Animal cells: label the main parts.

Plant and algal cells: label the parts

B2 Cells and simple transport: Part 1: cell, ribosomes, respiration, chemical reactions, protein, nucleus, cell membrane, chloroplasts, cell wall, mitochondrion, vacuole, photosynthesis, chlorophyll, sap, cytoplasm

ORGANELLE

FUNCTION

Type of cell where

found

Plant Animal

NUCLEUS Controls all activities of the cell. Contains genes on the chromosomes. Carries the instructions for making new cells or organisms.

Y Y

CYTOPLASM

Where chemical reactions take place

Y Y

CELL MEMBRANE

Controls the passage of substances into and out of the cell.

Y Y

MITOCHONDRIA Structures in the cytoplasm where oxygen is used and energy is released using respiration.

Y Y

RIBOSOMES

Where protein synthesis takes place, all proteins needed for the cell are made here.

Y Y

CELL WALL

Made of cellulose that strengthens and gives support to plant cells.

Y N

CHLOROPLASTS Found in the green parts of plants. They are green because they contain chlorophyll. Chlorophyll absorbs the light energy to make food by photosynthesis.

Y N

LARGE PERMENANT VACUOLE

Is the space in the cytoplasm filled with cell sap. This is important for keeping the cells rigid to support the plant.

Y N

Cell wall

Cell membrane

vacuole

Chloroplast

Cytoplasm

nucleus

nucleus

Cell membrane

Cytoplasm

mitochondrion

Yeast cells

Yeast is a single celled fungus.

Bacterial cells:

Key fact: Although bacteria contain genetic material, they do not have a nucleus.

Simple cell transport

Dissolved substances move into and out of cells by diffusion. The net (overall) movement of particles is from a high concentration to a lower concentration (down a concentration gradient). The greater the difference in concentration, the faster the rate of diffusion.

Example: Oxygen gas diffuses into cells through the cell membrane and is used during respiration.

B2 Cells and simple transport Part 2: diffusion, nucleus, oxygen, cell wall, high, faster, cytoplasm, lower, cell membrane, Yes, concentration, no.

A Yeast cell

Label the diagram:

A Yeast cell

Label the diagram:

o Cell membrane

o Nucleus

o Cytoplasm

o Cell wall

Feature Animal Plant or

algae

Bacteria Yeast

Cell

membrane

Yes Yes Yes Yes

Nucleus Yes Yes No Yes

Chloroplast No Yes No No

Cell wall No Yes Yes Yes

Cytoplasm Yes Yes Yes Yes

Cell wall

Cell membrane

nucleus

Cytoplasm

Cell wall

Cell membrane

Chromosome

Cytoplasm

Sperm cells

These have

many mitochondria. This allows faster respiration to provide energy for movement.

Neurones (nerve cells)

These are long and insulated. This allows them to transmit nerve impulses rapidly.

Red blood cells.

Unlike most animal cells, these do not contain a nucleus. This allows more space inside for haemoglobin which carries oxygen. The biconcave disc shape creates a larger surface area for faster diffusion of oxygen.

Mesophyll cells

These are found in plant leaves. They contain many chloroplasts for photosynthesis.

Root hair cells.

These are found on plant roots. They have a large surface area for rapid uptake of water and mineral ions from the soil.

Xylem and phloem

Xylem vessels are dead and hollow, allowing them to easily transport water and minerals up the plant.

Phloem cells are long, thin tubes which transport sugars up and down the plant.

Specialised cells Cells of multicellular organisms may differentiate and become adapted for specific functions.

B2 Specialised cells: mesophyll, surface area, haemoglobin, leaves, xylem, differentiate, energy, sugars impulses, chloroplasts, nucleus, water, oxygen, mitochondria, insulated, soil, phloem, root hair

The stomach: As an organ the stomach is made from several tissues, each with a specific function.

Muscular tissue, contracts

helping to mix and churn the food.

Glandular tissue, makes

digestive juices including

protease and hydrochloric acid.

Epithelial tissue covers the

outside and inside of the stomach.

