Topic 1

ALL CARDS COMPLETE!

What do animal cells have

• Nucleus

• Cell membrane

• Mitochondria

• Ribosomes

What do plant cells have

• Nucleus

• Cell membrane

• Mitochondria

• Ribosomes

• Cell wall

• Chloroplasts

• Vacuole

What do bacteria cells have

• Chromosomal DNA

• Plasmid DNA

• Cell membrane

• Ribosomes

• Flagella

Nucleus

• Contains DNA coding for a particular protein needed to build new cells

 

Cytoplasm

 

• Liquid substance in which chemical reactions occur

• Contains enzymes

 

Cell membrane

• Controls what enters and leaves the cell

 

Mitochondria

• Where respiration occurs

 

Ribosomes

• Where protein synthesis occurs

Chlorplast

• Where photosynthesis occurs

• Contains chlorophyll

Vacuole

• Contains cell sap

• Keeps cell rigid

Cell wall

Provides strength for the cell

Plasmid DNA

• Small rings of DNA

• Code for extra genes to chose provided by chromosomal DNA

Flagella

Tails attached to the bacteria so they can move

How are sperm cells specialised (4)

• Acrosome

  • contains enzymes which break down outer layers of the membrane of the egg cell

  • On the head of the sperm

• Haploid nucleus

  • Has 23 chromosomes rather than 46

• Mitochondria

  • Has many mitochondria

  • Means lots of respiration occurs -> more energy to allow sperm cell to move

• Tail

  • Long tail helps swimming

How are egg cells specialised (3)

• Nutrients in the cytoplasm

  • Allow for quick, repeated division as the embryo grows

• Haploid nucleus

  • 23 chromosomes

• Changes in the cell membrane after fertilisation

  • During fertilisation the cell membrane can only accept one sperm cell

  • After, it becomes impermeable

 

How are ciliated epithelial cells adapted to their function (1)

• Cilia

  • Long cilia waft bacteria (that has been trapped by mucus) down to the stomach

  • In the stomach the bacteria is killed by stomach acid

What is the order for prefixes

• Milli is the biggest

• micro

• nano

• pico is the smallest

Milli

• 10^-3

Micro

10^-6

Nano

10^-9

Pico

10^-12

Explain the mechanism of enzyme action

• Enzyme action is explained using the lock and key model

• Specific substrates will fit into the active site of an enzyme

• When an enzyme and its complementary substrate collide, an enzyme-substrate complex forms

• Then the enzyme catalyses the reaction and the product is released from the active site

 Explain how enzymes can be denatured due to changes in the active site

• If enzymes are exposed to extremes of pH or temperature, then the shape of the active site will change

• This means the substrates no longer fit the enzymes, so the enzyme has been denatured

 Explain the effects of temperature on enzyme activity

• As the temperature increases so does the rate of enzyme activity

• An optimum temperature is reached at a certain point and this is when it is optimum activity

Effects of pH on enzyme activity

• Changes in pH alter the shape of an enzyme's active site

• Each enzyme works best at a specific pH

• The optimum pH is where the enzyme usually works

Effects of substrate concentration on enzyme activity

• Enzymes work best where there is plenty of substrate

• As the concentration of substrate increases so does the rate of enzyme activity

What is the formula for rate of reaction

• Change / time

• E.g. If it takes 30 mins for protease enzyme to break down 5g of protein, we would do 5g / 30 mins

what is the test for starch

• Add iodine solution to a food sample

• If starch is present, colour will go from orange to blue/black

 

1.13 - what is the test for reducing sugars

• Add the solution you are testing and some blue Benedict's solution to a test tube

• Place in a boiling water bath for 5 minutes

• If there are reducing sugar's then the colour will be green to brick-red

 

1.13 - what is the test for proteins

• Biuret test

• Add sample of biuret to the food and shake well

• If there are proteins then it will go purple, if there are not it will stay blue

 

