bio - paper 1

describe how you would prepare a microscope slide for analysis

• peel off epidermal layer using forceps

• place sample on drop of water on microscope slide

• add drops of iodine solution to sample

• lower cover slip onto sample using mounting needle

why is a thin sample of tissue required

allows light to pass through so internal structures can be observed

why is water added to the slide before the sample is mounted

allows the sample to be suspended between the slide and the cover slip, and ensures the cover slip stays in place

why is iodine solution added to stain cells

iodine solutions adds contrast-reacts with starch in plant cells and turns blue-black; allows internal structures to become more visible.

why is the cover slip lowered using a mounting needle

ensures that no air bubbles are trapped

how would you measure the length of a cell viewed under the microscope

measure using eyepiece graticule and calibrate with stage micrometer

how would you calculate the magnification of an image

magnification=observed cell length / actual cell length

what safety precautions should be taken during this experiment

safety goggles when handling iodine solution

what antiseptic techniques can be used to avoid contamination?

• spray working area with disinfectant and wipe dry

• wash hands with antibacterial wash

• flame the neck of the culture bottle

• lift the lid of the agar plate at an angle

• dip spreader in ethanol and pass through bunsen flame before spreading bacteria

• use forceps to place antibiotic discs

describe how you could investigate the effect of antibiotics on bacterial growth using zones of inhibition

• divide agar plate with bacteria into three segments

• use forceps to place filter paper disc with antiseptic in each zone

• loosely tape lid onto agar plate to allow oxygen to reach bacteria

• incubate at 25*C for 48 hours

• measure the diameter of clear zones using a ruler from two opposite directions-calculate mean of measurements

• calculate area of clear zones.

how would you measure the zone of inhibition

use a ruler to measure from a point on one side to a point directly opposite

measure again at 90* to first diameter measurement in order to calculate a mean

why should you not completely seal the agar plate

to allow oxygen to enter the agar plate, preventing the growth of harmful anaerobic bacteria

why is it necessary to measure the diameter of the zone of inhibition twice?

clear zones are not always uniform-taking more than one measurement allows a mean diameter to be calculated

what equation is used to calculate the area of clear zones?

area = pi radius squared

what is osmosis?

the movement of water from a higher water potential to a lower water potential through a partially permeable membrane

describe how you would carry out an investigation into osmosis using potato tissue

• cut identical potato cylinders using a cork borer

• measure and record the length and mass of cylinders using ruler and balance

• add each cylinder to one of three solutions: 1m sugar solution, 0.5m sugar solution and distilled water

• leave cylinders in tubes overnight

• remove cylinders from tubes and blot them using paper towe;s

• record length and mass of each cylinder

• draw graph of change in mass in grams against concentration of solution in mol dm-3

why is it necessary to use a cork borer to cut the cylinders

results in equal sized samples so changes in length and mass can be compared easily

why is it necessary to blot the cylinders with paper after removing them

each cylinder may have a different amount of water on its surface, so masses may vary

blotting cylinders allows masses to be comparable

what safety precautions should be taken with this experiment

handle cork borer and scalpel with care

describe how you would prepare a sample of food to be tested

grind up food samples using pestle and mortar

mix with water

filter with funnel and filter paper

describe how you would test for the presence of starch in a sample

add iodine solution to sample

if starch is present, solution turns from brown to blue-black

describe how you would test for the presence of a reducing sugar in a sample

add Benedict’s reagent to sample

boil test tube in a hot water bath

if reducing sugar is present, a brick red precipitate forms, if not it remains blue

describe how you would test for the presence of protein in a sample

add biuret reagent

shake mixture

if protein is present, solution turns from blue to purple

describe how you would test for the presence of lipids in a sample

add ethanol to the sample

add water to the sample

shake test tube

white emulsion formed if lipid present

describe how you would investigate the effect of pH on the rate of reaction of the amylase enzyme

• place starch solution, amylase solution and buffer solution in a water bath at 25 for a few minutes

• combine solutions and add a drop of the mixture to iodine solution of a tile

• add the mixture to iodine solution drops on the tile at fixed 30s intervals until the iodine solution remains brown

• calculate the rate of reaction using 1 / time taken for solution to remain brown

• repeat at different pH values using different buffer solutions

• plot graph of rate against pH

which enzyme catalyses the breakdown of starch in the human digestive system

amylase-starch to maltose

why must samples be left in the water bath before solutions are mixed

to allow temperature to equilibrate

what is a buffer solution

a solution which can resist changes in pH

What is cellular respiration?

Process that releases energy from glucose in the presence of oxygen

What is aerobic respiration?

An exothermic reaction in which glucose is broken down using oxygen to produce carbon dioxide and water and release energy for the cells

How often does aerobic respiration occur?

All the time

Why is aerobic respiration called aerobic respiration?

It uses oxygen from the air

Why is aerobic respiration important?

It provides energy for an organism to survive

What is the word equation for aerobic respiration?

glucose + oxygen → carbon dioxide + water (energy transferred to the environment)

What is the symbol equation for aerobic respiration?

C₆H₁₂0₆ + 60₂ → 6CO₂ + 6H₂0 (+ energy transferred to the environment)

What is an exothermic reaction?

A reaction where energy is transferred to the surroundings

Why do boys (on average) need more energy than girls daily?

