Flashcards in BIOLOGY PART 1 and 2 Deck (216):
Animal cells contain
Plant cells contain
Contains DNA and controls cell activity, and instructions for making new cells/organisms
Controls what goes in and out of the cell
Liquid gel in which chemical reactions take place e.g. Respiration
Structures in the cytoplasm where energy is produced during respiration
Where protein synthesis takes place (making proteins from amino acids)
Made from cellulose to strengthen and supports the cell
Found in green parts of plants. Contains chlorophyll which absorbs light energy to make food by photosynthesis
Bacterial cells contain
Loop of DNA
Loop of DNA
Controls the cell, as bacterial cells do not have a nucleus
Slimy capsule around outside of cell wall to protect it from antibiotics
Fungal cells are ... than bacterial cells
Larger, and can be seen using a light microscope
A fungal cell wall is made of
Why were bacterial cells discovered later?
Not enough advanced technology
Bacterial cells are much smaller
Yeast cells are a
Single celled organism
Yeast cells contain
Palisade cell (from a leaf)
Absorbs light for photosynthesis
Contains chloroplasts which contain the pigment chlorophyll
Contracts to provide movement
Contains mitochondria which provides the energy for contraction
Root hair cell
Absorbs water and mineral salts from soil
Hair like structure to increase surface area to absorb more water/minerals
Fertilises female gamete
Tail to swim
Mid section is full of mitochondria for energy to swim
Red blood cell
Absorbs oxygen and transports it around the body
No nucleus - more haemoglobin can be packed in, more space to carry oxygen
Biconave shape so it's flexible and fits through small capillaries
Ciliated cell (in oviduct)
Moves egg near uterus
Cilia on surface - beats regularly so egg moves down oviduct
Contains mitochondria for energy so cilia can move
Nerve cell (motor neurone)
Transmits nerve impulses
Contains fibres (dendrites) that connect to other neurones
Axon surrounded by myelin sheath to insulate and speed up transmission of nerve impulse
Movement of particles from a high area of concentration to a low area of concentration. No energy required
The greater the difference in concentration, the ... the rate of diffusion
Diffusion occurs in
Gases and liquids
Why can diffusion not occur in solids?
Particles are not free to move
Large surface area ... the rate of diffusion
Increases, more area is exposed so more diffusion can take place
Higher temperature ... the rate of diffusion
Increases, the hotter it is the more kinetic energy for diffusion
The stomach is an organ that contains
Contracts for movement
Churn up contents
Produces hormones and enzymes
Produce digestive juices
Layer of cells
Make chemicals e.g. Acid
Lines inside of organs
Creates thick mucus to coat cells
Cover outside and inside of stomach
Smooth allowing organs to easily move
Layers of cells
Protective coat around the organ
Groups of similar cells that work to carry out a particular function
Groups of different tissues that work to perform a certain function
Group of organs working together to perform a function, organ systems form organisms
Digestive system - Salivary glands
Produces the enzyme amylase in saliva
Digestive system - Liver
Bile is produced
- neutralises stomach acid
- emulsified fats
Digestive system - Gall bladder
Where bile is stored before released into small intestine
Digestive system - Large intestine
Where excess water is absorbed from undigested foods, producing faeces
Digestive system - Small intestine
Where digested foods are absorbed and move into the blood
Produces amylase, lipase and protease to complete digestion
Digestive system - Rectum
Where faeces are stored, before leaving through the anus
Digestive system - Pancreas
Produces protease, amylase and lipase and releases them into the small intestine
Digestive system - Stomach
Pummels food with its muscular wall
Produces protease, amylase and lipase
Produces hydrochloric acid
- to kill bacteria
- give correct pH for protease enzymes to work (pH2 - acidic)
How are cone cells in the eye adapted to carry out its function?
-Outer segment of cell has a chemical called visual pigment - chemically changes in colour to allow you to see in colour
-The centre has lots of mitochondria, releases energy allowing visual pigment to reform
-Specialised nerve cell that transmits signals to brain so colour is continuously seen
How are fat cells adapted?
-small cytoplasm to allow space for fat to be stored
-few mitochondria as they do not use much energy
-can grow to 1000 times its original size
Tissues - examples?
