B1: Cell Structure and Transport

Special cells

Nerve cells

  • Carries electrical pulses - that is what they are specialised for Rapid Communication System

  • Adaptions

    o lots of drendrites - connect other nerve cells

    o axon - carries the nerve impulse

    o synapses - pass impulse between cells, nerve cells or a muscle

    o lots of mitochondria to provide energy to make transmitter chemicals

Sperm cells

  • A large nucleus contains the genetic information

  • Contain information from the male parent

  • Acrosome stores digestive enzyme for breaking the outer layer of the egg

  • Middle section contains mitochondria to make the tail move

  • Long tail to move through water or the female reproductive system

Muscle cells

  • These are specialised so the muscle can contract and relax in the pairs to move the bones

  • Contains special proteins to make the fibre contract

  • Contains mitochondria to transfer the energy for the chemical reactions of the cells transfer the energy needed for the fibres to contract

  • Can store glycogen which is used in cellular respiration by the mitochondria to transfer the energy needed for the fibres to contract

Red Blood cells

  • Delivers oxygen to the tissues in your body

  • No nucleus - allows more haemoglobin

  • Contains haemoglobin - red protein that combines with oxygen

  • Being small and flexible - to fit through narrow blood vessels

  • A biconcave shape - maximises surface area for oxygen absorption

Root Hair cells

  • Increases surface area available for water

  • Close to the tips of growing roots

  • Large, permeant vacuole to speed of movement of water by osmosis

  • Root hair cells help to take water and minerals up more efficient

  • Lots of mitochondria that transfer the energy used to transport of mineral ions

  • Close to the xylem tissue

Xylem cells

  • Transport tissue implants - carries water and mineral ions to the highest leaves

  • Helps support the plant

  • Lignin builds up in the cell walls killing cells and creating a hallow tunnel spiralling lignin make the cells strong to carry water

Photosynthesis cells

  • Chloroplast containing chlorophyll - trap light

  • Permeant vacuole - keep cell rigid and spread out - catch maximum light

  • Positioned in continuous layers and the leaves and outer layers of stem to catch maximum light

  • Make their own food

Phloem cells

  • Carry food, made by photosynthesis around the plant

  • Contains sieve plates to allow water carrying dissolved food to be freely up and down tubes

  • Lose a lot of structure, supported by companion cells

  • Mitochondria of the companion cells transfer the energy needed to move the dissolved food

Diffusion

What is diffusion?

Net movement of particles / spreading

What about the direction of movement with reference to concentration?

From high concentration to low concentration

Does it go up or down the concentration gradient?

It occurs down a concentration gradient

Does it require energy?

It does not require any energy

These are the factors that speed up diffusion:

  • Concentration gradient —> steeper, greater difference

  • Temperature —> hotter, more energy and moving quicker

  • size of particles —> smaller, less dense

Osmosis

What is osmosis?

Net movement or spreading of water particles

Which way will the water move?

From an area of high concentration to low concentration

Does water move up or down the concentration gradient?

It occurs down a water concentration gradient

Does osmosis require any energy?

No energy is required

What does osmosis have to occur across?

It occurs across a partially permeable membrane e.g. cell membranes and cell walls

Lots of water:

  • Dilute

  • High water concentration

  • Low solute concentration

Little water:

  • Concentrated

  • Low water concentration

  • High solute concentration

Active Transport

What is active transport?

Movement or spreading of particles or molecule or ions

What about the direction of movement?

From areas of low concentration to high concentration

Does it go up or down the concentration gradient?

It occurs up the concentration gradient

Does it require energy?

It requires energy and requires carrier proteins (on cell membranes)

Exchange surfaces in Organisms

  • Large surface area —> infolding membrane —> leaf, villi

  • Thin membrane —> give shorter diffusion distance —> leaf, villi

  • Rich blood supply/good network of capillaries —> maintains a steep concentration gradient —> heart, villi

  • Well ventilated —> maintains a steep concentration gradient