4th Form Trinity Biology Revision

What is the function of the cell membrane?

A semi-permeable membrane made of a phospholipid bilayer that controls what enters and exits the cell

What is the function of the cytoplasm?

A jelly-like substance where chemical reactions take place

What is the function of the nucleus?

Controls the activities of the cell and contains DNA providing information for the cell

What is the function of the ribosomes?

Where protein synthesis happens (making proteins)

What is the function of the mitochondria?

The site of respiration, where oxygen is used up and energy is released

What is the the function of the cell wall?

Gives the cell strength and support, permeable (allows anything through), made of cellulose

What is the function of the large permanent vacuole?

The space in the cytoplasm filled with cell space that helps keep the structure of the cell

What is the function of the chloroplasts?

Contains chlorophyll (green pigment) which absorbs sunlight and is the site of photosynthesis

Define a membrane-bound organelle

An organelle that is contained within its own membrane

Give an example of a membrane-bound organelle

Nucleus, mitochondria, large permanent vacuole, chloroplasts

Define a eukaryotic cell

Cells that have a nucleus and other membrane-bound organelles (e.g. animal cells, plant cells)

Define a prokaryotic cell

Cells that do not have a nucleus or membrane-bound organelles (e.g. bacteria)

What is the function of the plasmids?

Small loops of extra DNA that aren’t part of the chromosomes. These contain genes for things like drug resistance, and can be passed between bacteria

What is the function of the flagellum?

A long, hair-like structure that aids cell movement

What is the function of the pili?

Hair-like structures that sense the environment and aid cell movement

What is the function of the nucleoid region?

Houses the majority of the cell’s DNA

Define magnification

How many times larger the image is compared to the actual specimen

Define resolution

The ability to distinguish between two points

Can light microscopes examine live specimen?

Yes

Can electron microscopes examine live specimen?

No

Which type of microscope has higher resolution?

Electron microscope

Which type of microscope has higher magnification?

Electron microscope

Which microscope is easier to transport and use?

Light microscope

Can light microscopes view 3D images?

No

Can electron microscopes view 3D images?

Yes

What kind of images do Transmission Electron Microscopes view?

2D images with high resolution and magnification

What kind of images do Scanning Electron Microscopes view?

3D images with lower magnifications

Describe the preparation of an onion cell slide

Peel a thin layer of onion tissue using forceps. Place the onion tissue on a microscope slide using forceps. Add one or two drops of iodine solution to the slide. Place a coverslip on the onion tissue at an angle, ensuring to remove any air bubbles. Place the microscope slide onto the stage and view under the lowest magnification objective lens using the coarse and fine focus to bring it into view

What does the eyepiece lens do?

Further magnify the image produced by the objective lens

What does the objective lens do?

Produce an initial magnified image of the specimen

What is the magnification of the eyepiece lens?

x10

What is the magnification of the objective lens?

x4, x10, x40

Describe the preparation of epithelial cells

Use a sterile cotton wool bud to scrape the inside of your cheek to dislodge some epithelial cells. Touch the bud onto the surface of a clean microscope slide to transfer the cells. Add one drop of methylene blue stain to colour the cells. Place a cover slip onto the slide, avoiding air bubbles. Using low power x4 objective, bring the cells into focus. Continue observing using the x10 and x40 objective lens

Formula for calculating magnification

Magnification = image size/actual size

Define an enzyme

A protein that acts as a biological catalyst, meaning they speed up chemical reactions in an organism

What is a substrate?

Something that is broken down by an enzyme

What is the active site?

The region of the enzyme which the substrate binds to

The substrate is _____________ to the shape of the active site

Complementary

Describe what happens between a substrate and an enzyme

The active site is complementary to the substrate. The substrate will bind to the active site of the enzyme. This forms the enzyme-substrate complex. The enzyme has broken down the substrate into products. This is now called the enzyme-product complex. The products are released from the active site. The enzyme is unchanged

Why do sperm cells have an acrosome containing digestive enzymes?

To break down the egg cell membrane

Why do sperm cells have lots of mitochondria?

To release lots of energy to move

What is the function of a sperm cell?

Carrying genetic information and fertilising an egg cell to produce a zygote

What is the function of a red blood cell?

To transport oxygen around the body

Why do red blood cells have a biconcave shape?

To increase surface area to carry more oxygen

Why do red blood cells have no nucleus?

To carry more oxygen

Why are red blood cells small?

To fit through capillaries

Why do red blood cells contain haemoglobin?

To help the cell carry more oxygen

What is the function of ciliated epithelial cells?

They are present in the airways as a physical barrier to dust and bacteria

Why do ciliated epithelial cells have cilia (hairs)?

To trap bacteria and waft it up the mouth away from the lungs

What three factors affect the rate of enzyme activity?

Temperature, pH and substrate concentration

What is the optimum temperature?

The temperature at which the enzyme is working at its maximum rate

Why does the rate of enzyme activity decrease after the optimum?

The enzyme denatures

What does denature mean?

