Topic 1: Key Concepts In Biology

Question 1

What is the most common microscope used today?

Answer 1

This microscopes uses two lenses. It is referred to as Hooke’s microscope. It has a magnification of x30.

(Also known as light microscopes)

Question 2

How do you work out the microscopes magnification?

Answer 2

Multiply the magnification of the two lenses together.

E.g objective lens = 5x
Eye piece lens = 10x

5x10=50

Question 3

What two lenses are used in Hooke’s microscope?

Answer 3

Objective lens and eyepiece lens.

Question 4

Why was Hooke’s microscope not very powerful and what was its resolution?

Answer 4

Because it the glass lenses were of poor quality however today stronger lenses are used.

It’s resolution was 0.002mm.

Question 5

What does resolution mean?

Answer 5

The detail obtained by a microscope. This is the smallest distance between 2 points that can still be seen as 2 points.

Question 6

What is the best magnification of a light microscope today?

Answer 6

With the developments of stains, and better lenses and light sources the best magnification of a light microscope is 1500x which is 0.0001mm.

Question 7

What is the electron microscope?

Answer 7

Invented in the 1930s. Instead of light beams of electrons pass through a specimen to build up an image.
These microscopes can magnify up to 2,000,000x with resolutions down do 0.0000002mm.
They allow us to see cells with great detail and clarity.

Question 8

What does eukaryotic mean?

Answer 8

A cell with a nucleus an sub cellular structures.

Question 9

What does a ribosome do?

Answer 9

These make new protein for a cell. It is impossible to see them with a light microscope.

Question 10

What does the mitochondria do?

Answer 10

They are jelly bean shaped structures.in which aerobic respiration occurs. They are difficult to see in a light microscope.

Question 11

What is the field of view?

Answer 11

The circular area you see you see in a light microscope is the field of view.

Question 12

What does the cell membrane do?

Answer 12

It is like a very thin bag. It controls what enters and leaves the cell and separates one cell from another in an animal cell.

Question 13

What does the nucleus do?

Answer 13

Controls the cell and it’s activities. Inside it are chromosome which contain DNA.

Question 14

What is a scale graph on a micrograph?

Answer 14

Scale bars on micro graphs are used to estimate sizes.

Question 15

What does the vacuole so?

Answer 15

Plant sells have a permanent vacuole which stores nutrients and cell sap and helps to keep the cell rigid and firm.

Question 16

What are specialised cells?

Answer 16

Specialised cells have a specific function. There are about 200 different types of cells in humans. Specialist cells are adapted to their functions.

Question 17

How are cells specialised in the digestive system?

Answer 17

The cells that line the small intestine absorb small food molecules produced by digestion. They are adapted by having membrane with many tiny folds (called microvilli) these adaptations increase the surface area of the cell. The more area for molecules to be absorbed that faster absorption happens.

Question 18

How are enzymes in the small intestine/pancreas adapted?

Answer 18

Cells in the pancreas make enzymes needed to digest certain foods in the small intestine. The enzymes are proteins so are adapted by having lots of proteins.

Question 19

What are the two gametes that are specialised?

Answer 19

During sex two specialised cells (gametes) fuse to create a cell that develops into an embryo. These are the egg and sperm cell.

The only have 1 set of each chromosome so are haploid.

Question 20

How are egg cells specialised?

Answer 20

• cell membrane fuses with the sperm cell membrane. After fertilisation, the cell membrane becomes hard to stop other sperm entering.
• the cytoplasm is packed with nutrients, to supply fertilised egg with nutrients, to supply the fertilised egg cell with energy and raw materials for the growth and development of the embryo.
• haploid nucleus
• jelly coat protects the egg cell.

Question 21

How are sperm cell specialised?

Answer 21

• haploid nucleus
• streamline shape
• tail waves from side to side allowing sperm cell to swim.
• large number of mitochondria are arranged in a spiral around the top of the tail to release lots of energy to power the tail.
• tip of the headline contains a small vacuole called the acrosome. It contains enzymes that break down the substances in the egg cell’s jelly coat. This allows the sperm to burrow inside.

