Cells Flashcards
What is a Cell?
A cell is the basic unit of life, it cannot be viewed by the naked eye since it is too small.
The structures found within a cell are called?
Cell organelles. They have different functions and as they work together, they keep the cell (and therefore the organism) alive.
Characteristics of an animal cell
- Has no cell wall
- Does not have chloroplast
- Vacuoles are small and scattered throughout the cell. They may be temporary
-Cytoplasm is present throughout the cell
- Carbohydrates are stored as glycogen in glycogen granules
Characteristics of a Plant cell
- It is surrounded by the cell wall in addition to the cell membrane
- Chloroplasts are present in large numbers in most cells
- Vacuoles occur singly and is large and central in the cell. Vacuoles are permanent.
- Cytoplasm is confined to a thin layer at the edge of the cell.
- Carbohydrates are stored as starch in starch grains
What is a cell membrane and its function?
This is a cell’s protective coat.
- It separates and protects a cell from its surrounding environment.
- It controls the movement of substances into and out of the cell and is said to be partially permeable.
What is cytoplasm and its function?
A cell’s inner space.
- It is the watery material between the nucleus and the cell membrane with a jelly-like consistency.
- It contains mainly water and dissolved materials, allowing materials to move around the cell.
- The function of the cytoplasm, and the organelles which reside in it, are critical for a cell’s survival.
What is the Nucleus and its function?
A cell’s centre
- It is usually spherical, separated from the cytoplasm by a double membrane called the nuclear envelope.
- It stores deoxyribonucleic acid (DNA), which is wound into structures called chromatin. DNA is the genetic material of an organism, carrying instructions for cell activities and heredity.
Its function therefore, is to protect the cell’s genetic material and control cell activities. It plays an important role in DNA replication and protein synthesis.
What is a vacuole and its function?
This is a cell’s storage space
- In a plant cell, the vacuole is a permanent structure with a fixed shape, occupying a large central part of the cell. It is surrounded by a membrane (tonoplast) and contains cell sap, a solution of mineral salts and sugars.
Plant cells pump a lot of water into the vacuoles which expand and push against the cell wall. This creates a turgor pressure which is important to the plant to keep the cells turgid and thus provide support to the plant.
Vacuoles functions
- transporting materials,
- storing sugars,
- containing digestive enzymes to digest invading bacteria,
- helping the cell to expel excess water.
Mitochondria
This is a cell’s power house
- They are rod shaped and surrounded by a double membrane with an inner membrane extensively folded. They are sites of respiration (see Chapter 5) and are responsible for the release of energy which is subsequently stored in adenosine triphosphate (ATP) molecules.
- Cells which have a high metabolic rate need a constant supply of energy. These cells, such as muscle and liver cells, contain a large number of mitochondria.
What is a cell wall and its functions?
A plant cell and its armour
- It is found only in plant cells; it is an extra layer of material in addition to the cell membrane.
- Unlike the cell membrane, the cell wall is fully permeable. It is a rigid structure made up of cellulose and provides strength and shape to the cell.
It prevents the plant cell from bursting when too much water enters the vacuole.
Chloroplasts
This is a plant’s cell solar generator
- They are similar to mitochondria but are found only in plant cells which photosynthesise. They are flat discs, surrounded by a double membrane called the chloroplast envelope.
They are usually green in colour because of a pigment called chlorophyll. During photosynthesis, chloroplasts trap light energy from the Sun and energy is stored in ATP
What is cell specialisation?
- Multicellular organisms are composed of several different types of cells; each cell is differently adapted to perform a specific function.
- As the cells are produced and developed, they change their structure in some ways to specialise in a specific function.
- This process of development is known as cell differentiation.
What are some examples of specialized cells is plants and animals?
- Xylem vessels
- Root hair cells
- Red blood cells
Xylem cells Characteristics
- are pipe-like columns;
- provide support;
- transport water and mineral salts from roots to other parts.
Root hair cells Characteristics
- has a long narrow extension of the cell;
- has a large surface area to volume ratio;
- increases the rate of
diffusion of water
and mineral salts.
Red blood cells characteristics
- supply oxygen to other body cells;
- contain red pigment called haemoglobin – combine easily with oxygen;
- do not have nucleus – can pack more haemoglobin;
- are biconcave shaped – increase surface area;
- have an elastic cell membrane – allows them to be squeezed through narrow cap
What is a sperm cell?
These cells carry half the genetic information. They have tails to swim towards the egg shell.
What is a red blood cell?
These cells are adapted to carry oxygen to cells and carbon dioxide away from them
What is a nerve cell?
These cells can be very long (up to 2cm) to carry messages around the body.
What is a muscle cell?
These cells can change their length to help us move.
What is a root hair cell?
The root hair gives these cells a bigger surface area to take in water from the soil.
What is a palisade cell?
These cells contain chloroplasts to help the plant make food by photos
What is a ciliated epithelial cell?
These cells are found in tubes leading to the lungs and in the oviduct. The hairs (called cilia) move dirt out of the lungs and help to move eggs along the oviduct.
What are multicellular organisms?
This is composed of several different types of cells organised into organ systems which work with one another to ensure that the whole organism functions effectively.
The different levels of cell organization are?
- Similar cells work together as tissues to carry out a particular function.
- Different tissues work together as an organ to carry out a particular function.
- Different organs work together as an organ system to carry out a particular
- An organism consists of several organ systems with each carrying out its own function.
Plants are what kind of organisms?
Multicellular
Epidermal cells make up the…
Epidermal tissue
Xylem cells and phloem cells make up the…
Vascular tissue
Vascular tissue characteristics
- Found in all parts of a plant
- Carries food and water to various parts of the water
Epidermal tissue characteristics
- Found on surfaces of different parts of a plant
- Protects plants against injury and drying up
Supporting tissue characteristics
- Found mainly in the stems of plants
- Supports and strengthens the plant
The cells of Prokaryotes characteristics
- Lack a true nucleus
- Lack other membrane-bound organelles
- Have their DNA in a region called the nucleoid, which lacks a nuclear membrane, and also in smaller regions called plasmids.
Microbes or microorganisms are extremely small organisms that include:
- all members of the Prokaryotae kingdom, e.g., bacteria
- many members of the protoctista kingdom, e.g., Amoeba
- Some members of the Fungi kingdom, e.g., yeast
What is a capsule?
a slimy outer covering found in some bacteria. Protects the cell
What is Nucleoid?
a single, long, coiled loop of DNA. Controls all cellular activities
What are plasmids?
a small, circular piece of DNA
What is flagellum?
a long, whip-like projection. Aids in movement.
What is pseudopodium (false foot) ?
an extension of the membrane and cytoplasm. Used to engulf food and for movement
What is food vacuole?
contains ingested microscopic organisms. Where digestion occurs
What is contractile vacuole?
contains water. Collects and removes excess water from the cytoplasm