The active site changes shape so the substrate no longer fits into the active site because the substrate and the active site are no longer complementary

Describe the method for the practical of effect of pH on amylase activity

Drop 1 drop of iodine solution into each depression of a dimple tile. Measure 2cm3 of amylase solution into a test tube using a syringe. Add 1cm3 of your pH solution to the test tube using a second syringe. Record the pH of the solution that you are using. Using a third syringe, add 2cm3 of starch solution to the mixture and start the stopwatch. Use the pipette to stir the mixture. After 20 seconds, take a small amount of the mixture in the pipette and place 1 drop of it on the first iodine drop on the tile. Return the rest of the solution in the pipette to the test tube. If the iodine solution turns black, then there is still starch in the mixture and you should repeat step 5 (after 10 seconds). If it remains yellow, then all the starch is digested and you should record the time taken for this to happen. Repeat the experiment using a solution with a different pH

What is the test used to identify starch?

Iodine solution

What is the test used to identify reducing sugars?

Benedict’s solution (place in water bath)

What is the test used to identify proteins?

Biuret’s solution

What is the test used to identify lipids?

Emulsion test (ethanol + water + shake)

What is the positive result of the iodine solution?

Blue/black

What is the positive result of the Benedict’s solution?

Brick red

What is the positive result of the Biuret’s solution?

Purple

What is the positive result of the emulsion test?

Milky/cloudy

What is the negative result of the iodine solution?

Yellow/orange

What is the negative result of the Benedict’s solution?

Blue

What is the negative result for the Biuret’s solution?

Blue

What is the negative result for the emulsion test?

Colourless

What are calorimeters used for?

Calculating the energy content of food

What is the equation for energy absorbed?

Energy absorbed = 4.2 x mass of water x temp rise

What is the equation for energy per gram?

Energy per gram = 1.0/mass of sample x energy absorbed

Describe the practical of calorimetry

Use the measuring cylinder to put 20cm3 of water into a test tube. Clamp the test tube at the angle shown in the diagram. Record the temperature of the water in the test tube. Take a small food sample and record its mass. Fix the food sample on the end of a mounted needle. Set the food alight by holding it in the Bunsen flame. As soon as it is alight, hold it at arm’s length, so that the tip of the flame touches the test tube. If the flame goes out, quickly relight the food. When the food finally stops burning, drop the sample into a discard beaker. Stir the water in the test tube with the thermometer and record the temperature. Empty the test tube and refill it with another 20cm3 of water. Repeat steps 2 to 6 using a different food each time

What is the industrial version of a calorimeter?

Bomb calorimeter

Why does the laboratory experiment give us a less accurate measurement of energy absorbed than the bomb calorimeter?

Heat enegy will be lost to surroundings, not all the food is completely combusted, there is no stirrer

Why is it useful to stir the water in a bomb calorimeter?

So the heat is evenly distributed

Define diffusion

The net movement of particles from an area of high concentration to an area of low concentration

What does a passive process mean?

It does not require energy

How does the concentration gradient affect diffusion?

The steeper the concentration gradient, the faster the rate of diffusion

How does the surface area affect diffusion?

The bigger the surface area, the faster the rate of diffusion

How does the diffusion distance affect diffusion?

The longer the diffusion distance, the further the particles need to move, therefore the slower the rate of diffusion

How does the temperature affect diffusion?

The higher the temperature, the more kinetic energy the particles have. So, the rate of diffusion will be faster

Give an example of diffusion in the body

The alveoli - part of the respiratory system allowing gas exchange from the air in our longs we breathe in, into the blood

What are the vili (diffusion)?

Small extensions on the surface of the small intestine, aiding in the absorption of nutrients you eat, from the small intenstine into the blood

Define osmosis

The net movement of water molecules from a high water concentration to a low water concentration across a semi-permeable membrane

What is the water concentration like in a hypertonic solution?

Low water concentration

What happens to animal cells placed in a hypertonic solution?

Cells become crenated

What is the water concentration like in an isotonic solution?

The concentration of water is the same inside and outside the cell

What is the water concentration like in a hypotonic solution (e.g. pure water)?

High water concentration

What happens to animal cells placed in a hypotonic solution (e.g. pure water)?

Cell lysis occurs

What happens to plant cells that are placed in a hypertonic solution?

Cells become plasmolysed

What happens to plant cell placed in a hypotonic solution (e.g. pure water)?

Cells become turgid

Describe the potato practical for osmosis

Label the test tubes A-F. Bore 6 3cm long potatoes, dry with a paper towel and weigh them. Record the mass of each potato cylinder. Place one into each boiling tube. Cover with one of the solution in each test tube. Leave for at least 20 minutes. Remove and dry each potato core and weigh them. Record the mass of each potato cylinder in a table.

Define active transport

The net movement of particles from a low concentration to a high concentration, across a semi-permeable membrane, requiring energy and a carrier protein

Why do cells need to divide?

Asexual reproduction, repair of tissues, growth

What occurs during mitosis?

The cell divides into 2 cells

Define mitosis

The process of a cell dividing, producing two genetically identical diploid daughter cells

What happens during interphase?

The chromosome duplicates its DNA, splitting in 2 so each chromatid has a full set of DNA

What happens during prophase?

The nuclear membrane will break down, the chromosomes will condense and become visible and the spindle fibres will begin to form

What happens during metaphase?

The spindle fibres have attach to the chromosomes and the chromosomes line up along the equator (middle) of the cell

What happens during anaphase?

The spindle fibres shorten pulling the two chromatids apart to opposite poles of the cell

What happens during telophase?

The cell membrane pinches in the middle and begins to split into 2 cells and the nuclear membrane reform producing 2 new nuclei

What happens during cytokinesis?

The production of two genetically identical diploid daughter cells