Structure and Functions in Living Organisms - a, b, c, d, f

What are tissues?

cells with similar function grouped together

What are organs?

collection of several tissues carrying out a particular function

- Ogran system: different organs working togeth

What are organ systems?

different organs working together

Level of Organisation in Plants

have tissues and organs (leaves, roots, stems, flowers)

Level Organisation in Animals

jobs carried out by organ systems: digestive, gas exchange, circulatory, excretory, nervous, endocrine, reproductive

Cytoplasm

jelly-like substance, makes up most of cell, where chemical reactions take place (metabolism)

Nucleus

controls cell activities by determining which proteins cell can make, contains chromosomes which carry genetic material

Cell Membrane

thin layer, boundary between cytoplasm and outside, selectively and partially permeable, detects external environment and sends signals to rest of cell

Ribosomes

where proteins are assembled (protein synthesis)

Mitochondria

carry out reactions of aerobic respiration (most respiration), releases energy cells can use

Cell Wall

tough material, helps cell keep its shape, cellulose resists pressures when plants absorb water, gives plant support, freely permeable

Vacuole

large central space surrounded by permanent membrane, filled with cell sap which stores dissolved sugars, mineral ions

Chloroplast

absorbs light energy for photosynthesis, contains chlorophyll

Similarities between Animal and Plant Cells

have nucleus, cell membrane, mitochondria, cytoplasm, ribosome

Differences between Animal and Plant Cells

plant cells have a cell wall, chloroplast and vacuole, while animal cells do not

Diffusion

net movement of particles from a region of high to low concentration (down concentration gradient)

Osmosis

net diffusion of water from solution of high to low water potential across selectively permeable membrane

Osmosis in Plants (when cells absorb water)

swell up, cytoplams pushes against cell wall, turgid

Osmosis in Plants (when cells lose water)

shrivel, flaccid, plasmolyse

Osmosis in Animal Cells (when absorb water)

no cell wall, absorb water, swell, burst

Osmosis in Animal Cells (when lose water)

shrink

Active Transport

movement of particles from region of low to high concentration through selectively permeable membrane using energy from respiration in form of ATP

What factors affect the rate of movement of substances?

concentration gradient (steeper concentration gradient, more diffusion), surface area to volume ratio (greater SA:Vol, more diffusion), diffusion distance (lower distance, more diffusion, temperature (higher temperature, more KE, more diffusion)

Method to Investigate Diffusion

cut 1cm3 cube of agar (made using 0.1mol sodium hydroxide and coloured with phenolphthalein indicator), place cube in 0.5mol solution of hydrochloric acid for two minutes, remove cube and wash in water, cut cube in half and measure distance that agar has become colourless, repeat experiment two more times and calculate mean, repeat using 1, 1.5 and 2mol solutions of hydrochloric acid

Method to Investigate Effect of Osmosis using Non-living Systems

fill one boiling tube halfway with distilled water, another with concentrated sucrose solution and the other empty, peel potato and cut into three 5 by 1 by 1cm chips, blot each chip gently to remove excess moisture, find mass of each using mass balance, place one chip in each boiling tube, remove after 30 minutes, blot to remove excess liquid, reweigh, calculate percentage change

Method to Investigate the Effect of Osmosis on Living Systems

place drop of concentrated sucrose solution on microscope slide and drop of distilled water on another, remove two small squares of inner epidermis from the outer layers of an onion, place one on each slide, place drop of solution on each, add cover slip and blot excess liquid with filter paper, examine each slide through microscope

Chemical Elements in Carbohydrates, Proteins, and Lipids

carbon, hydrogen, oxygen

Chemical Elements in Proteins

hydrogen, carbon, oxygen, nitrogen (can have sulfur)

Chemical Elements in Lipids

carbon, hydrogen oxygen

Structure of Carbohydrates

monosaccharides are single sugars (glucose, fructose), disaccharides are made of two monosaccharides joint together (sucrose), polysaccharides are made of many monosaccharides joint together (starch, glycogen, cellulose)

Structure of Lipids

lipids are made up of glycerol and fatty acids, most are triglycerides which are made of one glycerol molecule joined to three fatty acids

