B3a

Question 1

What is the structure of an animal cell and the functions of the organelles?

Answer 1

• nucleus: contains genetic material, which controls the activities of the cell
• cytoplas: most chemical processes take place here, controlled by enzymes
• cell membrane: controls the movement of substances into and out of the cell
• mitochondria-most reactions involved in respiration take place here
• ribosomes: protein synthesis happens here

Question 2

What body cells need many mitochondria?

Answer 2

• cells that need lots of energy, as respiration produces energy
• e.g. liver cells carry out many energy-demanding metabolic reactions
• muscle cells need energy to contract

Question 3

What is the structure of an plant cell and the functions of the organelles.?

Answer 3

• everything structure in an animal cell and:
• cell wall Strengthens the cell, made of cellulose
• chloroplasts: Contain chlorophyll, which absorbs light energy for photosynthesis, where photosynthesis happens
• vacuole: Filled with cell sap to help keep the cell turgid

Question 4

What is the structure of an bacteria cell and the functions of the organelles.?

Answer 4

• cytoplasm
• cell membrane
• cell wall
• single circular strand of DNA that floats freely in the cytoplasm, no ‘true’ nucleus,

Question 5

What is the structure of DNA?

Answer 5

• DNA is coiled up as chromosomes
• double helix (double-stranded spiral)
• the two strands are made up of small groups called nucleotides
• each nucleotide contains a small molecule called a base
• there are four bases: A,C,G,T
• each base forms cross links to a base on the other strand, keeping the two strands tightly wound together

Question 6

What are complementary base-pairings?

Answer 6

• A always pairs with T

- C always pairs with G

Question 7

How was the first model of DNA made?

Answer 7

• Watson and Crick used data from other scientists
• x-rays showing DNA is a double helix formed from two chains wound together
• data showing bases occurred in pairs

Question 8

How does DNA replicate?

Answer 8

• DNA copies itself each time a cell divides
• the double helix unzips itself, forming two strands
• new nucleotides (freely floating in the nucleus) join on using complementary base-pairings
• cross links form between the bases and the old DNA strands, and the nucleotides are are joined together to form double strands

Question 9

How are proteins made?

Answer 9

• proteins are made of chains of amino acids
• each protein has a particular number and order of amino acids, giving it a different shape, and therefore different function
• a section of DNA called a gene codes for proteins
• the order of bases in a gene decide the order of amino acids in a protein
• each amino acid is coded for by a three bases in a gene
• amino acids are joint together to make protein, following the order of bases in the gene
• each gene contains a different sequence of bases, allowing it to code for a unique protein

Question 10

What is an mRNA?

Answer 10

• proteins are made in the cytoplasm by ribosomes
• DNA is too big to leave the nucleus
• a molecule called mRNA is a copy of DNA that acts as a messenger between DNA an ribosome, carrying the code between the two

Question 11

How do proteins produced in a cell effect how it functions?

Answer 11

• some proteins determine cell structure, other control cell reactions
• different cell types have different function because they make different proteins
• the cell only makes certain proteins because only some of the full set of genes is used in anyone cell, some are switched off, meaning the proteins they code for are not produced
• the switched on genes determine a cell’s function