Organs - examples?
Organ systems - examples?
Pancreas and salivary glands make digestive juices that
Carry enzymes to aid digestion
Breakdown of large food molecules into smaller particles that can pass through the gut wall and be absorbed into the blood
Process by which smaller food particles are taken into the blood. They pass through the gut-wall into the blood from the gut environment
Plant organs contain
Supports the plant
Transports substances through the plant
Produces food by photosynthesis
Anchors the plant
Takes in water/minerals from the soil
Leaf - upper epidermal tissue
Thin and transparent
Allows light to pass to the mesophyll to protect the leaf and stop water loss
Leaf - palisade mesophyll
Regular shaped cells
Near upper surface
(Where most chloroplasts are found)
Absorbs the maximum amount of sunlight
Leaf - spongy mesophyll
Irregular shaped cells
Increases surface area for CO2 absorption to maximise
Allows gases to diffuse
Leaf - lower epidermal tissue
Surrounded by guard cells
Allows gases to diffuse
Guard cells open/close stomata
Leaf: vascular bundles
Contains xylem and phloem tubes
Transport substances from roots to the shoots and leaves
Leaf - guard cells
Opens and closes stoma to allow gas exchange
Why do plants need glucose?
-used in respiration to release energy
-joined together to make starch for storage
-combined with nutrients to make proteins for growth
-joined to make cellulose for cell walls
-converted to fats and oils for the seeds
-converted to fructose for the fruit
Carbon dioxide + water -> (light energy) -> oxygen + glucose
Limiting factors - photosynthesis
What happens during photosynthesis?
Light energy is absorbed by chlorophyll (in chloroplasts)
The energy is used during by converting CO2 from the air and water from the soil into sugar (glucose)
Oxygen is a by product
Photosynthesis - light intensity
A shortage of light means less energy to power the reaction
Photosynthesis - temperature
A low temperature limits the rate of photosynthesis as molecules move slower so there are less reactions, however too high will cause enzymes to be denatured (40 degrees roughly)
Photosynthesis - CO2 concentration
This will limit the rate as there are less molecules in the reaction. A levelled off line on the graph shows it has reached its optimum point.
How can you grow plants in the ideal environment?
Grow then in a greenhouse as limiting factors can be controlled
Uses of glucose (from photosynthesis) in plants and algae
Converted into insoluble starch for storage
Used in respiration
Physical factors affecting organisms
Availability of nutrients
Availability of light
Availability of water
Availability of oxygen
Availability of CO2
How temperature affects organisms
Affects the rate of an organisms metabolism
Some cannot tolerate extreme temperatures
Organisms with a high temperature may also struggle to tolerate extreme conditions
How availability of nutrients affects organisms
Nutrients e.g. Nitrate are essential for growth of plants/microorganisms
A low concentration would cause organisms to struggle to grow and survive
How availability of light affects an organism
Required as an energy source for photosynthesis
In low light intensities, plants grow very slowly
How availability of water affects organisms
All organisms require water
Chemical reactions take place in water solutions
An absence of water causes cells and in turn, organisms to die
How availability of oxygen affects organisms
Essential for aerobic respiration
May become limited in soil - so roots cannot grow and absorb the minerals/water
May become limited in water, so aquatic organisms struggle to respire
How availability of CO2 affects organisms
Essential for photosynthesis
Limited where there are many plants - reducing rate of growth
Water and CO2 are used to ... food during respiration
Phosphate - plants
For growth and respiration
Component of DNA
Deficiency symptom - discoloured leaf and poor growth
Magnesium - plants
Makes chlorophyll green
Deficiency symptom - chlorophyll goes yellow
Nitrate - plants
Found in water, creates amino acids which create proteins
Lack of nitrate - stunted growth
Potassium - plants
For photosynthesis and respiration
Must be present for respiration enzymes to work
Deficiency symptom - discoloured leaves and poor growth
A line across a habitat/ part of a habitat
The number of organisms of each species can be observed and recorded at regular intervals along the transect
Organisms underneath, usually plants, can be identified and counted
Why should quadrats be randomly placed?
