Biology Flashcards
What do most human and animal cells have
A nucleus Cytoplasm A cell membrane Mitochondria Ribosomes
What is the function of a nucleus
To control the activities of the cell
What happens in the cytoplasm
Most chemical reactions take place
What is the function of a cell membrane
To control the passage of substances into and out of the cell
What is the function of mitochondria
To release energy from respiration
What is the function of ribosomes
Protein synthesis
What do most plant cells have
A nucleus Cytoplasm A cell membrane Mitochondria Ribosomes Chloroplasts Cell wall Vacuole
What is the function of a cell wall
To strengthen the cell. It is made of cellulose
What is the function of chloroplasts
To absorb light energy to make food (through photosynthesis)
What is a vacuole filled with
Cell sap
What does a bacterial cell consist of
Cytoplasm
Membrane
Cell wall
The genes are not in a distinct nucleus
What is yeast
A single-celled organism
What does a yeast cell consist of
A nucleus
Cytoplasm
Cell membrane
Cell wall
Why might cells be specialised
To carry out a particular function
What does diffusion allow
Dissolved substances to move into and out of cells
Oxygen required for respiration to pass through cell membranes
What is diffusion
The spreading of the particles of any substance resulting in a net movement from a region where there is a higher concentration to a region with a lower concentration
When is the rate of diffusion faster
When the difference in concentration is greater
What is a tissue
A group of cells with similar structure and function
What are some examples of tissues
Muscular tissue
Glandular tissue
Epithelial tissue
What can muscular tissue do
Contract to bring about movement
What can glandular tissue do
Produce substances such as enzymes and hormones
What can epithelial tissue do
Cover some parts of the body
What are organs made of
Tissues. One organ may contain several tissues
What does the stomach contain
Muscular tissues - to churn the contents
Glandular tissue - to produce digestive juices
Epithelial tissue - to cover the inside and outside of the stomach
What are organ systems
Groups of organs that perform a particular function
What is the digestive system
An organ system in which humans and other mammals exchange substances with the environment
What does the digestive system include
Glands The stomach The liver The small intestine The large intestine
What do glands do in the digestive systems
Glands, such as the pancreas and salivary glands, produce digestive juice
What happens in the stomach and small intestine
Digestion occurs
What does the liver do
Produce bile
What does the small intestine do
Absorb soluble food
What does the large intestine do
Absorb water from the undigested food, producing faeces
What do plant organs include
Stems, roots and leaves
Examples of plant tissues
Epidermal tissues - to cover the plant
Mesophyll - to carry out photosynthesis
Xylem and phloem - to transport substances around the plant
Equation for photosynthesis
Carbon dioxide + water (light energy) = glucose +oxygen
What happens during photosynthesis
Light energy is absorbed by chlorophyll, found in chloroplasts in plant cells
This energy is used by converting carbon dioxide (from the air) and water (from the soil) into sugar (glucose)
Oxygen is released as a by-product
What limits the rate of photosynthesis
Shortage of light
Low temperature
Shortage of carbon dioxide
What factors are enhanced in greenhouses
Light intensity
Temperature
Carbon dioxide concentration
What is glucose produced in photosynthesis converted into
Insoluble starch for storage in tubers or bulbs - does not affect water balance.
Plant cells also use some for respiration
What is some glucose in plants and algae used for
To produce fat or oil for energy storage (could be used as biofuel)
To produce cellulose, which strengthens the cell wall
To produce proteins
How do plants produce proteins
Using glucose and nitrate ions that are absorbed from the soil to make amino acids which then form proteins
What are physical factors affecting organisms
Temperature Availability of nutrients Amount of light Availability of water Availability of oxygen and carbon dioxide
How can quantitative data on the distribution of organisms be obtained by
Random sampling of quadrats
Sampling along a transect
What are protein molecules made up of
Long chains of amino acids. These long chains are folded to produce a specific shape that enables other molecules to fit into the protein.
What do proteins act as
Structural components of tissues e.g. muscles
Hormones
Antibodies
Catalysts
What do catalysts do
Increase the rate of chemical reactions.
