Cells and Organelles

What are eukaryotic cells?

'eukaryotic' means 'having a nucleus' - their cells contain a nucleus surrounded by a membrane, along with other membrane bound organelles, such as mitochondria and chloroplasts. These include animal and plants, fungi and protosists.

Characteristics of plants:

- All plants are multicellular - Their cell walls are made out of cellulose - Their cells contain chloroplasts that carry out photosynthesis - They store the carbohydrate starch - Sucrose the sugar is transported around the plant - Grass, flowering plants

Characteristics of viruses

- All viruses are parasites - Only produce inside living cells - The cell in which virus reproduce is called the host - Not made out of cells (no nucleus or cytoplasm) - Has a protein coat - Do not feed, respire, excrete, move or grow

what are the different systems in a person?

- Digestive system - Gas exchange system ( including the lungs, which exchange oxygen and carbon dioxde) - Circulatory system (including the heart and blood vessels - transport materials around the body) - Excretory system - including the kidneys, which filter toxic waste materials from the blood - Nervous system - consisting of the brain, spinal chord and nerves, which coordinate the body's actions - Endocrine system - glands secreting hormones, which act as chemical messenagers - Reproductive system - producing sperm in males and eggs in females and allowing the development of the embryo

Characteristics of Protosists

- Most are unicellular, some are multicellular - Some can photosynthesise called algae - Some are agents to disease

Characteristics of animals

- Multicellular - They gain their nutrition by feeding of other animals or plants - Don't have cell walls, making them able to change shape, helping them move place to place - They contain a nervous system - They store sugar as a compound called glycogen - Insects, humans, mammals

Characteristics of Fungi

- Multicellular (except yeast which is unicellular) - Cannot photosynthesise - Have cell walls composed of chitin - It feeds on saprotrophic nutrition (feeds of dead organisms, digestion takes place outside of the organism) - Mushrooms, moulds

There are eight life processes which take place in most living things. Organisms:

- Require nutrition (plants make their own food, animals eat other organism) - Respire (release energy from their food) - Excrete (get rid of waste products) - Respond to a stimulus (are sensitive to changes in their surroundings) - Move (by the action of muscles in animals, and slow growth movement in plants) - Control their internal conditions (maintain a steady state inside the body) - Reproduce (produce offspring) - Grow and develop (increase in size and complexity, using materials from their food)

Characteristics of bacteria

- Single celled organisms - All surrounded by cell wall, protects and keeps shape - No nucleus, instead genetic material is a single chromosome, loose in cytoplasm - Have structures that allows them to swim called a flagella - Some have structures called plasmids carrying genes - Some can photosynthesise - They are decomposers - Some are disease carrying - Can respire, excrete, grow and reproduce and some move

what are the factors affecting diffusion

- The concentration gradient - diffusion happens more quickly when there is a steep concentration gradient (i.e. a big difference in concentration between two areas) - The surface area to volume ratio - the larger surface area in proportion to the volume will increase the rate - The distance - the rate is decreased if the distance over which diffusion has to take place is greater. - The temperature - the rate is greater at higher temperatures. This is because a high temperature provides the particles with more kinetic energy

practical - osmosis

1. Place a potato chip into a beaker of pure water, and another in a sugar solution 2. Measure the length of potato chip in both beakers and leave it 3. After a while, measure the length again; potato in water should increase in size, and the one in the sugar solution should shrink

what are organs?

A collection of several tissues carrying out a particular function is called an organ. Plant organs include stems, flowers, leaves and roots. Human organs include skin, heart, lungs etc.

What is a pathogen?

A pathogen is a species of bacteria which causes disease.

What is active transport

Active transport is the movement of substances against a concentration gradient, using energy form respiration. During active transport a cell uses energy from respiration to take up substances, rather like a pump uses energy to move a liquid from one place to another. Cells use active transport to control the uptake of many substances Active transport is the movement of substances against a concentration gradient, using energy form respiration. Diffusion happens because the kinetic energy of the particles. It does not need an 'extra' source of energy from respiration. However, sometimes a cell needs to take in a substance when there is very little of that substance outside the cell, In other words against the concentration gradient. It can do this by another process called active transport.

