STRAND 2 LIVING THINGS.pptx GRADE 8 CBC NOTES

1. STRAND 2.0: LIVING THINGS AND
THEIR ENVIRONMENT
2.1 The Cell

2. SPECIFIC LEARNING OUTCOMES
• By the end of the sub strand the learner should be able to:
• outline the structure of plant and animal cells as observed under a light
microscope,
• describe the functions of components of cells as seen under the light
microscope,
• compare plant and animal cells as observed under a light microscope,
• determine the magnification of cells seen under the light microscope,
• appreciate that all living things are made of microscopic units.

3. THE COMPONENTS OF A CELL AS SEEN
UNDER THE LIGHT MICROSCOPE AND THEIR
FUNCTIONS

4. THE COMPONENTS OF A CELL AS SEEN
UNDER THE LIGHT MICROSCOPE AND
THEIR FUNCTIONS
• The components of a cell can be broadly categorized into
two main types: organelles and non-organelles. Organelles
are membrane-bound structures within the cell that
perform specific functions, while non-organelles are non-
membrane-bound structures that also contribute to the
overall functioning of the cell.

5. THE COMPONENTS OF A CELL AS SEEN
UNDER THE LIGHT MICROSCOPE AND
THEIR FUNCTIONS
• Nucleus: The nucleus is a membrane-bound organelle that contains the cell's
genetic material in DNA. It acts as the cell's control centre, regulating gene
expression and coordinating cellular activities.
• Cytoplasm: The cytoplasm refers to the region between the nucleus and the cell
membrane. It consists of a gel-like substance called cytosol, which contains various
organelles and is involved in cellular metabolism.
• Cell Membrane: It regulates the movement of substances in and out of the cell,
maintaining homeostasis and providing protection.

6. THE COMPONENTS OF A CELL AS SEEN
UNDER THE LIGHT MICROSCOPE AND
THEIR FUNCTIONS
• Endoplasmic Reticulum (ER): The endoplasmic
reticulum is a network of membranous tubules and sacs
involved in protein synthesis, lipid metabolism, and
detoxification processes.

7. THE COMPONENTS OF A CELL
• Golgi Apparatus: The Golgi apparatus is responsible for modifying,
sorting, and packaging proteins and lipids into vesicles for transport
within or outside the cell.
• Mitochondria: Mitochondria are often called the "powerhouses" of the
cell because they generate energy in the form of ATP through cellular
respiration.

8. THE COMPONENTS OF A CELL
• Lysosomes: Lysosomes are membrane-bound organelles that contain
digestive enzymes. They break down waste materials, cellular debris, and
foreign substances, crucial in cellular recycling and defense mechanisms.
Peroxisomes: Peroxisomes are involved in various metabolic processes,
including the breakdown of fatty acids and detoxification of harmful
substances..

9. THE COMPONENTS OF A CELL
Ribosomes: Ribosomes are the sites of protein synthesis in the cell. They can
either be free in the cytoplasm or attached to the rough endoplasmic reticulum.
Cytoskeleton: The cytoskeleton is a network of protein filaments that
provides structural support, maintains cell shape, and facilitates cell movement.

10. THE COMPONENTS OF A CELL
Vacuoles: Vacuoles are membrane-bound sacs involved in storage, waste disposal, and
maintaining turgor pressure in plant cells. In animal cells, vacuoles are smaller and less
prominent.
Centrioles (in animal cells): Centrioles play a crucial role in cell division by organizing
microtubules into spindle fibers during mitosis and meiosis.
Chloroplasts (in plant cells): Chloroplasts are responsible for photosynthesis, converting
light energy into chemical energy in glucose.

11. THE COMPONENTS OF A CELL
• Cell Wall (in plant cells): The cell wall is a rigid outer layer
found in plant cells that provides structural support and
protection.
• Nucleolus: The nucleolus is a dense region within the nucleus
where ribosomal RNA (rRNA) synthesis occurs and ribosomes
are assembled.

12. COMPARISON OF PLANT AND ANIMAL
CELLS AS OBSERVED UNDER A LIGHT
MICROSCOPE
• Plant and animal cells have distinct differences when observed under a light
microscope. Plant cells have a cell wall, chloroplasts, and a large central vacuole,
while animal cells lack these structures. However, both types of cells share
common features, such as a nucleus and various organelles within the cytoplasm.

13. CALCULATION OF THE MAGNIFICATION
OF CELLS SEEN UNDER THE LIGHT
MICROSCOPE
• The magnification of cells seen under the light microscope is determined by
multiplying the magnification power of the objective lens by that of the eyepiece lens.
This calculation provides the total magnification, which indicates the degree of
enlargement or size increase of the cells when observed through a light microscope.

