The Cell

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What a cell needs to survive

To survive a cell needs:

- nutrients

- water

- oxygen

- ions

- substrates

These are taken from it's immediate environment. In plants this is the outside environment they are in, eg. a garden, a house. In animals this is sometimes taken from the outside environment and sometimes taken from the blood stream.

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The Cell Membrane

aka. plasma membrane

- allows active and passive transport to take place

- stops the destruction of cells

- semi-permeable (allows certain molecules through protein channels)

- carries important information from nerves, hormones & in between cells

- has receptors that send certain signals to the cell

- bilayer of phospholipids and protein channels

- surrounded by a watery substance

- function: to protect the cell contents from the environment and control to entry & exit of substances

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Cell Membrane Bilayer

Phospholipids

- hydrophilic head -> attracts water

- two fatty hydrophobic tail -> repels water

Protein Channels -> float within membrane, some rest against surface & some penetrate right through phospholipids

- transport proteins -> penetrate water & form  channels for some substances to move through

- receptor proteins -> bind substances like hormones to bring about changes in cell's activities, means cells carry out different functions

- adhesion proteins -> allow cells to join together

- recognition proteins -> attached to carbohydrate molecules to form antigens which enable the immune system to identify foreign cells in the body

- carbohydrates -> on the outer surface & connected to proteins

Cholesterol Molecules -> give the membrane some water resistance decreasing permeability to small water soluble molecules, makes the cell membrane more rigid & make sure it doesn't break down

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Generalised Cell

Nucleus

- contains chromosomes which control cell activities -> made of DNA & proteins, contain genetic information

- cell division

- cell growth

Mitochondria

- respiration -> oxygen + glucose -> chemical energy from glucose transferred into useable ATP

- energy transformers

Cytoplasm

- ions, enzymes, food molecules & organelles

- cytosol -> semi-fluid substance in which organelles are suspended

- cytoskeleton -> gives shape to cell & provides internal organisation, consists of network of filaments & tubules, cell movement & division

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Generalised Cell cont...

Vacuoles

- filled with ions

- the solution inside cells

- storage, waste disposal & growth

Ribosomes

- manufacture proteins

- attached to endoplasmic reticulum -> network of membranes, continuous with outer membrane of nucleus,  

- rough side -> involved in synthesis of lipids & carbohydrates, no ribosomes, not involved in protein synthesis

- smooth side -> ribosomes attached, involved in protein synthesis

Golgi Apparatus

- stores, modifies & packages proteins & adds carbohydrates to them to ensure they get to their correct destination

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Generalised Coll cont2...

Chloroplasts

- contain green pigment: chlorofil

- only found in photosynthetic cells taking light energy, forming ATP & synthesising organic compounds from simple raw materials

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Passive Transport

- doesn't require energy

- factors affecting: temperature, size of molecules, steep of concentration gradient

Diffusion

- the movement of particles from a region of high concentration to a region of low concentration

- particles moves across the concentration gradient until equilibrium is reached

Osmosis

- the movement of water from a region of high concentration to a region of low concentation

- water moves across the concentration gradient until equilibrium is reached

Facilitated Diffusion

- the movement of molecules down a concentration gradient with the aid of special transport proteins

- protein channels open & let larger molecules through into the cell -> they change the particles shape to allow it through

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Types of Cell

- two types

- Eukaryotic -> plants, animals, fungi, protoctista -> clearly defined nucleus, found in all kingdoms excluding bacteria

- Prokaryotic -> monera (bacteria) -> no clearly defined nucleus

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Active Transport

- require energy

- move particles against the concentration gradient

- uses protein channels

- pumping of molecules against concentration gradient with the expenditure of energy (ATP)

Vesicular Transport

- endocytosis (into the cell) -> the process by which a cell can take in material from its environment by first engulfing it with its cell membrane (eg. white blood cells) -> pinocytosis (liquids) & phagocytosis (solids) 

- exocytosis (out of the cell)

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Active Transport cont...

ATP

- oxygen + glucose = energy + carbon dioxide + water

- energy = ATP

- 36-38 ATP molecules for every 1 glucose molecule

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