So a representative sample is taken
The validity and reproducibility of the results increases as the results from more quadrats are analysed
Made up of long chains of amino acids
Fold into a specific shape which dictates its function, another molecule will then fit into it
Uses of proteins in the body
Keratin in the hair/skin
Channels in cell membrane
Haemogoblin in red blood cells
Collagen in blood vessel walls, skin, tendon and bones
Fibrin in blood clots (scabs)
Elastin in lungs/blood vessel walls
Substances that speed up reactions without being changed or used up
Enzymes, enzymes are proteins
Found in long chains
Speed up reactions
Specific (only catalyse a particular reaction)
All proteins contain the elements
Reactions sped up by catalysts
You can change the shape of a protein by
Changing its pH
Reacting it with chemicals e.g ethanol
What happens if a proteins shape changes?
It will not be able to carry out its function
It will be denatured
How does pH affect the active sight?
It effects the forces that hold the enzyme molecule together
What factors affect enzymes
A specific shape that only a certain type of reactant (substrate) will fit into
How do enzymes affect activation energy?
It lowers the activation energy, so reactions occur at a greater rate
Particles do not need to collide with as much energy
How does temperate affect the rate of reaction with enzymes?
If it is too low, the rate of reaction falls as there is less kinetic energy
If it is higher, particles collide with more energy so the rate of reaction increases
If it is too high, the enzyme denatures and the active sight shape changes so the substrate can no longer bond. The rate of reaction falls
Break down big molecules into smaller ones
Big molecules (digestion - examples)
Small molecules (digestion - examples)
3 enzymes - digestive system
Concerts starch into maltose and other sugars
Converts protein into amino acids
Converts lipids into glycerol and fatty acids
Where is amylase made?
Where is protease made?
Where is lipase made in?
How does bile emulsify fats?
Breaks fats into tiny droplets
There is then a larger surface area of fat for lipase to work with so digestion is quicker
How does bile neutralise acid in the stomach?
The hydrochloric acid in the stomach makes the pH too acidic for enzymes to work
Bile is alkaline so it neutralises the acid
Where is bile stored and released into?
Stored in the call bladder
Released into small intestine
Biological washing powders
Contain enzymes (protease/lipase) to break down fats and proteins in stains
Enzymes must work well in solutions with a high pH because washing powders are
What is the range of temperatures enzymes must work at
When can enzymes be used in home and industry?
If microorganisms produce enzymes that pass out of the cells
Biological detergents are more effective at ... temperatures
Advantages of biological washing powders
Enzymes work at low temperature saving energy
More efficient at removing stains
Help delicate fabrics get cleaned without damaging then by a hot wash
Disadvantages of biological detergents
May lead to allergies and irritation
If clothes are not rinsed, the enzymes may remain in the clothing which would digest protein in the skin
Enzymes used in industry
Biological washing powders
'Pre-digested' baby foods
Diet foods/slimming products
How does the function of enzymes affect confectionary/slimming products?
Breaks cheap starch into glucose
This changes to fructose syrup (by isomerase) so less of it if needs to get a sweeter taste
How does the function of enzymes affect baby food?
Protease 'pre-digests' the proteins so it is easier for the babies to eat and absorb into their blood
How does the function of enzymes affect fruit juice?
It makes it sweeter
How does the function of enzymes affect meat?
It tenderises and makes it softer
Properties of industrial enzymes
Long shelf life
Withstand high temperatures
Can work in the presence if chemicals that would otherwise stop enzymes working
Enzymes in the home
Used to break down food stains as biological detergents
Advantage of enzymes
Enzymes lower the temperatures and pressures often needed for chemical reactions
They are specific
Disadvantages of enzymes
Sensitive to surroundings (changing pH or temperature may stop them working)
Expensive to control the conditions
The process of releasing energy from glucose, which goes on in every cell
glucose + oxygen -> carbon dioxide + water + energy
Aerobic respiration is respiration using...
Aerobic respiration occurs inside...
The energy respiration releases is used to...
-Build larger molecules from smaller ones (proteins from amino acids)
-Allow muscles to contact in animals
-Allow birds/mammals to maintain a constant body temperature
-In plants to build up sugars, nitrates and nutrients into amino acids which are built into proteins
A toxin that stops respiration by stopping enzymes involved in the process from working
How can exercise affect us?