14. THE USE OF A LIGHT MICROSCOPE
IN MAGNIFICATION
• The lenses in a light microscope can magnify the specimen up to 1000 times,
allowing scientists and researchers to observe minute details that are not visible
to the naked eye.
• Light microscopes are widely used in biological research and education. They
enable scientists to study the structure and function of cells, tissues, and organs.
• Light microscopes are used to analyze the structure and composition of
materials at the microscopic level

15. Movement of materials
in and out of the cell
Structure of the Cell Membrane:

16. Structure of the Cell Membrane:
• The cell membrane consists of lipids, proteins, and carbohydrates, with phospholipids
being the most abundant. They form bilayers with hydrophilic heads facing outward,
creating a hydrophobic core. The lipid bilayer contains essential proteins, including
integral and peripheral proteins. Integral proteins interact with lipid tails, while
peripheral proteins are easily detached. Carbohydrates, such as glycoproteins and
glycolipids, play a role in cell recognition and communication.

17. PROPERTIES OF THE CELL MEMBRANE:
• Selective Permeability
• Fluid Mosaic Mode
• Barrier Function
• Cellular Communication
• Cell Adhesion.
• Electrochemical Gradient

18. DISCUSS THE PROPERTIES OF THE
CELL MEMBRANE
• The cell membrane possesses several important properties
essential for the proper functioning of cells. Its structure,
selective permeability, fluidity, cholesterol content, protein
composition, glycocalyx, and electrical properties maintain
cellular integrity, regulate molecular transport, and facilitate
communication with neighbouring cells.

19. THE ROLE OF DIFFUSION IN LIVING
THINGS
• Diffusion is involved in the transport of nutrients into cells.
• Diffusion also plays a role in waste removal from cells.
• In cellular biology, diffusion allows for the movement of substances across
cell membranes.
• Diffusion is involved in the exchange of gases in the respiratory system.

20. EXPERIMENTS TO DEMONSTRATE THE
EFFECTS OF HEAT, DILUTED ACIDS, AND
ALKALIS ON THE CELL MEMBRANE
Effects of Heat on the Cell Membrane:

21. EFFECTS OF HEAT ON THE CELL
MEMBRANE:
• Heat can disrupt the structure and function of the cell membrane. To
demonstrate this effect, one common experiment involves using beetroot
cells. Beetroot contains a red pigment called betacyanin, which is normally
confined within the vacuole of the beetroot cells by the intact cell membrane

22. EFFECTS OF HEAT ON THE CELL
MEMBRANE:
• In this experiment, several beetroot slices are placed in different water baths
at varying temperatures. The water baths can range from room temperature
to higher temperatures such as 40°C, 60°C, and even boiling water at 100°C.
After a specific period, the beetroot slices are removed from the water baths,
and their colour intensity is measured using a colorimeter or visually
assessed.

23. EFFECTS OF HEAT ON THE CELL
MEMBRANE:
• The results of this experiment show that as the temperature increases, the
colour intensity of the beetroot slices also increases. This indicates that
higher temperatures cause more betacyanin to leak out of the cells. The
increase in colour intensity is due to the cell membrane disruption by heat,
allowing betacyanin to escape into the surrounding solution.

24. EFFECTS OF DILUTE ACIDS ON THE
CELL MEMBRANE:
• Dilute acids can also affect the integrity and permeability of the cell
membrane. An experiment using onion epidermal cells can be conducted
to demonstrate this effect.
• In this experiment, a thin layer of onion epidermis is placed on a
microscope slide and covered with a drop of dilute acid solution (e.g., 0.1
M hydrochloric acid). The slide is then observed under a microscope,
and the cell changes are recorded

25. EFFECTS OF DILUTE ACIDS ON THE
CELL MEMBRANE:
• The results of this experiment show that the dilute acid causes the cell
membrane to become more permeable. The release of cell contents or
changes in cell shape can observe this. The acid disrupts the cell membrane's
lipid bilayer, leading to increased permeability and potential damage to the
cells.

26. EFFECTS OF ALKALIS ON THE CELL
MEMBRANE
• Similar to dilute acids, alkalis can also impact the cell membrane. An experiment
using red cabbage leaves can be conducted to demonstrate this effect.
• In this experiment, red cabbage leaves are boiled in water to extract a purple pigment
called anthocyanin. The resulting purple solution is then divided into several test
tubes. Each test tube is treated with a different alkali solution concentration, such as
sodium hydroxide (NaOH).