Tissues, organs and organ systems

A group of similar cells working together to perform a function is called a tissue.

An organ is made from several types of tissue working together.

Organ systems are groups of organs that perform a particular function. eg digestive system.

The digestive system

B2 Tissues, Organs and Organ systems Organs, outside, glandular, churn, organ, faeces, absorption, liver, tissue, inside, cells, muscular, digestive, epithelial, small, water, digests, function, digestion, bile, salivary, large, systems

Large intestine – absorbs water from undigested food, producing faeces.

Small intestine – digestion and absorption of soluble food.

Liver – makes bile.

Salivary glands – make digestive juice.

Pancreas – a gland that makes digestive juice.

Stomach – digests proteins.

The vein contains: a) xylem tissue

which transports water and mineral ions.

b) phloem tissue which transports sugars

Mesophyll tissue carries out photosynthesis.

Plant Organs. Label the plant organs.

Inside a leaf:

As an organ the leaf contains several types of different tissues.

Upper epidermis covers the plant

B2 Plant tissues and organs: leaves, epidermis, stem, vein, tissues roots, phloem, water, mesophyll, xylem, photosynthesis, organ

Lower epidermis covers the plant

Roots

Leaves

Stem

Uses of glucose

1. Glucose may be converted

into insoluble starch

for storage.

2. Plant cells use some glucose during respiration.

(glucose + oxygen carbon dioxide + water)

3. Some glucose can

be made into fats

and oils for storage.

4. Glucose can be used

to make cellulose, which

strengthens plant

cell walls.

5. Glucose can used

with nitrate ions from

the soil to make proteins.

Photosynthesis

Plants and algae use light energy to make their own food. The word equation for photosynthesis is…

carbon dioxide + water glucose + oxygen

The role of chlorophyll

Inside the leaf, mesophyll tissue contains many chloroplasts. Chloroplasts contain chlorophyll which absorbs light energy needed for photosynthesis.

B2 Photosynthesis: mesophyll, respiration, chlorophyll, chloroplasts, walls, absorbs, carbon dioxide, insoluble, oxygen, storage, glucose, light, water, fats, proteins, oils, nitrate, cellulose

Light intensity

Limiting factors

The rate of photosynthesis may be limited by:

1. Shortage of light

2. Low temperature

3. Shortage of carbon dioxide

In reality all 3 factors interact and any one of them can be a limiting factor.

Greenhouses For optimum plant growth farmers may need to control light, temperature or carbon dioxide. This can be done by using artificial lighting, heaters/ventilation and addition of carbon dioxide. Increases in yield must be balanced against the costs involved if farmers are to make a profit.

B2 Photosynthesis and limiting factors Lighting, carbon dioxide, photosynthesis, limiting factor, temperature, increasing, yield, profit, light, increases, enzymes,

Carbon dioxide

Temperature

1. As the amount of light increases, so does the rate. The limiting factor is light.

2. Here, increasing the amount of light has no affect on the rate. The limiting factor is now carbon dioxide or temperature.

1. As the amount of carbon dioxide increases, so does the rate. The limiting factor is carbon dioxide.

2. Here, increasing the amount of carbon dioxide has no affect on the rate. Light or temperature is now the limiting factor.

temperature

rate

of

ph

oto

syn

thes

is

0oC 45oC

1 2

1. As temperature increases, so does the rate because photosynthetic enzymes work best in the warmth. Here, the limiting factor is temperature.

2. Most plant enzymes are destroyed at about 45°C. Here, photosynthesis stops and the rate falls to zero.

1

1

1

2

2

2

B2 Organisms in their environment

Quadrats A quadrat is a square frame used to outline an area to sample plants or slow moving animals in their habitat. The number of each different organism in the quadrat are counted. This creates quantitative data which can be used to compare different habitats. Quadrats can be placed at random to avoid bias by using a table of random numbers as coordinates. A large sample size (above 10 quadrats) allows you to calculate a more reliable mean, making the data more valid and reproducible. Collecting fieldwork data This is more difficult than collecting data in a lab because it is hard to control some variables in the environment, for example genetic variation in plants, exposure to rain and sunlight and the concentration of soil mineral ions. Your data is reproducible if another group get similar results/patterns. Your data is valid if it allows you to answer the question or hypothesis in your experiment.