The depth and rate of breathing increases
Heart rate increases
Increases supply of blood flow to muscles of sugar/oxygen
Removal of CO2 increases
How is glycogen used during exercise?
Glucose from food can be stored as glycogen
Mainly stored in the liver but each muscle has its own store
During vigorous exercise, glucose can be converted back to glucose to provide further energy
Glucose -> lactic acid + (some) energy
Anaerobic respiration is respiration without
What is anaerobic respiration?
The incomplete breakdown of glucose into lactic acid. It does not release as much energy as aerobic respiration but is useful in emergencies
Lactic acid - anaerobic respiration
Lactic acids builds up in muscles, which is painful.
It tires out muscles- they stop contacting efficiently
What is oxidation?
Blood flows through the muscles to removed the lactic acid by oxidising it to CO2 and water
Every cell contains ... pairs of chromosomes
What is a gene?
A section of DNA
What is a chromosome?
Made up of DNA
What is a diploid number?
A full set (23 pairs of chromosomes)
Sex cells only have ... single chromosomes
What is mitosis?
Mitosis is when a cell reproduces itself by splitting to form two identical offspring
Mitosis makes new cells for...
Repair damaged tissue
Replace worn out tissue
DNA fingerprinting is used for...
What do genes do?
They code for a specific protein
They tell cells the order for the amino acids
What is the exception to everyone having unique DNA?
Before cells divide in mitosis, what must happen?
The DNA must make a copy of itself
How does DNA make a copy of itself?
DNA is double stranded
The molecule unzips
This exposes DNA based
These bases then join to spare, complimentary bases
The bases then match to create an exact copy
Which DNA bases join together?
A - T
T - A
C - G
G - C
Mitosis is ... reproduction
Asexual, so there is no variation
How does the cell create an exact copy of itself in mitosis?
The two duplicated chromosomes like up in the centre of the cell
Spindle fibres form
Each chromosome splits into two identical copies
Each copy moves to opposite ends of the cell
A membrane forms around each set
This becomes the nuclei
The cytoplasm then divides leaving two new cells that are identical
Produces cells which have half the number of chromosomes (gametes)
Where does meiosis occur and what does it result in?
It happens in sex organs and results in variation
Before meiosis occurs what should happen?
Before the cell divides, it duplicates its DNA
How does a cell create gametes through meiosis?
In the first division, chromosome pairs line up in the centre
The pair gets pulled into two separate cells as they are attracted to opposite poles (each cell has one copy of each chromosome)
In the second division, they line up again in the centre and split
You are left with four gametes each with a single set of chromosomes
Why does meiosis occur?
For sexual reproduction
What happens to gametes during fertilisation?
A single body cell with new pairs of chromosomes are formed
This cell then divides repeatedly by mitosis to develop into a new individual
What are stem cells?
Embryonic stem cells can turn into any type of cell
Where can stem cells be found?
Adult bone marrow
What is differentiation?
The process by which a cell changes to become specialised for its job
Are stem cells undifferentiated?
How can stem cells be used?
Nerve cells- helping those paralysed by spinal cord injuries
Beating heart muscle cells- those with heart disease
Insulin producing cells- those with diabetes
Arguments for stem cells
- those who are alive are more important than an embryo
- unwanted embryos from fertility clinics could be used instead
- medicine uses them to cure disease
- could replace faulty cells
Arguments against stem cells
- each embryo is a potential human life
- scientists should find other ways to obtain stem cells rather than using them from embryos
In asexual reproduction, the offspring contain the ... alleles as the parent
Same (they are genetically identical)
Why does variation occur in sexual reproduction?
When the gametes fuse, one of each pair comes from the parents
What determine the sex of the offspring?
One of the 23 pairs of chromosomes is different, and carries the gene that determines sex
Which chromosomes determine male characteristics?
All men have an X and a Y chromosome
The Y chromosomes causes the male characteristics
What chromosome determines the female characteristics?
All women have to X chromosomes
The combination of XX is what allows female characteristics to develop
What is an allele?
An allele is a version of a gene
E.g. The gene could be Hh and the alleles would be H and h
What is a dominant allele?