Question 22

When does fertilisation occur and what cells in the female reproductive system are specialised and have adapted functions?

Answer 22

Fertilised occurs in the oviduct. Cells in the lining of the oviduct transport egg cells (or developing embryos after fertilisation) towards the uterus.
Oviduct cell’s are adapted to this by having hair like cilia. These wave from side to side to sweep substances along.

Question 23

What are epithelial cells and how are they different to ciliates epithelial cells?

Answer 23

Cells that line the structures in the body are called epithelial cells. epithelial cells cells with cilia are called ciliated epithelial cells.

Question 24

What is a flagellum?

Answer 24

It spins around a bacteria so it can move.

Question 25

What does prokaryotic mean? Give an example of an organism that is classified as this?

Answer 25

This means that their cells do not have a nuclei or chromosomes instead, the cytoplasm contains one large loop os chromosomal DNA, which controls cell activity. They do not have mitochondria or chloroplast and also have smaller loops of DNA called plasmids that control a few cell activities.
An example apple of this is a bacteria.

Question 26

How is a bacteria adapted?

Answer 26

-chromosomal DNA
-Slime coat (for protection-not all bacteria have this)
-cell membrane
-flagellum (is not covered in a membrane and not all bacteria have it)
-plasmids
Flexible cell wall (for support - not made out of cellulose)
-cytoplasm

Question 27

How do bacteria get energy from substances?

Answer 27

The release digestive enzymes into their environments and then absorb digested food into their cells.

Question 28

How do human digestive enzymes digest food?

Answer 28

In humans digestive enzymes turn the large molecules of our food into smaller subunits they are made of. The digested molecules are then small enough to be absorbed by the small intestine.

Question 29

What is it called when larger molecules get broken down?

Answer 29

Break down (digestion)

Or

Synthesis

Question 30

What do larger molecules get broken down into?

Answer 30

Protein molecule - amino acids
Starch molecule - glucose
Lipid molecule - fatty acids/glycerol

Lipids = fats an oils

Question 31

What is synthesis?

Answer 31

Once smaller molecules are absorbed into the body, they can be used to build larger molecules that are needed in cells and tissues.

Building larger molecules form smaller subunits is known as synthesis.

Question 32

What is a polymer?

Answer 32

Complex carbohydrates and proteins are both polymers.

Polymers are made of similar small molecules called monomers joined as a chain.

Question 33

How fast does digestion happen?

Answer 33

Breakdown of larger molecules happens slowly and only of the bonds between similar sub units have e ought energy to break. Synthesis happens slowly, since the subunits rarely collide with enough force or in the right orientation to form a bond.

Question 34

What is a catalyst?

Answer 34

Many reactions are speeded up by catalysts. In living organisms the catalysts that speed up breakdown and synthesis are ENZYMES.

Enzymes are biological catalysts that increase the rate of reaction

Question 35

What are substrates and products?

Answer 35

Substrates are substances that enzymes work on.

Products are the substance produced by an enzyme.

Question 36

Different type of enzyme catalysts?

Answer 36

Amylase- found in saliva and small intestine: breaks down starch to small sugars e.g maltose

Catalase- found in most cells but especially liver cells: breaking down hydrogen peroxide made in many cells reaction to water and oxygen.

Starch synthase- found in plants: helps with synthesis of starch form glucose.

DNA polymerase- found in nucleus: synthesis of DNA from its monomers.

Question 37

What are reducing sugars?

Answer 37

Small sugars (glucose and fructose)

Question 38

What happens when a food solution is mixed with an equal volume of Benedict’s solution and placed in ah or bath for a few minutes?

Answer 38

It reduces sugars in the food causing a reduction reaction, which changes the colour of the solution and may form a precipitate.

Different colours indicate different amounts of reducing sugars
Blue- no colour change, no reducing sugars
Greenish blue - very little reducing sugar
Orange - more reducing sugars
Red- lots of reducing sugars

Question 39

What is the biuret test and what happens happens in this test?