Physical factors affecting organisms in their environment Temperature (eg plants grow slowly in cold climates) Light (most plants need high light for growth) Nutrients (eg plants need nitrates for protein) Water (essential for all living cells/life) Oxygen (low O2 in water limits some animals) Carbon dioxide (a limiting factor for photosynthesis)

Maths skills Mean = sum of values ÷ number of values Median = middle value in the range Mode = most frequent value Find the mean, median and mode of the following numbers: 11, 7, 3, 6, 2, 7 Mean = 6 Median = 6.5 Mode = 7

Transects Transects are used to sample organisms along a line (from A → B). The quadrats are NOT placed at random, but are placed at regular distances along the line, allowing organisms to be sampled. This data shows how the distribution of organisms changes along the transect eg. from under a shady tree, to open field.

Proteins

Proteins are

long chains of

amino acids.

These long chains are folded to produce specific shapes which enable other molecules to fit into the protein. This is important for the function of many proteins.

Functions of proteins 1:

Some proteins

act as hormones

eg insulin. The

specific shape

of insulin

allows it to bind

to its target cells in the liver.

B2 Proteins and their functions Enzymes, amino acids, respiration, antibodies, shapes, structural, muscle, speed, catalysts, antigen, hormones, photosynthesis, liver

Functions of proteins 2:

Some proteins act as antibodies. The specific shape of antibodies allows them to bind to one type of antigen (often found on the surface of pathogens, remember B1!).

Functions of proteins 3:

Some proteins have a structural role. eg. muscle tissue is made from proteins.

Functions of proteins 4:

Some proteins act as catalysts. A catalyst increases the speed of chemical reactions. All enzymes are proteins. Enzymes speed up important reactions like digestion, respiration and photosynthesis. Label the diagram products

Reactants (substrate)

enzyme

Making digestive enzymes

Label the organs/glands which produce digestive enzymes.

The effect of pH

Different enzymes work best at different pH’s. The stomach makes hydrochloric acid, helping the protease enzymes in the stomach to function rapidly.

What is the pH optimum for each enzyme? Pepsin = pH 2; trypsin = pH 8

Where in the body does each enzyme function? Pepsin = stomach; trypsin = small intestine

Enzymes

Enzymes speed up chemical reactions, acting as catalysts. They can function inside or outside of cells.

High temperatures change the shape of enzymes, so that they are no longer able to function. Enzymes damaged by high temperatures are said to be denatured.

B2 Enzymes part 1 Protease, denatured, cells, temperatures, pH’s, catalysts, shape, hydrochloric acid,

Salivary glands

Stomach

pancreas

Small intestine

Protease

Lipase

Bile

Bile is NOT an enzyme.

Bile is made in the liver, stored in the gall bladder and released into the small intestine. Add the labels

Bile is alkaline. It neutralises acid from the stomach when it enters the small intestine, making the pH optimum for the enzymes present.

Bile breaks down large fat droplets into smaller droplets. This makes a larger surface area for lipase enzymes to attack.

Amylase

B2 Enzymes part 2: glands, neutralises, protease, gall bladder, gut, stomach, mouth, surface area, large, alkaline, small, digestion, enzyme, liver, small intestine, pH, lipase, fat, fatty acids + glycerol, starch, amino acids, amylase, salivary, pancreas,

Enzyme Made in Reaction catalysed Where it works

Amylase Salivary glands, pancreas, small intestine

starch glucose Mouth + small intestine

Protease Stomach, Pancreas, small intestine

protein Stomach + small intestine

Lipase Pancreas, small intestine

lipid Small intestine

Digestive enzymes:

These are produced by specialised cells in glands and in the lining of the gut.

The enzymes pass out of the cells and into the gut where they breakdown large food molecules into small ones. This process is called digestion.