It controls the development of a characteristic when it is present in only one of the chromosomes
What is a recessive allele?
It controls the development of characteristics only if the dominant allele is not present
What is a genotype?
What alleles you have
What is a phenotype?
The characteristic displayed by the genotype
What is a heterozygous?
2 different alleles
What is a homozygous?
2 of the same alleles
Who worked out the main principles of inheritance?
What 3 conclusions did Mendel reach?
-Characteristics in plants are determined by "hereditary units"
-Hereditary units are passed on from both parents (one unit from each parent)
-Hereditary units can be dominant or recessive - if an individual has both, the dominant characteristic will he expressed
What are hereditary units?
Why were Mendel's discoveries not recognised until after his death?
He published his work in an obscure journal
DNA, chromosomes and genes were not discovered yet
People couldn't accept the link between plants and animals
He was a monk, so wasn't as respected
What does DNA stand for?
Deoxyribose Nucleic Acid
How do genes control characteristics?
DNA forms a helix that protects it
Why do the bases match together?
The shape of the molecule allows them to fit together
Chromosomes have ... folded DNA
What are the four bases called?
Cytosine & Guanine
Adenine & Thymine
What is a triplet code?
Three bases joined with the opposite base
One triplet code creates an...
A chain of amino acids make a...
What forms the bond between bases?
A hydrogen bond
What is cystic fibrosis?
Genetic disorder of cell membranes
Body produces sticky mucus in air passages/ pancreas
Cystic fibrosis - explain the alleles
The allele that causes the disease is recessive 'f'
People with only one 'f' will not have the disorder (carriers)
To get the disorder, both parents must be carriers or sufferers
E.g. 1 in 4 chance if parents are both carriers
Only a sufferer if you have two 'f' alleles
What is Polydactyly?
Genetic disorder where baby's are born with extra fingers/toes
Not life threatening, little side effects
Polydactyly - explain the alleles?
Caused by the dominant allele 'D'
Can be inherited if one parent carries the defective allele
The parent with that allele will also suffer as the allele is dominant
E.g. 50% chance of child having disorder if one parents has the 'D' allele
What is embryo screening?
The screening of embryos to search if their alleles may cause a genetic disease m
Arguments for embryo screening
Stops people suffering
There are laws to stop it going too far
During IVF most embryos are destroyed anyways, this just allows the selected one to be healthy
Treating disorders is expensive
Arguments against embryo screening
People may use screening to pick their most desirable baby
Rejected embryos were potential human life
Screening is expensive
Implies those with disorders are 'undesirable' which increases prejudice
What is speciation?
The development of a new species
What 2 things lead to speciation?
What is a species?
A group of similar organisms that reproduce to give birth the fertile offspring
Why does speciation occur?
When populations of the same species become so different they can no longer breed to produce fertile offspring
What is isolation?
When a population is levies is separated
What are the 4 stages of speciation?
Isolation - 2 species become separated
Genetic variation - they show variation because of the range of alleles
Natural selection - pass on characteristics to next generations
Speciation - populations become so different that interbreeding is no longer successful
Extinction happens if you can't ... quickly enough
Reasons species become extinct
- new predators
- more competition
- catastrophic event e.g volcano
- new species develops (speciation)
- change in environment
What are fossils?
The remains of plants and animals
3 ways fossils form in rock
-Gradual replacement by minerals (most common)
-Casts and impressions
-Preservation in places where no decay occurs
How does gradual replacement by minerals cause fossils to form?
Thing like bones do not decay easily
They get replaced by minerals as they decay and form a rock like substance shaped like the original bone/shells/teeth etc.
The surrounding sediment turns to rock but the fossil stays distinct in the rock
How do casts and impressions lead to fossils?
Fossils can form if the organism is buried in a soft material like clay
The clay hardens and the organism decays leaving a cast
E.g a plants roots can be preserved as casts
Things like footprints leave impressions in soft materials
How does preservation lead to fossils forming?
-In tar pits/ amber (clear yellow stone made from fossilised resin) there's no oxygen or moisture
Therefore decay microbes cannot survive
-In glaciers it's too cold for decay microbes to work
-Peat bogs are too acidic for decay microbes