saddnes

• How do you calculate the size of a specimen when using a microscope?


  if scale bar is given,

  1. measure the length of specimen in mm

  2. measure the length of the scale bar in mm

  3. calculate how many scale bar lengths make the specimen (divide length by length of scale bar)

  4. calculate the real size of specimen by multiplying the scale bar label by answer from step 3

  
  

  if magnification is given,

  1. measure the length of the specimen in mm

  2. convert the length of the specimen image to nanometers

  3. divide the length of the specimen by the magnification
• How do you calculate the total magnification when using a microscope?


  Total magnification= objective lens x eyepiece

  
• How do you convert measurements?

  
• Contrast prokaryotic and eukaryotic cells.

  Prokaryote:

  Small

  No nucleus

  No membrane bound organelles

  Unicellular

  
  

  Eukaryote:

  Large

  Nucleus

  Membrane bound organelles

  Uni or multicellular

  
• Why are cells small?

  - maximize SA: which allows for efficient movement of substances into and out of the cell

  - crucial for nutrient transportation and waste disposal

  
• What is the function of the cell wall?

  - provides structure, protection and support (via turgor pressure)

  - regulates cell growth

  
• What is the function of the cell membrane?

  - provides protection for the cell

  - controls the movement of substances into and out of the cell

  - carries out metabolic reactions near the surface

  - selectively permeable as small substances diffuse easily, whereas large molecules (e.g. proteins) are prevented from moving through the membrane

  
• What is the function of the vacuole?

  - stores materials such as water, salts, proteins carbohydrates, and waste

  - involved in cell structure in plant cells

  
• What is the function of the mitochondria?

  - site of aerobic stage of cell respiration- produces ATP (energy for the cell)

  - 2 layers

  - inner layer heavily folded to increase SA:V efficiency and holds enzymes required for cell respiration

  - normal drown as an oval with a squiggle

  
• What is the function of chlorophyll?


  - captures the light energy of the sun and convert water and carbon dioxide to produce glucose and oxygen.

  
• What is the function of a lysosome?


  - digests cellular waste material and debris

  
• What is the function of the rough and smooth endoplasmic reticulum?

  RER:

  - modifies, packages, and transports proteins

  - transports materials through the cell

  SER:

  - synthesizes lipids

  
• What is the function of the Golgi body?


  - receives materials from the endoplasmic reticulum

  - processes and packages materials into membrane bound vesicles

  - distributes them to other parts of the cell

  - produces ribosomes

  
• What is the function of the nucleus?

  - contains the cell's genetic material (DNA)

  
• What is the function of the cytoplasm?

  - semifluid substance that suspends all organelles

  - made up of water, enzymes, salts, organelles, and various organic molecules

  - where most chemical reactions take place

  
• What is the function of the ribosomes?

  - synthesizes proteins using amino acids

  
• Contrast plant and animal cells

  plant cells: cell well, large vacuole, chloroplasts, no centriole or cytoskeleton

  animal cells: no well call, vacuole small or absent, no chloroplasts, centrioles and cytoskeleton present

  
• Explain why the cell membrane is described as "partially permeable'?

  - mostly consists of phospholipids which are composed of hydrophobic ( water hating ) tails and hydrophilic (water loving).

  - hydrophobic tail prevents unwanted polar ions and molecules to pass in the cell and restricts water soluble molecules like amino acids, glucose, and more to pass out of the cell. Also, the cholesterol has the same function. So, since it only allows small and non-polar molecules to pass in, it is described as partially permeable or semi-permeable. Those ions and molecules restricted by the phospholipids pass in and out of the cell via membrane proteins.

  
• Explain the phospholipid bilayer.


  - consists of 2 layers of phospholipids with a hydrophobic tail and hydrophilic head

  - hydrophilic head is polar

  - hydrophobic tail (fatty acid chains)

  - hydrophobic materials easily pass through the cell membrane (passive transport), if they are small enough, as they are hydrophobic like the cell membrane interior

  - hydrophilic materials cannot pass through the cell easily, and require cell from protein channels, as they repel against the hydrophobic interior of the cell membrane

  
• What is the cell membrane made of?

  - made of phospholipids proteins, carbohydrates, cholesterol or sterols.

  
• What is ATP and what is special about it?

  - adenosine triphosphate is a nucleotide

  - provides every to drive and support processes such as muscle contraction, nerve impulse propagation, condense dissolution and chemical synthesis

  - enables cells to store energy safely in small packets and release the energy for use only as and when needed

  
• Define Heterotrophs.


  - consumers that feed on plants, animals or decomposed materials

  
• Define Autotrophs.


  - producers that make their own food

  
• What is the balanced equation for photosynthesis?

  6CO2+6H2O->C6H12O6+6O2+6H2O

  
• What is the balanced equation for cellular respiration?

  C6H12O6 + 6O2 → 6CO2+ 6H2O + ATP

  
• Explain what happens during the light dependent stage of photosynthesis.


  - First stage of photosynthesis

  - Occurs in the thylakoid membranes of the chloroplast

  - Only takes place in the presence of light

  - Chlorophyll absorbs light energy (red and blue predominantly)

  - This energy excites electrons in the chlorophyll-a molecules, resulting in their release from the molecule

  - The E from the excited electrons is used:

  In the formation of 18 ATP molecules

  To decompose 12H2O molecules into 24H atoms and 6O2 molecules

  - The H atoms are taken up by a hydrogen accepter and the O2 released into the atmosphere

  - The electrons, having release their energy, are returned to the chlorophyll molecule

  
• Explain what happens during the light independent stage of photosynthesis.

