B1 - Key Concepts in Biology

Question 1

Define

subcellular structures.

Answer 1

the different parts of a cell

Question 2

What is the role of the

nucleus?

Answer 2

contains genetic material that controls the activities of the cell

genetic material is arranged into chromosones

Question 3

What is the

cytoplasm?

and what does it contain?

Answer 3

the gel-like substance where most of the chemical reactions happen, it contains enzymes that control these chemical reactions

Question 4

What is the role of the

cell membrane?

Answer 4

holds the cell together and controls what goes in and out

Question 5

What are the

mitochondria?

Answer 5

where most of the reactions for respiration take place

respiration transfers energy that the cell needs to work

Question 6

What is the role of the

ribosomes?

Answer 6

be involved in the translation of genetic material in the synthesis of proteins

Question 7

What is the role of the

cell wall?

And what is it made of?

Answer 7

it supports the cell and strengthens it

it is made of cellulose

Question 8

What is the role of the

large vacuole?

and what does it contain?

Answer 8

it maintains the internal pressure to support the cell

it contains cell sap, a weak solution of sugar and salts

Question 9

What is the role of the

chloroplasts?

Answer 9

where photosynthesis occurs, which makes food for the plant

they contain a green substance called chlorophyll

Question 10

What subcellular structures are found in (most)

animal cells?

(5)

Answer 10

• nucleus
• cell membrane
• mitochondria
• ribosomes
• (cytoplasm)

Question 11

What subcellular structures are found in (most)

plant cells?

(8)

Answer 11

• nucleus
• cell membrane
• mitochondria
• ribosomes
• cell wall
• large vacuole
• chloroplasts
• (cytoplasm)

Question 12

What subcellular structures are found in (most)

bacterial cells?

(5)

Answer 12

• chromosonal DNA
• ribosomes
• cell membrane
• plasmid DNA
• flagellum

Question 13

What is the role of the

chromosonal DNA

in bacterial cells?

Answer 13

controls the cell’s activities and replication, it floats free in the cytoplasm

(not a nucleus)

Question 14

What are the

plasmid DNA

in bacterial cells?

Answer 14

small loops of extra DNA that aren’t part of the chromosone

Question 15

What are the

flagellum

in bacterial cells?

Answer 15

long, hair-like structures that rotate to make the bacterium move

Question 16

Define

specialised cell.

Answer 16

a cell that has a structure which makes them adapted to their function

Question 17

What are the main functions of an

egg cell?

(2)

Answer 17

• carry the female DNA
• nourish the developing embryo in the early stages

Question 18

How is an egg cell adapted to its function?

(3 things)

Answer 18

• it contains nutrients in the cytoplasm to feed the embryo
• it has a haploid nucleus
• straight after fertilisation, its membrane changes structure to stop any more sperm getting in

Question 19

What is the function of

sperm?

Answer 19

transport the male’s DNA to the female’s egg

Question 20

How is a sperm cell adapted to its function?

(4)

Answer 20

• it has a long tail so that it can swim to the egg
• it has lots of mitochondria in the middle section to provide the energy (from respiration) needed to swim this distance
• it has an acrosome at the front of the ‘head’, where it stores enzymes needed to digest its way through the membrane of the egg cell
• it contains a haploid nucleus

Question 21

Define

resolution.

Answer 21

how well a microscope distinguishes between two points that are close together

Question 22

What are the benefits of electron microscopes over light microscopes?

(3)

Answer 22

• higher magnification
• higher resolution
• let us see the internal structure of mitochondria and chloroplasts

Question 23

How do you calculate

total magnification?

Answer 23

eyepiece lens magnification x objective lens magnification

Question 24

What equation links

magnification, image size and actual size?

Answer 24

image size = actual size x magnification

Question 25

# Define substrate.

Answer 25

the molecule **changed** in the reaction

Question 26

# Define active site.

Answer 26

the part where an enzyme joins on to its substrate to **catalyse** the reaction

Question 27

# What factors affect enzyme controlled reactions? | (3)

Answer 27

- temperature - pH - substrate concentration

Question 28

What reaction does the enzyme amalyse catalyse?

Answer 28

the breakdown of **starch** to **maltose**

Question 29

# How would you calculate rate of reaction?

Answer 29

change/time

Question 30

# What are carbohydrases? | And what is an example?

Answer 30

enzymes which convert **carbohydrates** into **simple sugars** | e.g. amylase

Question 31

# What are proteases?

Answer 31

enzymes which convert **proteins** into **amino acids**

Question 32

What reaction does lipase catalyse?

Answer 32

the conversion of **lipids** into **glycerol** and **fatty acids**

Question 33

What reaction does glycogen synthase catalyse?

Answer 33

the joining together of lots of chains of **glucose** molecules to make **glycogen**

Question 34

# Define biological molecule.

Answer 34

a molecule that is found in a living organism

Question 35

# How would you test for reducing sugars? | (4 steps)

Answer 35

1. Add **Benedict's reagent** (which is **blue**) to a sample 2. **Heat** it in a water bath that's set to **75°C** 3. If there are reducing sugars then a **coloured precipitate** will be formed 4. The **higher** the **concentration** of reducing sugar, the **further** the colour change goes | blue -> green -> yellow -> orange -> brick red

Question 36

# How would you test for starch? | (3 steps)

Answer 36

1. Add **iodine solution** to the test sample 2. If starch **is present**, the sample changes from **browny-orange** to a dark, **blue-black** colour 3. If there's **no starch**, it stays browny-orange

Question 37

# How would you test for lipids? | (3 steps)

Answer 37

1. **Shake** the test substance with **ethanol** for about a minute until it **dissolves**, then pour the solution into **water** 2. If there **are** any **lipids present**, they will **precipitate** out of the liquid and show up as a **milky emulsion**. 3. The **more lipid** there is, the **more noticeable** the milky colour will be

Question 38

# How would you test for proteins? | (4)

Answer 38

1. Add a few drops of **potassium hydroxide** solution to make the solution **alkaline** 2. Then add some **copper(II) sulfate** solution (which is **bright blue**) 3. If there's **no protein**, the solution will stay **blue** 4. If protein **is present**, the solution will turn **purple**

Question 39

How would you calculate the total amount of energy in the food after calorimetry?

Answer 39

energy (J) = mass of water (g) x temperature change of water (°C) x 4.2

Question 40

# Define diffusion.

Answer 40

the **net movement** of **particles** from an area of **higher concentration** to an area of **lower concentration**

Question 41

# Define osmosis.

Answer 41

the **net movement of water molecules** across a **partially permeable membrane** from an area of **higher water potential** to an area of **lower water potential**

Question 42

# Define active transport.

Answer 42

the **movement of particles** across a membrane against a concentration gradient **using energy** transferred during respiration

Question 43

# What is the formula for percentage change (in mass)?

Answer 43

(final mass - initial mass) / inital mass | (x100)