Download Biology Mid Year Exam Revision

Biology
Cells
Photosynthesis
Digestive
Co‐ordination
Respiration
Biology Cells and cell structure
All living things are made up of cells. The structures of different types of cells are related to their functions
Part
Function
Plant or animal
Nucleus
Contains genetic material, which controls the activities of the cell
Both
Cytoplasm
Most chemical processes take place here, controlled by enzymes
Both
Cell membrane
Controls the movement of substances into and out of the cell
Both
Mitochondria
Most energy is released by respiration here
Both
Ribosomes
Protein synthesis happens here
Both
Cell wall
Strengthens the cell
Plant ONLY
Chloroplasts
Contain chlorophyll, absorbs light energy for photosynthesis
Plant ONLY
Permanent vacuole
Filled with cell sap to help keep the cell turgid
Plant ONLY
Yeast: Yeast is a single‐celled organism. The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall.
Bacteria: Single‐celled organism.
A bacterial cell consists of cytoplasm and a membrane surrounded by a cell wall.
The genes are not in a distinct nucleus.
Cells are specialised for a particular function. Structure helps them to carry this function out. Biology ‐ Specialised cells
Cell
Diagram
Function
Adaptations
Leaf cell
Absorbs light for photosynthesis.
Lots of chloroplasts.
Root hair cell
Absorbs water and mineral ions from the soil.
Large finger like shapes to increase surface area.
Sperm cell
Fertilises an egg
Head contains an enzyme to help penetrate egg, lots of mitochondria so egg can swim to sperm.
Red blood cell
Carries oxygen to the cells.
Thin outer membrane so oxygen diffuses easily, no nucleus so more room for oxygen.
Goblet (mucus) and cilia cells are found in the lining of the gut and the tubes into the lungs. They are specialised to release and move mucus. Helps food slide down easily in the gut and helps trap dirt and bacteria before they enter the lungs. The cilia cells help move the mucus especially in the lungs. Cilia cells have lots of mitochondria. Biology ‐ Dissolved substances
Concentration gradient
A difference in concentration between two areas next to each other. Particles will move down
the concentration gradient High to Low.
The larger the difference in concentration the faster
the rate of diffusion. Diffusion is the spreading of the particles of a gas or liquid,
resulting in a movement of particles from a region where they are of a higher concentration to an area of lower concentration. Diffusion can occur in: Air ‐ smells from perfume etc. Liquids – tea from a tea bag, dye
in water etc. Through membranes – small intestines, blood cells etc.
Location
Small intestine
Particles move
From
To
Digested food Blood in Small products e.g. capillary of intestine glucose
villus
Lungs
Oxygen Blood Alveolar air circulating space
around the lungs
Biology – Leaf Structure
Plants organs
Stem support for the leaves and flowers. Water and glucose transported too. Leaves make the food for the plant where photosynthesis happens. Roots anchor the plant in the soil, take up water and mineral ions.
Flowers are reproductive organs to attract insects.
Tissue Definition
Epidermal
Covers the plant, contains stomata.
Mesophyl
Where photosynthesis takes place. Contains palisade cells and spongy layer. Xylem
Carries water and mineral ions from roots.
Phloem
Carries glucose from the mesophyll to the rest of the plant. Stomata
Pores on the underside of the leaf that allow gases to diffuse in and out. Biology ‐ Photosynthesis
Plants convert glucose into starch and store it.
Cover part of a leaf in black paper then test it for starch using iodine. Plant cells use some of the glucose produced during photosynthesis for respiration. Also use the glucose to make: oil for storage, cellulose for cell walls, proteins (also need nitrates for this from the soil).
Photosynthesis Photo = light, Synthesis = making of (glucose) Photosynthesis = making glucose using light
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Factors that can limit the rate of photosynthesis Light intensity – not enough light no photosynthesis CO2 concentration ‐ not enough light no photosynthesis Water availability – plants wilt, not enough no photosynthesis
Temperature – too low temp enzymes don’t work well
Greenhouses
Farmers can use greenhouses to increase plant growth. Artificial light ‐ allows photosynthesis to continue beyond daylight hours. Heating ‐ allows photosynthesis to continue at an increased rate heater can also give off extra carbon dioxide released into the greenhouse this allows photosynthesis to continue at an increased rate.
Biology – Digestive System
Organisation of a multicellular organism cells  tissues  organs 
organ systems
A TISSUE is a group of specialised cells working together to carry out a particular function. Tissue
Function
Muscular tissue
Contracts, bringing about movement
Produces Glandular substances such tissue
as enzymes and hormones
Epithelial tissue
Covers some parts of the body
Tissues in the stomach
The stomach is an organ
that contains:
muscular tissue, to churn the contents
glandular tissue, to produce digestive juices
epithelial tissue, to cover the outside and the inside of the stomach. The digestive system
An organ system which humans and other mammals have so they can exchange substances with the environment.