  - Does not need light energy

  - Occur in the stroma

  - Requires the products of the light-reactions

  - The H released in the light-reactions combines with CO2, using all the energy formed during the light-reactions, and extra ATP found in the cell to produce glucose.

  - This complex series of reactions is known as the Calvin cycle

  
• Contrast the light dependent and light independent stage of photosynthesis.

  Light dependent stage:

  Requires light to proceed

  Photosystems 1 & 2

  Uses light and water (&NADPH+)

  Makes ATP (18)

  Decomposes H2O molecules

  Not dependent on temperature

  Occurs in thylakoid membranes

  
  

  Light independent stage:

  Does not require light

  Calvin Cycle

  Uses ATP, CO2, and NADPH

  Uses ATP

  Uses those products to make glucose

  Dependent on temperature (enzymes)

  Occurs in the stroma

  
• What are factors that impact photosynthesis and how?

  Light intensity - increase rate until saturation point is reached.

  CO2 concentration - higher concentrations increase photosynthesis rate.

  Temperature - higher temps increase rate but can be detrimental at extremes.

  Water availability - essential for photolysis and maintaining turgor pressure; water stress inhibits photosynthesis.

  Chlorophyll concentration - higher concentrations enhance light absorption and photosynthesis activity.

  Nutrient availability - deficiencies can limit photosynthesis.

  Leaf surface area - larger - more area for light absorption

  
• Describe aerobic respiration


  Conditions for Occurrence: requires the presence of oxygen

  Efficiency: produces up to 36-38 molecules of ATP per molecule of glucose.

  Three Stages:

  1. Glycolysis:

  Glycolysis is the process in which glucose is broken down to produce energy. It produces two molecules of pyruvate, ATP, NADH and water. The process occurs in a cell's cytoplasm and does not require oxygen. It occurs in both aerobic and anaerobic organisms.

  2. Krebs cycle:

  Is a fundamental process in cellular respiration, occurring within the mitochondria of eukaryotic cells. It is crucial for generating energy in the form of ATP (adenosine triphosphate) and providing key molecules for other metabolic pathways.

  3. Electron Transfer Chain

  The electron transport chain (ETC) is a crucial part of cellular respiration, occurring in the inner mitochondrial membrane in eukaryotic cells or the plasma membrane in prokaryotic cells. It plays a central role in generating ATP, the cell's primary energy source, by transferring electrons through a series of protein complexes and other molecules.

  
• Describe anaerobic respiration


  Conditions for Occurrence: occurs when oxygen is unavailable or limited. This can happen in environments such as waterlogged soils, deep underground, or during intense physical exertion when oxygen demand exceeds supply.

  Efficiency: in glycolysis, the first stage of both aerobic and anaerobic respiration, only 2 molecules of ATP are produced per molecule of glucose.

  No oxygen

  Steps

  1. Glycolysis

  2. Fermentation

  Less efficient

  Animals: produces (2) ATP + ethanol + CO2

  Note: no ATP is produced in the fermentation step

  
• Contrast Aerobic and Anaerobic respiration


  Aerobic:

  Occurs in Cytosol and mitochondria

  Reactants: Glucose and oxygen

  Products: Carbon dioxide and water

  30-38 ATP total

  
  

  Anaerobic:

  Occurs in Cytosol

  Reactants: Glucose

  Products: Lactic acid (animals), Ethanol and CO2 (plants/fungi)

  2 ATP total

  
• What is an enzyme?

  Enzymes are biological catalysts. A catalyst is a chemical that changes the rate of a reaction without being consumed by the reaction. (part of reactions but not used up in a reaction).

  
• How do enzymes work?

  Lower activation energy needed to start a chemical reaction, without being consumed in the reaction.

  
• Define substrate.


  The reactant that bonds to the enzyme

  
• Define reactant and products

  reactant: starting materials of reactions (left)

  product: end materials of reactions (right)

  
• Explain the lock and key hypothesis

  the active site of an enzyme has a specific shape, which only allows one substrate to fit which gives the enzyme its specificity → active site is complementary shape to substrate

  
• Explain denaturing.


  - the inhibition of an enzyme permanently (i.e. it stops it working) - the usually happens outside of optimal conditions, or in the presence of certain chemicals. This process changes the shape of the active site and or enzyme.

  
• Define optimal conditions of an enzyme.

  - conditions under which a particular enzyme is most active

  
• Give examples and explain conditions that impact enzyme activity.

  Temperature: Raising temperature generally speeds up a reaction, and lowering temperature slows down a reaction. However, extreme high temperatures can cause an enzyme to lose its shape (denature) and stop working.

  
  

  pH: Each enzyme has an optimum pH range. Changing the pH outside of this range will slow enzyme activity. Extreme pH values can cause enzymes to denature.

  
  

  Enzyme concentration: Increasing enzyme concentration will speed up the reaction, as long as there is substrate available to bind to. Once all of the substrate is bound, the reaction will no longer speed up, since there will be nothing for additional enzymes to bind to.