Practical - diffusion in a jelly

Agar is a jelly that is used for growing cultures of bacteria. It has a consistency similar to the cytoplasm of a cell. Like cytoplasm it has a high-water content. Agar can be used to show how substances diffuse through a cell. Uses the reaction between acid and potassium permanganate solution. When hydrochloric c acid comes into contact with the potassium permanganate, the purple colour of the permanganate disappears. A petri dish is prepared which contains a 2cm deep layer of agar jelly, dyed out purple with potassium permanganate. Three cubes of different sixes are cut out of the jelly, with sides 2, 1 and 0.5cm. the cubes have different areas and volumes. They also have a different surface to volume ratio. Notice the smaller cube has the largest surface area to volume ratio. The same is true with all cells, the small cell has a larger surface area to volume ratio than a large cell. The cubes are carefully dropped into the hydrochloric acid. The time taken for each cube to turn colourless is noted.

what is the life cycle of a pathogen

All types of pathogen have a simple life cycle. They infect a host, reproduce themselves or replicate if it is a virus, spread from their host and infect other organisms. They also all have structural adaptations that make them successful at completing their life cycles, which enable them to cause further disease.

conclusion of agar diffusion practical

As the surface area to volume ratio increased, the more diffusion takes place If we were to change concentration of HCL: As the concentration of hydrochloric acid increased the distance the colour change of the agar, from pink to colourless, also increased. This shows that greater diffusion of the hydrochloric acid into the agar occurred at higher concentrations.

What do animals cells contain?

Cell membrane, nucleus, mitochondria, cytoplasm, ribosome

what is a chloroplast?

Cells of the green parts of plants, especially leaves contain another very important organelle, the chloroplasts. Chrloroplasts absorb light energy to make food in the process of photosynthesis. They contain a green pigment called chlorophyll. Cells from the parts of a plant that are not green, such as flowers, roots and woody stems have no chloroplasts

what are cells and tissues?

Cells with a similar function are grouped together as tissues. For example, the muscle of you arm contains millions of similar muscle cells, all specialised for one function - contraction to move the arm bones. This is muscle tissue. However a muscle also contains other tissues, such as blood, nervous tissue and epithelium (lining tissue)

what is diffusion

Diffusion is the net movement of particles (molecules or ions) from a region of high concentration to a region of low concentration. i.e down a concentration gradient

how can a disease tranferred?

Direct contact - This can be sexual contact during intercourse or non-sexual contact, like shaking hands. Water - Dirty water can transmit many diseases, such as the cholera bacterium. Air - When a person who is infected by the common cold sneezes, they can spray thousands of tiny droplets containing virus particles to infect others. Unhygienic food preparation - Undercooked or reheated food can cause bacterial diseases like Escherichia coli which is a cause of food poisoning. Vector - Any organism that can spread a disease is called a vector. Many farmers think tuberculosis in their cattle can be spread by badgers

what is a system?

In animals, jobs are usually carried out by several different organs working together. This is called an organ system. For example, the digestive system consists of the gut, along with glands such as the pancreas and gall bladder. The function of the whole system is to digest food and absorb the digested products into the blood.

when does diffusion occur? example

Many substances can pass through the membrane by diffusion. Diffusion happens when a substance is more concentrated in one place than another. For example, if the cell is making carbon dioxide by respiration, the concentration of carbon dioxide inside the cell will be higher than the outside. This difference in concentration is called a concentration gradient. The molecules of carbon dioxide are constantly moving about because of their kinetic energy. The cell membrane is permable to carbon dioxide, so the molecules can move in either direction through it. Since there is a higher concentration of carbon dioxide molecules inside the cell than outside, over time, more molecules will move from inside to outside than move in the other direction. We say that there is a new movement of the molecules out of the cell

What are vacuoles?

Mature (fully grown) plant cells often have a large central space surrounded by a membrane, called a vacuole. This vacuole is a permanent feature of the cell.is is filled with a water liquid called cell sap, which is a store of dissolves sugars, mineral ions and other solutes. Animal cells do contain vacuoles but they are only small, temporary structures.

What is the mitochondria?