Part(s)
Function
Pancreas/ salivary glands
Produce digestive juices
Stomach
Digests food
Liver
Produces bile
Small intestine
Digest and absorb soluble food
Large intestine
Absorbs water/ produces faeces
Biology Proteins ‐ Enzymes
Protein molecules are 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. Proteins: structural components of tissues e.g. muscles, hormones, antibodies, enzymes.
Enzymes made of proteins they are biological catalysts ‐
substances that increase the rate of chemical reactions
without being used up.
Uses of enzymes: Biological detergents: Contain protease and lipase, break down protein and fats in stains. Baby food: Protease, Pre digest proteins. Diet products: isomerase is used to convert glucose syrup into fructose syrup, which is much sweeter, can be used in smaller quantities in slimming foods
To begin with heat will help increase collisions between the enzymes and substrates BUT too hot and it will denature (remember denature NOT die)
DENATURED
Enzymes are also easily affected by pH changes. Need specific conditions to keep them working at their best. OPTIMUM CONDITIONS! Biology Enzymes –Digestive enzymes
Digestion and absorption occurs in the gut this goes from the mouth to the anus. Enzymes for respiration, photosynthesis and protein synthesis work inside cells. Other enzymes produced by specialised cells and released from them e.g. digestive enzymes. Catalyse means to speed up.
Enzyme
Reaction catalysed
Where produced
Amylase
Starch → sugars
Salivary glands, pancreas, small intestine
Protease
Lipase
Proteins → amino Stomach, pancreas, acids
small intestine
Lipids → fa y acids + glycerol
Pancreas, small intestine
Digestion and pH: The stomach releases acid. The enzymes made in the stomach work best in acidic conditions. The enzymes made in the pancreas and small intestine
work best in alkaline conditions. The liver produces bile which is released into the small intestine. Bile neutralises the acid that was added to the food in the stomach.
Biology The nervous system
Types of Neurone : Sensory neurones send impulses from receptors in the sense organs to the CNS.
Motor neurones send impulses from the CNS to muscles and glands.
Relay neurones found in the spinal cord/brain. The link sensory and motor neurones. The nervous system uses electrical impulses to send messages along neurons. These are VERY fast and allow you to respond quickly to changes in the environment.
Neurone – a cell that transmits electrical impulses in the nervous system. Central Nervous system (CNS) – Brain and Spinal cord. Peripheral Nervous system (PNS) ‐ nerves connecting the sense organs and effectors to the CNS
Sense organs – detect changes both in and outside your body. They contain receptor cells Eye; Ear; Skin; Mouth; Nose
Stimulus – Anything your body is sensitive to e.g. noise, heat, light. Impulses – Electrical signals in the nervous system that travel through neurones. The Reflex Arc – an automatic response
Light receptor cells, like most animal cells, have a nucleus, cytoplasm and cell membrane.
A – Receptor (reacts to a stimulus)
B – Sensory Neuron (carries message to the co‐ordinator/CNS)
C – Relay Neuron Gaps between neurons are called SYNAPSES
D – Motor Neuron (carries message away from co‐
ordinator/CNS
E – Effector (a muscle or gland) Biology Control in the human body – Hormones and Homeostasis
Hormones: The endocrine system produces hormones in parts of the body called glands. These are chemicals that help control body functions. The glands release the hormones into the blood
where they are carried to target organs.
Hormones travel a lot slower than nerve messages but their effects are usually longer lasting and they act quickly. Hormones control things like menstruation in women as well as the changes that occur to our bodies during puberty and homeostasis. Factors controlled by homeostasis: Water content– water leaves the body by: lungs when we breathe out, skin when we sweat, kidneys in the urine Ion content– ions are lost by: skin when we sweat, kidneys in the urine
Temperature – to maintain the temperature at which enzymes work best for chemical reactions in the cells. Normal body temperature is 37oC
Blood glucose levels – controlled by the pancreas to provide the cells with a constant supply of energy.
SAS survival manual says to conserve water:
‐ Avoid exercise, stay in the shade, don’t lie on hot ground – no sweating.
‐ Don’t eat – digestion uses up water.
‐ Don’t talk and breathe through your mouth –
so no water lost from mouth. Biology Control in plants ‐Auxins
Uses of plant Hormones
Tropism – plant growth response to a stimulus.
Phototropism – Plant growth response to light.
Geotropism –Plant growth response to gravity.
Positive Tropism – towards the stimulus.
Negative Tropism – away from the stimulus.
Auxin – Plant growth hormone.
Selective Weed killers – Auxin makes broad leaved plants grow out of control and die.
Rooting Powder – Auxin makes cuttings develop roots quickly.
