Cell Level Systems

Question 1

What are Eukaryotes?

Answer 1

living ( e.g. all animals and plants) made out from complex cells

Question 2

What are Prokaryotes?

Answer 2

They are smaller and simpler cells like bacteria

Question 3

Name and explain the structures in an animal cell.

Answer 3

Nucleus - Contains DNA in the form of chromosomes that controls the cell’s activity
Cytoplasm- gel-like substance where most of the chemical reactions happen.
Mitochondria - this is where cellular respiration happens and they contain the enzymes needed for the reactions involved
Cell membrane - holds the cell together and controls what goes in and out by providing a selective barrier. They also contain receptor molecules used for cell communication

Question 4

Name and explain the structure of plant cells that aren’t in common with animal cells.

Answer 4

Rigid cell wall - it is made of cellulose and gives support for the cell
Chloroplasts - where photosynthesis occurs. They contain a green substance called chlorophyll
Vacuole - filled with cell sap to help keep the cell turgid.

Question 5

What are the organelles/ structure of a bacterial cell?

Answer 5

Chromosomal DNA - it is one long circular chromosome. It controls the cell’s activities and replication. It floats free in the cytoplasm
Plasmids - small loops of extra DNA that aren’t part of the chromosome. They contain genes for things like drug resistance and can be passed between bacteria
Cell membrane - controls what goes in and out and supported by cell wall

Question 6

What are ribosomes?

Answer 6

The ribosomes are where proteins are made. We sometimes call them the site of protein synthesis.

Question 7

What are the parts of the microscope and what do they do?

Answer 7

Eyepiece lens- looked through to see the image
Objective lens - magnifies the image there are three of them
Stage - A surface to put the specimen
Clip - to put the slide and stabilise it which the specimen is on top of
Handle - to carry the microscope
Lamp - shines light through the slide so the image can be seen more easily
Focusing knobs- to move the stage up and down to bring image into focus

Question 8

How do you prepare your specimen before it being analysed by the microscope?

Answer 8

• The specimen needs to let light through it so you can see it clearly.
• Take a clean slide and use a pipette to drop of water in the middle. This secures the specimen in place
• Use tweezers to place it on the slide
• Add a drop of stain if it is colourless or transparent
• Place a cover slip at one end of the specimen
• Press it down gently with the needle so no air bubbles are trapped

Question 9

What is the difference between light microscopes and electron microscopes?

Answer 9

Light ones let us see things like nuclei and chloroplasts
and can analyse live cells
-But the electron one let us see much smaller things in more detail like the internal structure of mitochondria.
-They only show tiny things like viruses or bacteria. They have a higher magnification and resolution but are expensive and you can’t analyse a live cell it has to be dead

Question 10

What is the equation for total magnification?

Answer 10

total magnification = eyepiece lens magnification x objective lens magnification

Question 11

What is the equation for magnification of the specimien?

Answer 11

Magnification = image size ÷ real size

Question 12

Describe the DNA

Answer 12

• It is a double helix structure which have two DNA strands
• It is a polymer and are made of small monomers called nucleotides
• DNA stands for deoxyribose nucleic acid

Question 13

What is a nucleotide and what does it contain?

Answer 13

• It is a monomer
• Thousands are joint in chemical reactions to make a DNA strand
• It is made of three different things :
• Phosphate group
• Deoxyribose sugar ring
• Nitrogenous base

Question 14

What are the complementary pairs in the DNA?

Answer 14

A = T
C = G

Question 15

What is a gene?

Answer 15

It is a specific sequence of DNA molecule and it encodes for a specific protein molecule

Question 16

What are proteins?

Answer 16

Proteins are made up of chain of molecules called amino acids. They code for a different characteristic. Each amino acid is coded as threes which is call a triplet code

Question 17

What is the process of protein synthesis?

Answer 17

Since the DNA can’t move out of the nucleus since it is really big the DNA is synthesized.

• An enzyme unzips the two strands of DNA. It is used as a template to make mRNA as they make complementary pairs. But instead of A matching with T they replace T with U. This whole step is called transcription
• The mRNA then moves out of the nucleus and travels through the cytoplasm and attaches to a ribosome.
• For every three bases in the Mrna the Trna matches three complementary bases forming amino acids. This is called translation
• The hundreds of amino acids join together to make a polypeptide chain

Question 18

What are enzymes and what do they do?

Answer 18

• They are protein molecules which are biological catalysts
• They speed up the rate of a chemical reaction by reducing the activation energy
• Each enzyme molecule can only fit a specific substance in its active site and catalyse it

Question 19

Explain the process of the lock and key model

Answer 19

The substrate goes into the active site of the enzyme. The enzyme breaks down the substrate but the enzymes is left unchanged

Question 20

What are the factors that affect rate of enzyme activity

Answer 20

• Temperature
• pH
• Substrate concentration

Question 21

Explain the effect of temperature on the rate of enzyme activity

Answer 21

• As temperature increases, the molecules gain more kinetic energy and more collisions takes place between the substrates and the active site of an enzyme
• The rate increases until the optimum temperature
• As it increases above optimum temp the enzyme is denatured and loses the shape of its active site and no enzyme substrate complexes are formed

Question 22

How does the pH affect enzyme activity

Answer 22

Different enzyme molecules work best at different pH. If it’s too high or too low this changes the shape of the active site and can irreversibly denature the enzyme

Question 23

How does enzyme concentration affect rate of reaction

Answer 23

• More enzymes then more likely substrate molecule will find an active site.
• But if the substrate amount is limited so there is no effect of more enzymes

Question 24

How does substrate concentration affect rate of reaction up to a point?

Answer 24

-The higher the substrate concentration the faster the reaction but if there are many and there aren’t enough enzymes adding more won’t make a difference.

Question 25

Explain how increasing the temperature can cause an enzyme to denature

Answer 25

• High temperatures start to break the bonds holding the enzyme together
• This causes the enzyme and its active site to change shape
• This means the enzymes active site will no longer be complementary to the substrate

Question 26

Name all the the digestive enzyme and its products

Answer 26

Carbohydrates:
- Amylase / Carbohydrase 
- Product - glucose
Proteins:
-Protease
- Amino acids
Lipids: 
-Lipase
- Fatty acids and glycerol

Question 27

What is the formula for rate of reaction?

Answer 27

Rate of reaction = change ÷ time

Question 28

What is respiration?

Answer 28

A chemical reaction that takes place in a mitochondrion of all animal and plant cells.
-It is the process of transferring energy from the breakdown of glucose

Question 29

What is the energy used for that is released in respiration?

Answer 29

• Building smaller molecules into larger ones
• Breaking down large molecules
• Active transport of molecules
• Muscle contraction so you can move
• To maintain a constant body temperature
• To make new cells and repair damaged cells
• Transmission of nerve impulses