Amino acids

Fatty acids + glycerol

liver

Gall bladder

pancreas Small intestine

Sugar syrups

Carbohydrases are used to convert starch into glucose (sugar) syrup.

carbohydrase

Starch Glucose

Isomerase enzyme is used to convert glucose syrup into fructose syrup.

isomerase

Glucose Fructose

Fructose syrup is sweeter than glucose syrup. It can be used in smaller quantities, adding fewer calories to sweeten slimming products.

Baby foods

Proteases are used to pre-digest some baby foods. This makes them easier for the baby to digest.

Some microbes produce enzymes that pass out of their cells. These enzymes have many uses in the home and industry.

Biological detergents

Biological detergents contain protease and lipase enzymes to breakdown and remove stains made from protein and fats or oils.

Biological detergents are more effective at lower temperatures than ordinary detergents. Using them helps to save energy, as low temperature washes cost less.

B2 Uses of enzymes Microbes, glucose, stains, sweeter, proteases, baby, temperatures, slimming, lipase, digest, protease, energy, carbohydrases, fructose,

Aerobic respiration Like all chemical reactions respiration is controlled by enzymes. Aerobic respiration takes place continuously (day + night) in both plants and animals.

Glucose + oxygen → carbon dioxide + water (+ energy)

Uses of energy

Respiration releases energy used to …

1. Build larger molecules from smaller ones.

2. Enable muscles to

contract.

3. Maintain a constant body temperature in colder

surroundings

(mammals + birds)

4. Plants, make amino acids from sugars and nitrate ions, so that proteins can be made.

Mitochondria

Most of the reactions of aerobic respiration occur inside mitochondria found in the cytoplasm of cells.

B2 Aerobic Respiration: temperature, water, plants, energy, contract, proteins, animals, amino, larger, colder, smaller, birds, mitochondria, day, enzymes, carbon dioxide, oxygen, glucose

Glycogen

Muscles store glucose as glycogen. During exercise glycogen is converted into glucose for use in respiration.

Glycogen → glucose

Effect of exercise on heart and breathing rates During exercise heart rate increases. The rate and depth of breathing also increases. These changes increase blood flow to muscles and so increases the supply of oxygen and glucose (sugar) allowing faster rates of respiration to provide extra energy needed during exercise. Increased blood flow also helps to remove waste carbon dioxide.

Anaerobic respiration

During exercise if not enough oxygen is reaching muscles they respire anaerobically to obtain energy.

Glucose → lactic acid (+ energy)

Effect of exercise on muscles

Long periods of vigorous exercise may cause a build-up of lactic acid. This can cause muscles to fatigue, stopping them from contracting efficiently.

Massaging muscles helps to increase blood circulation and removes lactic acid from muscles. It is transported to the liver where it is oxidised (see oxygen debt).

Oxygen debt (HT only)

In anaerobic conditions the breakdown of glucose is incomplete. Much less energy is released than during aerobic respiration.

Vigorous exercise creates an oxygen debt. This must be re-paid after exercise. Extra oxygen is needed to oxidise lactic acid …

lactic acid + oxygen → carbon dioxide + water

B2 Anaerobic Respiration + exercise: oxygen, carbon dioxide, lactic acid, rate, liver, oxidise, muscles, depth, circulation , glycogen, heart, blood, glucose, respiration, exercise, less, aerobic, oxygen debt, water

Breathing rate remains higher and deeper after exercise. This helps the blood absorb more oxygen in the lungs. This oxygen is used to repay the oxygen debt, helping to oxidise lactic acid.

B2 Comparing types of respiration and typical graph to show the effects of exercise: muscles oxygen, breathing, lactic acid, pre-exercise, blood, exercise

Substance Reactants Products

Aerobic Anaerobic Aerobic Anaerobic

carbon dioxide N N Y N

lactic acid N N N Y

oxygen Y N N N

water N N Y N

loads of energy N N Y N

little energy N N N Y

glucose Y Y N N

Heart and breathing rates finally return to pre-exercise rates.

Complete the table with Y (yes) and N (no) to compare the types of respiration in humans.

