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Cells


L.O  To understand the difference between plant and animal cells and to learn about the different cells and there functions.

All living organisms are made up of cells. Cells are the building blocks of life. Because there are a vast number of cells, some cells are specialized to ensure they provide a specific function.

 

Specialized cells

Type of Cell

Function

Special Features

Red Blood cell

To carry oxygen in the blood.

Has hemoglobin which carries the oxygen

Has a concave, donut like shape

Does not have a nucleus so it can carry more oxygen

Has a large surface area to allow to carry more oxygen

Nerve Cell

Carries nerve impulses (messages) from the body to the brain and back again.They are long, have many connections so can reach every corner of the body

They carry electrical signals so the impulse is relayed quickly

Egg cell

To join with the sperm cell and provide nutrition for the zygote (new cell) when formed.It is large and contains lots of cytoplasm for reaction to take place.

Sperm Cell

To reach the egg cell and join.Has a tail, which allows it to move.

Also has a head to carry genetic information and penetrate the egg cell.

Root Hair Cell

To absorb water and minerals.Has a large surface area, which allows it to absorb as much as possible.
Palisade cell (Leaf cell)To absorb sunlight to allow the plant to photosynthesize.

Has a large surface area and many chloroplasts, which allow it to absorb as much sunlight as possible.

 

EXAM TIP

Never call the nucleus the “brain of the cell”, it is not a very good description and will not get you any marks.

EXAM TIP

Learn the difference between animal and plant cells, as it is a very common question.

Animal cells and plant cells

Animal cells have a very irregular shape and often look uneven and unequal however plant cells have a very regular shape. Plant cells and animal cells differ in function due to the different parts they have.

This is highlighted in the diagram below

PART

FUNCTIONFOUND IN

Cell membrane

Outer part of cell, which acts as a barrier controlling what goes in and out

Animal and plant cells

Cytoplasm

This is where all the reactions occur

Animal and plant cells

Nucleus

Controls the cell and carries all the genetic information

Animal and plant cells

Chloroplast

This is where photosynthesis occurs as it contains chloroplasts

Plant cells

Vacuole

Keeps the cell firm as it contains a liquid call cell sap

Plant cells

Cell wallOuter wall which supports the cell ensuring its structure

Plant cells

 

Unicellular organisms

A unicellular organism is one that only has one cell for example bacteria, protozoa and fungi.

Unicellular organisms

 

Bacteria

Bacteria are very small cells, they differ from normal animal cells as they do not contain a nucleus so the DNA is either floating free or kept in small containers called plasmids they also may have a tail like structure usually called a Flagellum allowing the cell to move.

bacteria

Protozoa

Protozoa are also unicellular organisms however it has certain characteristics that are similar to animal cells. It has feet like projections that allow it to move and take food into the cell.

Yeast

Yeast is commonly used in bread making and making alcohol as it converts sugar into alcohol. Yeast is similar to plant cells in that, they have cells walls, which means they can absorb sugars.

Cells, tissues, organs and systems

Tissues are a group of cells working together to perform a specific function e.g. muscle, lining the intestines or lungs .

Organs are a group of tissues which work together to perform a larger task e.g. heart, lungs, stomach.

Organ systems are a group of organs working together to perform a task in the body e.g. Cardiovascular system or the reproductive system.

reproductive system

Diffusion

Diffusion is the movement of particles from one place to another.  Diffusion usually occurs in both gases and liquids, as those particles are free to move around. A common type of diffusion occurs in gases, as one set of gas particles will move from one area to another. The gas particles move from an area of high concentration to an area of low concentration.

This explained in the diagram below.

Diffusion

Cell membranes help with the diffusion process. Cell membranes not only help keep the structure of the cells, but also control what moves in and out. The cell membranes have tiny holes, which allow small particles such as oxygen to pass through, but they do not large particles such as protein to pass through. That is why proteins have to be broken down into smaller articles such as amino acids

 

 

 

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