What are enzymes
Biological catalysts. They are also proteins
What is vital for the enzyme’s function
The shape of an enzyme. High temperatures denature the active site
What do different enzymes work best at
Different pH values
What does xylem tissue transport
Water
What does phloem tissue transport
Food
Where is amylase produced
In the salivary glands, the pancreas and the small intestine
What does amylase do
Catalyses the breakdown of starch into sugars in the mouth and small intestine
Where is protease produced
In the stomach, pancreas and the small intestine
What does protease do
Catalyse the breakdown of proteins into amino acids in the stomach and the small intestine
Where do some enzymes work
Outside the body
Where are digestive enzymes produced
By specialised cells in glands and in the lining of the gut
What do digestive enzymes do
Pass out of the cells into the gut where they come into contact with food molecules. They catalyse the breakdown of large molecules into smaller molecules
Where is lipase produced
In the pancreas and small intestine
What do lipase enzymes do
Catalyse the breakdown of lipids into fatty acids and glycerol in the small intestine
What are lipids
Fats and oils
What does the stomach produce
Hydrochloric acid. The enzymes in the stomach work most effectively in these acid conditions
What does the liver produce
Bile
Where is bile stored
In the gall bladder before being released into the small intestine
What does bile do
Neutralise the acid that is added to food in the stomach (increases pH). This provides alkaline conditions in which enzymes in the small intestine work most effectively
It also emulsifies fats by breaking down large globules (fat droplets) in smaller ones
What do some microorganisms produce
Enzymes that pass out of the cell
What use do enzymes that pass out of cells have in homes
They are in biological detergents which may contain protease and lipase. Biological detergents are more effective at low temperatures than other types of detergents
What use does protease have in industry
Proteases are used to ‘pre-digest’ the protein in some baby foods
How are enzymes used in industry
To bring about reactions at normal temperatures and pressures that would otherwise require expensive energy-demanding equipment
What is the problem with how enzymes are used in industry
Most enzymes are denatured at high temperatures
Costly to produce (supply food/O2 and waste removed)
Expensive to control pH within narrow limits
What do enzymes control
Chemical reactions inside cells
What is aerobic respiration
Respiration that uses oxygen
Which chemical reactions occur during aerobic respiration
Reactions that use glucose and oxygen and reactions that release energy
What takes place continuously in both plants and animals
Aerobic respiration
Where do most reactions in aerobic respiration take place
Inside mitochondria
What is the equation for aerobic respiration
Glucose + oxygen = carbon dioxide + water (+ energy)
How is energy released during respiration used
To build larger molecules from smaller ones
In animals, to enable muscles to contract
In mammals and birds, to maintain a steady body temperature in colder surroundings
In plants, to build up sugars, nitrates and other nutrients into amino acids which are then built up into proteins
What happens during exercise
The heart rate increases
The rate and depth of breathing increases
Glycogen stored in muscles are converted to glucose for cellular respiration
The flow of oxygenated blood to the muscles increase
What do the changes that happen in exercise increase
The blood flow to the muscles and so increase the supply of glucose and oxygen and increase the rate of removal of carbon dioxide
What do muscles store glucose as
Glycogen, which can then be converted back to glucose for use during exercise
When is anaerobic respiration used
By the muscles when insufficient oxygen is reaching them to obtain energy
What is anaerobic respiration
The incomplete breakdown of glucose and produces lactic acid
What does anaerobic respiration result in and why
An oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water. This is because the breakdown of glucose is incomplete as much less energy is released than during aerobic respiration
When do muscles become fatigued
If muscles are subjected to long periods of vigorous activity, ie they stop contracting efficiently
What is a cause of muscle fatigue
The build up of lactic acid in the muscles
How can lactic acid be removed
Blood flowing through the muscles
How are chromosomes normally found in body cells
In pairs
