Section 1 - Key Concepts in Biology

Question 1

What is a eukaryote?

Answer 1

An organism made from eukaryotic cells or a singular eukaryotic cell.

Question 2

What is a prokaryote?

Answer 2

An organism made of a singular prokaryotic cell.

Question 3

What are the two main differences between a eukaryotic cell and a prokaryotic cell?

Answer 3

A eukaryotic cell is larger and has a nucleus.

Question 4

What are the common subcellular structures of an animal cell?

Answer 4

The nucleus
Cytoplasm
A cell membrane
Mitochondria
Ribosomes

Question 5

What are the common subcellular structures of a plant cell?

Answer 5

The nucleus
Cytoplasm
A cell membrane
Mitochondria
Ribosomes
A cell wall
A large permanent food vacuole
Chloroplasts

Question 6

What is the nucleus and what does it do?

Answer 6

The control centre of the cell, it contains all of the cell’s genetic material and uses it to instruct the cell’s other subcellular structures.

Question 7

What is cytoplasm and what does it do?

Answer 7

A gel-like substance that houses most of the cell’s chemical reactions, it contains enzymes.

Question 8

What is the cell membrane and what does it do?

Answer 8

A membrane that both holds the cell together and controls what can enter and exit the cell.

Question 9

What are mitochondria and what do they do?

Answer 9

Subcellular structures that house most of the reactions for respiration in order to provide energy for the cell.

Question 10

What are ribosomes and what do they do?

Answer 10

Subcellular structures responsible for the translation of genetic material in the synthesis of proteins.

Question 11

What is the cell wall and what does it do?

Answer 11

A strong layer around the cell made of cellulose to support the cell and strengthen it.

Question 12

What is a large permanent food vacuole and what does it do?

Answer 12

A subcellular structure that contains cell sap and is used to maintain the internal pressures of a cell.

Question 13

What are chloroplasts and what do they do?

Answer 13

Subcellular structures responsible photosynthesis, they contain chlorophyll which gives them their green colour.

Question 14

What are bacteria?

Answer 14

Simple prokaryotic monocellular organisms.

Question 15

What are the subcellular structures of bacteria cells

Answer 15

Chromosomal DNA
Ribosomes
Cell membrane
Plasmid DNA
Cytoplasm
Mitochondria
Flagella

Question 16

What is chromosomal DNA and what does it do?

Answer 16

One long circular chromosome that floats in the cytoplasm of a bacteria and controls the cell’s activities.

Question 17

What is plasmid DNA and what does it do?

Answer 17

Small loops of DNA that aren’t part of the main chromosome and contains genes that give the bacteria properties like drug-resistance which can be passed between bacteria.

Question 18

What are flagella and what do they do?

Answer 18

Hair like structures that rotate to propel the cell.

Question 19

What are specialised cells?

Answer 19

Cells found in multicellular organisms whose structures have adapted for their specific function

Question 20

What is an egg cell and what is its purpose?

Answer 20

A cell necessary for sexual reproduction in animals.

Its purpose is to carry the female DNA and nourish the developing embryo in the early stages.

Question 21

How are egg cells adapted to their purpose?

Answer 21

The cytoplasm contains nutrients to nourish the embryo.
It has a haploid nucleus.
After fertilisation, the cell membrane changes structure to prevent additional sperm from entering, to ensure the offspring has the right amount of DNA.

Question 22

What is a sperm cell and what is its purpose?

Answer 22

A cell necessary for sexual reproduction in animals. Its purpose is to transport the male DNA to the female egg.

Question 23

How are sperm cells adapted to their purpose?

Answer 23

It has a long tail in order to swim to the egg.
It has many mitochondria in the middle section to provide the energy needed to swim the distance.
It has an acrosome at the front of its “head” where it stores enzymes to digest through the membrane of the egg cell.
It has a haploid nucleus.

Question 24

What are epithelial cells?

Answer 24

Cells that line the surface of organisms.

Question 25

What are cilia what do they do?

Answer 25

Hair like structures found on the top surface of some cells, the cilia move substances in one direction across a tissue’s surface.

Question 26

What are ciliated epithelial cells what is their purpose?

Answer 26

Epithelial cells with cilia lining their top surface, their job is to move substances in one direction, such as shifting mucus out of the airways, into the throat to be swallowed, coughed or spat out so it doesn’t reach the lungs.

Question 27

What is microscopy?

Answer 27

The use of microscopes.

Question 28

What is a microscope?

Answer 28

A tool used to magnify and increase the resolution of images so that it is possible to study things smaller than the eye can see.

Question 29

What are light microscopes, how do they work, when were they invented and what can we see through them?

Answer 29

Light microscopes are microscopes that work by passing light through a specimen, they were invented in the 1590s, they allow us to see things like the nuclei and chloroplasts and allow us to study living cells.

Question 30

What are electron microscopes, how do they work, when were they invented and what can we see through them?

Answer 30

Electron microscopes are microscopes that work by passing electrons through a specimen, they were invented in the 1930s, they allow us to see things like the internal structure of mitochondria which helps us understand how cells actually work, but they cannot study live cells because the electrons would kill them.

Question 31

What are the functional parts of a light microscope?

Answer 31

The eyepiece lens
The high-low power objective lenses
The coarse adjustment knob
The fine adjustment knob
The stage and clips
The lamp/mirror

Question 32

What are the equations for magnification?