Seedless Fruit – Flowers sprayed with hormones to make fruit develop but not seeds. Fruit Ripening – Farmers use hormones to control fruit ripening. Phototropism
Geotropism
Auxin produced in the tip of the shoot
Auxin moves to shaded side of the stem
Auxin causes cell elongation
Auxin produced in the tip of the root
Auxins have opposite effect in the root
Auxins stop elongation and root grows down
Biology Aerobic respiration
RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY.
Aerobic Respiration The process of releasing energy from food in cells. Aerobic respiration ‐
uses oxygen. All chemical reactions inside cells are controlled by enzymes.
Aerobic respiration (with oxygen)
glucose + oxygen → carbon dioxide + water (+ energy)
Glucose reacts with oxygen, producing carbon dioxide and water as waste products. To release energy. This takes place continuously in animals and plants.
Released energy is used for:
To build up larger molecules using 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.
Mitochondria: Tiny organelles found in most plant and animal cells. Where the respiration
reactions happen. More active cells have more
mitochondria
e.g. muscle cells, sperm cells.
During exercise changes take place: the heart rate and breathing increases. Blood flow increases so more glucose and O2 to cells. Muscles store glucose as glycogen – the glycogen
gets converted back to glucose during exercise. Biology Anaerobic respiration RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY.
During exercise, too little oxygen is reaching the muscles they use anaerobic respiration to RELEASE energy. It is the incomplete breakdown of glucose and produces lactic acid. Anaerobic respiration (without oxygen)
glucose → lac c acid (+ small amount of energy)
Lactic Acid
If muscles have long periods of exercise they get fatigued‐ they stop contracting properly. One cause is the build‐up of lactic acid in the muscles. Lactic acid is poisonous. We can only tolerate small amounts in our body. Blood flowing through the muscles
removes the lactic acid.
Higher Tier OXYGEN dept: Anaerobic respiration results in an oxygen debt that has to be repaid in order to change lactic acid to carbon dioxide and water. The extra oxygen needed is called the oxygen debt.
‐The heart continues to pump faster.
‐The breathing rate remains high.
‐This delivers the extra oxygen to the muscles.
‐This pays back the oxygen debt.
In yeast anaerobic respiration produces ethanol and carbon dioxide (which is why we used it to make beer and bread) we call this fermentation. Biology –Responding to stimuli
Keywords – (all from previous slide B1.12 and 1.13 also needed)
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Reflex – a response to a stimulus that does NOT require processing by the brain. The response is automatic.
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Examples: Blinking/ removing hand from hot surface/ knee jerk reflex/ covering ear to loud noise
Reflex Arc – Connection of a sensory neurone to a motor neurone (usually via a relay neurone) that allows reflex actions to occur.
Neurotransmitter – Substance that diffuse across the synapse between two neurones and triggers an impulse to be generated in the neurone on the other side of the synapse.
Synapse ‐ Point at which 2 neurones meet. There is a tiny gap which cannot transmit an impulse without a neurotransmitter.
Myelin Sheath – fatty covering around the axons of many neurones. It speeds up transmission of impulses and help to insulate them from one another.
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1. Stimulus
2. Receptor 3. Sensory neurone 4. Relay neurone
5. Motor neurone
6. Effector
Biology Hormones and B1.15 Diabetes
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Hormone – Chemical messengers that cause certain parts of the body to respond to their presence. E.g. Human Growth Hormone causes bones and muscles to grow at a faster rate during puberty.
Endocrine glands – Glands that produce and release hormones.
Target organ – an organ on which a hormone has an effect. (e.g. Insulin has an effect on the Liver)
Pancreas‐ organ that produces digestive enzymes and the hormones insulin and glucagon.
Insulin – hormone that decreases blood glucose concentration by causing liver cells to convert glucose into glycogen for storage.
Glucagon – hormone that causes liver cells to convert glucagon back into glucose to increase blood glucose concentration
Examples of hormones and their effects
Hormone
Released from
Effect
Anti‐Diuretic Hormone
Pituitary gland
Causes the kidney to make more concentrated urine
Oestrogen
Ovaries
Development of the female reproductive system during puberty
Adrenaline
Adrenal Gland
Speeds up the heatbeat
Testosterone
Testes
Development of the male reproductive system during puberty
Biology Diabetes Type 1 Diabetes
1. Pancreas does NOT produce insulin
2. Inject insulin daily (into the fat layer beneath the skin)
3. Exercise and diet are used to help lower blood glucose levels too
Type 2 Diabetes
1. Cells respond less well to insulin (they become resistant)
2. Control by changes in diet and exercise .
3. Risk factors of developing it are:
1.
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High‐fat diets
Lack of exercise
Getting older
Obesity
The diagram shows normal blood sugar control (without diabetes)