27. EFFECTS OF ALKALIS ON THE CELL
MEMBRANE
• The colour changes observed in each test tube indicate the effects
of alkalis on the cell membrane. Alkalis cause the anthocyanin
pigment to change colour, typically from purple to green or
yellow. This colour change indicates that alkalis disrupt the
structure and function of the cell membrane, leading to the
leakage of pigments from the cells.

28. HOW IS DIFFUSION AND OSMOSIS
IMPORTANT IN LIVING?
• Diffusion is the spontaneous movement of particles
from an area of higher concentration to an area of
lower concentration. It occurs in gases, liquids, and
solids and is driven by the random motion of particles.

29. HOW IS DIFFUSION AND OSMOSIS
IMPORTANT IN LIVING?
• One of the primary functions of diffusion is to enable the transport of
gases, such as oxygen and carbon dioxide, across cell membranes.
• Diffusion enables the exchange of gases, such as oxygen and carbon dioxide,
across respiratory surfaces in organisms.
• Diffusion is involved in cell signaling and communication.
• Diffusion also plays a crucial role in transporting nutrients and waste
products within organisms

30. OSMOSIS IMPORTANT ON LIVING
• Osmosis, on the other hand, is a specific type of diffusion involving water
molecules' movement across a selectively permeable membrane. It occurs when
there is a difference in the concentration of solutes (substances dissolved in water)
on either side of the membrane.
• In living organisms, osmosis regulates the water content of cells.
• Osmosis involves various physiological processes, such as kidney function and
blood pressure regulation.
• Osmosis also plays a vital role in plant cells. Plant roots absorb water from the soil
through osmosis

31. DEMONSTRATE THE PROCESS OF
OSMOSIS IN LIVING THINGS.
• When plant cells are in a hypotonic solution, water enters the mobileular
via osmosis, inflicting the vacuole to enlarge and exert stress towards the
mobileular wall. Animal cells no longer have an inflexible mobileular
wall like plant cells, so they're at greater risk of adjustments in tonicity.
For example, purple blood cells hold their form and capability because
of the regulated motion of water via osmosis. If purple blood cells are
uncovered to a hypotonic solution, water enters the cells, inflicting them
to swell and doubtlessly burst.

32. THE SIMILARITIES AND DIFFERENCES
BETWEEN OSMOSIS AND DIFFUSION
Similarities

33. SIMILARITIES
• Movement of Molecules: Both osmosis and diffusion involve the movement of
molecules. In both processes, molecules move down their concentration gradient,
which means they move from an area of higher concentration to an area of lower
concentration.
• Passive processes; Osmosis and diffusion are passive processes, meaning they do not
require energy input. The movement of molecules occurs spontaneously due to the
random motion of particles
• Equilibrium: Both osmosis and diffusion aim to establish equilibrium.

34. DIFFERENCES
• Nature of Molecules: Osmosis refers explicitly to the
movement of water molecules across a selectively permeable
membrane, while diffusion can involve any type of molecule,
including gases (such as oxygen and carbon dioxide) and solutes
(such as ions and small molecules).

35. DIFFERENCES
• Membrane Involvement: Osmosis occurs through a selectively permeable
membrane, which allows only certain molecules or ions to pass through.
Diffusion can occur through various mediums, including gases, liquids, and
solids, without requiring a membrane.
• Driving Force: Osmosis is driven by the difference in solute concentration
on either side of a membrane. Water movement occurs to equalize the
concentration of solutes on both sides of the membrane. On the other hand,
diffusion is driven solely by the concentration gradient, with molecules
moving from areas of higher concentration to areas of lower concentration

36. DIFFERENCES
• Rate of Movement: Osmosis generally occurs at a slower rate compared to
diffusion. This is because the movement of water molecules across a membrane is
influenced by factors such as the size of the membrane pores and the presence of
solutes that may hinder or facilitate water movement
• Biological Significance: Osmosis is crucial in maintaining cell shape and
regulating water balance in organisms. On the other hand, diffusion involves
various biological processes, including gas exchange in the respiratory system,
nutrient absorption in the digestive system, and waste removal in the excretory
system.

37. FACTORS AFFECTING DIFFUSION
AND OSMOSIS
• several factors influence the processes of diffusion and
osmosis in biological systems. These factors include
concentration gradient, temperature, molecular size, surface
area, distance, membrane permeability, pressure, electrical
charge, carrier proteins, and pores or channels.

38. ASSESSMENT
• Compare plant and animal cells as observed under a light
microscope
• Explain the role of diffusion and osmosis in living things
• Demonstrate diffusion and osmosis in living things
• Outline the menstrual cycle and its related challenges in human
beings
• Develope a plan to manage challenges related to menstrual cycle in
human beings