Rapid increase in heart and breathing rates during exercise, increasing the circulation of glucose and oxygen to muscles.

Meiosis

Gametes (sex cells) are made by

meiosis. In humans sperm are

made in the testes and eggs are

made in ovaries.

First each chromosome is copied

(the DNA molecules replicate).

The cell then divides twice to

make four gametes, each with one set of chromosomes

(23 in human gametes).

Fertilisation Gametes join at fertilisation forming a single body cell. This cell then divides by mitosis repeatedly. Most types of animal cells differentiate at an early stage and become specialised cells (eg nerve cells, muscle cells)

Mitosis

Body cells divide by mitosis to form new cells needed for growth and repair.

First each chromosome is copied (the DNA molecules replicate). The cell then divides once to make two genetically identical cells.

Asexual vs sexual reproduction Some organisms can reproduce using a single parent and no gametes. Cells of offspring made by asexual reproduction are produced by mitosis, so they are genetically identical to their parents (no variation in alleles). Sexual reproduction results in genetic variation because… a) Gametes fuse at random. b) Every gamete is unique, with a different combination of alleles.

B2 Cell division: gametes, body, mitosis, once, repair, asexual, copied, growth, two, testes, twice, differentiate, four, fertilisation, gamete, genetic, random, ovaries, identical

Stem cells

Stem cells from human embryos and adult bone marrow can differentiate into many different types of cells.

Treatment with stem cells

may be able to help conditions

such as paralysis.

Differentiation. When cells become specialised, they are said to have differentiated. In animals, most cells differentiate at an early stage (in the embryo). Many plant cells can differentiate throughout life.

Chromosomes

Most body cells have a nucleus containing two sets of chromosomes. Human cells have 23 pairs, making a total of 46.

Chromosomes contain genetic

information and are made

from DNA. Each DNA

molecule has a double helix structure.

A short section of chromosome DNA which codes for a characteristic is called a gene.

Genes can exist as different forms called alleles, eg. the eye colour gene has a blue (b) allele and brown (B) allele.

B2 Chromosomes and stem cells: DNA, cancer, nucleus, 46, helix, 23, gene, alleles, embryos, animals, medical, long, plant

Say YES to stem cells: 1. May cure paralysis.

2. Makes use of spare IVF embryos.

Say NO to stem cells:

1. Destroys embryos which have a right to

life. 2. Unknown long term effects – stem cells may cause cancer. 3. Money could be

spent on other medical research

Mendel (1822-1884) Mendel studied inheritance in peas. His idea was that organisms passed on separate characteristics via “inherited factors” (we now call genes). He recognised that some “inherited factors” were dominant, whilst others were recessive. The importance of Mendel’s work was not recognised until after his death because: 1. DNA, genes and chromosomes had not

been discovered. (Chromosomes were first seen under a microscope in about 1900. The idea of genes being small sections of chromosomes which could be inherited then followed).

2. People struggled to understand his theories.

Genetic crosses key terms (HT only) Homozygous = When an organism has two identical copies of the same allele. For example TT or tt. Heterozygous =When an organism has two different alleles of the same gene. For example Tt. Phenotype = The appearance or characteristics caused by a particular allele. Genotype = The combination of alleles found in the cell. For example TT, Tt or tt. Family trees: These can be used to track the inheritance of genetic diseases over several generations.

If the disease shown is caused by a dominant allele, what are the genotypes of parents 1 and 2 (use the letters A and a for alleles)? State clearly if they are homozygous or heterozygous.

1 = Aa, heterozygous.

2 = aa, homozygous.

B2 Genetics: chromosomes; genes; DNA; recessive; heterozygous; death; phenotype; homozygous; genotype; allele;

Parents

Genetic disorders Genetic disorders can be inherited. They are caused by faulty alleles. The presence of disease causing alleles can be confirmed by embryo screening. Parents can then make informed decisions about termination of a pregnancy.

