Biology

From cells to inheritance

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Animal Cells

A Nucleus - to control cell activities; holds genetic material; 23 chromosomes which makes up the DNA.

Cytoplasm - where chemical reactions take place; controlled by enzymes.

A Cell Membrane - that controls the movement in and out of the cell.

Mitochondria - where energy is released during aerobic respiration.

Ribosomes - where proteins are synthesised/made.

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Plant Cells

A Nucleus - to control cell activities; holds genetic material; 23 chromosomes which makes up the DNA.

Cytoplasm - where chemical reactions take place; controlled by enzymes.

A Cell Membrane - that controls the movement in and out of the cell.

Mitochondria - where energy is released during aerobic respiration.

Ribosomes - where proteins are synthesised/made.

Cell Wall - made of cellulose. Supports and strengthens the cell.

Chloroplasts - contains chlorophyll; absorbs light energy for photosynthesis.

Permanent Vacuole - filled with cell sap; to help keep the cell turgid.

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Specialised Cells

When a egg is fertilised it begins to grow and develop.

At first there is a growing ball of cells. Then as the organism gets bigger some of the cells change and become specialised.

There are many different specialised cells e.g

  • Some cells in plants may become xylem or root hair cells.
  • Some cells in animals will develop into nerves or sperm cells.

Sperm cells function is fertilise a egg cell; the head contains genetic information nad an enzyme to help penetrate the egg cell membrane; the middle section is packed with mitochondria for energy.

Red blood cells which contains haemoglobin to carry oxygen to the cells; thin outer membrane to let oxygen diffuse through easily; the shape increase to allow more oxygen to be absorbed; no nucleus just haemoglobin.

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Diffusion and Osmosis

Osmosis - is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.

Osmosis in plants is very important. Osmosis happens through their roots. If plants don't gain enough water, they will not be turgid or stiff for them be able to stand/hold themselves upright.

Diffusion - is the passive movement of particles from an area of high concentration to an area of low concentration.

The larger the difference in concentration, the faster the rate of diffusion:

  • the diffusion of oxygen into cells of the body from the bloodstream as the cells are respiring (and using up oxygen)
  • the diffusion of carbon dioxide into actively photosynthesising plant cells
  • the diffusion of simple sugars and amino acids from the gut through cell membranes
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Photosynthesis

carbon dioxide + water (+ light energy)=glucose + water

FOUR THINGS NEEDED FOR PHOTOSYNTHESIS:

  • LIGHT - from the sun
  • CHLOROPHYLL - absorbs energy in sunlight
  • CARBON DIOXIDE - enters leaf from surrounding air
  • WATER - comes from soil; up the roots and steam; into leaf

The carbon dioxide is taken in by the leaves, and water by the roots.

The chlorophyll traps the energy needed for photosynthesis.

In photosynthesis the sugar glucose (a carbohydrate) is made. Oxygen is given off as a waste gas.

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Limiting Factors

Light - as the light exposure level is raised, the rate of photosynthesis increases steadily. However on sunny days, light may be limited on the floor of a wood or rainforest.

Carbon Dioxide - this will also slow down the process. Carbon Dioxide is limited in enclosed spaces like greenhouses.

Temperature - like most enzymes they work best up 40 degrees.C, any higher then the enzymes become denatured and the reaction stops completely.

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Glucose and Minerals

Glucose - is used for respiration and product of photosynthesis; helps produce new materials; can be stored in some plants as insoluble starch; this has no effect on osmosis.

Magnesium - produce chlorophyll to help with photosynthesis; yellow leaves shows the deficiency in magnesium.

Nitrates - produce proteins for growth; if dont absorb enough the plant will have stunt growth.

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Biomass and Energy Loss

Biomass is the mass of living material in plants and animals.

Pyramid of biomass shows a more accurate picture.

FOUR WAYS OF ENERGY LOSS: (Sankey Diagrams)

  • GROWTH
  • MOVEMENT
  • HEAT
  • FAECES/URINE

The shorter the food chain, the less energy is loss. So it is more efficent for us to eat plants than meat.

  • Preventing animals to move
  • Keeping animals warm at a controlled temperature
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Enzymes

Enzymes are biological catalysts - speed up reactions.

Enzymes are picky on the temperature and acidity of the area they are in.

If these things don't suit them the enzymes will become denatured.

If the factors are good for the perfect enzymes this will give the enzymes more energy and kore of a change of a successful collision.

AEROBIC RESPIRATION = Mitichondria

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

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Enzymes in Digestion

AMYLASE - salivary glands, the pancreas and the small intestines. Digests starch into sugar in the mouth and small intestines. ALKALINE

PROTESE - produced by the stomach, the pancreas and the small intestines. Breaks down proteins into amino acids in the stomach and the small intestines. ACID

LIPASE - produced by the pancreas and the small inestines. Breaks down lipids (fats and oils) to fatty acids and glycerol. ALKALINE

BILE - produced by the liver; stored in the gall bladder; squirted into small intestines and neutralises the stomach acid.

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Uses of Enzymes

PROTEASE - to pre - digest in some baby foods

ISOMERASES - converts glucose to fructose; much sweeter, so less is added to foods; therefore not fatting.

CARBOHYDRASES - convert starch into sugar syrup fr use in foods.

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Homeostasis

TEMPERATURE RISES:

  • Blood vessels dilate allowing more blood through. Heat loss = radiation
  • Sweat glands = sweat - evaporated; energy required for it to evporate makes us cool down.

TEMPERATURE FALLS:

  • Blood vessels constrict allowing less blood through. Less heat radiated.
  • Muscles contract quickly. Respiration = energy produced = heat energy.
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Diabetes - Contolling Blood Sugar

The pancreas monitors and controls the level of sugar in our blood.

If there is too much sugar in our blood the pancreas produces the horomone insulin that results in the excess sugar being stored in the liver as glycogen. If insulin is not produced the blood sugar level may become fatally high.

If the pancreas is not producing enough insulin, this is known as diabetes. It can sometimes be controlled by diet or the person may need insulsin injections.

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