One organelle that is found in the cytoplasm of all living cells Is the mitochondrion. In cells that need a lot of energy such a muscle or nerve cells, there are many mitochondria. This gives us a clue to their function. They carry out some of the reactions of respiration releasing energy that the cells can use. Most of the energy from respiration is released in the mitochondria. powerhouse that makes energy

What is osmosis

Osmosis is the net movement of water from a dilute solution to a more concentrated solution across the partially permeable cell membrane. Water moves across cell membranes by a special sort of diffusion, called osmosis. Osmosis happens when the total concentrations of all dissolved substances inside and outside the cell are different. Water will move across the membrane from the more dilute solution to the more concentrated one. The water moves from where there is a higher concentration of water molecules to a lower concentration of water molecules. Osmosis can only happen if the membrane is permeable to water but not to some other solutes. We can say that it is partially permeable

what is a cell wall

The cell wall is a layer of non-living material that is found outside the cell membrane of plant cells. It is mainly made of a carbohydrate called cellulose, although other chemicals can be added to the wall in some cells. Cellulose is a tough material that helps the cell keep its shape and is one reason why the 'body' of a plant has a fixed shape. Animal cells so not have a cell wall and tend to be more variable in shape. Plant cells absorb water, producing an internal pressure that pushes against adjacent cells, giving the plant support. Without a cell wall strong enough to resist these pressures, this method of support would be impossible. The cell wall is porous, so it not a barrier to water or dissolved substances. We call it freely permeable.

What does the nucleus do

The largest organelle in the cell is the nucleus. Nearly all cells have a nucleus. The few types that don't are usually dead (xylem vessel in a stem, or that don't live very long (red blood cells). The nucleus controls all the activities of the cell. It contains chromosonmes (in human cells) which carry the genetic material, or genes. Genes control the activities in the cell by determining which proteins the cell can make. The DNA remains in the nucleus to the cytoplasm, where the proteins are assembled on tiny structures called ribosomes. A cell contains thousands of ribosomes, but they are too small to be seen through a light microscope.

What does the cytoplasm do

The living material that makes up a cell is called cytoplasm. It has texture like sloppy jelly, between a solid and a liquid. Cytoplasm is made out of many different structures called organelles. All reactions take place in the cytoplasm.

what are prokaryotic cells?

There are also organisms made of simpler cells, which have no nucleus, mitochondria or chloroplasts. These are called prokaryotic cells. 'prokaryotic' means 'before nucleus' the main forms of prokaryotic organisms are the bacteria.

what are examples of pathogens

Viruses - HIV leading to AIDS Bacteria -Salmonella Fungi -Athletes foot Protists -Malaria

way to remember life processes

You can remember this by: MRS GREN M - movement R - reproduction S - sensitivity G - growth R - respire E - excretion N - Nutrition

what are enzymes

biological catalysts. One very important group of proteins found In cells are enzymes. Enzymes control the chemical reactions that take place in the cytoplasm.

What are the different levels of an organism?

cells -> tissues -> organ -> organ system

what are only found in plant cells?

chloroplasts and cell wall and large vacoule

diseases caused by other pathogens are called

communicable diseases. This means they can be transferred from one person to another.

what is a cell membrane

controls what goes in and out of the cell. All cells are surrounded by a cell membrane, sometimes called the cell surface membrane to distinguish it from other membranes inside the cell. This is a thin layer like a 'skin' on the surface of the cell. It forms a boundary between the cytoplasm of the cell and the outside. However, it is not a complete barrier. Some chemicals can pass into the cell and others can pass out. We say that the membrane is partially permeable. The membrane can go further than this and actually control the movement of some substances - it is selectively permeable.

what are the three main ways that molecules and ions can move through the membrane

diffusion, osmosis and active transport

Example of diffusion, osmosis and active transport

diffusion: gases, carbon dioxide and oxygen osmosis: water in body active transport: digestion of food from intestine to blood

What are all living things made of?

of units called cells. The simplest organisms are made from single cells but more complex plants and animals are composed of millions of cells. In many-celled (multicellular) organisms, there may be hundreds of different types of cells with different structures. They are specialised so that they can carry out particular functions in the animal or plant.

what do the ribosomes do

synthesize proteins