ATI TEAS Biology Summary

The mitochondria carry out cellular respiration, which uses oxygen to break down food molecules and store the energy as ATP. That is why they are called the "powerhouse" of the cell.

Wrong choices

• Ribosome: Ribosomes make proteins.
• Nucleus: The nucleus holds the cell's DNA.
• Golgi apparatus: The Golgi apparatus packages and ships proteins.

Ribosomes read the instructions carried by messenger RNA (mRNA) and link amino acids together in the right order to build proteins.

Wrong choices

• Lysosomes: Lysosomes break down waste and worn-out cell parts.
• Mitochondria: Mitochondria make energy (ATP).
• Cell membrane: The cell membrane controls what enters and leaves the cell.

DNA bases pair in a fixed way: A with T and C with G. In RNA, uracil (U) takes the place of thymine, so A pairs with U.

Wrong choices

• Uracil (U): Uracil replaces thymine in RNA, not DNA.
• Guanine (G): Guanine pairs with cytosine.
• Cytosine (C): Cytosine pairs with guanine.

Mitosis copies the chromosomes and splits them evenly, making two identical cells with the full chromosome number. It is used for growth and repair. Meiosis makes four sex cells with half the chromosomes.

Wrong choices

• Four cells, each with half the number of chromosomes: This is the result of meiosis, which makes sex cells.
• Two cells, each with half the number of chromosomes: Mitosis keeps the full number of chromosomes.
• Four cells that are identical to the parent cell: Mitosis makes two cells, not four.

Use a Punnett square for Pp × Pp.

1. Possible offspring: PP, Pp, Pp, pp
2. Only pp shows white flowers (white is recessive).
3. 1 out of 4 = 25%

Check: 1 PP + 2 Pp + 1 pp = 4 boxes; 3 of 4 are purple (75%) and 1 of 4 is white (25%).

Wrong choices

• 50%: 50% is the chance of a Pp offspring, which has purple flowers.
• 75%: 75% is the chance of purple flowers.
• 0%: Both parents carry a p allele, so pp offspring are possible.

Making a protein has two main steps:

1. Transcription (in the nucleus): a gene's DNA is copied into mRNA.
2. Translation (at the ribosome): the mRNA is read to build a protein.

Wrong choices

• Ribosomes build a protein by reading mRNA.: This is translation, the step after transcription.
• The whole DNA molecule is copied before the cell divides.: This is DNA replication.
• Proteins are shipped out of the cell.: This is secretion, handled by the Golgi apparatus and vesicles.

Chloroplasts carry out photosynthesis, using sunlight to make sugar. Plant cells have them; animal cells do not. Plant cells also have a rigid cell wall, which animal cells lack.

Wrong choices

• Mitochondrion: Both plant and animal cells have mitochondria.
• Nucleus: Both plant and animal cells have a nucleus.
• Cell membrane: Both plant and animal cells have a cell membrane.

Egg and sperm cells are made by meiosis, which halves the chromosome number.

1. 46 ÷ 2 = 23

At fertilization, 23 from the egg + 23 from the sperm = 46 again.

Wrong choices

• 46: 46 is the number in body cells; sex cells have half that number.
• 92: 92 is double the body-cell number.
• 12: This is about half of 23, which is too few.

Bacteria are prokaryotes: single cells whose DNA floats in the cell instead of inside a nucleus. They can live and reproduce on their own. Viruses, by contrast, are not cells and must use a host cell to make copies of themselves.

Wrong choices

• They can reproduce only inside a host cell.: This describes viruses, not bacteria.
• They are made of many cells with a nucleus in each.: Bacteria are single cells, and they have no nucleus.
• They make their own food using chloroplasts.: Bacteria do not have chloroplasts.

In transcription, each DNA base is paired with its RNA partner: A → U, T → A, C → G, G → C.

1. T → A, A → U, C → G gives AUG
2. G → C, G → C, A → U gives CCU

Check: the result AUG CCU contains no T, as mRNA should.

Wrong choices

• ATG CCT: mRNA uses uracil (U), not thymine (T).
• UAC GGA: This only swaps T for U; each base must be paired with its partner.
• TAC GGA: This copies the DNA exactly instead of pairing the bases.