Answer 32

M=Mₑ×Mₒ
M=Sᵢ÷Sᵣ
M=Magnification
Mₑ=Eyepiece lens magnification
Mₒ=Objective lens magnification
Sᵢ=Image size
Sᵣ=Real size

Question 33

What is the standard form for millimetres?

Answer 33

×10⁻³m

Question 34

What is the standard form for micrometres?

Answer 34

×10⁻⁶m

Question 35

What is the standard form for nanometres?

Answer 35

×10⁻⁹m

Question 36

What is the standard form for picometres?

Answer 36

×10⁻¹²m

Question 37

What is standard form?

Answer 37

A method of writing very large or very small numbers with a lot of 0s in a simplistic way by replacing the 0s at the start or end of the number by multiplying by a power of 10.

Question 38

What are enzymes?

Answer 38

Catalysts produced by living organisms.

Question 39

What are catalysts?

Answer 39

Chemicals that speed up a chemical reaction without being used up or altered chemically at all.

Question 40

Why do organisms use enzymes?

Answer 40

They are a more effective method of speeding up useful reactions to break down or build large molecules, as they are very specific as to which reactions they catalyse, whereas methods like heating would speed up all of the reactions, useful or not.

Question 41

Why are enzymes able to work?

Answer 41

They have a specific shape, which is called the active site, which only one substrate can fit into, this is called the lock and key mechanism.

Question 42

What is a substrate?

Answer 42

A substance which is affected in an enzyme catalysed reaction.

Question 43

How does the temperature affect the rate of an enzyme catalysed reaction?

Answer 43

Like most reactions, higher temperatures mean faster rates of reaction, however, after the temperature reaches an enzyme’s optimum temperature the rate stops increasing if you exceed the optimum temperature, the rate decreases and if it gets too hot, the enzyme will denature and the reaction will stop.

Question 44

How does the pH affect the rate of an enzyme catalysed reaction?

Answer 44

At the enzyme’s optimum pH, the reaction goes fastest, too high or too low it will slow down and if it goes too far in either direction, the pH affects the bonds holding the enzyme together, denaturing it.

Question 45

How does the substrate concentration affect the rate of an enzyme catalysed reaction?

Answer 45

The higher the concentration, the higher the rate of reaction, until all of the active sites are full up and the rate stays the same.

Question 46

What does it mean if an enzyme denatures?

Answer 46

The enzyme has been made useless due to the shape of its active site being changed because of the conditions around, most commonly because it is too hot or the pH is either too high or too low.

Question 47

What is the equation for the rate of reaction?

Answer 47

R=P÷t
R=Rate of reaction
P=Amount of product formed (cm³)
t=time (s)

Question 48

Why do our bodies break large molecules down into smaller molecules in digestion?

Answer 48

They would be too large to pass through the walls of our intestines otherwise.

Question 49

What is the name for enzymes that convert carbohydrates into simple sugars?

Answer 49

Carbohydrases.

Question 50

What is the name for enzymes that convert proteins into amino acids?

Answer 50

Proteases.

Question 51

What is the name for enzymes that convert lipids into glycerol and fatty acids?

Answer 51

Lipases.

Question 52

What is calorimetry?

Answer 52

The measuring of heat transfers in a chemical reaction.

Question 53

What is the formula for energy in food and energy per gram of food?

Answer 53

E=m₁×Δθ×4.2
E/g=E÷m₂
E=Energy in food
m₁=Mass of water
m₂=Mass of food
Δθ=Temperature change
E/g=Energy per gram of food

Question 54

What is diffusion?

Answer 54

The net movement of particles from an area of higher concentration to an area of lower concentration.

Question 55

Why does diffusion not occur in solids?

Answer 55

Because the particles in a solid cannot move freely like the particles in liquids or gasses.

Question 56

Why can’t large molecules like starch and proteins diffuse through a cell membrane?

Answer 56

They are too large so they cannot pass through like the smaller molecules

Question 57

What is osmosis?

Answer 57

The net movement of water particles across a partially permeable membrane from a region of higher water concentration to an area of lower water concentration.

Question 58

What is a partially permeable membrane?

Answer 58

A membrane with tiny holes in it that only allow small molecules through.

Question 59

What does it mean if something is the net something?

Answer 59

It means that it is the total of the thing.

Question 60

What is active transport?

Answer 60

The movement of particles across a membrane against the concentration gradient using energy transferred from respiration.

Question 61

How would you test for reducing sugars?

How would a positive result appear?

Answer 61

Mixing a sample with Benedict’s Reagent, which is blue, if the solution changes colour, there is sugar present. Benedict’s Reagent changes from blue to green, yellow, orange or red depending on the concentration.

Question 62

How would you test for starch?

How would a positive result appear?

Answer 62

Add iodine to the sample, if starch is present the iodine will change from browny-orange to a blue-black colour.

Question 63

How would you test for lipids?

How would a positive result appear?

Answer 63

Shake the test substance with ethanol for about a minute until it dissolves. Then pour it into some water. If there are lipids present they will precipitate out of the solution to become a milky emulsion. The more lipid there is, the more noticeable the milky colour will be.

Question 64

How would you test for proteins?

How would a positive result appear?

Answer 64

Add a few drops of potassium hydroxide solution to the sample solution turn the solution alkaline. Then add some copper(II) sulfate solution, which is bright blue. If protein is present, the solution will turn purple.