How do body cells divide
By mitosis
What do chromosomes contain
Genetic information
What happens when a body cell divides by mitosis
Copies of the genetic material are made
Then the cell divides once to form two genetically identical body cells
When does mitosis occur
During growth or to produce replacement cells
How many sets of chromosomes do body cells have
Two
How many sets of chromosomes do gametes have
One
What is meiosis
The type of cell division in which a cell divides to form gametes
What happens when a cell divides to form gametes
Copies of the genetic information are made
Then the cell divides twice to form four gametes, each with a single set of chromosomes
What happens when gametes join at fertilisation
A single body cell with new pairs of chromosomes is formed
How is a new individual developed after gametes have joined at fertilisation
The single body cell repeatedly divides by mitosis
At which stage do most types of animal cells differentiate at
An early stage whereas many plant cells retain the ability to differentiate throughout life
What is cell division mainly restricted to
Repair and replacement
What are stem cells
Cells from human embryos and adult bone marrow
What do human stem cells have the ability to do
Develop into any kind of human cell
What may treatment with stem cells be able to help
Conditions such as paralysis
What are the cells of the offspring produced by asexual reproduction produced by
Mitosis from the parental cells. They contain the same alleles as the parents
Why does sexual reproduction give rise to variation
Because when gametes fuse, one of each pair of alleles comes from the parents
What determines a person’s sex
One of the 23 pairs of chromosomes that carries the genes
In what gender are the sex chromosomes the same
Female (XX)
In what gender are the sex chromosomes different
Male (XY)
What are some characteristics controlled by
A single gene
What is an allele
A different form of a gene
What is a dominant allele
An allele that controls the development of a characteristic when its present in only one of the chromosomes
What is a recessive allele
An allele that controls the development of characteristics only if the dominant allele is not present
What are chromosomes made up of
Large molecules of DNA which has a double helix structure
What is a gene
A small section of DNA
What does each gene code for
A particular combination of amino acids which make a specific protein
Who are the only people who do not have unique DNA
Identical twins
What is DNA fingerprinting
A process used to identify individuals because of their unique DNA
What is polydactyly
Having extra fingers and/or toes
What is polydactyly caused by
A dominant allele of a gene and can therefore be passed on by only one parent who has the disorder
What is cystic fibrosis
A disorder of cell membranes
From who must cystic fibrosis be inherited from
Both parents
What is cystic fibrosis caused by
A recessive allele of a gene and can therefore be passed on by parents, neither of whom has the disorder but is a carrier
What can embryos be screened for
The alleles that cause polydactyly, cystic fibrosis and other genetic disorders
Where does evidence for early forms of life come from
Fossils
What are fossils
The ‘remains’ of organisms from many years ago, and are found in rocks.
How may fossils be formed
From the hard parts of animals that do not decay easily
From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
When parts of the organism are replaced by other materials as they decay
As preserved traces of organisms, e.g. footprints, burrows and rootlet traces
What were many early forms of life
Soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity
What can we learn from fossils
How much or how little organisms have changed as life developed on Earth
What may extinction be caused by
Changes to the environment over geological time
New predators
New diseases
New, more successful, competitors
A single catastrophic event, e.g. volcanic eruption or asteroid collisions
Through the cyclical nature of speciation
What do new species arise as a result of
Isolation
Genetic variation
Natural selection
Speciation
How do new species arise as a result of isolation
When two populations of a species become separated e.g. geographically
How do new species arise as a result of genetic variation
When each population has a wide range of alleles that control their characteristics
How do new species arise as a result of natural selection
When in each population, the alleles that control the characteristics which help the organisms to survive are selected.
