whole subject revision cards

  • Created by: naomi
  • Created on: 05-03-12 19:46

Animal and Plant Cells

Organ = P.O.B that has a specific function to carry out. e.g. heart function - to pump blood around the body

Organelle = P.O.C that has a specific function e.g. nucleus - controls cell activity

 Two other organelles are: Mitochondria Where respiration takes place                         Ribosomes Where proteins are made in a cell

Respiration - Release of energy from food

 Word Equation: Glucose + Oxygen ---> Energy + C02 + Water vapour

Building blocks of proteins are called AMINO ACIDS

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Every living thing needs oxygen and glucose

Diffusion = The movement of a substance from a region of HIGH concentration to a region of low concentration.

e.g. Spray particles moving at random and spreading out.

How do gases move in and out of the blood?

As the blood is in a continuous circle, the blood coming in is of low concentration, low in oxygen. It comes back to the high concentration area to collect oxygen in every breath.

(It is low as other organ have gradually taken a bit at a time)

Diffusion of particles takes place down a concentration gradient

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Osmosis is a special type of diffusion that is important to plants - They gain water through their roots. Water moves into plant cells by osmosis - makes them able to hold the plant upright. 

Osmosis = The movement of water molecules from a high concentration to a low concentration through a partially permeable membrane.

 For osmosis to happen you need:

  • two solutions with different concentrations
  • a partially permeable membrane to separate them

The level on the more concentrated side of the membrane rises, level on less concentrated side falls. When concentration = same on both sides of membrane, movement of water molecules = same in both directions. At this point, the net exchange of water is zero and there is no further change in the liquid levels. 

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What are enzymes and how do they work?

Enzymes are biological catalysts (Catalyst - to speed up a chemical reaction)

All enzymes are 3D proteins

Substrate - any molecule that fits into an enzymes active site. (An active site is a groove (lock) in an enzyme which recognises the shape of the substrate (key).

Denatured (caused by high temperatures or extremes of pH) enzymes - won't fit active site.

Enzymes reduce the activation energy needed for a reaction to proceed and produce products. 

As the temperature increases, so does the rate of reaction.

The optimum pH for an enzyme depends on where it normally works. For example, intestinal enzymes have an optimum pH of about 7.5. Enzymes in the stomach have an optimum pH of about 2.

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Enzymes and Respiration

Enzymes in cells catalyse photosynthesis, protein synthesis - joining amino acids together, and aerobic respiration.

Respiration is a chemical process in which energy is released from food substances, such as glucose - a sugar.

Aerobic respiration needs oxygen to work. Most of the chemical reactions involved in the process happen in tiny objects inside the cell cytoplasm, called mitochondria. Equation for aerobic respiration:

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

The energy released by respiration is used to make large molecules from smaller ones. In plants, for example, sugars, nitrates and other nutrients are converted into amino acids. Amino acids can then join together to make proteins. The energy is also used:

  • to allow muscles to contract in animals
  • to maintain a constant body temperature in birds and mammals

Enzymes end in ase and sugars end in ose

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Enzymes and Digestion

Digestion is the breakdown of carbohydrates, proteins and fats into small soluble substances that can be absorbed into the blood.

Lipases and proteases are used in biological detergents, and enzymes are used in the manufacture of food and drink.

Digestion happens inside the gut, and relies on enzymes.

enzymereaction catalysed and where produced amylase starch    ->    sugars         Salivary glands, pancreas, small intestine protease proteins   -> amino acids     Stomach, pancreas, small intestine lipase lipids    ->    fatty acids + glycerol    pancreas, small intestine

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The Digestive System

Mouth = Breaks down food so you can swallow it

Gullet = Connects mouth and stomach

Stomach = Made of muscle which contracts and contains acid pH2. Contractions mix the food with acid.

Liver = Works with the pancreas to make blood glucose at the right concentration

Pancreas = Produces 3 enzymes; amylase to digest starch, protease to digest protein and lipase to digest fat

Small intestine = More proteases, carboydrase and lipase are produced here to finish digestion. Digested food is absorbed through the walls into the blood stream.

Large intestine = Water is absorbed from the waste leaving semi - solid faeces

Rectum = Faeces are stored here, muscle in walls control release.

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Homeostasis and Thermo-regulation

  • Core body temperature 37 = optimum temperature for body enzymes
  • Body temperature is monitored/controlled by the TRC (Thermo regulatory centre) aka Hypothalemers
  • TRC contains temperature receptor cells- monitor temperature of blood flowing through. 
  • Skin has temperature receptor cells that respond to external temperature.

Blood temp too high:

  • Sweat glands activated - sweat evaporates = heat removed from skin
  • Blood vessels supplying to capillaries dilate = more heat lost from surface of skin

Blood temp too low

  • Muscles contract violently = shivering = shivering requires energy to contract muscles. Some energy is released as heat.
  • Blood vessels supplying capillaries in skin constrict = less heat loss and blood warms. 
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Discovery of Insulin

  • Before 1912 most diabetics would die from their condition (fatal)
  • Two canadian scientists discovered the hormone insulin
  • Insulin reduced blood gucose levels
  • Insulin is produced in special cells called islets, found in the pancreas.
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Genetic Diagrams to predict genetic outcomes


  • Gene
  • Allele = different forms of the same gene
  • Recessive
  • Dominant
  • Heterozygous = when alleles are different e.g. Bb = recessive 
  • Homozygous = when both alleles are the same e.g. BB = dominant

Capital letter = Dominent genes/ Allele   e.g. B

Lower case letter = Recessive allele       e.g. b

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DNA - Has a double helix shape (twisted ladder) - the chemical that chromosomes are made of

Chromosome - Thread-like structure, made of DNA, found in the nucleus - There are 23 paira (=46) in body cells

Gametes - Sex cells - Sperm and egg

Gene - A section of DNA - code for a single characteristic e.g. hair colour.