Polydactyly This is caused by a dominant allele so can be passed on by only one parent who has the disorder. Sufferers have extra fingers or toes. Show the outcome of a cross between two parents, one of which is healthy, whilst the other has one copy of the disease causing allele. Let d = healthy allele, D = polydactyly allele Parents phenotype: healthy x polydactyly Parents genotype: dd x Dd Offspring: 1 healthy : 1 polydactyly ½ (50%) chance of healthy baby, ½ (50%) chance of baby with polydactyly.

Cystic fibrosis

This is caused by a recessive allele, so sufferers need to inherit two copies, one from each parent. The parents may be suffers of the disease or symptomless carriers.

The disorder affects the cell

membranes, especially in the

lungs, causing a build up of sticky mucus.

Show the outcome of a cross between two parents, both of which are healthy, but carriers of cystic fibrosis.

Let F = healthy allele, f = cystic fibrosis allele

Parents phenotype: healthy x healthy

(carrier) (carrier)

Parents genotype: Ff x Ff

Offspring:

3 healthy : 1 cystic fibrosis

¾ (75%) chance of healthy baby, ¼ (25%) chance of baby with cystic fibrosis.

B2 Genetic disorders: carriers, lungs, recessive, two, dominant, screening, mucus, phenotype, faulty, fingers, polydactyly, termination, one, toes, healthy, (letters and outcomes of crosses not included)

gametes F f

F

FF (healthy) Ff (carrier)

f Ff (carrier) ff (cystic fibrosis

gametes d d

D

Dd (polydactyly) Dd (polydactyly)

d dd (healthy) dd (healthy)

Genetic fingerprinting: Each person (except identical twins) has unique DNA. Genetic fingerprinting is used to identify people. Related people share some bands eg the child and Man B share bands 10 + 16, 12 + 20 so Man B is likely to be the child’s father.

Sex chromosomes

In human body cells one of the 23 pairs of chromosomes carries the genes that determine sex. In females the sex chromosomes are the same (XX), in males they are different (XY).

Parents phenotype: male x female

Parents genotype: XY x XX

Offspring:

Ratio 1 male : 1 female

½ (50%) chance of male baby, ½ (50%) chance of female baby.

Genetic terms Gene = small section of DNA. Alleles = different forms of the same gene. Dominant = an allele that controls a characteristic even if present on only one chromosome. Recessive = an allele that controls a characteristic only if the dominant allele is absent.

Genetic code (higher tier)

Each gene codes for a particular combination of amino acids which makes a specific protein.

B2 Genetics terms, sex chromosomes, genetic code and genetic fingerprinting: related, 12, XX, protein, gene, father, fingerprinting, dominant, alleles, recessive, XY, females, unique, 16, 23, amino, sex, males. (No outcome values listed).

gametes X X

X

XX (female) XX (female)

Y XY (male) XY (male)

Using fossils Scientists cannot be certain about how life on earth began 3-4 billion years ago because… a) Early life forms were soft-bodied, so few became fossils. b) Most early fossils have been destroyed by geological activity. By comparing fossils of different ages and living organisms, scientists can see how much or little organisms have evolved.

Extinction The permanent loss of all members of a species from the planet is termed extinction. Causes of extinction include. 1. New predators 2. New diseases 3. New, more successful competitors 4. Asteroid collisions/massive volcanic eruptions 5. Changes to the environment

Fossils Fossils are the remains of organisms from many (often, millions) of years ago, often found in rocks. Fossils can be formed …… 1. From hard parts of animals that do not decay. 2. From parts of animals that did not decay due to a lack of oxygen, warmth or moisture. 3. When parts of an organism are replaced by other materials (such as rock minerals) as they decay. 4. From preserved traces of organisms eg footprints.

Speciation (formation of new species) (HTonly)

Two populations of the same species get isolated (eg mountains)

Genetic variation exists in each population.

Natural selection occurs in each population and the most successful alleles and characteristics allow survival.

Each population becomes so different that interbreeding between them is not possible.

B2 Old and new species: decay; isolated; asteroid; oxygen; minerals; soft; millions; competitors; natural; rocks; warmth; diseases; interbreeding; extinction; evolved; predators; billion; geological; variation;