How do new species arise as a result of speciation
When the populations become so different that successful interbreeding is no longer possible
Where can diffusion happen
In both solutions and gases - the particles in these substances are free to move about randomly
What can diffuse through cell membranes
Very small molecules - oxygen, glucose, amino acids and water. Big molecules such as starch and proteins cannot fit
How are palisade leaf cells adapted for photosynthesis
Several chloroplasts at the top of the cell so they’re nearer the light (more photosynthesis)
Tall shape = more surface area = more C02 absorbed from the air
Thin shape = several packed at the top of leaf
How are guard cells adapted to open and close pores
Special kidney shape - opens and closes stomata
When the plant is full of water, the guard cell fills up and goes turgid. This makes the stomata open so gases can be exchanged for photosynthesis
When the plant is short of water, the cells lose water and go flaccid so the stomata closes - stops water vapour escaping
Thin outer walls and thick inner wall - why the opening and closing works
Sensitive to light and close at night - saves water and does not lose out on photosynthesis
How are red blood cells adapted to carry oxygen
Concave shape - big surface area - absorbs more oxygen. Also helps to pass smoothly through capillaries to reach body cells
Packed with haemoglobin
No nucleus - more space for haemoglobin
What is haemoglobin
The pigment that absorbs the oxygen
How are sperm and egg cells specialised for reproduction
Egg cell contains larger food reserves to feed the embryo
After they fuse the egg’s membrane changes so no more sperm can get in - offspring end up with the right amount of DNA
Sperm cell has long tail and streamlined head - swim
Sperm cell has a lot of mitochondria - provide it with energy
Sperm cell carries enzymes to digest egg cell membrane
What is differentiation
The process by which cells become specialised for a particular function
When does differentiation occur
During the development of a multicellular organism
Why do large multicellular organisms have different systems inside them
For exchanging and transporting materials
Structure of a leaf
Waxy cuticle Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis
How does a greenhouse affect the rate of photosynthesis
Creates a warm atmosphere
Increases the rate of photosynthesis
Plants grow faster
Can grow fruits unsuitable for British climate
How to increase the rate of photosynthesis in greenhouses
Using paraffin lamps - produces CO2 and increases temperature
Use artificial light - photosynthesis can continue beyond daylight hours
Add fertiliser to the soil
What is hydroponics
Growing plants in water with the right balance of mineral ions
What is aquaponics
Growing plants in water with fish - mineral ions obtained from fish faeces
What is osmosis
Diffusion of water molecules
How can plants adapt to survive in low light levels
Increasing surface area of leaves and increasing the number of chloroplasts
How can plants prevent water loss
No leaves - prevents water loss through transpiration
Smaller surface area of leaves
What is quantitative sampling used to do
Compare the distribution of the same organism in different habitats
Measure changes in the distribution of an organism over time
Why are transects useful
Identifies impact of changes in physical factors on organism distribution
What is a substrate
A molecule on which an enzyme acts in a biochemical reaction
What is an active site
An area on the enzyme molecule to which the substrate attaches to during the reaction
Why does increasing the temperature increase the rate of enzyme activity until the optimum temperature is reached
Substrate molecules broken down faster -> more kinetic energy -> more successful collisions
What is the route of food through the digestive system
Mouth Oesophagus Stomach Small Intestine Large Intestine Rectum Anus
What does digestion do
Convert large, insoluble food molecules into small molecules that can be absorbed
Why does lipase decrease pH
Increases in fatty acids (product from lipid digestion)
Adaptations of stomach for enzymes
Glands in lining of stomach -> secretes protease enzymes to digest protein
HCl acid produced in stomach -> Ideal environment for enzymes to work effectively and kills most bacteria
Thick layer of mucus -> protects stomach walls against digestion by enzymes and acid
Advantages of using enzymes in industry
Processes using enzymes are usually cheap to run
Work at low to normal pressures
Catalyses reactions at low temperatures
What use does carbohydrase have in industry
Carbohydrases are used to convert starch into sugar syrup
Used in processed food productions
Cheap source to sweeten food
Makes fuel (ethanol) from plants
What use does enzymes have when slimming
Isomerase is used to convert glucose syrup into fructose syrup, which is much sweeter and therefore can be used in smaller quantities in slimming food
Why is there an increased breathing rate during exercise
Compensate for oxygen being lost
Remove CO2 faster
More O2 -> break down glucose -> respiration gives cells energy -> muscles keep working
Why is there an increased heart rate during exercise
The heart needs to pump faster to circulate the oxygen and glucose to the cells needed and get rid of the CO2
Why do people get flushed skin during exercise
Increased blood flow
Release excess heat - blood vessels dilate (greater surface area and closer to skin’s surface)
Why do people sweat during exercise
To cool the body down (evaporation) so the enzymes can keep working
