Biology Terms Flashcards
Organelles
are tiny structures that are present in a cell’s cytoplasm as discrete units normally surrounded by a membrane and responsible for a specialised function (such as photosynthesis)
Ultra structure
The ultrastructure of a cell is its fine structure as revealed at high magnification.
Cell Membrane
The cell membrane controls the movement of molecules into and out of the cell. It is described as selectively permeable.The cell membrane is made up of two types of molecule: proteins and phospholipid.
Passive Transport
Passive transport is the movement of molecules down a concentration gradient from a high concentration to a lower concentration, and does not require energy for it to take place.
Diffusion
The movement of a molecule down a concentration gradient from a high concentration to a lower concentration.
Osmosis -
Osmosis is a special case of diffusion that specifically involves water.
Active Transport -
The movement of molecules and ions against a concentration gradient, from a region of low concentration to a region of high concentration.
Mitosis
Normal cell division and provides new cells for growth and repair of damaged cells and maintains the diploid
chromosome complement
Complementary base pairing
Holds DNA strands together.
A-T
G-C
Base sequence codes
The order of bases (C-G-T-A) on a DNA/mRNA strand. The base sequence determines the amino acid sequence in a protein
mRNA
MRNA carries a complementary copy of the code from the DNA, in the nucleus, to a ribosome
Ribosomes
The site of protein synthesis - The protein is assembled from amino acids
Amino acids
coded from the sequence of base pairs. IT makes up proteins.
Biological catalysts
Speed up biochemical reactions in cells and remain unchanged in the process
Active site
Area on an enzyme’s surface that binds with a specific substance
Substrate
The reactant(s) in a reaction, and is specific to an enzyme
Optimum conditions
Are the temperature and pH which the enzymes work best at
Denatured
When the active site permanently changes shape and affects the rate of the enzyme reaction
Genetic engineering
Transferring genetic information (DNA) from one cell into another
Light reactions
Stage one of respiration that breaks one molecule of glucose down into 2 molecules of pyruvate and releases enough energy to make 2 ATP molecules
Carbon fixation
Stage 2 with oxygen (aerobic respiration) breaks pyruvate down into carbon dioxide and water and yields 36 ATP molecules
Respiration
A series of enzyme-controlled reactions which release the chemical energy stored in glucose
ATP
Adenosine triphosphate
Molecule that is the main energy carrier molecule in cells
Aerobic respiration
Type of respiration requiring oxygen in which substrates such as glucose are completely broken down to water and carbon dioxide to release large amounts of energy
Anaerobic respiration
Respiration where oxygen isn’t present
Fermentation
Stage 2 of respiration without oxygen is called
Stem cells
Unspecialised cells which can divide in order to self- renew or differentiate (specialise) to become specialised cells
Specialisation
Specialisation leads to the formation of A variety of cells, tissues and organs
Reflex arc
Receptor – sensory neuron – relay neuron – motor neuron – muscle
Central Nervous System
The brain and the spinal cord
Cerebellum
part of the brain that controls balance and co-ordination
Medulla
part of the brain that controls unconscious control of body temp, heart and breathing rate, etc.
Cerebrum
part of the brain that controls conscious thought, intelligence, language
Receptors
Detect stimuli / sensory information
Hormones
Chemical messengers produced by endocrine glands which carry messages in the blood stream to target
tissues
Gametes
Haploid sex cells
Continuous variation
Where there is a range of values on a scale e.g. height
Discrete variation
Discontinuous, where the values do not occur in a range and fall into distinct groups (usually descriptions
e.g. colour)
Polygenic characteristics
Caused by many genes working together. They show continuous variation and very common in phenotypes.
Phenotype
The visible physical characteristic you see as a result of a gene
Genotype
The pair of alleles a person has which control one characteristic, e.g. AA, aa or Aa
Homozygous
When a genotype has two alleles exactly the same, e.g. AA or aa
Xylem vessel
Dead and contain spirals of lignin for support and transport Water and minerals up the stem
Phloem vessel
Phloem transports sugar and is made of Living cells consisting of cytoplasmic strands and porous end plates between cells that allow sugar to move from
cell to cell. Companion cells provide energy for sieve tubes
Veins
blood vessels that carry blood back to the heart, into the atria
Arteries
blood vessels that carry blood away from the heart, from the ventricles. They carry blood under high pressure.
Alveoli
Gas exchange in the lungs happens here.
The alveoli are adapted for diffusion by
1. having a large surface area (there are many of them)
2. having a good blood supply (covered by capillary
networks)
3. having thin walls (one cell thick) for more efficient diffusion
Villi
Villi are
- thin walled
- have a large surface area (there are many of them)
- have a good blood supply to aid absorption- each villus contains a network of capillaries)
Biotic factors
Living e.g competition, disease, food availability, grazing, predation
Abiotic factors
Any condition affecting the environment that results from non-living sources
Biodiversity
The variety of species living in a habitat
Niche
The role that an organism plays within a community
Intraspecific competitions
Between members of the same species competing for all the same resources they require and is therefore much
more intense that interspecific
Interspecific competition
between members of different species competing for one or a few similar resources the require
Population
All the organisms of one species in a habitat
Absorption
Absorption
Process by which small, soluble molecules are taken up by cells
Adenosine diphosphate
Molecule similar to ATP with one less phosphate group
Community
All the living organisms living in a habitat
Ecosystem
All the organisms (community) living in a habitat and the non-living components with which the organisms interact (the abiotic factors)
Transpiration
The evaporation of water through leaves
phagocytes
White blood cells called phagocytes carry out Phagocytosis to engulf and destroy pathogens
Lymphocytes
White blood cells called Lymphocytes produce Antibodies which destroy pathogens
Dominant
An allele which is always seen in the phenotype if it is present (in the genotype)
Recessive
An allele which is only seen in the phenotype if there is no dominant allele present
Alleles
Different forms of a gene which control one characteristic
Gene
A section of DNA which codes for a protein (characteristic)
