Class+Topical+Activities

= Contents =
 * 1) Cells
 * 2) Homeostasis
 * 3) Biomolecules
 * 4) Photosynthesis
 * 5) Energy, Matter & Organisation

= 1. Cells =
 * __Difference between a plant and animal cell__**
 * **Plant Cell** || **Animal Cell** ||
 * Has cellulose cell wall and plasma membrane || Only has plasma membrane ||
 * Presence of chloroplasts || Absence of chloroplasts ||
 * Most have a large central vacuole || One or numerous small vacuoles ||
 * Mostly regular in shape || Varied shapes ||
 * Centrioles only present in lower plant forms || Centrioles present ||
 * Lysosomes usually not evident || Lysosomes occur in cytoplasm ||


 * __Difference between an eukaryote and prokaryote__**
 * **Eukaryote** || **Prokaryote** ||
 * Presence of defined nucleus || Absence of defined nucleus ||
 * Has several chromosomes || One long DNA strand ||
 * Simple cilia and flagella || Complex cilia and flagella ||
 * Presence of Golgi apparatus || Absence of Golgi apparatus ||
 * Lysosomes in animal cells mostly || Absence of lysosomes ||
 * Has endoplasmic reticulum || No endoplasmic reticulum ||

**Animal Cell ([|click for link] )
 * __Concept Maps__

Plant Cell ([|click for link] ) =** 2. Homeostasis **= What I recall about homeostasis: - Maintain a stable internal environment within the cell - Regulate the movement of substances in and out of the cell (plasma membrane) - E.g. osmosis, diffusion, facilitated diffusion, active transport - Maintain equilibrium in a living system

My definition of homeostasis in **one sentence**: Homeostasis is the maintenance of a stable internal environment within the cell through regulating the movement of substances in and out of the cell.

Definition of homeostasis: The ability of a body or cell to seek and maintain a condition of equilibrium or stability within its internal environment when dealing with external changes.

**__Energy, Matter & Organisation - Biomolecules__** //** Living systems are complex and highly organized, and they require matter and energy to maintain this organization.

**Energy is stored in the organization of matter. // Living organisms use matter and energy to build and maintain body structures. Living organisms obtain and process matter and energy. The structure of a molecule always dictates its function. The structure and function of biological living systems obeys the laws of thermodynamics. Communities of organisms depend on the cycling of matter and the flow of energy. The constant flow of energy and cycling of matter in the biosphere leads to a balanced or steady state.
 * e.g. biomolecules such as proteins, lipids, carbohydrates.
 * Such as protein synthesis by the ribosomes. The proteins manufactured will have specific functions in the cell and in the body.
 * Glucose is used as chemical energy, which is converted to heat energy, mechanical energy etc.
 * For example, an enzyme (protein) has a specific structure for its active site which allows it to only bind with a corresponding substrate.
 * Another example is the phospholipid bilayer of the plasma membrane. The tails are hydrophobic, and the heads are hydrophilic, thus explaining the way they are arranged, and their properties (fluid).
 * E.g. circulatory system
 * In the water cycle, water is continuously recycled. The main source of energy is the Sun. Organisms depend on water for life.
 * Energy cannot be created or destroyed, it is only converted. During the process of conversion, energy may be lost in the form of heat energy
 * The carbon cycle, nitrogen cycle and water cycle are examples of constant flow of energy.

This balance is achieved through various biogeochemical cycles and the processes of photosynthesis and cellular respiration - //focus is on ENERGY//

The questions we ask about ourselves and the world around us: 1. Are we just chemicals? 2. Are we what we eat? 3. Why is the carbon molecule suitable for life as we know it? 4. Why is the chemistry of water suitable for life?

__Are we just chemicals?

Are we what we eat?__ Yes, we are what we eat. Whatever that is in our diet will eventually be used by our body to build structures, store energy, and perform other functions.

__Why is the carbon molecules suitable for life as we know it?__ The carbon atom has four valence electrons. Thus it can bond to four other atoms. The bonds formed are strong covalent bonds. Double bonds can also be formed, and the carbon atom is able to bond to other carbon atoms. A backbone is hence formed. The carbon atom can be found in carbohydrates, proteins and fats.

