Term 1 - Cells and cellular structures

Cell Theory

- The basic unit of life

- All organisms are made up of one cell or multiple cells

- All cells come from pre-existing cells

Organelles

- Cell structures ensure they are functioning for survival - called organelles (little organs)

-  Each organelle has a specific function

- They work together with other organelles to keep the celll alive

Organelle functions

Mitochondria - Produces the cell’s energy through a special chemical reaction called respiration. Acts as the cell’s power plant

- Chloropast - Contains chlorophyll, which enables it to convert energy from sunlight into simple sugars (food) through a chemical process called photosynthesis

- Nucleus - Holds the genetic information in the cell, which is stored as chromosomes made of protein and DNA coiled together

- Rough ER - Appears rough, as it is covered in ribosomes that produce proteins. This organelle assists in transporting the protein after production

- Smooth ER - Function depends on specific type of cell. Function can include producing lipids and steroid hormones

- Golgi body - A stack of membrane-bound vesicles that package proteins and other molecules for transport

- Lysosomes - Contains enzymes to aid digestion. It can also produce enzymes that are involved in immune responses to destroy foreign bodies

- Vacuole - Can store nutrients and wastes. Can collect water to provide rigidity in plants. It is typically larger in plant cells than animal cells

- Cell Wall - An additional protective layer for the cell, found beside the cell membrane. It provides structural support and reduces dehydration

Capsule - An external layer found on some prokaryotes that aids their ability to attach to other cells or surfaces

- Pilli- Hair-like structures on the cell surface. Some types of this structure aid attachment to surfaces, while other types allow a twitching type of motion. Some types can also be used to exchange genetic material with other cells

- Flagellum - A tail-like structures that uses motor-proteins to whip around. This provides the cell’s  with mobility

- Nuclear envelope - Two lipid membranes that are studded with special proteins that seperates the nucleus and its contents from the cytoplasm

- Nuclear pores - Tiny holes called nuclear pores are found in the nuclear envelope and help to regulate the exchange of materials (such as RNA and proteins) between the nucleus and the cytoplasm

- Chromatin - Thin long strands of DNA proteins

- Nucleolus - Two nucleolus makes RNA another type of nucleic acid

- Inner membrane -  contains many folds called Cristal which contain specialised membrane proteins that enable the mitrochondria to synthesis ATP. Inside the inner membrane is a jelly-like matrix

Types of cells

- Prokaryotes - usually single cells that have no membrane bound organelles (e.g. bacteria and archaea)

- Eukaryotes - Can be bothe unicellular and multicellular and contain membrane bound organelles (e.g. fungi, protists , plants and animal cells)

Cell Membrane

- Boundary of cell

- Made up of phospholipid bilayer

Nucleus

-  Control centre of the cell

-  Contains DNA

- Surrounded by a double membrane

- Usually the easiest organelle to see under a microscope

- Usually one per cell

-  Controls the metabolic functions

- Produces mRNA which encodes for enzymes (e.g. insulin)

- Controls the structure of the cell. By transcribing DNA which encodes for structural proteins ( e.g. actin and keratin)

Smooth ER

- Does NOT have any ribosomes attached

- Involved in the synthesis of lipids ( e.g. oils, phospholipids and steroids)

- Responsible for metabolism of carbohydrates, regulation of calcium concentration and detoxification of drugs

Rough ER

- Is covered with ribosomes giving ER a rough appearance

- Responsible for protein synthesis

- Plays a role in membrane production

- The folds present in the membrane increase the surface area allowing more ribosomes to be present in the ER, allows for greater protein production

Lysosomes

-  Created by Golgi body or ER

- Contains digestive enzymes that break down wastes

Centriole

- Aids in cell division

-  Usually found only in animal cells

- Made of microtubules

Cytoskeleton

- Acts as skeleton and muscle

- Provides shape and structure

- Helps move organelles around the cell

- Made of three types of filaments ( microtubules (25- nm diameter), actin filaments( 7-nm diameter) and intermediate filaments (10- nm diameter))

Endoplasmic Reticulum (ER)

- Connected to nuclear membrane

- Highway of the cell

- Rough ER - Studded with ribosomes; it makes proteins

- Smooth ER - No ribosomes; it makes lipids (fats)

- Found in eukaryotic cells only

- Has a double membrane consisting of a network of hollow tubes, flatten sheets and round sacs called cisternae

- Located in the cytoplasm and is connected to the nuclear envelope

Ribosomes

- Site of protein synthesis

- Found attached to rough ER or floating free in cytoskeleton

- Produced in a part of the nucleus called the nucleolus

Golgi Apparatus

- Looks like a stack of plates

- Stores,modifies and packages proteins

- Molecules transported to and from the Golgi by the means of vesicles

Mitochondria

- “powerhouse of the cell”

- Cellular respiration occurs here to release energy for the cell to use

- Bound by a double membrane

- Has its own strand of DNA

- Coontains two phospholipid belayers ( outer and inner membrane)

Chloroplasts

- Found only in plant cells

- Contains the green pigment chlorophyll

- Site of food (glucose) production

- Bound by a double membrane

- Structured to trap and store energy in plants

Cell Wall

- Found in plant and bacterial cells

- Rigid protective barrier

- Located outside of the cell membrane

- Made of cellulose (fibre)

Robert Hooke

- Was the first to determine the structure of organisms and he termed it ‘’cella’ - leading to the term cell

- Scientists used a magnifying glass to view objects. They aimed to view objects in greater detail and invented the first microscope

Investigating Cells

- The main tool used by scientists to study cells in the microscope

- There are many different types of microscopes

         - Light microscope

         - Electron microscope

Impact of evolving technology

- Cells are so small that they require improved technology to study

- The advancement of the electron microscope has allowed scientists to observe more closely ((higher resolution)

- This leads to make conclusions and observe the cell and cellular structure

Vacuoles

- Large central vacuole usually in plant cells

- Many smaller vacuoles in animal cells

- Storage cointainer for water, food , enzymes, wastes, pigments, etc

- Plays important role in digestion and excretion of cellular waste and storage of water and organic and inorganic substances

- The vacuole takes in and releases water by osmosis in response to changes in the cytoplasm as well as the environment around the cell

- Responsible for maintaining the shape of plant cells

- When the cell is full of water, the vacuole exerts pressure outwards, pushing the cell membrane against the cell wall

- The pressure is called turgor pressure

- If water is not sufficient , pressure exerted by the vacuole is reduced and the cells become flaccid causing the plant to wilt