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Flashcards in B456 Deck (55)
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What is the function of the nucleus, cytoplasm, cell membrane and mitochondria?

Nucleus - contains DNA for making proteins.
Cytoplasm - enzymes are made here and some reactions occur here.
Cell membrane - controls what goes in and out.
Mitochondria - where aerobic respiration occurs.


Contrast the contents of animal cells, plant cells, yeast and bacteria.

Animal cells have a nucleus, cytoplasm, cell membrane and mitochondria.
Plant cells have the above and a cell wall, vacuole and chloroplasts.
Yeast are the same animal cells though they have a cell wall.
Bacteria have a cell membrane, cell wall, cytoplasm and a circular DNA molecule.


What is an enzyme?

A protein that speeds up a chemical reaction.


How are enzymes specific?

The lock and key model shows that one substrate fits only one enzyme's active site. Also, they have optimum temperature and pH - the enzyme denatures if these change too much.


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

Respiration is a series of chemical reactions that release energy by breaking down large food molecules. The energy released is used for movement, active transport and synthesis of large molecules.


What are the word equations for aerobic and anaerobic respiration?

Aerobic - Glucose + oxygen -> Carbon dioxide + Water
Anaerobic in animals - Glucose -> Lactic acid
Anaerobic in plants and yeast - Glucose -> Ethanol + Carbon dioxide


What can fermentation be used for?

Production of biogas, bread and alcohol.


What is the word equation for photosynthesis?

Carbon dioxide + Water -> Glucose + Oxygen


What three main ways do plants use glucose?

Chemicals for Growth


What three factors can limit photosynthesis?

Amount of light
Amount of carbon dioxide


How can you take a transect?

1) Run a tape measure between two points.
2) Move along the tape measure and collect the data you want.
3) Keep going till you reach the end of the transect.


What other three things apart from a transect can be used to collect data about photosynthesis?

Identification key
Light meter


What is diffusion?

The passive overall movement of particles from a region of higher concentration to a region of lower concentration.


What is osmosis?

Diffusion of water through a partially permeable membrane.


What is active transport?

The overall movement of chemicals across a cell membrane from a region of lower concentration to a region of higher concentration using energy released from respiration.


How do nucleotides pair up?

Adenine with Thymine
Cytosine with Guanine


How does DNA code for proteins?

Each triplet of three bases codes for one amino acids.


How are proteins made?

Messenger RNA makes a copy of the DNA. It then moves out of the nucleus and joins with a ribosome. The ribosome then joins amino acids together into a protein.


Outline how mitosis occurs.

The cell grows and the DNA splits. The cell then duplicates the content of the DNA. The cell then forms chromosomes. The chromosomes line up and cell fibres pull them apart. The two sets form membranes, and finally the cytoplasm divides. This forms two cells identical to the original.


How many chromosomes do human gametes have?



How does meiosis occur?

The original cell first duplicates its contents and the pairs are then pulled apart, forming two new cells. In the second division, the individual arms of the chromosomes are pulled apart. This forms four gametes with only one set of chromosomes in each.


How do adult and embryonic stem cells differ? How can each be used to cure disease?

Adult stem cells are not entirely undifferentiated, and can be used to cure blood diseases by replacing faulty blood cells, whereas until the eight cell stage, all embryonic stem cells can become any type of cell, which means that they could be used to cure almost any disease, however, some people think this is unethical.


How can stem cells be made by cloning?

1) Take an egg cell and remove its nucleus.
2) A nucleus which is to be cloned is inserted into the egg cell.
3) Inactive genes can be turned on to form an embryo. Embryonic stem cells can be removed from the embryo.


What are meristems?

Meristems are the only mitotically active parts of plants. They act like stem cells, and can become any specialised cell.


How can cuttings be used to form clones?

Cuttings taken from a growing part of a plant contain meristems. These can thus be used to grow an identical plant. This is an important part of selective breeding.


How does rooting powder help cuttings grow?

Rooting powder contains auxins, which help the plant to grow very quickly.


What is phototropism and where does it occur in a plant?

Phototropism is growing away or towards light. Shoots are positively phototropic and roots are negatively phototropic.


How do auxins help a plant to grow towards light?

Auxins accumulate on the side of a plant in the shade. This causes the plant to elongate on that side and the shoot grows towards the light.


How do nucleotides pair up?

Adenine with Thymine
Cytosine with Guanine


How does DNA code for proteins?

Each triplet of three bases codes for one amino acids.