Nat 5 bio - cell stuff

nucleus

Directs all the cells activities; contains the cells DNA

cell membrane

Controls what enters and exits the cell, protects and supports cell, and helps cells communicate with other cells. When seen under a microscope it can be seen as a double layer. It is a very flexible structure and can change shape easily. It can be described as a fluid mosaic.

cytoplasm

Where chemical reactions take place, holds organelles in place

cell wall

Protects and supports the cell, made of cellulose fibres

sap vacuole

Used for storage of water and other minerals

chloroplast

Contains chlorophyll which absorbs light energy for photosyntheis

ribosomes

intercellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell.

mitochondria

site of aerobic respiration, where ATP is produced. found in large numbers in cells that are very active and require a lot of energy. They contain enzymes.

Bacterial cells are:

Prokaryotic cells that are smaller than the other cells, they are single celled micro organisms, the DNA is not contained in the nucleus, instead it contains a single circular chromosome. In addition to this there are other smaller rings of DNA called plasmids.

Fungal cells

Yeast is a unicellular fungus -made of single cells, have a nucleus, cytoplasm and cell wall.. has no chloroplasts so cannot preform photosynthesis

Phospholipids

amphipathic molecules, containing hydrophobic and hydrophilic regions. They are 2 layers of lipid molecules in the cell membrane which have proteins embedded in them. have a head and tail end. All the tail point inwards and the tails point outwards.

Proteins

they are embedded in the phospholipid bilayer, some are involved in the transport of materials across the membrane. There are 2 types of proteins transmembrane proteins and partially embedded proteins.

Selectively permeable

only allows certain things to pass through (based on their size) by means of active of passive transport

passive transport

the movement of substances across a cell membrane without the use of energy by the cell

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Osmosis

Diffusion of water through a selectively permeable membrane

When a animal cell bursts this means it...

Gains water by osmosis

Animal cell shrinks

Looses water by osmosis

turgid cell

a plant cell that has absorbed water (by osmosis) and has cytoplasm that is pressing outwards on the cell wall

Plasmolysed Cell

A plant cell in which the the vacuole has shrunk and the membrane has pulled away from the wall due to water loss

Active transport

Energy-requiring process that moves material across a cell membrane against a concentration gradient

concentration gradient

difference in the concentration between 2 solution or cells.

Bacterial cell walls are made of:

made of peptidoglycan (also called murein), which is made from polysaccharide chains cross-linked by unusual peptides containing D-amino acids.

only in plant cells

cell wall, chloroplast, central vacuole

How to calculate the size of cells:

Cells are very small so we use special units called micrometers. There are 1000 micro meters in 1 millimetre. If you are given a cell size in m you may need to convert it to um. You do this by multiplying by 1000. If u are given cell side in um, you may need to convert it to mm. You do this by dividing by 1000.

Visiting tubing

Selectively permeable material that acts like a cell membrane. We can use it to demonstrate which molecules can pass through

Examples of active transport:

the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants.

Examples of passive transport:

It occurs when molecules such as glucose or amino acids move from high concentration to low concentration facilitated by carrier proteins or pores in the membrane.