MATSEC SEC Biology flashcards
MATSEC SEC Biology · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Cell theory
- The principle that all living organisms are composed of cells, that the cell is the basic unit of life, and that new cells arise from existing cells by division.
- Prokaryotic cell
- A cell with no membrane-bound nucleus and no membrane-bound organelles. Its genetic material lies free in the cytoplasm. Bacteria are prokaryotes.
- Eukaryotic cell
- A cell containing a true nucleus enclosed by a nuclear membrane, plus membrane-bound organelles such as mitochondria and chloroplasts. Plants, animals and fungi are eukaryotes.
- Cell membrane
- A partially permeable layer of phospholipid and protein surrounding the cell. It controls which substances enter and leave and allows diffusion, osmosis and active transport.
- Mitochondrion
- An organelle with a folded inner membrane where aerobic respiration takes place. It releases energy as ATP. Cells needing much energy, such as muscle cells, contain many mitochondria.
- Chloroplast
- A green organelle containing chlorophyll, found in plant cells. It absorbs light energy and carries out photosynthesis, converting carbon dioxide and water into glucose and oxygen.
- Diffusion
- The net movement of particles from a region of higher concentration to a region of lower concentration. It is passive and needs no energy from the cell.
- Osmosis
- The diffusion of water across a partially permeable membrane from a region of higher water potential to one of lower water potential. It is passive and does not require energy.
- Active transport
- Movement of substances across a membrane against a concentration gradient using carrier proteins and energy from respiration. Root hair cells use it to absorb mineral ions.
- Enzyme
- A protein that acts as a biological catalyst, speeding up reactions. It has a specific active site and is denatured by high temperature or extreme pH.
- Photosynthesis
- The process in green plants using light energy, absorbed by chlorophyll, to convert carbon dioxide and water into glucose and oxygen. It stores energy in chemical bonds.
- Aerobic respiration
- The breakdown of glucose in the presence of oxygen to release energy, producing carbon dioxide and water. It releases more energy per glucose molecule than anaerobic respiration.
- Anaerobic respiration
- Release of energy from glucose without oxygen. In muscle it produces lactic acid; in yeast it produces ethanol and carbon dioxide, a process called fermentation.
- DNA
- Deoxyribonucleic acid, a double helix of nucleotides that carries genetic information. A gene is a section of DNA coding for a protein.
- Gene
- A section of DNA on a chromosome that codes for a particular protein or characteristic. Alleles are different versions of the same gene.
- Mitosis
- Cell division producing two genetically identical diploid daughter cells. It is used for growth, repair and asexual reproduction, and maintains the chromosome number.
- Meiosis
- Cell division producing four genetically different haploid gametes. It halves the chromosome number and involves crossing over and independent assortment, creating variation.
- Dominant allele
- An allele whose effect is shown in the phenotype even when only one copy is present. It is represented by a capital letter, such as B for brown eyes.
- Recessive allele
- An allele whose effect appears in the phenotype only when two copies are present. It is represented by a lower-case letter and can be hidden in carriers.
- Genotype and phenotype
- The genotype is the combination of alleles an organism carries, such as BB, Bb or bb. The phenotype is the observable characteristic that results from that genotype.
- Sex determination
- In humans, females have XX and males have XY sex chromosomes. A sperm carrying X or Y determines the sex of the offspring, so the father determines it.
- Homeostasis
- The maintenance of a constant internal environment, such as body temperature and blood glucose, by negative feedback mechanisms that reverse changes from the norm.
- Insulin
- A hormone released by the pancreas when blood glucose is too high. It causes cells to take up glucose and the liver to store it as glycogen.
- Glucagon
- A hormone released by the pancreas when blood glucose is too low. It causes the liver to convert stored glycogen back into glucose and release it into the blood.
- Negative feedback
- A control mechanism in which a change from the normal value triggers a response that reverses the change, restoring the internal environment to its set point.
- Natural selection
- The process by which individuals with variations suited to their environment survive and reproduce more successfully, passing on the advantageous alleles so the population changes over generations.
- Population
- All the individuals of one species living in a particular area at the same time. It is a component of a community within an ecosystem.
- Community
- All the populations of different species living and interacting together in a particular habitat. It excludes the non-living physical factors.
- Ecosystem
- A community of organisms interacting with each other and with the non-living environment, including factors such as light, temperature, water and soil.
- Food chain
- A sequence showing the transfer of energy from producer to consumer. Arrows point in the direction of energy flow, and only about 10 percent passes to each level.
- Decomposer
- An organism such as a bacterium or fungus that breaks down dead organisms and waste, releasing nutrients such as nitrates back into the soil for reuse by plants.
- Global warming
- The rise in average global temperature caused by increased greenhouse gases, especially carbon dioxide from burning fossil fuels, which trap heat in the atmosphere.