__Why is the chemistry of water suitable for life?__ Water exists in three states. It expands when it is cooled below 4 degrees Celsius, thus the density is lower than in the liquid state. In the solid state, it floats. Ice floats on water.

=** 3. Biomolecules **= __**Carbohydrates**__ Carbohydrates are classified as:
 * 1) **Monosaccharides** eg glucose, fructose, galactose
 * 2) **Disaccharides** eg sucrose, maltose, lactose
 * 3) **Polysaccharides** eg cellulose, glycogen, starch

- used as a primary energy source for fueling cell metabolism. - **single-sugar** molecules - include glucose (grape sugar, blood sugar) - include fructose (honey, fruit juices) - most commonly occurring monosaccharides contain between 3 and 7 carbon atoms in their carbon chains - the 6C hexose sugars occur most frequently - all monosaccharides are reducing sugars (participate in reduction reactions) - Triose e.g. Glyceraldehyde - Pentose e.g. Ribose, Deoxyribose - Hexose e.g. Glucose, Fructose, Galactose
 * Monosaccharides**

- **double-sugar** molecules - used as energy sources - used as building blocks for larger molecules - the type of disaccharide formed depends on the monomers involved and whether they are in their alpha- or beta- form - Only a few disaccharides (e.g. lactose) are classified as reducing sugars - Examples include - Sucrose = alpha-glucose + beta-fructose - Maltose = alpha-glucose + alpha-glucose - Lactose = beta-glucose + beta-galactose - Cellobiose = beta-glucose + beta-glucose
 * Disaccharides**

- made from condensing many similar monosaccharides (polymerization)
 * Polysaccharides**

In layman terms: Condensation - Building up/Storing Energy Hydrolysis - Breaking down the larger molecules to smaller ones
 * Reactions**

Condensation - Monosaccharides combining to form compound sugars - Two monosaccharides are joined together to form a disaccharide with the **release of a water molecule** - Energy is supplied by a nucleotide sugar (e.g. ADP-glucose)

Hydrolysis - When compound sugars are broken down to simple monosaccharides - When a disaccharide is split (e.g. in digestion), a water molecule is used as a source of **hydrogen** and **hydroxyl** group - Reaction is catalyzed by **enzymes** - Glycosidic bond ( a type of [|functional group] that joins a [|carbohydrate] (sugar) molecule to another group)


 * Starch & Glycogen**
 * - Their molecules have many side branches where glucose molecules can be removed from their tips (by enzymes)
 * - Their insolubility stops them interfering with osmosis
 * - Their compactness provides an efficient way to store lots of glucose for future cellular respiration
 * - E.g. Glycogen granules in skeletal muscles, and starch grains in potato cells


 * **Cellulose**
 * - Made from long, straight chains of glucose
 * - Chains cross-linked by H-bonds which holds them tightly together (excludes water)
 * - Chemically very inert and insoluble – few ‘tips’ on molecule make it difficult to digest
 * - Many molecules form strong fibrils
 * - Only some bacteria, fungi and a very small number of animals can secrete cellulase enzymes.


 * Function of Starch**
 * 1) Form supporting structures E.g. cellulose cell wall.
 * 2) Source of energy - glucose is the raw material needed for cellular respiration yielding ATP, the energy molecule.
 * 3) Converted into other organic compounds E.g. amino acids
 * 4) For formation of nucleic acids
 * 5) Synthesis of lubricants, e.g. mucus
 * 6) Produce nectar in some flowers.