1.13 - what is the test for lipids

• Ethanol emulsion test

• Add some ethanol to food and shake thoroughly

• If lipids are present then there will be a cloudy emulsion at the top

• If there are no lipids it will be colourless

 What are the three ways that substances can be transported in and out of cells

• Diffusion, osmosis or active transport

 

1.15 - explain diffusion

• Does not require energy

• Molecules move in every direction and collide with each other

• Net movement is from an area of high concentration to low concentration

 

1.15 - explain osmosis

• Does not require energy

• Only applies to water

• Movement is from a dilute solution to a more concentrated solution, across a selectively permeable membrane

 

1.15 - explain active transport

• Requires energy

• Energy comes from ATP

• Movement is across a concentration gradient - so from an area of low concentration to an area of high concentration

1.16 - explain the method for investigating osmosis in potatoes

• Cut potatoes into small discs of equal size

• Blot gently with tissue paper to remove excess water

• Measure the initial mass of each disk

• Place disks in sucrose solutions of different concentrations

• Blot with tissue paper again and record new mass

• Work out percentage change to see the loss / gain of mass

1.16 - what are the variables in this experiment

• Independent = concentration of sucrose solution

• Dependent - change is mass of potato disks

• Control = diameter of potato disks

 

1.16 - what is happening in this experiment

• Water is moving by osmosis from a more dilute solution (potato) to a more concentrated solution (sucrose solution) across a selectively permeable membrane

 

1.17 - calculate percentage change of mass in osmosis

• (change in mass / start mass) x 100

1.3 - Explain how changes in microscope technology have enabled us to see cell structures and organelles in more clarity and detail

• The development of the electron microscopes helped scientists to learn about the sub-cellular structures involved in aerobic respiration called mitochondria

• The scientists developed their explanations about how the structure of the mitochondria allowed it to efficiently carry out aerobic respiration

ESQ: Describe how to use a microscope to view onion plant on a slide

• Place the slide on the stage of the microscope

• Look through eyepiece lens

• Turn the focusing wheel to obtain a clear image

• Start from the lowest objective lens magnification and increase it

 

ESQ: How to put a specimen at x400 magnification

• 10x eyepiece lens

• 40x objective lens

 

Method for putting a specimen on a slide

• Get thin slice of specimen

• Use a pipette to put a drop of water on the slide, to secure the specimen in place

• Using tweezers place the specimen on the water

• Add a drop of stain to see the specimen clearly

• With a toothpick, lower the coverslip down at 45 degrees so that there are no air bubbles

• Clip the slide securely to the stage

 

After you have put the specimen on the slide what do you do

• Start with the lowest objective lens

• Use the coarse focusing wheel to move the stage up

• Move the slide so the cell is in the middle

• If needed, use higher power objective lens

• Use the fine focusing wheel to focus on the cell

How to set up an experiment for investigating pH on enzyme activity

• Put a Bunsen burner on a heat-resistant mat, and a tripod and gauze over it

• Put a beaker of water on the tripod and keep the temperature constant

• Place a drop of iodine on every depression of a spotting tile

• Add amylase solution to a test tube

• Add starch solution to a test tube

• Add pH solution to the test tube

 

What to do next

• Mix the solution and place it inside the beaker of water

• Use a pipette to remove a few drops of solution every 20 secs, then put it in the spotting tile

• Repeat until iodine solution stops turning black

• Record the time this takes

• Repeat with different solutions

Why are enzymes important in terms of their role

• Enzymes are biological catalysts - they speed up the rate of reaction without being used up themselves

• Some enzymes synthesise larger molecules from smaller molecules

 

What molecules can enzymes break down into what

• Carbohydrates are synthesised into sugars

• Proteins are synthesised into amino acids

• Lipids are synthesised into fatty acids and glycerol

1.14 - Explain how energy contained in food can be measured using calorimetry

• Small samples of a material are placed in a calorimeter which burns them

• The energy given off when the material burns is measured

• This is displaced in joules or calories on food packaging