Biology revision

Plant and animal cells

cell- the smallest part of a living thing

Image result for animal cell diagram gcse (http://www.bbc.co.uk/staticarchive/c9550754291e0fb70dd13b3989391336eeb42067.gif)

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Features

Nucleus- Controls all activities of the cell. Contains the genes on chromosomes made of DNA

Ribosomes- All the protein needed for the cell are synthesised here

Mitochondria- Where most of the energy is released during respiration

Cell membrane- Controls all the movement in and out of the cell

Cell wall- Made of cellulose and strengthens and supports cells

Cytoplasm- All chemical (metabolic) reactions occur here

Chloroplast- Contains chlorophyll which is a green substance that absorbs light to make food by photosynthesis

Permanent vacuole- Contains sell sap which helps keep cells rigid to support the plant

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Specialised cells

Red blood cell- trabsports oxygen

  • has no nucleus so it can fit more haemoglobin
  • has haemoglobin so it can carry oxygen
  • special shape makes it flexible so it can squeeze through small blood

Muscle cell- contracts and enables movement of the body

  • more than one nucleus
  • protein strands to allow contraction
  • lots of mitochondrion as lots of energy is released

Ciliated cell- found in windpipe and fallopian tube (ovaries and uterus)

  • have cilia so they can sweep mucus which has trapped bacteria and dust away from the lungs
  • In ovaries- can sweep away the trapped eggs
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...specialised cells

Root hair cell- absorbs minerals and water from the soil

  • no chloroplast as its underground, no photosynthesis
  • has a lot of root hair cell- increases surface area for absorbtion of water and mineral ions

Sperm cell- transfers genes from the male body to female during sexual reproduction

  • has a tail to allow it to swim to the egg cell
  • contains many mitochondrion to supply ATP for energy
  • its head contains enzymes that are released to help it break through the outer membrane of the egg cell

Egg cell- found in ovary

  • has a haploid nucleus containing only half the number of chromosomes
  • large cytoplasm- contains the nutrients and mitochondria needed for mitosis (cell division)
  • Cell membrane which only allows one sperm to fertillise it

Xylem cell- transports waste and solutes from the root to the leaves

  • doesnt have any cell walls
  • it is hollow (doesnt have any insides)- lets more water through
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Bacteria and yeast cells

Bacteria cells:

  • Slime capsule
  • Flagellum
  • Cell membrane
  • Plasmid
  • Cytoplasm

Yeast cells:

  • Nucleus
  • Cytoplasm
  • Cell wall
  • Cell membrane
  • vacuole
  • food storage granule
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Diffusion

Diffusion: is when particles spread. They move from a region where they are in a high concentration to a region where they are in a low concentration.

Factors affecting the rate of diffusion:

Distance- The greater the distance the slower the rate of diffusion as particles have further to travel so it takes longer

Temperature- The higher the temperature the faster the rate of diffusion as particles gain more kinetic energy which makes them move around faster

Surface area- The greater the surface area the faster the rate of diffusion because the particles have more space to spread around

Concentration difference- The bigger the difference in concentration the faster the rate of diffusion

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Why is diffusion important?

All living cells rely on diffusion. They use it for:

  • getting raw materials for respiration
  • removing waste products
  • plants use of photosynthesis
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Tissues, organs and organ systems

Smallest DNA- nucleus-cell-tissue-organ-organ system-organism Largest

cell: buliding blocks which make up living things

tissue: group pf similar cells which all look the same and function the same way

Organ: made up of different tissues which work together to do a particular job

Organ system: different organs which work together

Organism: made up of different organ systems

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Digestive system

Digestion: is the breakdown of large food molecules using enzymes into small molecules which can be absorbed into the bloodstream.

Mouth

Ingestion is the process of taking food and drink into the body through the mouth. Chewed food is mixed with saliva which contains a carbohydrate enzyme called amylase which digests starch to sugar. Mucus is a slimy substance in saliva which helps food slip down the throat.

Stomach

The stomach churns producing digestive juices. These contain protease whcih digests proteins to amino acids. T

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Digestive system

Digestion: is the breakdown of large food molecules using enzymes into small molecules which can be absorbed into the bloodstream.

Mouth

Ingestion is the process of taking food and drink into the body through the mouth. Chewed food is mixed with saliva which contains a carbohydrate enzyme called amylase which digests starch to sugar. Mucus is a slimy substance in saliva which helps food slip down the throat.

Stomach

The stomach churns producing digestive juices. These contain protease which digests proteins to amino acids. The juices also contain hydrochloric acid because stomach protease works best in pH acid.

Pancreas

The pancreas produces pancreatic juices which contain an epithelial tissue to cover the inside and outside of it and a glandular tissue which produces the pancreatic juices.

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...digestive system

Liver

The liver produces bile which:

  • is alkaline so it neutralises the acid which was added to the food in the stomach
  • emulsifies fats which incresse surface area so the lipase enzyme can work faster

Small intestines-where the absorbtion of soluble food occurs

it contains:

  • glandular tissue- secretes enzymes
  • epithlial tissue- covers the inside and outside of the small intestine
  • muscle tissue
  • nerve tissue

Large intestines- where water is absorbed from the undigested food, producing faeces

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