 * Fibre**
 * Indigestible e.g. cellulose
 * Provides bulk to intestinal contents
 * Aids in peristalsis - rhythmic wave like contractions along the gut
 * Prevents constipation
 * Sources : fresh fruits, vegetables, bran, cereals, wholemeal bread

= 4. Photosynthesis =

Watch the video "The Private Lives of Plants - Growing" and answer the following questions: o Why do young seedlings of climbers grow away from light? o What are the forces that cause the leaves to unfold during growth? o Why are some of the leaves and leaf stalks “hairy”? o Name as many different types of leaf shape as possible. o Name a few strategies that plants use to gather light. o Why do roots have root hairs? What are their characteristics? o How much water is loss through the stomata? o How do trees “pump” water up its trunk to the leaves in the canopy layer? o What are the properties of these “pipes”? What are they called? o How do plants prevent the problem of having too much water accumulating on its large leaf surface especially in the tropics? o Why do proboscis monkeys have to spend so many hours eating? Why do they have a large belly? o How do you tell the difference between a leaf that has been eaten by a caterpillar and that of a grasshopper? o What are the damages that are inflicted on plants? What strategies do these plants employ to protect themselves? Use the examples featured in the show to explain their strategies e.g. Acacia, Nettle, pebble plant, passion flowers, bracken, mimosa, Venus fly trap, marsh pitcher
 * They need to find a tree for support, so that they can grow upwards to obtain sunlight.
 * Water pressure.
 * The hair helps to trap water to reduce water loss.
 * Needle-like
 * Elliptic/Oval
 * Linear (Long and Narrow)
 * Obtuse (Blunt tip)
 * Heart-shaped
 * Triangular
 * Sickle-shaped
 * Large leaves for increased surface area
 * Grow to great heights to emerge from thick canopies
 * Ensure leaf growth such that there is no overlapping
 * Root hairs help increase the surface area to volume ratio for efficient water transport into the roots (osmosis), and nutrient uptake (diffusion). Root hairs are very thin and small, and the walls of the root hair are thin as well.
 * 90%
 * There are different explanations for this. One explanation is capillary action in the thin xylem tubes. Another is the creation of a vacuum when water evaporates at the top, which then 'sucks' the water at the bottom up.
 * These 'pipes' are hollow and thinner than the phloem food tubes.
 * Leaves have drip-tips which direct water to flow off the leaf, and the leaves also droop downwards.
 * Leaves do not provide much nutrition. Their bellies are large because animals do not have the necessary enzymes to break down cellulose, and the help of bacteria is required.
 * Caterpillars cut a semi-circular shape out of the side of the leaf, using it as a cover to prevent predators from spotting it.
 * Acacia - have spikes on the leaves
 * Nettle - Poisonous spikes. Another species of nettle which is not poisonous makes use of this advantage because animals e.g. rabbits do not dare to come close to it, thinking it is the poisonous species.
 * Mimosa - Leaves close upon contact/touch

=** 5. Energy, Matter & Organisation **= __What is the relationship between energy and matter?__ E=mc^2, where //E// represents units of energy, //m// represents units of mass, and //c^2// is the speed of light squared. Matter and energy are really different forms of the same thing. Matter can be turned into energy, and energy into matter. Einstein's formula tells us the amount of energy this mass would be equivalent to, if it were all suddenly turned into energy. It says that to find the energy, you multiply the mass by the square of the speed of light, this number being 300,000,000 meters per second. [1] __How is energy significant to biological systems?__ Biological systems rely on energy to live and continue existing.

__Can an organism survive without the exchange of matter with its environment?__ No it cannot. An organism requires different substances in order to survive, and it cannot possibly manufacture all of them on its own. It requires to take in substances from the external environment, either to use them directly, or convert them into a form they can use.

__Are all matters living and all living organisms made of matter?__ Yes, living organisms are made up of matter.

__Can living organisms create and destroy energy?__ No, energy cannot be created nor destroyed, much less by living organisms. Energy can only be transferred from one form to another, which include heat energy, kinetic energy, potential energy, light energy, electrical energy, chemical energy, etc.

__Can living organisms create and destroy matter?__ Just like energy, matter cannot be created or destroyed. Living organisms deal with matter in the form of molecules, ions, atoms, etc. and 're-package' them into other useful forms which they can utilise.

References: [1] E=mc2 Explained, http://www.worsleyschool.net/science/files/emc2/emc2.html