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Genetic Disorders

Cystic Fibrosis  (cf) Recessive genetic disorder

  • Cf is a disorder of the cell membrance
  • e.g. lung cell membrane produces too much mucus
  • The two major organs affected are the lungs and pancreas

Huntington's Disorder

  • Affects brain/central nervous system
  • Usually symptoms occur later in life e.g. late 40s 
  • Progressive disorder: speech, co-ordination deteriorates
  • Fatal disorder
  • Caused by one dominent allele (e.g. H)
  • Dominant disorder: HH = huntington's, Hh = huntington's, hh = no disorder

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Stem Cells

Different types of stem cells:

  • Adults stem cells
  • Embryonic stem cells
  • Faetal stem cells

Stem cells are unspecialised cells that have the potential to grow into any cell

Adult stem cells e.g. found in bone marrow are able to specialise into red or white blood cells.

Embryonic stem cells are taken from an embryo (ball of cells from a fertilized egg)

Uses of stem cells:

  • Adult stem cells can be used in bone marrow transplants
  • Embryonic stem cells might be used in the future to treat some inherited disorders and spinal injuries.
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Cell Division by Mitosis and Meiosis

Mitosis is a type of cell division that results in 2 identical cells. (called daughter cells = clones)

Meiosis is a type of cell division that results in the formation of gametes (sex cells) sperm/eggs

Double division!


Gametes have 1/2 the number of DNA.

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Food Chains

Community - A collection of species living in one particular place

Predator - Hunts and kills it's prey/food

Prey - An animal that is hunted

Producer - Makes it's own food

Consumer - Eats food

Herbivore - A plant eater

Food chain - A diagram showing what eats what

Food web - A diagram showing what eats what in a habitat

Carnivore - A meat eater

Biomass - The material that plants and animals are made of

Pyramid of number - the number of organisms within each stage of a food chain ( arrows show the flow of energy

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Pyramids of Biomass

Biomass is the biological material e.g. for animals = skin, muscle bones. For plants = leaves, roots etc.

Energy is stored in the materials that make up organisms. These materials are called biomass.

Biomass contains energy: Biomass = biological material = ENERGY

Only biomass can be passed up the food chain/pyramid so energy must be lost in/ used for:

  • New biomass e.g. growth and repair
  • Movement
  • Heat if animal is warm blooded
  • Respiration
  • Waste e.g. urine/ faeces

The food chain is limited and energy is lost at each stage of a food chain. 

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Intensive Versus Free Range Farming


  • Less space available
  • More injury and disease
  • Animal welfare is low
  • No movement - less energy required

Free Range

  • More space available e.g. outside
  • Less injury and disease
  • Animal welfare is high

(Both are looking for profit)

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The Decay Cycle and The Nutrient Cycle

The Decay Cycle:

Detritus(dead material) Feeders = Organism that lives off 'dead' matter. 

Decomposer Microbes = Bacteria/fungi that feed on dead matter.

  • Nature's way of recycling nutrients - nutrients get back into soil to be re-used by plants and nutrients are fertilisers for plants.

The Nutrient Cycle:

Why do nutrients need to be recycled? Nutrients(fertiliser) recycled back into soil to be used for plant growth.

What ways are there to increase decomposition? Occurs best when: Suitable temperature (e.g. sprint/summer) (too much heat = denatures microbes), Oxygen is available, Moisture is available.

How are composters designed to increase decay? Slats are built in to help oxygen circulate and covers are included to keep it at a suitable temperature. 

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The Carbon Cycle

Carbon is a key element for all living things. It is found in:

  • Carbohydrates
  • Proteins
  • Fats

There are three compounds that make up the structure of cells:

E.g. Glucose (C6H1206) is a carbohydrate needed for respiration(release of energy from food)

Fats contain carbon and fats are the key substance in cell membranes. Proteins contain carbon and are needed for the growth and repair of cells. Remember all enzymes are proteins so contain carbon.

Carbon is so useful that nature recycles it.

Carbon dioxide from the atmosphere is taken in by plants which then use photosynthesis to create glucose which humans eat. Humans then recycle it into the atmosphere through respiration as they convert glucose into carbon dioxide.

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Carbon Dioxide + Water + Light Energy --> Sugar + Oxygen

Inputs: Carbon dioxide, water, light energy

Outputs: Sugar and oxygen

Most photosynthesis takes place in leaf cells (Palisade cells - specialised plant cells - because of it's high density of chloroplasts).

Chloroplasts contain chlorophyll

Job of chlorophyll: To absorb sunlight from photosynthesis

Limiting Factors: The rate of photosynthesis can vary over a 24 hour period and depends on the time of year (Seasonal changes). The rate increase if key factors are plentiful and decrease when one or more key  factors are in short supply, known as limiting factors.

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