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1: Molecules Of Life Biochemistry (Study of life’s chemistry) Molecules of life ➔ Lipids ◆ Basic structure: glycerol unit connected to fatty acids (long chains of carbon atoms)

Triglyceride ◆ Long chains of C-C bonds = good energy storage ◆ Cholesterol: VITAL to us! ● Forms basis of many signalling molecules eg. testosterone ● Stabilises cell membranes: controls the lipids in cell membrane (phospholipids): ○ Amphipathic:

Important because animals need water in their bodies to survive. Therefore essential for these oils to be able to bond with water How these cells behave in water:

Forms a bilayer. Hydrophillic on

○

Membrane lipids:

➔ Proteins (polymers) ◆ Made up of polymers ◆ Humans: 20 diff amino acids (made into proteins). How they acids are arranged will affect the function and shape of the protein. ◆ Proteins can be: ● enzymes (speed up reactions) ● Support structures in cell ● Transport molecules ● Signalling molecules (can be used as hormones) ➔ Carbohydrates (polymers) ◆ Monomer: monosaccharide. Therefore carb can be called polysaccharide ◆ Carbs can be: ● energy storage molecule ● Communication ➔ Nucleic Acids ◆ Info carrying molecules: contains code for structure and function of living things ◆ 2 types: ● DNA (deoxyribonucleic acid) ○ Sugar (deoxyribose), PO4, Sugar, PO4 etc.. ○ Base contains the info (connected to sugar) ○ These molecules are repeated (therefore are polymers) ○ Monomer: nucleotide (sugar, phosphate, base) ○ Located in the nucleus ○ Bases: T, G, A, C ● RNA (ribonucleic acid) ○ Same as above, but has ribose sugar ○ Bases: G, A, C, U DIFFERENCE: type of sugar and base is different

Revision: What are the four major molecules of life? Lipids, proteins, carbohydrates and nucleic acids. What is a polymer and which of the molecules fit this description? A polymer is a molecule that is made from repeated sequences of monomers. Proteins, carbohydrates and nucleic acids are polymers. What are some of the roles that these molecules play in living things? - Lipids are energy storing fats. Cholesterol forms the basis of many signalling molecules such as testosterone (hormone). Also stabilises the cell membrane by raising the melting point when it is hot, and inserting itself between the phospholipids in the membrane when it is cold to prevent them from stiffening and clumping together. - Proteins are also energy storing, enzymes, transportation and signalling molecules (hormones). - Carbs are energy storing, communicating molecules. - Nucleic acids store the coding for the function and structure of living things.

2: The Cell Life’s Smallest Unit Cell Membrane

➔ Cell membrane ◆ made up of lipids (refer to BB1): “lipid bilayer”. One side interacts with watery environment outside cell and other side interacts with inside ◆ Has proteins in it (refer to BB1) ◆ Semi-permeable membrane: cell chooses which molecules can enter (needed) and which comes out (waste products)

Eukaryotic Cell

Animal

➔ ➔

Human/animal cells

Plant

➔ Control centre: nucleus ◆ Contains nucleic acid (refer to BB1) ◆ Transmits info to other parts of cell via RNA (refer to BB1) ◆ Protected by two layers of membrane. Pores on the membrane control what goes in and out (“security gates”) ➔ Endoplasmic reticulum (ER) ◆ Continuous with the nuclear membrane ◆ Two forms ● 1. Rough: ○ Looks bumpy: covered in ribosomes ○ Because of ribosomes, therefore rough produces protein for the cell ○ Protein is transported along the structure ● 2. Smooth ○ No ribosomes ○ Role: toxin removal and lipid production. Can be found in liver ➔ Vesicles ◆ Products of ER end up here in these “transport bubbles” ➔ Golgi Apparatus ◆ “Post office” ◆ Can modify products received from ER, package them into approp. Combos and then ship them off to where they’re needed! ● Go to cell membrane or other areas ➔ Mitochondria ◆ “Powerhouse of the cell”: aerobic cellular respiration: breakdown of glucose in the presence of oxygen to provide cell with usable energy. ◆ Usable energy: Adenosine Triphosphate (ATP). What cell uses to drive every reaction. ➔ Cytoskeleton ◆ Organelles in eukaryotic cells held in place by long strands of protein (cytoskeleton) ◆ Roles: ● Internal structural support

