Biology

GCSE

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  • Created by: ash995
  • Created on: 28-02-09 16:42

Active Transport

ACTIVE TRANSPORT is the movement of particles, like sugar and ions, against a concentration gradient.

Uses up energy from respiration

Proteins found in cell membranes transport materials across

Used in the intestine to absorb the maximum amount of digested material

Used in the kidney tubules to reabsorb sugar (glucose)

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Diffusion

DIFFUSION = the random net movement of particles from a low concentration to a high concentration across a partially permeable membrane.

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How Your Body Reacts to Exercise

Increased heart rate to pump more oxygen to cells

Increase in depth and rate of breathing to increase amount of oxygen supplied to lungs and therefore to bloodstream, and also to get rid of waste carbon dioxide quicker

Arteries near muscles dilate, allowing more blood access to the cells to provide oxygen + glucose and carry away waste carbon dioxide

GLYCOGEN stores are broken down to glucose to use during respiration

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5 Features of animal cells and their functions

Cell Membrane: Controls what goes in and out of the cell.

Nucleus: Controls activitiesof the cell. Contains the DNA.

Cytoplasm: Chemical reactions occur here. Contains lots of enzymes, organelles and ribosomes. Jelly consistency.

(Note: Organelles are to Cells what Organs are to the body, e.g. ribosomes, mitochondria, chloroplasts)

Ribosomes: Involved in protein synthesis

Mitochondria: Aerobic respiration - energy from oxygen and glucose.

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Additional features found in plant cells

Cell Wall: Prevents cell from bursting. Made of cellulose.

Chloroplasts: Contain chlorophyll (which makes them green). They absorb light to make food by photosynthesis.

Sap Vacuole: Stored molecules and pigments. Helps control water potential of cell.

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Osmosis

Osmosis is the diffusion of WATER from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules.

Water + Diffusion + Partially permeable membrane = Osmosis.

The movement is still HIGH > LOW.

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Chemical Reactions in cells

Respiration: Most of the enzymes are in the mitochondria.

Photosynthesis: Most of the enzymes are in the chloroplasts.

Protein synthesis: Most of the enzymes are on the surface of the ribosome’s.

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Examples of specialised cells

Cells may be specialised to carry out a particular function. Sperm
- Long Tail means they can swim
- Middle section contains tons of mitochondria to provide energy for the tail.
- Acrosome stores digestive enzymes to break down the outer layers of the egg..
- Large nucleus contains genetic information to be passed on.

Root Hair
- Finger like means they have a large SA to take in water

Fat Cell
- Not much cytoplasm so loads of room for fat.

Then they can expand some more! (Up to 1000X the original size)
- There is not many mitochondria because they don't need much energy.

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Rates of diffusion

The rate of diffusion increases when there is a big difference between the two areas (a steep concentration gradient) or the temperature is increased (because the random movement of particles is decreased)

Net movement = particles moving in - particles moving out.

Eventually there will be no net movement and there will be equilibrium. Particles will still be moving though, but the same amount in each direction.

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Diffusion in living organisms

Diffusion is used in the transportation of:

Water

Simple sugars (e.g. glucose and amino acids)

Oxygen (from the air into your lungs)

 

 

Cells can be adapted to make diffusion easier and more rapid.

Increasing the surface area means there is more space for diffusion to take place. Often the SA is increased by having a folded membrane (of a cell) or tissue lining (of an organ).

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