Answer 39

Potassium hydroxide is mixed with a solution of the food. Two drops of copper sulphate solution are then added. If the plate blue solution turns purple, this indicated protein in the food.

Question 40

What is the ethanol emulsion test?

Answer 40

This tests lipids. The food is mixed with ethanol and shaken. Some of that mixture is then lured into water and shaken again. Fats and oils dissolved in ethanol float to the surface, forming a cloudy emulsion, when the mixture is left to stand.

Question 41

What is a calorimeter?

Answer 41

The amount of energy in a food is measured by burning it in a calorimeter.

The amount of energy from the burning food to the water can be calculated form the increase in water temperature.

Question 42

What is the active site?

Answer 42

Thinks where the sub state of the enzyme fits at the start of a reaction. Different substances have different shapes and different enzymes have different active sites.

This explains why every enzyme can only work with specific substrates that fit the active site.

Question 43

Name a model of how enzymes work?

Answer 43

Lock and key hole model, because of how the enzyme and substrate fit together.

Question 44

He does an enzyme become denatured and what if the effect of this?

Answer 44

Changes of pH or temperature (to high) can change the active site of an enzyme. This means the substrate will no longer fit in. The enzyme can therefore no longer be a catalyst for the reaction and becomes denatured.

Question 45

What happens as temperatures increase to the substrate and molecules?

Answer 45

As the temperature increases, molecules be faster. Higher speeds increase the chance of substrate molecules bumping into enzymes molecules and slotting into the active site.

Question 46

What is the optimum temperature?

Answer 46

The temperature in which an enzyme works fastest.

Question 47

What is diffusion?

Answer 47

Particles in bases and liquids are constantly moving past each other in random directions. This causes an overall movement of particles from where there is a high concentration of them to a low concentration of them.

Question 48

What is a concentration gradient?

Answer 48

A difference between two concentration forms a concentration gradient. Particles diffuse down a concentration gradient. The bigger the difference between concentration the steeper the concentration gradient and the faster diffusion occurs.

Question 49

What does diffusion all oxygen and carbon dioxide to do?

Answer 49

It allows small molecules such as oxygen and carbon dioxide to move into and out of cells.

Question 50

What is osmosis?

Answer 50

The diffusion of small molecules of a solvent such as water through a semi preamble membrane.

Question 51

What causes osmosis?

Answer 51

If there are more water molecules in a certain volume on one side of the membrane than the other, there will be an overall movement of water molecules from the side where there are more after molecules (a more dilute solute concentration) to the side where there are fewer molecules (a more concentrated solution of solute)

Question 52

How do you workout percentage change?

Answer 52

Percentage change = final mass - initial mass / initial mass x 100

Question 53

What is active transport?

Answer 53

Cells that transport molecules against a concentration gradient or transport molecules that are too big to diffuse through a cell membrane.

Question 54

How is active transport carried out?

Answer 54

The process is carried out by proteins in cell membrane. The transport proteins capture certain molecules and carry them across the cell membrane. This requires energy where as osmosis and diffusion at passive processes so do not require an input of energy.

Question 55

What is the task for the Osmosis potatoes slice practical?

Answer 55

Measuring osmosis in a plant tissue, by comparing the mass of the tissue before and after soaking in sucrose solution. Sucrose is used because the molecules are too large to diffuse through cell membranes. The change in the mass of the tissue shows how much water is absorbed or lost.

Question 56

What is the method for the osmosis potato slice?

Answer 56

1- label a sedate test tube with the sucrose solution concentration of each solution you will test.
2- cut similar-sized pieces of potato, enough for 1 per tube.
3-Blot each potatoes piece dry, measure and record its mass and put it in an empty tube.
4- fill each tube with the solution of the appropriate concentration. Ensure you cover the potatoes with the solution.
5-after at least 15 minutes, remove each potato piece and blot it dry. Measure and record outs mass again.