Structure of Proteins

proteins are polymers made from different amino acids linked in long chains, which fold or twist into spirals held by cross-links, different proteins have different amino acid sequences resulting in them having different shapes (shape of protein determines its function)

Test for Lipids

add ethanol and water, cloudy emulsion forms

Test for Glucose

add Benedict’s reagent, heat, from blue to orange/red

Test for Starch

add iodine, from yellow to black

Test for Protein

add biuret, from blue to purple

Role of Enzymes

biological catalysts which speed up reaction without being used up itself, necessary to carry out reactions at fast enough speed to allow life to go on

Process of an Enzymatic Reaction

substrate attaches to specific enzyme's active site, lowers energy needed to start reaction, allows products to be formed more easily, product released from the active site, enzyme free to act on more substrate

Affect of Temperature on Enzyme Function

increase in temp, increase kinetic energy of enzyme and substrate, more collisions, above 40, enzyme denatures (permanently changes shape), substrate does nto fit in active site, enzyme cannot catalyse reaction

Method to Investigate the Effect of Enzyme Function on Enzyme Activity

1. Add three drops of iodine solution in each dip of spotting tile

2. Place 5cm³ of starch suspension with a syringe in a boiling tube, and 5cm³ of amylase solution in another tube, using a different syringe.

3. Place both boiling tubes in beaker of water for 5 minutes and record the temperature.

4. Pour amylase solution into starch suspension, and place test tube in water bath.

5. Immediately remove small sample of mixture using a pipette and add to 1 drip of iodine solution on spotting tile. Record colour of iodine.

6. Repeat this every 30 seconds for 10 minutes until the iodine solution remains yellow.

7. Repeat experiment, with water bath at different temperatures between 20-60 °C

8. Calculate the RoR (volume of starch/ time taken)

Affect of pH on Enzymes Function

- optimum pH: 7

- rate of reaction decreasing at more acidic or alkaline pH levels.

- At extremes, enzyme denatures (permanently changes shape), substrate no fit in active site, enzyme no longer catalyse reaction.

Method to Investigate how Enzyme Activity can be Affected by Changes in pH

- Place 5cm3 of potato extract (contains catalyse, breaks down hydrogen peroxide to water and oxygen) in a boiling tube using a syringe and 5cm3 of pH 7 buffer solution (resist pH change) in from another syringe.

- Shake gently, and leave for 5 mins.

- Add 5cm3 of 5% hydrogen peroxide solution in with a third syringe, and quickly insert the bung, delivery tube, and beaker of water.

- Count the bubbles of oxygen gas produced in the first minute.

- Repeat the experiment using different pH buffer solutions.

Aerobic Respiration

- Aerobic respiration is a process where glucose is oxidised, releasing carbon dioxide, water, heat, and producing ATP as the main energy source for cells.

- glucose + oxygen → carbon dioxide+ water

Differences between Aerobic Respiration and Anaerobic Respiration

- Aerobic respiration occurs in the presence of oxygen, while anaerobic respiration occurs when in short supply or absent

- In anaerobic respiration, glucose is not completely broken down, so less energy is released.

- Anaerobic respiration occurs in the cytoplasm, whilst aerobic respiration occurs in the mitochondria.

Anaerobic Respiration in Yeast Cells

Glucose is partly broken down into ethanol (alcohol) and carbon dioxide with the release of some ATP.

Anaerobic Respiration in Muscle Cells

- Glucose is broken down into lactate and release some ATP.

- Lactate levels rise, produces oxygen debt (extra oxygen needed to remove lactate, why breathing and heart rate high)

Colour Change of Hydrogen Carbonate Indicator

- increase in CO₂: orange to yellow

- decrease in CO₂: orange to purple

Method to Investigate the Evolution of Heat

1. Soak peas in water for 24 hours to allow them to germinate.

2. Boil a second batch of peas to kill them

3. Wash each batch with 1% bleach solution to kill bacteria present on surface, and rinse twice in distilled water, to remove bleach

4. Place each batch in a inverted vacuum flask to easily measure temperature changes, leaving some air in each to allow dense CO₂ out (which could kill peas)

5. Measure the temperature, leave the apparatus for a couple of days and measure the temperature at the end.