Girls are generally smaller than boys, and boys have more muscle cells

Why does having more muscle cells result in more energy required?

More cells mean more mitochondria, meaning more fuel is needed for aerobic respiration

Where are enzymes made for respiration (in a cell)?

The cytoplasm

What are mitochondria?

Organelles that provide energy for the cell

Where do most of the reactions for respiration happen in your cells?

Mitochondria

What feature of the mitochondria enhance cellular respiration?

A folded inner membrane

Why do folded inner membranes of mitochondria aid cellular respiration?

They provide a large surface area for the enzymes involved in aerobic respiration

What amount of x shows how active a cell is?

Mitochondria

What are the four reasons why an organism needs to respire?

1. To carry out the basic functions of life (synthesis reactions and digestion)

2. Muscular activity

3. Thermoregulation

4. Moving mineral ions in plants and convert sugars into amino acids

4. Moving mineral ions in plants and convert sugars into amino acids

What is metabolism?

Sum of all chemical reactions in the body (which are controlled by enzymes)

What is anaerobic respiration?

Respiration without oxygen

What is the word equation for anaerobic respiration?

glucose → lactic acid + energy

Does anaerobic respiration release more or less energy that aerobic?

Less as the glucose isn't fully oxidised

When do we use anaerobic respiration?

During times of increased physical activity when we use up oxygen faster than we can inhale and exhale

What do plants and yeast produce when they respire anaerobically?

Ethanol and carbon dioxide (instead of lactic acid)

What is the word equation for anaerobic respiration in plant and yeast cells?

glucose → ethanol + carbon dioxide

What is anaerobic respiration in yeast cells called?

Fermentation

Why is fermentation of yeast of value?

To produce bread and alcoholic drinks (makes bread rise, produces alcohol)

What happens to your respiration when you exercise?

You respire more

Why do you respire more when you exercise (2 reasons)?

- Muscles need energy from respiration to contract

- More moving muscles = more energy

What happens to you when you exercise? (physical response)

Your breathing rate and heart rate increase to get more oxygen into the blood to create energy at your muscles and to get carbon dioxide out quicker

What happens when you do vigorous exercise?

You anaerobically respire

What does anaerobic respiration during exercise lead to?

An oxygen debt

What does the build up of lactic acid cause?

Muscle fatigue and cramps

What is an oxygen debt?

The amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells

What is the effect of an oxygen debt on you?

You breathe heavier to get more oxygen in your blood

Apart from reacting with oxygen, how else does the body get rid of lactic acid?

Converting it back to glucose in the liver

How can you measure the effect of exercise on the body?

Measure breathing rate by counting breaths and heart rate through measuring a pulse (eg: you have a higher breathing rate whilst running than sitting)

How can we reduce the rate of errors in studies of exercise?

Use a larger sample and plot the average

What gas do plants require to perform photosynthesis?

Carbon Dioxide

What is the main energy carrier found in all cells?

ATP

What is the main energy source needed by all cells?

Glucose

What light absorbing molecules gather energy from the sun?

Pigments

What are the two parts of photosynthesis?

Light dependent reaction and calvin cycle.

What does the light dependent reaction give the calvin cycle?

ATP NADPH

Organisms that make their own food.

Autotrophs

Organisms that dont make their own food

Heterotrophs

Three Parts of an ATP molecule?

Adenosine Triphosphate Ribosome

When is energy released from an ATP molecule?

When the third phosphate breaks off

What makes up an ADP molecule.

Adenosine Diphosphate ribosome

What did Van Helmont conclude

Plants gain their mass from water

What did Ingenhousz prove?

Plants only produce oxygen in light.

Photosynthesis converts water and carbon dioxide into what?

Oxygen Glucose

What is the name of the main pigment found in plants?

Chlorophyll

What are the colors of the visible spectrum?

Red Orange Yellow Green Blue Indigo Violet

What is a granum?

Thylakoid stack

What is the stroma?

area in the chloroplast between granum

What is the product of the calvin cycle?

Glucose NADP+ ADP

What affects the rate of photosynthesis?

Water temperature light

Equation of photosynthesis

6H2O + 6CO2 -> 6O2 + C6H12O2

What is the process of converting glucose into chemical energy in the presence of oxygen.

Cellular Respiration

What is the process of breaking a glucose molecule down into 2 pyruvic acids?

Glycolysis

Where does cell respiration take place?

Cytoplasm Mitochondria

What process occurs without oxygen and converts NADH back to NAD+

Fermintation

Two types of energy carriers in the cell.

Glucose ATP

What are the three parts of cell resperation?

Glycolysis Krebs Cycle electron transport chain

Chemical equation for cell resperation?

6O2 + C6H12O2 -> 6CO2 + 6H20 + 36ATP

What are the two types of fermintation?

Alcohol Lactic Acid

Chemical equation for lactic acid fermintation?

Pyruvic Acid + NADH -> lactic acid + NAD+

Chemical equation for alcohol fermintation?

Pyruvic Acid + NADH -> Alcohol + CO2 + NAD+

What gas is released in cellular respiration?

Carbon Dioxide

How many ATP are produced from a single glucose molecule?

2 ATP

What are the products of cell respiration?

NADH, FADH2 2 ATP and CO2