medicine. Ex) enzyme from snake venom can break
down blood clots. Product
x

-
&
#// Enzyme
My, ->
Hi,
Lock & Keyhypothesis
Questions on enzymes and biological molecules
1. a) fatty acid
b) Enzymes, triglyceride i i) The enzyme locks on the substrates and
c) Bone, Muscle brings them together like it is the key and
D) cut or grind the seed and place in a locks the substrates into a product.
test tube. Then add drops of biuret B) i) Amylase digests starch while proteases
solution into the tube. If the seed breaks down proteins into amino acids.
turns blue, then protein is present. i ) enzymes' optimum temperature is 37
degrees. Past that point, enzymes denature.
2. A) To increase the accuracy of the Therefore, they do not catalyse reactions at
practical 73 degrees because they have been
B) denatured.
C) i) so that the enzymes in the mixtures
Orange juice: 2/2.4 = 0.83cm^3/g
wouldn't denature because of high
Grapefruit juice: 2/3.1 = 0.65cm^3/g temperatures and to keep a control variable
Apple juice: 2/9.4 = 0.21cm^3/g to enable a fair test.
ii)
3. A) i) a: substrate b: Enzyme c:
product
i ) As shown in the diagram, it speeds up
the reaction by bringing two
substrates together.
 -

i i) Because pH affects the

activity of enzymes, this graph
it
-

shows that neutral pHs such

N 35 -

as 6 or 7 is when enzyme
X

Mi
Wi
30
-

activity increases the most.

25- 20-

15 -

10 -

5- X
I 11 I
O I 2 3 4

pH
4. A) i)

Earegen
carbon hydenwitgencakium Phosphors the
other

i)
I believe pie charts are better to show
C data. Pie charts are more visual
therefore it shows the contrast
O ⑧
H between the highest and lowest value by
N
first glance.
L

I
B) i) Water i ) proteins i i) water iv) Carbohydrates v) lipid vi) the bones
5.
A) i) valid i ) valid i i) valid iv) invalid
B) A tube that acts like a control variable to prove that the practical is working
because there are no enzymes in water.
C) repeat and calculate the average
D) Glucose - benedict's test can be used to identify reducing sugars