● ●

Transport pathways (eg. for vesicles) Centrosome (animal only): specialised area where cell division happens

➔ Plant Cells (differences) ◆ Has cell wall: made of cellulose (carb) ◆ Has vacuole: large bubble: contains fluid, used to store starch (energy) and toxins (isolate it from rest of cell) ◆ Has chloroplast: allows plants to create their own food (glucose) ● Chlorophyll: the pigment inside (green)

●

site of photosynthesis (converting CO2 into O2 and sugar with light as energy)

Prokaryotic Cell ➔ Representative of earliest form of cell ➔ Eg. bacteria

Revision: What are the major cell types and what differs between them? Major cell types: Eukaryotic (has lots of internal compartments) and prokaryotic (has no internal membranes). Prokaryotic cells are also much smaller. What is the cell membrane composed of and what is its role? The cell membrane is composed of a lipid bilayer and its role is to control what goes into the cell (things that are needed) and what goes out (waste products) Can you draw and label a simple diagram of a eukaryotic cell? Can you explain the function of each organelle? Nucleus: the control centre of the cell. Contains nucleic acid which stores the code for structural info and functional info. Endoplasmic reticulum: Two types: Rough (because of ribosomes) - produces protein via

ribosomes. Smooth - toxin removal and lipid production. Protein is transported along the structure of the ER. Vesicles: Protein from the ER ends up here in these “transport bubbles” that deliver them to the Golgi apparatus. Golgi apparatus: receives the ER, can modify them, and package them in combinations that are needed in other parts of the cell. It then ships them off to parts of the cell. Mitochondria: “powerhouse” of the cell. Where aerobic cellular respiration occurs. Make the energy “Adenosine Triphosphate” (ATP) Cytoskeleton: long strands of protein inside the cell that holds each organelle in place. Can also act as transport pathways (eg for vesicles). Centrosome: an area where cell division occurs. For Plant cells: Vacuoles: a large bubble filled with liquid which is used to store starch (energy source for plant) and toxins (to isolate it from the rest of the cell) Cell wall: made of cellulose (carb) Chloroplast: contains chlorophyll which is the green pigment. Also where photosynthesis occurs.

3: Cell Replication Replication One Cell into Two (eg. cheek cells) ➔ Need one cell (parent cell) and divide into 2 identical cells (daughter cell) ➔ Replicated in a cycle: “cell cycle”. ➔ Eg. Garlic root tip:

Garlic root tip cells undergoing stages of ◆ Granulated appearance/strands are chromosomes. Only visible when undergoing mitosis. ➔ Chromosomes ◆ Each species has a constant chromosome number. Eg. humans have 48, dogs have 47, carrots have 18 ◆ Chromatin: uncondensed chromosome. Made up of DNA, coils around proteins “histones”

◆ Exists in two ● 1. Single stranded ○ 1 molecule of DNA (one per strand)

forms

●

2. Double stranded (strand is called chromatid. ONLY USED FOR DOUBLE STRAND!) ○ 2 molecules of DNA (one per strand)

Cell Cycle ➔ 4 stages: M, G1, S, G2 ◆ 1. Mitosis: start with double stranded DNA. End with single strand. ● Interphase: DNA and histone are v loosely coiled (granular appearance in nucleus). As cell is about to divide, we start seeing chromosomes and they condense. ● Metaphase: chromosomes start lining up across the sphindle (a part of the cytoskeleton) ● Anaphase: chromosome break up into single strands (i.e. separation of chromatids) and form single stranded chromosomes.

5: Respiration ➔ Happens in every living cell ➔ Our energy comes from complex carbs being broken down into co2 and water ➔ Overall reaction:

➔ ATP: energy molecule: adenosine triphosphate ◆ This molecule moves around cell and delivers energy to where it is needed ◆ Made by: combine adenosine diphosphate with 3rd phosphate group in a high energy bond

➔ 2 parts: ◆ Glycolysis: ● Takes 6 carbon atoms from glucouse and makes 2 pyruvate (3 carbon atoms) ● Net output: 2 ATP ● ‘Anaerobic respiration’: does not require oxygen ● Continue the reaction = fermentation (production of ethanol, CO2 (plants) or lactic acid (animals))

◆ Mitochondria: When available

oxygen IS

●

Happens in the inner membrane

➔ “Electron carrier” molecules ◆ NAD:

◆ FAD:

◆ These molecules take “high energy” electrons away from the steps in glucose breakdown and then deliver them to the membrane of the cristae. The energy is used to pump hydrogen ions across the membrane, creating a high conc of H+ on one side

➔ ATP synthase: (molecular machine) ◆ Allows hydrogen ions to move back across the membrane ◆ When this happens, ATP is synthesized from ADP and phosphate.

Revision: 1. 2. 3. 4. 5.

Why do cells respire? Where does respiration occur? What compounds are used in respiration? What waste products are produced? What molecule is used to deliver useful energy around a cell?

6: Photosynthesis ➔ Heterotrophs: ◆ Get glucose/energy by eating other things. ➔ Autotrophs: ◆ Make their own food: i.e. plants (photosynthesis) ➔ Overall reaction:

◆ Light energy is needed to drive this reaction ◆ Chlorophyll is responsible for trapping light energy. ● Embedded in the chloroplast (refer to BB1) ● Light energy hitting chlorophyll excites electrons, and this energy is spent moving hydrogen ions across the membrane. Membrane has ATP synthase. When hydrogen move across this synthase, it produces ATP. Some of the energy also made into NADPH

➔ Two parts: ◆ Photo: trapping the light ● ‘Light reaction’: chlorophyll catches light energy, H2O donates electrons

●

and by-product is o2. Packaged into ATP and NADPH, then shipped to synthesis side of reaction

◆ Synthesis: synthesizing the carb ● Making the glucose: ○ Rubisco is an enzyme that draws the CO2 into the cycle

◆ Energy is transferred between the two parts via ATP and electron carriers (NADPH)

Revision: 1. 2. 3. 4. 5. 6. 7.

What is an Autotroph? What is photosynthesis? Where does photosynthesis occur? What molecule traps the light energy? What molecules are used in the overall chemical reaction? What does the light reaction produce? What does the Calvin-Benson cycle produce?

8: The Scientific Method: Show Me the Evidence Evolution of Thinking ➔ Aristotle: observation and explanation, but no experimental testing ◆ Spontaneous generation (life emerged from non-living matter) ➔ Francesco Redi: Test aristotle’s theory: meat experiment - first recorded use of a control

➔

What Makes a Good Hypothesis? ➔ Concise and objective explanation of an observed phenomenon ➔ Based on prior observations and/or experiments ➔ Includes measurable variables

➔ Leads to specific testable predictions ➔ HYPOTHESIS does NOT EQUAL THEORY

What Makes a Good Experimental Design? ➔ ➔ ➔ ➔ ➔

Specifically addresses a prediction arising from a hypothesis May be controlled (manipulative) or comparative (unmanipulated) Includes enough replicates to be statistically valid Minimises bias Repeatable

Controlled Experiment ➔ ➔ ➔ ➔

Attempts to isolate the cause of the effect observed in the experimental group Negative control: no result Positive control: has a result Unexpected results in control group (positive result for negative control and vice versa) you need to repeat your experiment as your results are invalid

Revision: 1. 2. 3. 4. 5.

What are the basic steps in the scientific method? What are some of the features of a good hypothesis and experimental design? What is a control and why is it important? How would you respond to unexpected results in your control group? If your hypothesis was rejected, what steps would you take?

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